[0001]The present invention relates to a power supply system, in particular, is suitably used to convert the DC power to AC power.
Background technique
[0002]
　As an apparatus for converting DC power to AC power, there is a device using a magnetic energy recovery switch (see Patent Document 1). Magnetic Energy Recovery Switch described in Patent Document 1 has a four switches and a capacitor. Four switches are connected to the full bridge circuit is configured. Capacitor is connected between the DC terminals of the full bridge circuit. Load is connected between the output terminals of the full bridge circuit. Four switches includes a positive terminal and a negative terminal. Four conducting state from the negative terminal of the switch to the positive terminal is a state in which the current always flows. On the other hand, the conductive state from the positive terminal of the four switches to the negative electrode terminal, and a state in which the state and the current which the current flows not flow is switched by a signal from the outside. Such a magnetic energy recovery switch circuit, ON the four switches, by changing the frequency of switching the OFF, it is possible to change the frequency of the AC power converted from DC power.
[0003]
　Further, Patent Document 2, on the input side of the magnetic energy recovery switch, it is described that provide a capacitor for improving the input power factor of the magnetic energy recovery switch. Further, Patent Document 2, the connecting transformer across the capacitor of the magnetic energy recovery switch, it is described that a capacitor in series with the capacitor of the transformer and the magnetic energy recovery switch. This capacitor is used to increase the transformer input voltage.
[0004]
　In Patent Document 3, by using two magnetic energy recovery switch, it is disclosed that constitutes the DCDC converter.
　Further, Patent Document 4, between the AC terminals of the magnetic energy recovery switch, it is described that a capacitor is connected parallel to the inductive load. In Patent Document 4, by connecting the capacitor in parallel with the inductive load is to be able to reduce the current flowing through the magnetic energy recovery switch.
CITATION
Patent Literature
[0005]
Patent Document 1: WO 2011/74383
Patent Document 2: Japanese Patent 2012-125064 JP
Patent Document 3: Japanese Patent 2012-34522 JP
Patent Document 4: Japanese Patent No. 4460650 Publication
Summary of the Invention
Problems that the Invention is to Solve
[0006]
　The magnetic energy regenerative switch as described above, having various have been proposed. However, determined by using a magnetic energy recovery switch as an inverter, when supplying AC power to the inductive load, the impedance of the inductive load seen by the output side of the inverter, the reactance due to the inductance of the inductive load resistor and It is. Therefore, magnetic energy recovery switch, it is necessary to supply to the inductive load reactive power in addition to the active power. Therefore, the capacity of the magnetic energy recovery switches (rated output) increases.
[0007]
　In the technique described in Patent Document 4, the reactance of the inductive load seen by the output of the inverter (Magnetic Energy Recovery Switch) decreases. However, the technique described in Patent Document 4 aims to reduce the current flowing through the magnetic energy recovery switch. To that end, between the AC terminals of the magnetic energy recovery switch, the capacitor is connected in parallel with the inductive load. Then, the inductive load, a closed circuit is formed by a capacitor connected to the inductive load. Operating the magnetic energy recovery switch in this state, the oscillating current flows in the closed circuit. As a result, the inductive load, the current output from the magnetic energy recovery switch, the oscillating current and are together superimposed current flowing through the closed circuit flows. Therefore, unexpected current flows in the inductive load. Therefore, it is impossible to stabilize the current flowing through the inductive load. Therefore, although additional circuitry for suppressing vibration current flowing through the closed circuit is considered. However, addition of such a circuit results in an increase in cost.
[0008]
　The present invention has been made in consideration of the above problems, and to stabilize the current to be transmitted to the load without using a particular device, to realize the reducing capacity of the Magnetic Energy Recovery Switch for the purpose.
Means for Solving the Problems
[0009]
　An example of a power system of the present invention, supply and magnetic energy recovery switch, and a frequency setting device, a control device, and a quasi-resonant elements, converts the DC power into AC power, the AC power to the inductive load a power supply system for the magnetic energy recovery switch has one or more of the first capacitor, and a plurality of switches, wherein the frequency setting device sets the output frequency of the magnetic energy recovery switch and, wherein the control device, the operation of the on-off of the plurality of switches, the control based on the output frequency set by the frequency setting device, the magnetic energy recovery switches, the plurality of switches on and off by the fact that by recovering magnetic energy stored in the inductive load accumulates as electrostatic energy into said first capacitor, said storage And the electrostatic energy is performed and supplying to the inductive load, the quasi-resonant element comprises at least one passive device includes a second capacitor, the first capacitor, to said inductive load are arranged in series Te, the second capacitor, the said inductive load side from the output terminal of the magnetic energy recovery switches, which are connected in series with the inductive load, the magnetic energy recovery the value of the inductive reactance of the inductive load side from the output terminal of the switch, rather than the output end of the magnetic energy recovery switch exceeds the value of the capacitive reactance of the inductive load, wherein the plurality of switches, said when the voltage across the first capacitor is 0 (zero), a power system for switching on and off.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010]
[1] Figure 1 is a diagram showing a configuration of a power supply system according to the first embodiment.
FIG. 2 is a diagram showing an example of the configuration of a power supply system equivalent power supply system of Figure 1.
FIG. 3 is the power supply system according to the first embodiment, is a diagram illustrating the current flow in the inverter unit.
[Figure 4A] Figure 4A, the power supply system according to the first embodiment, between the switching signal of the second switch and the third switch, and a voltage of the first capacitor, the current output from the inverter section it is a diagram illustrating a first example of the relationship.
[Figure 4B] Figure 4B, the power supply system according to the first embodiment, between the switching signal of the second switch and the third switch, and a voltage of the first capacitor, the current output from the inverter section it is a diagram illustrating a second example of the relationship.
FIG. 5 is the power supply system according to a first embodiment and shows an example of a voltage applied to the smoothing capacitor.
[Figure 6A] Figure 6A, the power supply system according to a first embodiment and showing a first example of the simulation results of the power supply system.
[Figure 6B] Figure 6B, the power supply system according to a first embodiment and showing a second example of the simulation results of the power supply system.
FIG. 7 is a simulation result of a power supply system of the comparative example and the power supply system of the invention example illustrates in tabular form.
[8] FIG. 8 is a diagram showing a configuration of a power supply system according to the second embodiment.
[9] FIG. 9 is a diagram showing a configuration of a power supply system according to the third embodiment.
FIG. 10 is the power supply system according to the third embodiment, a diagram illustrating the current flow in the inverter unit.
FIG 11A] FIG 11A illustrates a switching signal of the first switch, the voltage across the high side capacitor, a voltage across the low-side capacitor, a first example of the relationship between current output from the inverter section it is a diagram.
FIG 11B] FIG 11B illustrates a switching signal of the first switch, the voltage across the high side capacitor, a voltage across the low-side capacitor, a second example of the relationship between current output from the inverter section it is a diagram.
DESCRIPTION OF THE INVENTION
[0011]
　Hereinafter, with reference to the drawings, an embodiment of the present invention.
(First Embodiment)
　First, a first embodiment.

　FIG. 1 is a diagram showing a configuration of a power supply system 100 according to the first embodiment. Power system 100 includes a DC power supply unit 110, the inverter unit 120, quasi-resonant element 130, current transformer 140, a switch controller 150, a current control unit 160 and a frequency setting device 170,. Each configuration of the power supply system 100 may, for example, may be arranged in a dispersed by communicatively coupled via the communication unit. The power supply system 100 does not have a specific device for suppressing vibration current (vibration suppression circuit).
[0012]
[DC power supply 110]
　DC power supply unit 110 supplies the DC power to the inverter unit 120. DC power supply unit 110 has an AC power source 111, a rectifier 112, and a reactor 113. AC power supply 111 outputs an AC power. The input end of the rectifier 112, an AC power supply 111 is connected. The one end of the output side of the rectifier 112 is one end of the reactor 113 is connected. Rectifier 112 outputs a DC power by rectifying the AC power supplied from the AC power source 111. As a rectifier 112, for example, the thyristor rectifier is used. However, the rectifier 112 is not limited to such. For example, rectifier 112 includes a diode rectifier and a voltage control circuit (temperature, step-down chopper, etc.) and the like may be configured with. Reactor 113 is for smoothing the DC power waveform output from the rectifier 112. In this embodiment, the DC power supply unit 110 was configured to convert AC power into DC power. However, the DC power supply unit 110 is not limited to such. For example, DC power supply 110 directly, or may be a power supply for supplying a direct current. For example, the DC power supply unit 110 includes a battery, may be configured using a current control circuit or the like.
[0013]
[Inverter 120]
　The inverter unit 120, the DC power output from the DC power supply unit 110, and converts the AC power of the same frequency as the switching frequency for switching the respective switches of the inverter unit 120. Inverter 120 supplies the AC power of the frequency for the inductive load 180. The inverter unit 120, the magnetic energy recovery switches; having (MERS Magnetic Energy Recovery Switch).
　An example of a configuration of the inverter unit 120 of the present embodiment (Magnetic Energy Recovery Switch) will be described.
　The inverter unit 120 includes a first switch U, the second switch X, the third switch V, the fourth switch Y, the first AC terminal 121, the second AC terminal 122, the first DC terminal 123, second DC terminals 124, and a first capacitor 125.
[0014]
　First, the first switch U, the second switch X, the third switch V, and a fourth switch Y will be described.
　In the present embodiment, the first switch U, the second switch X, the third switch V, and the fourth switch Y have the same configuration. First switch U, the second switch X, the full bridge circuit is constituted by a third switch V, and a fourth switch Y.
[0015]
　The first switch U has a self-turn-off devices S1 and a freewheeling diode D1. The second switch X has a self-turn-off devices S2 and reflux diode D2. Third switch V has a self-turn-off devices S3 and reflux diode D3. Fourth switch Y has a self-extinguishing element S4 and a reflux diode D4.
[0016]
　Self-turn-off elements S1 ~ S4 are made conductive, and a state in which current can flow, one of the state of the state where no current can flow, can be switched by a signal from the outside.
[0017]
　Reflux diodes D1 ~ D4 has a first end and a second end. Reflux diodes D1 ~ D4 are made conductive, from the first end to a second end through a current, but has only state not conduct current from the second end to the first end . The direction from the first end of the reflux diodes D1 ~ D4 to a second end, a forward direction in the reflux diodes D1 ~ D4. A first end of the reflux diodes D1 ~ D4 and the end of the forward side. The second end of the reflux diodes D1 ~ D4 and the ends of the forward and reverse side.
[0018]
　Self-turn-off elements S1 ~ S4 has a first end and a second end. Self-turn-off elements S1 ~ S4, if a state in which current can flow, passing a current from the first end to the second end. Self-turn-off elements S1 ~ S4, if a state in which no current can flow, does not pass current from a first end to the second end. Also, the self-turn-off devices S1 ~ S4, even in any state, does not pass current from the second end to the first end. The direction from the first end of the self-turn-off elements S1 ~ S4 to the second end, a forward direction in the self-turn-off elements S1 ~ S4. A first end of the self-turn-off elements S1 ~ S4, the end of the forward side. The second end of the self-turn-off elements S1 ~ S4, the ends of the forward and reverse side. Self-turn-off elements S1 ~ S4 are not limited to bipolar transistors. For example, self-turn-off elements S1 ~ S4 are field effect transistor (FET), insulated gate bipolar transistor (IGBT), an electron injection enhancement gate transistor (IEGT), gate turn-off thyristors (GTO thyristors), or a gate commutated turn-off thyristor it can be adopted (GCT thyristor).
[0019]
　Self-turn-off devices S1 and reflux diode D1 is forward connected in parallel to have opposite to each other. This is a self-turn-off device S2 and reflux diodes D2, a self-turn-off devices S3 and reflux diodes D3, the same for self-turn-off devices S4 and freewheeling diode D4.
[0020]
　And the end of the forward side of the reflux diodes D1, D2, D3, D4, and self-turn-off devices S1, S2, S3, S4 forward and reverse side of the end portion and the negative terminal to the connection point of the. A self-turn-off devices S1, S2, S3, S4 ends of the forward side, and reflux diodes D1, D2, D3, D4 and forward and reverse side of the end portion of the connection points positive terminal.
[0021]
　And the negative terminal of the first switch U, and the positive terminal of the second switch X are connected to each other. And the positive terminal of the first switch U, and the positive terminal of the third switch V are interconnected. And the negative terminal of the fourth switch Y, the negative terminal of the second switch X are connected to each other. And the positive terminal of the fourth switch Y, the negative terminal of the third switch V are interconnected.
[0022]
　First AC terminal 121 is connected to the connection point between the positive terminal of the negative terminal and the second switch X of the first switch U. Second AC terminal 122 is connected to the connection point of the third negative terminal of the switch V and the positive terminal of the fourth switch Y. In the present embodiment, the first AC terminal 121 and the second AC terminal 122 is an output terminal of the inverter 120.
[0023]
　The first DC terminal 123 is connected to the connection point between the positive terminal of the positive electrode terminal and the third switch V of the first switch U. The first DC terminal 123, the other end of the reactor 113 is connected. Second DC terminals 124 are connected to the connection point between the negative terminal of the negative terminal and the fourth switch Y of the second switch X. The second DC terminals 124, the other end of the output side of the rectifier 112 is connected. In the present embodiment, the first DC terminal 123 and the second dc terminal 124 is an input terminal of the inverter 120.
　DC power supply 110 is connected between the above manner with the first direct-current terminal 123 and the second DC terminal 124.
[0024]
　First switch U, the second switch X, the third switch V, and the fourth switch Y is as long as it has a conduction state as described above, necessarily, a freewheeling diode D1, D2, D3, D4, self-turn-off devices S1, S2, S3, S4 and may not have. For example, the first switch U, the second switch X, the third switch V, and the fourth switch Y may be a metal oxide semiconductor field effect transistor having a parasitic diode is built (MOS transistor) .
[0025]
　The first capacitor 125 is connected between a first DC terminal 123 and the second DC terminal 124. That is, one end of the first capacitor 125, a first DC terminal 123 are connected to each other. The other end of the first capacitor 125, a second DC terminals 124 are connected to each other. The first capacitor 125 is a capacitor having a polarity.
[0026]
[Quasi-resonant elements 130]
　quasi-resonant element 130, the apparent inductance of the inductive load 180 at the output end of the inverter 120, is used to reduce. Quasi-resonant element 130 is comprised of at least one passive device includes a second capacitor. In this embodiment, quasi-resonant element 130 is composed of a second capacitor. The second capacitor is a non-polar capacitor.
　Quasi-resonant element 130, between the first AC terminal 121 of the inverter 120 and the second AC terminals 122, are connected in series with the inductive load 180. In the example shown in FIG. 1, one end of the quasi-resonant element 130, and a second AC terminal 122 of the inverter 120 is connected to each other.
[0027]
[Inductive load 180]
　inductive load 180, between the first AC terminal 121 of the inverter 120 and the second AC terminal 122, is connected in series with the first capacitor 125. In the example shown in FIG. 1, one end of the inductive load 180, and the other end of the quasi-resonant elements 130 are connected to each other. The other end of the inductive load 180, a first AC terminal 121 of the inverter 120 is connected to each other. Inductive load 180 as described above, is connected between the first AC terminal 121 and the second AC terminal 122. Also, quasi-resonant element 130 is connected in series with the inductive load 180 between the first AC terminal 121 and the second AC terminal 122.
[0028]
　Inductive load 180 is a load having an inductance component. Inductive reactance of the inductive load 180 is larger than that capacitive reactance of the inductive load 180. For simplicity, the following description, the capacitive reactance of the inductive load 180 is assumed to be 0 (zero). Inductive load 180 is, for example, a coil and the heated object for induction heating an object to be heated such as a steel plate. Coil for induction heating an object of the inductive load 180, an alternating current is supplied from the inverter unit 120, to generate the magnetic field lines. The magnetic field lines, the eddy current flows in the object to be heated. The eddy currents, the object to be heated is heated in a non-contact manner. Incidentally, inductive load 180 is not limited to a coil for inductively heating an object to be heated. For example, the inductive load 180, resistance spot welding may be a plurality of metal plates (e.g., steel) to be applied. In this case, a plurality of metal plates serving as the inductive load 180 is energized and heated. Further, in the present embodiment, there is no load connected in parallel with the first capacitor 125.
[0029]
[Current transformer 140]
　current transformer 140 measures the alternating current flowing through the inductive load 180.
Frequency setting apparatus 170]
　frequency setting device 170 sets the first switch U, the second switch X, the switching frequency for switching the third switch V, and a fourth switch Y. Inductive load 180, when a coil for inductively heating an object to be heated, the frequency suitable for heating induces an object to be heated is set as the switching frequency. Frequency suitable for induction-heating an object to be heated, for example, the specifications of the induction heating apparatus, the shape of the object to be heated, width, thickness is determined based on the conditions including a heating temperature. For example, the operator, as a frequency suitable for heating induces an object to be heated, and specifications of the induction heating apparatus, the shape of the object to be heated, the width, the switching frequency when made different from the thickness, and the heating temperature pre-investigation. Frequency setting apparatus 170 is capable of prestored The thus investigated the frequency in a storage device such as a ROM. The frequency setting unit 170, based on the operator of the operation through the input interface such as a screen for inputting the frequency, it is also possible to input information of the switching frequency.
[0030]
Switch controller 150]
　The switch control unit 150, the switching frequency set by the frequency setting device 170 switches the first switch U, the second switch X, the third switch V, and the fourth switch Y It generates a switching signal for. Then, the switch controller 150 outputs a switching signal to the first switch U, the second switch X, the third switch V, and a fourth switch Y. Based on the switching signal, the first switch U, the second switch X, conductive state of the third switch V, and a fourth switch Y of the self-turn-off devices S1, S2, S3, S4 switched. Hereinafter, the self-turn-off devices S1, S2, S3, S4 is referred to as ON state in which current can flow. Also, the self-turn-off devices S1, S2, S3, S4 is referred to as the OFF state in which no current can flow.
[0031]
　Switch controller 150, when a first switch U and the fourth switch Y is ON, the second switch X and a third switch V to OFF. The switch controller 150, a first switch U and the fourth switch Y if it is OFF, to ON and the second switch X and a third switch V. The switch controller 150, the switching frequency set by the frequency setting device 170, a first switch U, the second switch X, the third switch V, and each ON the fourth switch Y, OFF the switches. The current I inverter unit 120 outputs inv frequency of (will be described in detail later in this point) is set as the switching frequency. In the present embodiment, the first switch U, the second switch X, the third switch V, and a fourth switching frequency for switching the switch Y becomes the output frequency of the magnetic energy recovery switch.
[0032]
　Switch control unit 150, a first switch U, the second switch X, the third switch V, and the switching frequency for switching the fourth switch Y and f. In this case, the inverter unit 120, to the inductive load 180, current I of the frequency f inv supplies.
[0033]
[Current control device 160]
　The current control device 160 monitors the current measured by the current transformer 140. Then, the current controller 160, the current measured by the current transformer 140 so that the target value, and controls the operation of the rectifier 112. Inductive load 180, when a coil for inductively heating an object to be heated, the target value is determined based on the physical properties and size, etc. of the object to be heated. If the object to be heated is a steel sheet, the physical properties, for example, include permeability and resistivity.
[0034]

　where the inductive reactance of the inductive load 180, assuming a capacitive reactance of a quasi-resonant element 130 an inductive load with the reactance subtraction, as an inductive load apparent as viewed from the inverter unit 120 to. As described below, the inductive reactance of the inductive load 180 is greater than the capacitive reactance of the quasi-resonant element 130. Therefore, inductive load apparent has an inductance component.
[0035]
　Angular frequency ω [rad / s] is expressed by 2πf with frequency f [Hz]. The inductance of the inductive load 180 to L. The inductance of the inductive load apparent to L '. Further, the capacitance of the second capacitor quasi-resonant elements 130 C r and. Then, the reactance ωL of the inductive load of the apparent 'is given by the following equation (1).
[0036]
[Number 1]

[0037]
　That is, the circuit configuration of the power supply system 100, between the first AC terminal 121 and the second AC terminal 122 of the inverter 120 is connected to the inductive load of inductance L 'shown in (2) circuit the equivalent to.
　Figure 2 is a diagram showing an example of the configuration of an equivalent power system and power supply system 100 of FIG. 2, instead of a quasi-resonant element 130 and the inductive load 180 shown in FIG. 1, a diagram of arranging the inductive load 210 apparent.
　As shown in FIG. 2, power supply system 200 has no quasi-resonant element 130 has a inductive load 210 the apparent inductance is L '. The power supply system 200 shown in FIG. 2 as the power supply system 100 shown in FIG. 1, elements constituting the circuit are different. However, the power supply system 200 shown in FIG. 2 is equivalent to the power supply system 100 shown in FIG. That is, the power supply system 100 of the present embodiment, by having a quasi-resonant elements 130 connected in series with the inductive load 180, the apparent inductance of the inductive load 180, is reduced.
[0038]

　Next, an example of operation of the inverter unit 120. Figure 3 is a diagram illustrating an example of a current flow in the inverter unit 120. Figure 4A, the switching signal V-X of the second switch X, and the third switch V Gate and the voltage V according to the first capacitor 125 Mersc and the current I is output from the inverter unit 120 inv relationship with it is a diagram illustrating a first example. Figure 4B, the switch signal V-X of the second switch X, and the third switch V Gate and the voltage V according to the first capacitor 125 Mersc and the current I is output from the inverter unit 120 inv relationship with it is a diagram illustrating a second example.
[0039]
　First, the voltage V according to the first capacitor 125 Mersc period T remains 0 (zero) 0 with reference to FIGS. 3 and 4A an example of the operation of the inverter unit 120 in the case where is greater than 0 (zero) explain.
　The initial state is the first capacitor 125 is charged, the first switch U and the fourth switch Y is OFF, the state second switch X, and the third switch V is is ON.
[0040]
　As in the state A in FIG. 3, the first capacitor 125 begins to discharge, current emitted from the first capacitor 125 is directed to the first DC terminal 123. A first switch U is OFF, since the third switch V is ON, the current flowing into the first DC terminal 123, via the third switch V, the second AC terminals 122 towards flows. Then, the current flowing into the second AC terminal 122, because the fourth switch Y is OFF, the can not flow into the positive terminal side of the fourth switch Y, quasi-resonant element 130 and the inductive load 180 flowing against. Current through the inductive load 180, toward the first AC terminal 121. Current flowing into the first AC terminal 121, since the second switch X is ON, the via the second switch X, toward the second DC terminal 124. Current flowing into the second DC terminal 124 returns to the first capacitor 125.
[0041]
　And transition of the voltage across the first capacitor 125 after the first capacitor 125 starts to discharge, and a transition of the current output from the inverter unit 120 will be described with reference to Figure 4A. V-X Gate , the switch controller 150 is a signal to be transmitted to the second switch X, and the third switch V, the second switch X, and the third switch V ON, the switching signal OFF it is. The switching signal V-X Gate when indicates the value ON, the second switch X, and the third switch V is in a state ON, the switching signal V-X Gate when indicates the value OFF, the second the switch X and the third switch V is in a state of OFF. Also, here it is not shown, the switch controller 150, also the switching signal U-Y to the first switch U and the fourth switch Y Gate transmits the. Switching signal U-Y Gate value of indicates the value of the switching signal and the reverse to be transmitted to the second switch X, and the third switch V. That is, the switching signal U-Y Gate value of the switching signal V-X Gate represents the value of the OFF when has a value of ON, the switching signal V-X Gate indicating the value of the ON when has a value of OFF . V Mersc shows the voltage across the first capacitor 125. I inv shows the current outputted from the inverter unit 120. t 0 represents the time at which the first capacitor 125 begins to discharge. When the first capacitor 125 begins to discharge, current I is output from the inverter unit 120 inv increases in the positive direction, the voltage V according to the first capacitor 125 Mersc begins to decrease. When the first capacitor 125 has finished discharging, voltage V according to the first capacitor 125 Mersc becomes 0 (zero). t 1 indicates the time at which the first capacitor 125 has completed the discharge.
[0042]
　Time t 1 in, when the discharge of the first capacitor 125 is completed, the current I is output from the inverter unit 120 inv peaked, the voltage V of the first capacitor 125 Mersc becomes 0 (zero). A first DC terminal 123 because the voltage between the second DC terminal 124 is 0 (zero), and the first DC terminal 123 is formed between the second DC terminal 124, current does not flow. In this case, as in the state B in FIG. 3, a portion of the flowed current to the first AC terminal 121 is directed to the first DC terminal 123 via the freewheeling diode D1 of the first switch U, the via the third switch V, toward the second AC terminal 122. Others of flown current to the first AC terminal 121, via the second switch X toward the second DC terminal 124, via the freewheeling diode D4 of the fourth switch Y, the second directed to the AC terminal 122. In this case, the voltage V according to the first capacitor 125 Mersc is 0 (zero). Thus, the first switch U, the second switch X, the third switch V, and also according the voltage to the fourth switch Y becomes 0 (zero). Voltage V of the first capacitor 125 Mersc the period is 0 (zero) T 0 and.
[0043]
　In state B in FIG. 3, the current flowing through the inverter 120 and the inductive load 180 in accordance with a time constant determined from the inductance and the resistance component of the inductive load 180, gradually decreases. As shown in FIG. 4A, the current I is output from the inverter unit 120 inv , the time t 1 ~ time t 2 to reduce the duration of the.
[0044]
　Switch controller 150, the time t discharge of the first capacitor 125 is completed 1 period T from 0 the time t has elapsed 2 in, it turns ON the first switch U and the fourth switch Y, the second switch switch to OFF X and third switch V. At this time, the voltage V according to the first capacitor 125 Mersc the soft switching so is 0 (zero). Here, the soft switching, means that the switch is switched from OFF to ON or from ON to OFF when the voltage across the switch is theoretically zero.
[0045]
　Switches to the first switch U and the fourth switch Y is ON, the second switch X, and the third switch V is switched to OFF, as in the state C in FIG. 3, flows into the first AC terminal 121 it current, since the second switch X is OFF, the can not flow to the second switch X, toward the first DC terminal 123 via the first switch U. Current flowing into the first DC terminal 123, because the third switch V is OFF, the can not flow to the third switch V, toward the first capacitor 125. Current flowing into the first capacitor 125 is used for charging the first capacitor 125 is gradually decreased. This current, until the first capacitor 125 has completed charging, flow as a state C in FIG. 3, a 0 (zero) at the time when the charging of the first capacitor 125 is completed. In Figure 4A, the first capacitor 125, the time t 3 and to complete the charging in.
[0046]
　As shown in FIG. 4A, time t 2 ~ time t 3 between the voltage V according to the first capacitor 125 Mersc rises. Further, the voltage V according to the first capacitor 125 Mersc in accordance with the increase of the current I outputted from the inverter unit 120 inv decreases. Time t 3 when the charging of the first capacitor 125 is completed in the voltage V according to the first capacitor 125 Mersc reaches a peak. At this time, the current I outputted from the inverter unit 120 inv becomes 0 (zero).
[0047]
　After the charging of the first capacitor 125 is completed, the first capacitor 125 begins to discharge. As in the state D of FIG. 3, the current emitted from the first capacitor 125, toward the first DC terminal 123. This current is a first switch U is ON, since the third switch V is OFF, the through the first switch U, toward the first AC terminal 121, inductive load 180 and pseudo It flows into the resonant element 130. Current flowing into the quasi-resonant element 130, toward the second AC terminals 122, a fourth switch Y, via a second direct-current terminals 124, toward the first capacitor 125. Thus, a second current flowing toward the first AC terminal 121 through the AC terminal 122 of the quasi-resonant element 130 and the inductive load 180 in the initial state, derived from the first AC terminal 121 to flow to the second AC terminals 122 via sexual load 180 and quasi-resonant element 130. That is, the direction of the current flowing into the quasi-resonant element 130 and inductive load 180 is reversed, the state A ~ C. Thus, the inverter unit 120, the switching frequency f which is set by the switch control unit 150, a first switch U, the second switch X, the third switch V, and a fourth switch Y of ON, OFF by switching the current I of the same frequency as the switching frequency f inv outputs a.
[0048]
　In Figure 4A, the first capacitor 125, the time t 4 at complete discharge. As shown in FIG. 4A, a voltage V according to the first capacitor 125 Mersc , the time t in accordance with the discharge of the first capacitor 125 3 continued to decrease from the time t 4 becomes 0 (zero) in the. The current I output from the inverter unit 120 inv is in accordance with the discharge of the first capacitor 125, the time t 0 ~ time t 3 to the direction of increase in the reverse direction. The current I output from the inverter unit 120 inv the discharge of the first capacitor 125 is completed time t 4 , the time t 0 ~ time t 3 to the direction of reach in the direction opposite to the peak. Time t 3 ~ time t 4 the current I outputted from the inverter unit 120 during the inv direction, the time t 0 ~ time t 1 the current I outputted from the inverter unit 120 during the inv reversed direction of . Therefore, in the graph of FIG. 4A, time t 3 ~ time t 4 the current I outputted from the inverter unit 120 during the inv value of a negative value.
[0049]
　Time t 4 in, when the discharge of the first capacitor 125 is completed, the voltage V according to the first capacitor 125 Mersc becomes 0 (zero). Since voltage is 0 (zero) between the first DC terminal 123 and second DC terminals 124, such as in a state E of FIG. 3, between a first DC terminal 123 and the second DC terminal 124 the current does not flow. In this case, a portion of the flowed current to the second AC terminal 122, via the return diode D3 of the third switch V toward the first DC terminal 123, via the first switch U, toward the first AC terminal 121. Others of flown current to the second AC terminal 122, via the fourth switch Y toward the second DC terminal 124, via the freewheeling diode D2 of the second switch X, first directed to the AC terminal 121.
[0050]
　In state E of FIG. 3, the current flowing through the inverter 120 and the inductive load 180, according to the time constant due to inductance and resistance components of the inductive load 180, gradually approaches 0 (zero). As shown in FIG. 4A, the current I is output from the inverter unit 120 inv , the time t 4 ~ time t 5 approaches 0 (zero) in the period.
[0051]
　Switch controller 150, the time t discharge of the first capacitor 125 is completed 4 period T from 0 time t 5 in switches the first switch U and the fourth switch Y to OFF, the second switching to oN the switch X and the third switch V. At this time, the voltage V according to the first capacitor 125 Mersc the soft switching so is 0 (zero).
[0052]
　First switch U and the fourth switch Y is switched to OFF, the second switch X, and the third switch V is switched to ON, so that the state F of FIG. 3, flows into the second AC terminals 122 I current, since the fourth switch Y is OFF, the heading to the first DC terminal 123 via the third switch V. Current flowing into the first DC terminal 123, since the first switch U is OFF, the heading to the first capacitor 125. Current flowing into the first capacitor 125 is further approaches 0 (zero). This current, until the first capacitor 125 has completed charging, flow as a state F of FIG. 3, a 0 (zero) at the time when the charging of the first capacitor 125 is completed.
[0053]
　As shown in FIG. 4A, time t 5 ~ time t 6 between a voltage V according to the first capacitor 125 Mersc rises. Further, the voltage V according to the first capacitor 125 Mersc in accordance with the increase of the current I outputted from the inverter unit 120 inv approaches 0 (zero). Time t 6 when the charging of the first capacitor 125 is completed in the voltage V according to the first capacitor 125 Mersc reaches a peak. At this time, the current I outputted from the inverter unit 120 inv becomes 0 (zero).
[0054]
　Time t 6 in, the first capacitor 125 has completed charging, since the first switch U and the fourth switch Y is OFF, the second switch X, and the third switch V is in ON, initial returns to the state a is a state. The inverter unit 120 will repeat the above operations.
[0055]
　As shown in state C and the state F of FIG. 3, during the charge of the first capacitor 125, current flows from the first DC terminal 123 to the first capacitor 125. That is, the first capacitor 125 is always accumulate positive charge to the first DC terminal 123 side, a negative charge is accumulated in the second DC terminal 124 side. Therefore, as a first capacitor 125, a capacitor having a polarity are available. The direction of the current flowing into the second capacitor included in the quasi-resonant element 130 is not constant. Therefore, as a second capacitor, it can not be utilized capacitor having a polarity, so that the use of non-polar capacitor.
[0056]
　As shown in FIG. 4A, the current I is output from the inverter unit 120 inv as, one period of the current of the alternating current is output. That is, the inverter 120 outputs an alternating current having the same frequency as the switching frequency f.
[0057]
　In Figure 4A, a voltage V according to the first capacitor 125 Mersc period T remains 0 (zero) 0 indicates the case where is greater than 0 (zero). In contrast, in FIG. 4B, the voltage V according to the first capacitor 125 Mersc period T remains 0 (zero) 0 shows the case is 0 (zero). Hereinafter, the voltage V according to the first capacitor 125 Mersc period T remains 0 (zero) 0 reference to FIGS. 3 and 4B, an operation example of the inverter section 120 of the case is 0 (zero) It will be described.
[0058]
　The initial state is the first capacitor 125 is charged, the first switch U and the fourth switch Y is OFF, the state second switch X, and the third switch V is is ON.
[0059]
　Voltage V of the first capacitor 125 Mersc period T remains 0 (zero) 0 if it is 0 (zero), as shown in FIG. 4B, the first capacitor 125, the time t 0 ~ Time T 1 to discharge into. Then, the time t 1 the voltage V according to the first capacitor 125 in mersc becomes 0 (zero). Time t shown in FIG. 4B 0 ~ time t 1 the operation of the inverter unit 120, the time t shown in FIG. 4A 0 ~ time t 1 is the same as the operation of the inverter unit 120 of.
[0060]
　In the example shown in FIG. 4A, time t 1 after the voltage V of the first capacitor 125 Mersc period T remains 0 (zero) 0 provided. In contrast, in the example shown in FIG. 4B, the voltage V according to the first capacitor 125 Mersc period T remains 0 (zero) 0 is 0 (zero). Thus, the switch controller 150, the discharge is completed at time t of the first capacitor 125 1 in (i.e., without leaving time from the discharge of the first capacitor 125 is completed), the first switch U and switch to oN and the fourth switch Y, switches the second switch X, and the third switch V to OFF.
[0061]
　Then, the first capacitor 125, the time t 1 ~ time t 2 and charges during the time t 2 ~ time t 3 to discharge between. Then, the time t 3 , the voltage V according to the first capacitor 125 Mersc becomes 0 (zero). In the example shown this way in Fig. 4B, the first switch U, the second switch X, the third switch V, and the fourth switch Y transitions to state C from the state A in FIG. 3, state B the not taken. Time t is shown in FIG. 4B 1 ~ time t 3 the operation of the inverter unit 120 during the time t shown in FIG. 4A 2 ~ time t 4 is the same as the operation of the inverter section 120 between.
[0062]
　Thereafter, in the example shown in FIG. 4A, a voltage V according to the first capacitor 125 Mersc period T remains 0 (zero) 0 provided. In contrast, in the example shown in FIG. 4B, the voltage V according to the first capacitor 125 Mersc period T remains 0 (zero) 0 is 0 (zero). Thus, the switch controller 150, the discharge is completed at time t of the first capacitor 125 3 in (i.e., without leaving time from the discharge of the first capacitor 125 is completed), the first switch U and switches the fourth switch Y to OFF, it switches the second switch X, and the third switch V to oN.
[0063]
　Then, the first capacitor 125, the time t 3 ~ time t 4 for charging during. In the example shown this way in Fig. 4B, the first switch U, the second switch X, the third switch V, and the fourth switch Y transitions to state F from state D of FIG. 3, state E the not taken. Time t shown in FIG. 4B 3 ~ time t 4 the operation of the inverter unit 120 during the time t shown in FIG. 4A 5 ~ time t 6 is the same as the operation of the inverter section 120 between.
[0064]
　As shown in FIG. 4B, the current I is output from the inverter unit 120 inv , the time t 0 increases from the direction of the positive with the discharge of the first capacitor 125. The current I output from the inverter unit 120 inv the discharge of the first capacitor 125 is completed time t 1 peaks at. Current I outputted from the inverter unit 120 inv , the time t 1 from the approaches 0 (zero) with the charge of the first capacitor 125. The current I output from the inverter unit 120 inv , the charging of the first capacitor 125 is time t completed 2 consisting of a 0 (zero).
[0065]
　Current I outputted from the inverter unit 120 inv orientation, the time t 2 from time t 0 ~ time t 2 becomes opposite to that in. Current I outputted from the inverter unit 120 inv , the time t 2 from, with the discharge of the first capacitor 125, the time t 0 ~ time t 2 to the direction of increase in the reverse direction. The current I output from the inverter unit 120 inv the discharge of the first capacitor 125 is completed time t 3 , the time t 0 ~ time t 2 to the direction of reach in the direction opposite to the peak. Current I outputted from the inverter unit 120 inv , the time t 3 from the approaches 0 (zero) with the charge of the first capacitor 125. The current I output from the inverter unit 120 inv , the charging of the first capacitor 125 is completed time t 4 becomes 0 (zero) at.
[0066]
　Switch controller 150, the voltage V according to the first capacitor 125 Mersc time t is 0 (zero) 1 and time t 3 in a first switch U and the fourth switch Y, the second switch X and a third ON the switch V, switching means OFF. In this manner, the switch controller 150, the voltage V according to the first capacitor 125 Mersc period T remains 0 (zero) 0 even if it is 0 (zero), it is possible to realize a soft switching .
[0067]
　Further, the period related to the charging and discharging of the first capacitor 125, the capacitance C of the first capacitor 125 m and, in a half cycle of the resonance frequency determined from the inductance L 'of the inductive load 210 apparent is there. Therefore, as shown in FIG. 4B, the voltage V according to the first capacitor 125 Mersc period T remains 0 (zero) 0 If 0 (zero), the current I is output from the inverter unit 120 inv the frequency is equal to the capacitance of the first capacitor 125, a resonance frequency determined from the inductance L 'of the inductive load 210 apparent.
[0068]
　As apparent from the above description, a first switch U and the fourth switch Y, the second switch X and a third ON the switch V, the first switch U by switching OFF, the second switch X, the third switch V, and a fourth on the path of all or alternating current flowing through a portion of the switch Y, the first capacitor 125 and a quasi-resonant elements 130 are arranged in series. In this embodiment, the alternating current, the inverter unit 120, not shunt unless the state of the state B and state E shown in FIG.
[0069]
　Further, as shown in FIG. 1, in a state in which the voltage depends on the first capacitor 125 (state of performing charge and discharge), the inverter unit 120, quasi-resonant element 130 and the inductive load 180, the first capacitor 125, quasi-resonant element 130, and the inductance L inductive load 180 can be regarded as a series resonant circuit connected in series. Also, quasi-resonant element 130 and inductive load 180 is equivalent to the inductive load 210 apparent with an inductance L '. Thus, the series resonant circuit the inverter unit 120, quasi-resonant element 130 and the inductive load 180, are connected in series, a first capacitor 125, and a series resonant inductive load 210 apparent are connected in series it can be regarded as a circuit.
[0070]
　Therefore, the first capacitor 125, the capacitance C of the first capacitor 125 m and determined from the inductance L 'of the inductive load 210 and the apparent resonant frequency f res (= 1 / (2 [pi × √ (L '× C m half cycle of))), That is, the voltage V according to the first capacitor 125 Mersc is at the start of charging of the first capacitor 125 0 (zero), rises with charging of the first capacitor 125, the first capacitor 125 It decreases with discharge. Then, from the timing the charging is started for the first capacitor 125, the frequency f res when half period of has passed, the voltage V according to the first capacitor 125 Mersc becomes again zero.
[0071]
　That is, the capacitance C of the first capacitor 125 m and a resonance frequency f determined from the inductance L 'of the inductive load 210 apparent res in, the first capacitor 125, and inductive load 210 apparent There resonates. A first capacitor 125, in order to resonate with the inductive load 210 The apparent first capacitor 125, the synthesis reactance of the inductive load 210 Apparent (= ωL'-1 / (ω × C m )) needs to exist become angular frequency omega 0 (zero). = 1 omega / √ (L '× C m to) and a angular frequency omega is present, L' × C m should have a positive real number. Capacitance C of the first capacitor 125 m is a positive value because the scalar value. Therefore, L '× C m is to be a positive real number, the inductance L of the inductive load 210 the apparent' is, there must be a positive value (i.e. 0 (zero) value greater than).
[0072]
　Voltage V of the first capacitor 125 Mersc When becomes 0 (zero), a first switch U and the fourth switch Y, the second switch X and a third ON the switch V, the switching of the OFF until done, no current flows through the first capacitor 125. Switch controller 150, at this timing, the first switch U and the fourth switch Y, the second switch X and a third ON the switch V, by switching OFF, to realize the soft switching can.
[0073]
　The switch controller 150, the voltage V according to the first capacitor 125 Mersc by adjusting the period is 0 (zero), voltage I is output from the inverter unit 120 inv can adjust the frequency of the . Voltage V of the first capacitor 125 Mersc from the time when becomes 0 (zero), a first switch U and the fourth switch Y, the second switch X and a third ON the switch V, OFF period until the time when the switching of is performed, the voltage V according to the first capacitor 125 Mersc period T becomes 0 (zero) 0 is the same as. Then, the following equation (3) the relationship is established.
[0074]
[Number 2]

[0075]
　(3) from equation, the resonance frequency f res period of one cycle of can be expressed by the following equation (4).
[0076]
[Number 3]

[0077]
　Voltage V of the first capacitor 125 Mersc period T becomes 0 (zero) 0 is 0 (zero) or more. Therefore, the capacitance C of the first capacitor 125 m and a resonance frequency f determined from the inductance L 'of the inductive load 210 apparent res one cycle of a following one period of the switching frequency f of the inverter unit 120 Become. That is, the capacitance C of the first capacitor 125 m and a resonance frequency f determined from the inductance L 'of the inductive load 210 apparent res must be greater than the switching frequency f. Therefore, the capacitance C of the first capacitor 125 m is required to be a value that satisfies the following equation (5).
[0078]
[Formula 4]

[0079]
　If the resonant frequency f res is, if less than the switching frequency f of the inverter 120, the inverter unit 120, the voltage V according to the first capacitor 125 Mersc will be a case that it is 0 (zero) is not generated, soft switching can not be.
[0080]
　Thus, the switching frequency f of the inverter unit 120, a first capacitor 125, the resonant frequency f of the resonant circuit including a quasi-resonant element 130 and the inductive load 180, res set to be below.
　Thus, the power supply system 100, when the switching frequency of the inverter unit 120 is f, L '> 0, and that satisfies the expression (5), a first capacitor 125, quasi-resonant element 130, induction it is necessary to have a sexual load 180. (5) If the equation is satisfied, √ (L '× C m ) is a positive value. Capacitance C of the first capacitor 125 m has a positive value. Therefore, L '> 0 also satisfies the equation.
[0081]
　Therefore, the power supply system 100, when the switching frequency of the inverter unit 120 is f, only have (5) that satisfies equation first capacitor 125, quasi-resonant element 130, inductive load 180 It will be Bayoi.
[0082]
　As described above, the power supply system 100, by reducing the inductance of the apparent inductive load 180 as viewed from the inverter unit 120, to reduce the reactance of the apparent of the inductive load 180, the output from the inverter unit 120 voltage V is inv can be reduced. If current output from the inverter unit 120 are the same, towards the case of having a quasi-resonant element 130, than if no quasi-resonant element 130, requires less capacity of the inverter unit 120.
[0083]
　The power supply system 100, the switching frequency f or more frequencies of the inverter unit 120, a first capacitor 125, by resonating with the inductive load 210 apparent, the voltage V of the first capacitor 125 mersc can be generated period becomes 0 (zero). The power supply system 100, during that period, it is possible to realize a first switch U and the fourth switch Y, the second switch X and a third ON the switch V, and soft switching by switching means OFF.
[0084]
　The power supply system 100, at all frequencies, which may take as a switching frequency f of the inverter unit 120, (5) that satisfies equation first capacitor 125, quasi-resonant element 130, so as to have an inductive load 180 to. In this way, the power supply system 100, even when the switching frequency f of the inverter 120 is changed by the switch control unit 150, a voltage V is outputted from the inverter unit 120 inv reduce (i.e., the inverter unit 120 It can be realized reduction) and soft switching capacity.
[0085]
　Also, quasi-resonant element 130 is not in parallel with the inductive load 180 are connected in series. Further, the inductive load 180 side from the inverter unit 120, (passive element having a capacitive reactance) capacitor connected in parallel with the inductive load 180 is not. Thus, quasi-resonant element 130 and inductive load 180 is not to constitute a closed circuit. Thus, the oscillating current does not occur. Therefore, with respect to the inductive load 180, it is possible to prevent the unexpected current flows. From the above, the inverter unit 120, without using a specific apparatus such as a vibration suppression circuit, it is possible to transmit a desired current vibration is suppressed in the inductive load 180.
[0086]
　The inverter unit 120 performs a first switch U and the fourth switch Y, the second switch X and a third ON the switch V, and the switching of the OFF as described above. Therefore, the inverter unit 120, and to charge the first capacitor 125 accumulates magnetic energy stored in the inductive load 180 as recovered, electrostatic energy, electrostatic energy accumulated in the first capacitor 125 repeatedly performing supplying the inductive load 180. Therefore, the voltage V according to the first capacitor 125 Mersc , as shown in FIGS. 4A and 4B, the AC voltage including a period during which a 0 (zero). That is, the first capacitor 125 is not intended for smoothing the DC power waveform output from the rectifier 112. If the first capacitor 125, when the waveform of the DC power output from the rectifier 112 is for smoothing the voltage across the first capacitor 125, although sometimes the variation due to pulsating flow occurs as shown in FIG. 5, substantially constant value E d becomes not take a value of 0 (zero). Furthermore, in this case, it is necessary to resonate only at the quasi-resonant element 130 and the inductive load 180. However, (5) Under the condition shown in the expression, only quasi-resonant element 130 and the inductive load 180 does not resonate.
[0087]
(Method of reducing the capacity of the inverter unit 120)
　voltage V output from the inverter unit 120 inv , the current outputted from the inverter unit 120 I inv , the voltage applied to the quasi-resonant element 130 V r , the inductive load 180 such voltage V Load and. Capacity of the inverter unit 120, I inv × V inv is. Further, the voltage V according to the inductive load 180 load , the voltage V is supplied from the inverter unit 120 inv and the voltage V according to the quasi-resonant element 130 r is the sum of the. Accordingly, it holds the following equation (6)
V load = V inv +　V r · · · (6)
　i.e., an inverter unit 120 and the quasi-resonant element 130 share the voltage across the inductive load 180.
[0088]
　Current control device 160, a current I outputted from the inverter unit 120 inv values of so that a target value, controls the operation of the rectifier 112. Therefore, the capacity of the inverter unit 120 (= I inv × V inv to reduce the value of) the voltage V is outputted from the inverter unit 120 inv may be reduced. Voltage V is outputted from the inverter unit 120 inv is expressed by the following equation (7).
[0089]
[Formula 5]

[0090]
　Therefore, the capacitance C of the first capacitor 125 m larger the voltage V output from the inverter unit 120 inv decreases.
　In the state that the voltage depends on the first capacitor 125, first capacitor 125, a quasi-resonant element 130 and the inductive load 180, the resonant frequency f res resonates at (resonance frequency f res for (5) see). The resonance frequency f res When unchanged, the capacitance C of the first capacitor 125 m As you increase the inductance L 'is reduced. Inductance L ', since is expressed by the following equation (8), the electrostatic capacitance C of the second capacitor quasi-resonant element 130 r extent that becomes smaller, the inductance L' is reduced.
[0091]
[Number 6]

[0092]
(Specifically designed method)
　Here, the electrostatic capacitance C of the first capacitor 125 m will be described a specific example of a method of designing a. Here, the switch controller 150, a first switch U and the fourth switch Y, the second switch X, and the third switch V, 9.9 [kHz] ~ 7.0 of [kHz] and to switch the switching frequency f. In this case, current I is output from the inverter unit 120 inv frequency becomes 9.9 [kHz] ~ 7.0 [kHz ].
[0093]
　Capacitance C of the second capacitor quasi-resonant element 130 r is assumed to be 30 [μF]. Current I outputted from the inverter unit 120 inv inductance L of the inductive load 180 for each frequency of is measured in advance, and are as follows.
　When 9.9 [KHz]; L = 23.7
　[MyuH] 7.0 [KHz] at the time; L = 24.2 [μH]
[0094]
　In this embodiment, the inductive load 210 apparent with synthetic reactance of the inductive load 180 and the quasi-resonant element 130, it was decided to resonance caused by the first capacitor 125. However, this resonance can also be regarded as the combined capacitance of the first capacitor 125 and the quasi-resonant element 130 is the resonance between the capacitor and the inductive load 180 having a capacitance. Here, assume a capacitor having a combined capacitance of the first capacitor 125 and the quasi-resonant element 130 as an electrostatic capacitance. Also, it will be referred to as the capacitor and combined capacitor. Further, the capacitance of combined capacitor C res and. Then, the electrostatic capacitance C of the combined capacitor res , in order to resonate with the inductance L of the inductive load 180 is as following equation (9).
[0095]
[Number 7]

[0096]
　Current I outputted from the inverter unit 120 inv capacitance C of the combined capacitor during frequency of 9.9 [kHz] res is about 10 [μF] (≒ 1 / ((2π × 9.9 × 10 3 ) 2 × 23.7 × 10 -6 a). synthesis reactance of pseudo viewed from the inverter unit 120 resonance element 130 and the inductive load 180 (= ω × L '), the table in the next (10) since the, below is established (11).
[0097]
[Expression 8]

　inductance of the inductive load 210 the apparent L ', since it must be a value greater than 0 (zero), and to satisfy the expression (11) than the next (12) of the relationship to.
[0098]
[Number 9]

[0099]
　In these conditions, a first switch U and the fourth switch Y, the second switch X and a third ON the switch V, so switching of the OFF becomes soft switching, the first capacitor 125 capacitance C m and may be designed.
[0100]
　Current I outputted from the inverter unit 120 inv when frequency is 9.9 [kHz], the voltage V according to the first capacitor 125 Mersc period T remains 0 (zero) 0 to 2. 5 [Myusec] (T 0 = 2.5 [Myusec]) to. Voltage V of the first capacitor 125 Mersc period T remains 0 (zero) 0 can be expressed by equation (3) from, the following equation (13).
[0101]
[Formula 10]

[0102]
　Here, f is a switching frequency of the inverter unit 120 (= 9.9 [kHz]) . f res is the capacitance C of the first capacitor 125 m is the resonance frequency determined from the, the inductance L 'of the inductive load 210 apparent.
　From this equation (13), the resonant frequency f res is expressed by the following equation (14), about 10.4 [kHz] (≒ 1 / (1 / 9.9 × 10 3 -2 × (2.5 10 × -6 becomes)).
[0103]
[Number 11]

[0104]
　Here, the frequency is, the electrostatic capacitance C of the first capacitor 125 m and a resonance frequency f determined from the inductance L 'of the inductive load 210 and the apparent res angular frequency ω when a res is the following ( 15) the formula.
　omega res = 2 [pi] f res　· · · (15)
　the capacitance of the first capacitor 125 C m , in order to resonate with the inductance L 'of the inductive load 210 apparent, the following equation (16) holds.
[0105]
[Number 12]

[0106]
　L = 23.7 [μH], Cr = 30 [μF] So, from (16), C m becomes ≒ 15 [μF]. That is, the first capacitor 125, the capacitance is that it may be utilized capacitor 15 [μF]. Note that (16) is a modification using (5) of the portion of the equation (8). Capacitance C of the first capacitor 125 m is (5) from equation it is sufficient to satisfy the following equation (17).
[0107]
[Formula 13]

[0108]
Then,　C m as = 15 [μF], the switch control unit 150, description will be given of a case where changing the switching frequency f of the inverter 120 to 7.0 [kHz].
　Since L '> 0, equation (8), the electrostatic capacitance C of the second capacitor quasi-resonant element 130 r value of, it is necessary to satisfy the following equation (18) in relation . (18) to deform equation as the following equation (19).
[0109]
[Number 14]

[0110]
　Frequency, the angular frequency ω when a switching frequency f of the inverter 120, 2 [pi × 7.0 × 10 3 is [rad / s]. Inductance L of the inductive load 180 when the switching frequency f of the inverter 120 is 7.0 [kHz] is 24.2 [.mu.H] as described above.
[0111]
　Therefore, (19) than the capacitance C of the second capacitor quasi-resonant element 130 r is about 21.4 [microfarads] (≒ 1 / ((2 [pi × 7 × 10 3 ) 2 × 24.2 10 × -6 must exceed the)). Here, the capacitance C of the second capacitor quasi-resonant element 130 r , since a 30 [microfarads], thereby satisfying the expression (19). That is, the value of the inductance L 'of the inductive load 210 the apparent since positive values, quasi-resonant element 130 and the inductive load 180, resonates with the first capacitor 125.
[0112]
　Further, the inductance L 'is of the inductive load 210 an apparent switching frequency f of the inverter 120 is 7.0 [kHz], from equation (8), about 7.0 [μH] (= 24.2 10 × -6 -1 / ((2 [pi × 7.0 × 10 3 ) 2 × 30 × 10 -6 a)). An inductance L 'of the inductive load 210 the apparent capacitance C of the first capacitor 125 m resonance frequency f determined from the res , from (5), about 15.5 [kHz] (= 1 / (2 [pi × √ (7.0 × 10 -6 × 15 × 10 -6 )) and becomes. Accordingly, the switching frequency f of the inverter unit 120 is higher than 7.0 [kHz]. Therefore, the inverter unit 120 , even when the switching frequency f is 7.0 [kHz], can be realized soft switching.
[0113]
　Capacitance C of the second capacitor quasi-resonant element 130 r is the inductance L of the inductive load 180 in response to the switching frequency f, is determined so as to satisfy the equation (18). Capacitance C of the first capacitor 125 m , an electrostatic capacitance C of the second capacitor quasi-resonant elements 130 defined in this way r with, are determined so as to satisfy the equation (17) . For example, if the inductive load 180 is a coil and the object to be heated for induction heating an object to be heated such as a steel plate, the electrostatic capacitance C of the second capacitor quasi-resonant element 130 r , for example, 6.5 [μF] ~ 250 [μF] range appropriate value is selected from the capacitance C of the first capacitor 125 m , for example, a suitable value from the range of 0.06 [μF] ~ 20 [μF ] There is selected.
[0114]
(Simulation Results)
　Figures 6A and 6B are views showing an example of an operation simulation result of the power supply system 100 of the present embodiment. Waveform of FIG. 6A, the switching frequency f of the inverter 120 is 9.9 [kHz], the waveform when the inductance L of the inductive load 180 is 23.7 [μH]. Waveform of FIG. 6B, the switching frequency f of the inverter 120 is 7.0 [kHz], the waveform when the inductance L of the inductive load 180 is 24.2 [μH]. Further, the waveforms shown in FIGS. 6A and 6B, the capacitance C of the first capacitor 125 m is 15 [microfarads], the electrostatic capacitance of the second capacitor quasi-resonant elements 130 C r is 30 [microfarads is a waveform of the time is a.
[0115]
　I inv shows the current outputted from the inverter unit 120. V inv shows the voltage output from the inverter unit 120. V Mersc shows the voltage across the first capacitor 125. Note that in FIGS. 6A and 6B, the current I is output from the inverter unit 120 inv Arms that subjected beside the waveform is the waveform (current I inv shows the effective value of). Further, the voltage V is outputted from the inverter unit 120 inv voltage V according to and the first capacitor 125 Mersc Vrms which is attached to the side of the waveform of the relevant waveform (voltage V inv , V Mersc shows the effective value of) .
[0116]
　U-Y Gate shows a switching signal transmitted from the switch controller 150 to the first switch U and the fourth switch Y. The switch control unit 150, to the second switch X, and the third switch V, U-Y Gate switching signal opposite that shown in the switching signal V-X Gate transmits the.
[0117]
　6A and 6B, the switching signal U-Y Gate voltage V according to a first capacitor 125 Mersc Looking at the, in any of the switching frequency f, voltage V according to the first capacitor 125 Mersc of when the value is 0 (zero), the switching signal U-Y Gate can be seen that the switching of being performed. That is, the first switch U, the second switch X, the third switch V, and the fourth switch Y is, ON, that is switched with OFF seen in a state of voltage to the first capacitor 125 is not applied . Therefore, it is understood that soft switching is achieved. The current I output from the inverter unit 120 inv than also be seen that the oscillating current is not generated.
[0118]
　Figure 7 is a simulation result of a power supply system of the comparative example and the power supply system of the invention example illustrates in tabular form. Power system of the inventive example is a power supply system 100 of the present embodiment. Power system of the comparative example is from the power supply system 100 of the present embodiment except for the quasi-resonant element 130. Except the presence of quasi-resonant element 130 is not different from in the power supply system of the comparative example power supply system of the inventive example. Incidentally, Arms shown in FIG. 7, Vrms, like FIGS. 6A and 6B, indicating that it is an effective value.
[0119]
　In Figure 7, the switching frequency f of the inverter 120 exhibits a 9.9 [kHz] and 7.0 the results of a simulation of the two types of [kHz]. Further, the electrostatic capacitance C of the first capacitor 125 of the power supply system m is 15 [μF]. Capacitance C of the pseudo power supply system of the invention Example resonant element 130 (second capacitor) r is 30 [μF]. First capacitance of the capacitor 125 of the power supply system of the comparative example is 9.3 [μF]. Further, the inductance L of the inductive load 180, when the switching frequency f is 9.9 [kHz], Ri is 23.7 [.mu.H], the case of 7.0 [kHz], in 24.2 [.mu.H] is there. Further, in the simulation, the inverter unit 120 of the invention examples and comparative examples, it was decided to output the same current.
[0120]
　As shown in FIG. 7, in any of the switching frequency f, the voltage V is outputted from the inverter unit 120 inv has been shown that the direction of the power supply system 100 of the inventive example is smaller. As a result, the capacity of the inverter unit 120 of the power supply system 100 of the inventive example is smaller than the capacitance of the inverter unit 120 of the power supply system of a comparative example. That is, by using the quasi-resonant element 130, it is possible to reduce the capacity of the inverter unit 120 of the power supply system.
[0121]

　In the present embodiment, a quasi-resonant element 130 has a case made of the second capacitor is described as an example. However, quasi-resonant element 130 may include at second capacitor. Further, the second capacitor, even one capacitor, may be a plurality of capacitors connected to each other. The plurality of capacitors, be connected to each other in series, be connected in parallel to each other, and connected portions in parallel with the connecting portion in series may be mixed. When configuring the second capacitor by a plurality of capacitors connected to each other, in the description of this embodiment, the electrostatic capacitance C of the second capacitor quasi-resonant element 130 r is composite electrostatic of the plurality of capacitors the capacity.
[0122]
　Further, the capacitive reactance due to the capacitance of the second capacitor included in the quasi-resonant element 130 is larger than the inductive reactance of the inductive load 180, quasi-resonant element 130, in addition to the second capacitor, it may have a reactor. However, in the same manner as described in the present embodiment, the value of the inductive reactance of the inductive load 180 side from the output terminal of the magnetic energy recovery switch, the inductive load 180 side from the output end of the Magnetic Energy Recovery Switch to exceed the value of the capacitive reactance.
[0123]
　In this case, in the description of the present embodiment, for example, the inductance L of the inductive load 180, the inductive load 180, may be replaced with combined inductance of a reactor included in the quasi-resonant element 130. Therefore, the value of the composite reactance of the inductive reactance of the inductive load 180 and the inductive reactance of the quasi-resonant element 130, to exceed the value of the capacitive reactance of the quasi-resonant element 130. Then, the electrostatic capacitance C of the second capacitor r is the combined inductance of the inductance of the inductance and inductive load 180 of quasi-resonant element 130, a first switch U, the second switch X, the third switch V , and a fourth value greater than the reciprocal of a value obtained by multiplying the square of the switching angular frequency corresponding to the switching frequency f to switch the Y ω (= 2πf). That is, the capacitance C of the second capacitor r satisfies the conditions the combined inductance of the inductance (19) of L of formula, inductance and inductive load 180 of quasi-resonant element 130.
[0124]
　Further, in this embodiment, a case where the first capacitor 125 is composed of one capacitor is described as an example. However, the first capacitor 125 may be composed using at least one capacitor. A material obtained by connecting a plurality of capacitors each other may be used as the first capacitor 125. The plurality of capacitors, be connected to each other in series, be connected in parallel to each other, and connected portions in parallel with the connecting portion in series may be mixed. In this case, in the description of this embodiment, the electrostatic capacitance C of the first capacitor 125 m will combined capacitance of the plurality of capacitors.
[0125]
(Second Embodiment)
　Next, a second embodiment will be explained. In the present embodiment, the current I is output from the inverter unit 120 inv described power supply system can be adjusted. Specifically, an inverter unit 120, between the quasi-resonant element 130 and the inductive load 180, to place the transformer. Thus, in the present embodiment, with respect to the first embodiment, and obtained by adding a transformer. Accordingly, in the description of this embodiment, the first embodiment and the same parts, and detailed description thereof is omitted equal denoted by the same reference numerals as those in FIGS. 1 to 7. Also, in this embodiment, like the first embodiment, a quasi-resonant element 130 will be described with a case made of the second capacitor as an example.
[0126]
　Figure 8 is a diagram showing an example of the configuration of a power supply system 800. Power system 800 includes a DC power supply unit 110, the inverter unit 120, quasi-resonant element 130, current transformer 140, a switch controller 150, a current control unit 160, and in addition to the frequency setting device 170 comprises a transformer 810. The power supply system 800 does not have a specific device for suppressing vibration current (vibration suppression circuit).
[0127]
　Transformer 810, a voltage V is outputted from the inverter unit 120 inv for boosting or reducing. One end of the primary winding of the transformer 810 (the input side of the winding), and a second AC terminal 122 is connected to each other. The other end of the primary winding of the transformer 810, a first AC terminal 121 is connected to each other. One end of the secondary winding of the transformer 810 (the output side of the winding), and one end of the quasi-resonant elements 130 are connected to each other. And the other end of the secondary winding of the transformer 810, the other end of the inductive load 180 is connected to each other. One end of the inductive load 180 is connected to the other end of the quasi-resonant element 130.
[0128]
　Here, the turns ratio of the transformer 810 and n. Turns ratio n is the number of turns of the primary winding of the transformer 810, is divided by the number of turns in the secondary winding (n = number of turns of turns ÷ 2 windings of the primary winding) to. If the transformer 810 is a step-down transformer turns ratio n is greater than 1. If the transformer 810 is step-up transformer turns ratio n is less than 1.
[0129]
　Hereinafter, for simplicity of explanation, the transformer 810 is ideal transformer. (Voltage applied to the primary winding) primary voltage of the transformer 810, a voltage V is outputted from the inverter unit 120 inv is. The secondary voltage of the transformer 810 (the voltage generated in the secondary winding) is the primary voltage and the product of the inverse of the turns ratio n (= (1 / n) V inv represented by). Moreover, (the current flowing through the primary winding) primary current of the transformer 810, current I is output from the inverter unit 120 inv is. Secondary current of the transformer 810 (the current flowing through the secondary winding) is the primary current and the product of the turns ratio n (= nI inv represented by). Accordingly, current flowing through the inductive load 180, the current I is output from the inverter unit 120 inv becomes n times.
[0130]
　When using the step-down transformer as a transformer 810, current flowing through the inductive load 180, the current I is output from the inverter unit 120 inv greater than. On the other hand, when using a step-up transformer as a transformer 810, current flowing through the inductive load 180, the current I is output from the inverter unit 120 inv smaller than. Therefore, the power supply system 800 of the present embodiment, the turns ratio n of the transformer 810, it is possible to adjust the current flowing through the inductive load 180. When using the step-down transformer as a transformer 810, without flowing a large current to the inverter unit 120, a large current can be passed to the inductive load 180. Thus, for example, the first switch U, the second switch X, the third switch V, the fourth switch Y, and a first capacitor 125, it is not necessary to use an element for large current.
[0131]
　Impedance Z looking into the inductive load 180 side from the output terminal of the inverter unit 120 is expressed by the following equation (20).
[0132]
[Number 15]

[0133]
　Here, R is the resistance of the inductive load 180 [Omega]. L is the inductance [H] of the inductive load 180. C r is the capacitance of the second capacitor quasi-resonant elements 130 [F]. n is the turns ratio of the transformer 810. j is the imaginary unit.
[0134]
　As described in the first embodiment, the synthetic reactance of quasi-resonant element 130 and the inductive load 180 as viewed from the inverter unit 120 (= ω × L ') is expressed by equation (10). Further, since the inductance L of the inductive load 210 and the apparent 'needs exceed the 0 (zero), (11) from equation (12) below holds. On the other hand, in this embodiment, the synthetic reactance of quasi-resonant element 130 and the inductive load 180 as viewed from the inverter unit 120 (= ω × L ') are those shown in (20) the right side of equation parentheses in the second term to become. Thus, the inductance L of the inductive load 210 and the apparent 'is greater than 0 (zero), it is necessary to satisfy the following equation (21).
[0135]
[Number 16]

[0136]
　(21) from equation (12) below holds. That is, even if transformer 810, the electrostatic capacitance C of the second capacitor quasi-resonant element 130 r is determined in the same manner as the first embodiment.
　Further, from equation (20), in the present embodiment, the inductance L 'is of the inductive load 210 apparent, is expressed by the following equation (22).
[0137]
[Formula 17]

[0138]
　Therefore, (22) Substituting expression (5) below, it holds the following equation (23).
[0139]
[Equation 18]

[0140]
　Therefore, in this embodiment, (17) instead of equation so as to satisfy the equation (23), the electrostatic capacitance C of the first capacitor 125 m may be designed to.
　Also in this embodiment, it is possible to adopt a modification described in the first embodiment.
[0141]
(Third Embodiment)
　Next, a third embodiment. In the first embodiment and the second embodiment was described by taking a case of constituting the magnetic energy recovery switches in a full-bridge circuit as an example. In contrast, in the present embodiment will be described with a case of constituting the magnetic energy recovery switches in a half bridge circuit as an example. The thus this embodiment and the first embodiment and the second embodiment, the configuration of the magnetic energy recovery switch is mainly different. Accordingly, in the description of this embodiment, the first and second embodiments and the same parts, and detailed description thereof is omitted equal denoted by the same reference numerals as those in FIGS. 1 to 8.
[0142]

　FIG. 9 is a diagram showing an example of the configuration of a power supply system 900. Power system 900 includes a DC power supply 110, an inverter 920, quasi-resonant element 130, current transformer 140, a switch controller 150, a current control unit 160 and a frequency setting device 170,. The power supply system 900 does not have a specific device for suppressing vibration current (vibration suppression circuit).
[0143]
[Inverter 920]
　The inverter unit 920, like the inverter unit 120 of the first embodiment and the second embodiment, the DC power output from the DC power supply unit 110, a switching frequency for switching the respective switches of the inverter section 920 It converted into AC power of the same frequency. Inverter 920 supplies the AC power of the frequency for the inductive load 180. Inverter 920 has a magnetic energy recovery switch.
[0144]
　An example of a configuration of the inverter unit 920 of the present embodiment (Magnetic Energy Recovery Switch) will be described.
　The inverter unit 920, a first switch U, the second switch X, the first freewheeling diode D5, a second reflux diode D6, the first AC terminal 921, the second AC terminals 922,925, first DC terminals 923, a second first capacitor dc terminal 924, and the plural. In the present embodiment, the inverter 920, a plurality of first capacitor, having a high side capacitor 926 and the low side capacitor 927.
[0145]
　The first switch U is the same as the first switch U described in the first embodiment. The second switch X are the same as the second switch X described in the first embodiment. Accordingly, no detailed description of the first switch U and the second switch X. Like the first embodiment, to the end of the forward side of the reflux diodes D1, D2, and the ends of the forward and reverse side of the self-turn-off devices S1, S2, and a connection point negative terminal. And the end of the forward side of the self-turn-off devices S1, S2, to the ends of the forward and reverse side of the freewheeling diode D1, D2, of the connection point to the positive terminal.
[0146]
　Reflux diodes D5, D6 has a first end and a second end. Reflux diodes D5, D6 is made conductive, from the first end to a second end through a current, but has only state not conduct current from the second end to the first end . The direction from the first end of the reflux diodes D5, D6 to the second end, a forward direction in the reflux diodes D5, D6. A first end of the reflux diodes D5, D6 to the negative terminal. The second end of the reflux diodes D5, D6 to the positive terminal.
[0147]
　For each part of the connection of the inverter unit 920 will be described.
　And the negative terminal of the first switch U, and the positive terminal of the second switch X are connected to each other. And the negative terminal of the first freewheeling diode D5, and the positive terminal of the second reflux diode D6 is connected to one another. And the positive terminal of the first switch U, and the positive terminal of the first freewheeling diode D5 is connected to each other. And the negative terminal of the second switch X, and the negative terminal of the second reflux diode D6 is connected to one another.
[0148]
　First AC terminal 921 is connected to the connection point between the positive terminal of the negative terminal and the second switch X of the first switch U. Second AC terminals 922,925 are connected to the negative terminal of the first freewheeling diode D5, to a connection point between the positive terminal of the second reflux diode D6. The second AC terminals 922,925, one end of the quasi-resonant element 130 is connected. In the present embodiment, the first AC terminal 921 and the second AC terminals 922,925 is an output terminal of the inverter 120. In FIG 9, for convenience of notation, it shows two of the second AC terminals 922,925, these can be regarded as one terminal.
[0149]
　The first DC terminal 923, a positive terminal of the first switch U, is connected to a connection point between the positive terminal of the first freewheeling diode D5. The first DC terminal 923, the other end of the reactor 113 is connected. Second DC terminals 924 and the negative terminal of the second switch X, is connected to a connection point between the negative terminal of the second reflux diode D6. The second DC terminals 924, the other end of the output side of the rectifier 112 is connected. In the present embodiment, the first DC terminal 923 and the second DC terminal 924 is an input terminal of the inverter 120. DC power supply 110 is connected between the first DC terminal 923 and second DC terminals 924 as described above.
[0150]
　High side capacitor 926, a positive electrode and a connection point of the resonator, the negative terminal and the connection of the positive terminal of the second reflux diode D6 of the first freewheeling diode D5 of the first switch positive terminal and a first reflux diode U D5 It is connected between the points. As described above, the positive terminal of the first switch U, the connection point between the positive terminal of the first freewheeling diode D5, the first DC terminal 923 is also connected. Moreover, the negative terminal of the first freewheeling diode D5, to a connection point between the positive terminal of the second reflux diode D6, is connected a second AC terminal 922. The high side capacitor 926 is a capacitor having a polarity.
[0151]
　Low side capacitor 927, a negative electrode and a connection point of the resonator, the negative terminal and the positive terminal of the connection point of the second reflux diode D6 of the first freewheeling diode D5 of the second switch negative terminal and a second reflux diode X D6 It is connected between the. As described above, the negative terminal of the second switch X, in a connection point between the negative terminal of the second reflux diode D6, is connected the second DC terminal 924. Moreover, the negative terminal of the first freewheeling diode D5, to a connection point between the positive terminal of the second reflux diode D6, one end of the high side capacitor 926 is connected. That is, of the high-side capacitor 926 and the low side capacitor 927 constituting a plurality of first capacitor, one end of the high side capacitor 926 is one first capacitor is the low side capacitor 927 is the other of the first capacitor and the one end are connected to each other. Low side capacitor 927 is a capacitor having a polarity.
[0152]
[Inductive load 180]
　inductive load 180, between the first AC terminal 921 of the inverter 920 and the second AC terminals 922,925, connected in series with the high side capacitor 926 and the low side capacitor 927 It is. In the example shown in FIG. 9, one end of the inductive load 180, and the other end of the quasi-resonant elements 130 are connected to each other. The other end of the inductive load 180, a first AC terminal 921 of the inverter 920 is connected to each other. Inductive load 180 as described above, is connected between the first AC terminal 921 and the second AC terminals 922,925. Also, quasi-resonant element 130 is connected in series with the inductive load 180 between the first AC terminal 921 and the second AC terminals 922,925.
[0153]

　Next, an example of operation of the inverter 920. Figure 10 is a diagram illustrating an example of a current flow in the inverter 920. Figure 11A is a switching signal U of the first switch U Gate and the voltage V according to the high side capacitor 926 Mersc1 and the voltage V according to the low side capacitor 927 Mersc2 a current I outputted from the inverter unit 920 inv relationship between it is a diagram illustrating a first example of. 11B is a switching signal U of the first switch U Gate and the voltage V according to the high side capacitor 926 Mersc1 and the voltage V according to the low side capacitor 927 Mersc2 a current I outputted from the inverter unit 920 inv relationship between it is a diagram illustrating a second example of.
[0154]
　First, the voltage V applied to the high-side capacitor 926 and the low side capacitor 927 Mersc1 , V Mersc2 0 period T remains (zero) 0 is describing an example of operation of the inverter 920 when greater than 0 (zero).
　Initial state, the high-side and the capacitor 926 is charged, has completed discharge of the low-side capacitor 927, a first switch U is ON, the state second switch X is turned OFF.
[0155]
　As in the state A in FIG. 10, when the high side capacitor 926 begins to discharge, current emitted from the high side capacitor 926, toward the first DC terminal 923. Since the first switch U is ON, the current flowing into the first DC terminal 923, via the first switch U, flows toward the first AC terminal 921. Then, the current flowing into the first AC terminal 921, since the second switch X is OFF, the can not flow into the positive terminal side of the second switch X, inductive load 180 and quasi-resonant element 130 flowing against. Current through the quasi-resonant element 130 flows into the second AC terminals 922, back to the high side capacitor 926.
[0156]
　And transition of the voltage across the high side capacitor 926 and the low-side capacitor 927 after the high side capacitor 926 starts to discharge, and a transition of the current output from the inverter unit 920 will be described with reference to FIG 11A. U Gate , the switch controller 150 is a signal to be transmitted to the first switch U, ON the first switch U, a switching signal OFF. The switching signal U Gate when indicates the value ON, the first switch U is in the state ON, the switching signal U Gate when indicates the value OFF, the first switch U is a state of OFF. Also, here it is not shown, the switch controller 150, also switching signal X to the second switch X Gate transmits the. Switching signal X Gate value of indicates the switching signal and the inverse of the values to be transmitted to the first switch U. That is, the switching signal X Gate value of the switching signal U Gate represents the value of the OFF when has a value of ON, the switching signal U Gate indicating the value of the ON when indicates a value of OFF. V Mersc1 shows the voltage across the high-side capacitor 926. V Mersc2 shows the voltage across the low-side capacitor 927. I inv shows the current output from the inverter 920. T 0 indicates the time at which the high-side capacitor 926 begins to discharge.
[0157]
　When the high side capacitor 926 begins to discharge, current I is output from the inverter unit 920 inv increases in the negative direction, the voltage V according to the high side capacitor 926 Mersc1 begins to decrease. When the high side capacitor 926 has completed the discharge, the voltage V according to the high side capacitor 926 Mersc1 becomes 0 (zero). T 1 shows the time at which the high-side capacitor 926 has completed the discharge. Time T 0 in the discharge of the low-side capacitor 927 has been completed. In addition, the time T 0～ time T 1 in the period of, on the low side capacitor 927 current does not flow. Therefore, the voltage V according to the low-side capacitor 927 during this period mersc2 is 0 (zero).
[0158]
　Time t 1 in, when the discharge of the high side capacitor 926 is completed, the current I is output from the inverter unit 920 inv peaked, the voltage V of the high side capacitor 926 Mersc1 becomes 0 (zero). Therefore, the voltage between the first DC terminal 923 and the second DC terminal 924 becomes 0 (zero). In this case, as in the state B in FIG. 10, the current flowing into the second AC terminals 922, toward the first DC terminal 923 via the freewheeling diode D5, via the first switch U, toward the first AC terminal 921. In this case, the voltage V applied to the high-side capacitor 926 and the low side capacitor 927 Mersc1 , V Mersc2 is 0 (zero). Accordingly, the voltage of the first switch U and the second switch X also becomes 0 (zero). Voltage V applied to the high-side capacitor 926 and the low side capacitor 927 Mersc1 , V Mersc2 the period is 0 (zero) T 0 and.
[0159]
　In state B in FIG. 10, the current flowing through the inverter 920 and the inductive load 180 in accordance with a time constant determined from the inductance and the resistance component of the inductive load 180, gradually decreases. As shown in FIG. 11A, the current I is output from the inverter unit 920 inv , the time t 1 ~ time t 2 to reduce the duration of the.
[0160]
　Switch controller 150, the time t discharge is completed the high side capacitor 926 1 period T from 0 the time t has elapsed 2 in, turns OFF the first switch U, switches the second switch X to ON. At this time, the voltage V applied to the high-side capacitor 926 and the low side capacitor 927 Mersc1 , V Mersc2 the soft switching so is 0 (zero).
[0161]
　First switch U is switched to OFF, the second switch X is switched to ON, so that the state C in FIG. 10, the current flowing into the second AC terminals 922,925 may include a first switch U because it is OFF, toward the low side capacitor 927. Current that flows to the low-side capacitor 927 is used for charging of the low-side capacitor 927, gradually decrease. This current, until the low-side capacitor 927 has completed charging, flow as a state C in FIG. 10, a 0 (zero) at the time the charge is completed in the low-side capacitor 927. In FIG. 11A, the low-side capacitor 927, the time t 3 and to complete the charging in.
[0162]
　As shown in FIG. 11A, the time t 2 ~ time t 3 between the voltage V according to the low side capacitor 927 Mersc2 rises. Further, the voltage V according to the low side capacitor 927 Mersc2 in accordance with the increase of the current I is output from the inverter unit 920 inv decreases. Time t 3 when the charging of the low-side capacitor 927 is completed in the voltage V according to the low side capacitor 927 Mersc2 reaches a peak. At this time, the current I outputted from the inverter unit 920 inv becomes 0 (zero). Time T 1 in the discharge of the high-side capacitor 926 has been completed. In addition, the time T 1～ time T 3 in the period, the high-side capacitor 926 current does not flow. Therefore, the voltage V according to the high side capacitor 926 during this period mersc1 is 0 (zero).
[0163]
　After the charging of the low-side capacitor 927 is completed, the low-side capacitor 927 starts discharging. As in the state D of FIG. 10, current emitted from the low side capacitor 927 is directed to the second AC terminals 922,925. This current, since the first switch U is OFF, the flow into the quasi-resonant element 130 and the inductive load 180. Flowing in the inductive load 180 current is directed to the first AC terminal 921, it flows into the first AC terminal 921. Current flowing into the first AC terminal 921, the first switch U is OFF, the order the second switch X is ON, the flow returns via the second switch X to the low side capacitor 927. That is, the direction of the current flowing into the quasi-resonant element 130 and inductive load 180 is reversed, the state A ~ C. Thus, the inverter 920, the switching frequency f which is set by the switch control unit 150, a first switch U and the second switch X to ON, by switching the OFF, current of the same frequency as the switching frequency f I Inv to output.
[0164]
　In FIG. 11A, the low-side capacitor 927, the time t 4 at complete discharge. As shown in FIG. 11A, the voltage V according to the low side capacitor 927 Mersc2 , the time t in accordance with the discharge of the low-side capacitor 927 3 continued to decrease from the time t 4 becomes 0 (zero) in the. The current I output from the inverter unit 920 inv is in accordance with the discharge of the low side capacitor 927, the time t 0 ~ time t 3 to the direction of increase in the reverse direction. Then, the current I is output from the inverter unit 920 inv the discharge is completed at time t of the low-side capacitor 927 4 at time t 0 ~ time t 3 to the direction of reach in the direction opposite to the peak.
[0165]
　Time t 3 ~ time t 4 the current I outputted from the inverter unit 920 during the inv direction, the time t 0 ~ time t 1 the current I is output from the inverter 920 between the inv reversed compared with . Therefore, in the graph of FIG. 11A, the time t 3 ~ time t 4 the current I outputted from the inverter unit 920 during the inv value of a positive value. The time t 3 ~ time t 4 even in the period, the current does not flow to the high side capacitor 926, the voltage V according to the high side capacitor 926 Mersc1 is 0 (zero).
[0166]
　Time t 4 in, when the discharge of the low-side capacitor 927 is completed, the voltage V according to the low side capacitor 927 Mersc2 becomes 0 (zero). Therefore, the voltage between the first DC terminal 923 and the second DC terminal 924 becomes 0 (zero). In this case, as in the state E of FIG. 10, the current flowing into the first AC terminal 921, via the second switch X toward the second DC terminal 924, through the second reflux diode D6 to, toward the second AC terminal 922.
[0167]
　In state E of FIG. 10, the current flowing through the inverter 920 and the inductive load 180, according to the time constant due to inductance and resistance components of the inductive load 180, gradually approaches 0 (zero). As shown in FIG. 11A, the current I is output from the inverter unit 920 inv , the time t 4 ~ time t 5 approaches 0 (zero) in the period.
[0168]
　Switch controller 150, the discharge time t has been completed the low-side capacitor 927 4 period T from 0 time t 5 in, switches the first switch U to ON, it switches the second switch X to OFF. At this time, the voltage V applied to the high-side capacitor 926 and the low side capacitor 927 Mersc1 , V Mersc2 the soft switching so is 0 (zero).
[0169]
　First switch U is switched to ON, the second switch X is switched to OFF, as in the state F of FIG. 10, the current flowing into the first AC terminal 921, the first switch U is ON There, since the second switch X is OFF, the heading to the first DC terminal 923 via the first switch U. Current flowing into the first DC terminal 923 toward the high side capacitor 926. Current flowing to the high side capacitor 926, further approaches 0 (zero). This current, until the charging of the high side capacitor 926 is completed, flow as a state F of FIG. 10, a 0 (zero) at the time when the charging of the high side capacitor 926 is completed.
[0170]
　As shown in FIG. 11A, the time t 5 ~ time t 6 between a voltage V according to the high side capacitor 926 Mersc1 rises. Further, the voltage V according to the high side capacitor 926 Mersc1 in accordance with the increase of the current I is output from the inverter unit 920 inv approaches 0 (zero). Time t 6 when the charging of the high side capacitor 926 is completed in the voltage V according to the high side capacitor 926 Mersc1 reaches a peak. At this time, the current I outputted from the inverter unit 920 inv becomes 0 (zero). Time t 4 in the discharge of the low-side capacitor 927 is completed. In addition, the time T 4～ time T 6 in the period, to the low-side capacitor 927 current does not flow. Therefore, the voltage V according to the low-side capacitor 927 during this period mersc2 is 0 (zero).
[0171]
　Time t 6 in, the high side capacitor 926 has completed charging, a first switch U is ON, since the second switch X toggled OFF, the flow returns to the state A is the initial state. Inverter 920 and repeats the above operation.
[0172]
　As shown in state C of FIG. 10, when the charging of the low-side capacitor 927, current flows from the second AC terminals 922,925 to the low side capacitor 927. Further, as shown in the state F of FIG. 10, when the charging of the high side capacitor 926, current flows from the first DC terminal 923 to the high side capacitor 926. That is, the high side capacitor 926 is always accumulate positive charge to the first DC terminal 923 side, a negative charge is accumulated in the second AC terminals 922,925 side. Low side capacitor 927 is always accumulate positive charges to the second AC terminals 922,925 side, negative charge is accumulated in the second DC terminal 924 side. Therefore, as a high side capacitor 926 and the low side capacitor 927, a capacitor having a polarity are available. The direction of the current flowing into the second capacitor included in the quasi-resonant element 130 is not constant. Therefore, as a second capacitor, it can not be utilized capacitor having a polarity, so that the use of non-polar capacitor.
[0173]
　As shown in FIG. 11A, the current I is output from the inverter unit 120 inv as, one period of the current of the alternating current is output. That is, the inverter 920 outputs an alternating current having the same frequency as the switching frequency f. In the present embodiment, the switching frequency for switching the first switch U and the second switch X becomes the output frequency of the magnetic energy recovery switch.
[0174]
　In FIG. 11A, the voltage V applied to the high-side capacitor 926 and the low side capacitor 927 Mersc1 , V Mersc2 period T remains 0 (zero) 0 indicates the case where is greater than 0 (zero). In contrast, in FIG. 11B, the voltage V applied to the high-side capacitor 926 and the low side capacitor 927 Mersc1 , V Mersc2 period T remains 0 (zero) 0 shows the case is 0 (zero). Hereinafter, the voltage V applied to the high-side capacitor 926 and the low side capacitor 927 Mersc1 , V Mersc2 0 period T remains (zero) 0 is described is 0 An example of the operation of the inverter 920 when it is (zero) .
[0175]
　Initial state, the high-side and the capacitor 926 is charged, has completed discharge of the low-side capacitor 927, a first switch U is ON, the state second switch X is turned OFF.
[0176]
　Voltage V applied to the high-side capacitor 926 and the low side capacitor 927 Mersc1 , V Mersc2 period T remains 0 (zero) 0 if it is 0 (zero), as shown in FIG. 11B, the high side capacitor 926, time T 0～ time T 1 to discharge into. Then, the time t 1 the voltage V according to the high side capacitor 926 in mersc1 becomes 0 (zero). Time t is shown in FIG. 11B 0 from time t 1 the operation of the inverter 920 during the time t shown in FIG. 11A 0 ~ time t 1 is the same as the operation of the inverter 920 between.
[0177]
　In the example shown in FIG. 11A, the time t 1 after the voltage V applied to the high-side capacitor 926 and the low side capacitor 927 Mersc1 , V Mersc2 period T remains 0 (zero) 0 provided. In contrast, in the example shown in FIG. 11B, the voltage V applied to the high-side capacitor 926 and the low side capacitor 927 Mersc1 , V Mersc2 period T remains 0 (zero) 0 is 0 (zero). Thus, the switch controller 150, the discharge is completed at time t of the high side capacitor 926 1 in (i.e., without leaving the Discharge of the high side capacitor 926 is completed time), the OFF the first switch U switching, switches the second switch X to oN.
[0178]
　Then, the low-side capacitor 927, the time t 1 from the time t 2 and charges during the time t 2 from time t 3 to discharge between. Then, the time t 3 , the voltage V according to the low side capacitor 927 Mersc2 becomes 0 (zero). In the example shown this way in FIG. 11B, the first switch U and the second switch X transitions to the state C from the state A in FIG. 10, not take state B. Time t is shown in FIG. 11B 1 ~ time t 3 the operation of the inverter 920 during the time t shown in FIG. 11A 2 ~ time t 4 is the same as the operation of the inverter 920 between.
[0179]
　Thereafter, in the example shown in FIG. 11A, the voltage V according to the low side capacitor 927 Mersc2 period T remains 0 (zero) 0 provided. In contrast, in the example shown in FIG. 11B, the voltage V according to the low side capacitor 927 Mersc2 period T remains 0 (zero) 0 is 0 (zero). Thus, the switch controller 150, the discharge is completed at time t of the low-side capacitor 927 3 in (i.e., without leaving the Discharge of the low side capacitor 927 is completed time), switches the first switch U to ON, switching the second switch X to OFF.
[0180]
　Then, the high-side capacitor 926, time T 3～ time T 4 for charging between. In the example shown this way in FIG. 11B, the first switch U and the second switch X transitions to state F from state D of FIG. 10, not take state E. Time t shown in FIG. 11B 3 ~ time t 4 the operation of the inverter 920 during the time t shown in FIG. 11A 5 ~ time t 6 is the same as the operation of the inverter 920 between.
[0181]
　As shown in FIG. 11B, the current I is output from the inverter unit 920 inv , the time t 0 from the increases in the negative direction due to the discharge of the high side capacitor 926. Then, the current I is output from the inverter unit 920 inv the discharge is completed at time t of the high side capacitor 926 1 peaks at. Current I outputted from the inverter unit 920 inv , the time t 1 from the approaches 0 (zero) with the charge of the low side capacitor 927. Then, the current I is output from the inverter unit 920 inv , the charging of the low side capacitor 927 is completed time t 2 becomes at 0 (zero).
[0182]
　Current I outputted from the inverter unit 920 inv orientation, the time t 2 from time t 0 ~ time t 2 becomes opposite to that in. Current I outputted from the inverter unit 920 inv , the time t 2 from, with the discharge of the low side capacitor 927, the time t 0 the time t from the 2 to the direction of increase in the reverse direction. Then, the current I is output from the inverter unit 920 inv the discharge is completed at time t of the low-side capacitor 927 3 , the time t 0 ~ time t 2 to the direction of reach in the direction opposite to the peak. Current I outputted from the inverter unit 920 inv , the time t 3 from the approaches 0 (zero) with the charging of the high side capacitor 926. Then, the current I is output from the inverter unit 920 inv , the charging of the high side capacitor 926 is completed time t 4 becomes at a 0 (zero).
[0183]
　Switch controller 150, the voltage V applied to the high-side capacitor 926 and the low side capacitor 927 Mersc1 , V Mersc2 time t is 0 (zero) 1 and time t 3 in a first switch U, the second switch X ON and switches the OFF. In this manner, the switch controller 150, the voltage V applied to the high-side capacitor 926 and the low side capacitor 927 Mersc1 , V Mersc2 period T remains 0 (zero) 0 even if it is 0 (zero) , it is possible to realize a soft switching.
[0184]
　Also, such period and this period to discharge the charge of the high side capacitor 926 and the low-side capacitor 927, the capacitance C of the high-side capacitor 926 and the low side capacitor 927 m1 , C m @ 2 and the inductance of the inductive load 210 apparent a half cycle of the resonance frequency determined from the L '. Therefore, as shown in FIG. 11B, the voltage V applied to the high-side capacitor 926 and the low side capacitor 927 Mersc1 , V Mersc2 period T remains 0 (zero) 0 If 0 (zero), the inverter unit 920 current I is output inv frequency of the capacitance C of the high-side capacitor 926 and the low side capacitor 927 m1 , C m @ 2 equal to each and, a resonance frequency determined from the inductance L 'of the inductive load 210 apparent .
[0185]
　As apparent from the above description, a first switch U, ON of a second switch X, of the AC current flowing through a portion of the first switch U and the second switch X by switching OFF on a path, the high side capacitor 926 and the low side capacitor 927 and the quasi-resonant elements 130 are arranged in series.
[0186]
　The capacitance C of the high-side capacitor 926 and the low side capacitor 927 m1 , C m @ 2 design, the capacitance C of the first capacitor 125 described in the first embodiment m and the high side capacitor 926 and the low side capacitor 927 capacitance C m1 , C m @ 2 can be achieved by replacing each. For example, the capacitance C of the high-side capacitor 926 and the low side capacitor 927 m1 , C m @ 2 together are C a m when A, the capacitance C of the high-side capacitor 926 and the low side capacitor 927 m1 , C m @ 2 is first capacitance C of the first capacitor 125 described in the embodiment m is determined in the same manner as.
[0187]
　That is, the capacitance C of the high-side capacitor 926 and the low side capacitor 927 m1 , C m @ 2 , the following expression (24) must satisfy the equation (25). Power system 900, when the switching frequency of the inverter 920 is f, (24) and Equation (25) that satisfies equation high side capacitor 926 and the low side capacitor 927, quasi-resonant element 130, the inductive load there is a need to have a 180.
[0188]
[Number 19]

[0189]
(Method of reducing the capacity of the inverter 920)
　the electrostatic capacitance C of the second capacitor quasi-resonant element 130 r capacitance C of the high-side capacitor 926 and the low side capacitor 927 m1 , C m @ 2 is the first embodiment in the column of in described (method of reducing the capacity of the inverter unit 120), the electrostatic capacitance C of the first capacitor 125 m , and the electrostatic capacitance C of the high-side capacitor 926 and the low side capacitor 927 m1 , C m @ 2 replaced respectively the thing was.
[0190]
　That is, the capacitance C of the high-side capacitor 926 and the low side capacitor 927 m1 , C m @ 2 is the following formula (26), it is sufficient to satisfy the equation (27).
[0191]
[Number 20]

[0192]
　In other words, the electrostatic capacitance C of the high-side capacitor 926 and the low side capacitor 927 m1 , C m @ 2 for each, described in the first embodiment (17) it is sufficient to satisfy the equation. Further, the pseudo capacitance C of the second capacitor of the resonance element 130 r has been described in the first embodiment (19) it is sufficient to satisfy the equation.
　As described above, even if a magnetic energy regeneration switch half-bridge circuit, it is possible to obtain the effects described in the first embodiment.
[0193]
　Also in this embodiment, it is possible to adopt a modification described in the first embodiment. Further, the present embodiment may be applied to the second embodiment. In this case, the electrostatic capacitance C of the high-side capacitor 926 and the low side capacitor 927 m1 , C m @ 2 for each, so as to satisfy the described (23) in the second embodiment.
[0194]
　Embodiments of the present invention described above are all merely illustrate concrete examples of implementing the present invention, the technical scope of the present invention these should not be construed as limiting is there. That is, the present invention without departing from its spirit or essential characteristics thereof, can be implemented in various forms.
Industrial Applicability
[0195]
　The present invention can be utilized such as the current or heating by alternating current power.

we claim

[Claim 1]A magnetic energy recovery switch has a frequency setting unit, and a control unit, and a quasi-resonant elements, converts the DC power to AC power, a power supply system for supplying the AC power to the inductive load,
　the magnetic energy recovery switch has one or more of the first capacitor, and a plurality of switches, and
　the frequency setting device sets the output frequency of the magnetic energy recovery switch,
　the control device, the plurality of the operation of the switch on and off, the control based on the output frequency set by the frequency setting device,
　the magnetic energy recovery switch, the on-off of the plurality of switches, accumulated in the inductive load was the fact that by the magnetic energy is recovered and accumulates as an electrostatic energy to the first capacitor, the accumulated electrostatic energy of the inductive Performed and supplying the load,
　the quasi-resonant element comprises at least one passive device includes a second capacitor,
　the first capacitor is arranged in series with the inductive load,
　the first the second capacitor, said inductive load side from the output terminal of the magnetic energy recovery switches, which are connected in series with the inductive load,
　the induction than the output end of the magnetic energy Recovery switch the value of the inductive reactance of sexual load side than the output end of the magnetic energy recovery switch exceeds the value of the capacitive reactance of the inductive load,
　wherein the plurality of switches, the voltage across the first capacitor when There is a 0 (zero), the power supply system, characterized in that for switching on and off.
[Claim 2]
　Value of the combined reactance of the inductive reactance and the inductive reactance of the inductive load of the quasi-resonant element, the power supply system according to claim 1, characterized in that above a value of the capacitive reactance of the quasi-resonant element .
[Claim 3]
　The value of the capacitance of the second capacitor, the combined inductance of the inductance and the inductance of the inductive load of the quasi-resonant element, the angular frequency when the frequency of the on-off of the switch is the output frequency the power supply system according to claim 1 or 2, characterized in that the a values ​​above the reciprocal of a value obtained by multiplying the square.
[Claim 4]
　The output frequency is less than or equal resonant frequency,
　the resonant frequency, claims, characterized said first capacitor, and the quasi-resonant element, that the resonance frequency of the resonant circuit including said inductive load power system according to any one of 1 to 3.
[Claim 5]
　Wherein the capacitance of the first capacitor C m [F], the combined inductance of the inductance and the inductance of the inductive load of the quasi-resonant element L [H], the electrostatic capacitance of the second capacitor C r [F], claims frequency of the on-off of the switch, wherein the angular frequency when the output is a frequency when the ω [rad / s], is satisfied that the following formula (a) power system according to any one of 1-4.
[Number 1]

[Claim 6]
　Wherein the output end of the magnetic energy recovery switch has the quasi-resonant element and further arranged transformer between said inductive load,
　the first electrostatic capacity C of the capacitor m [F], the simulate a combined inductance of the inductance of the inductance and the inductive load of the resonant element L [H], the electrostatic capacitance of the second capacitor C r [F], the frequency of the on-off of the switch the output frequency the angular frequency ω [rad / s] when it is, if the turns ratio of the winding number of the transformer primary winding is divided by the number of turns in the secondary winding of the transformer is n the power supply system according to any one of claims 1 to 4, characterized in that the following equation (B) holds.
[Number 2]

[Claim 7]
　The quasi-resonant element is made from the second capacitor,
　the power supply system according to any one of claims 1 to 6, wherein the inductive reactance and the inductance of the quasi-resonant element is 0 (zero) .
[8.]
　The magnetic energy recovery switches, the first AC terminal, a second AC terminal, a first DC terminal, and further includes a second DC terminal,
　said plurality of switches, a first switch, the second switch, the third switch, and a four switches of the fourth switch,
　each of the four switches, and a positive and negative terminals,
　the positive electrode from each of said negative terminal of said four switches conductive state to the terminal is always the state where current can flow,
　the conductive state from each of the positive terminal of said four switches to the negative terminal, on of the switch by a signal from the control device the off, become one of the states of a state that can not be a state in which current can flow,
　the positive terminal of the second switch and the negative terminal of the first switch Bets are connected to each other, wherein the first of the positive terminal of the switch the third of said switch and the positive terminal is connected to one another,
　the said fourth of said second switch and the negative terminal of the switch and the negative electrode terminal are connected to each other, the said fourth switch and the positive terminal and the negative terminal of the third switch being connected to each other,
　the first AC terminal, the said first switch is connected to the connection point between the second switch,
　the second AC terminal is connected to said third connection point of the switch and said fourth switch,
　wherein the first DC terminal, said first said switch being connected to the positive terminal and the third of the positive terminal of the switch,
　the second DC terminals, the said negative terminal of said second of said and the negative terminal of the switch a fourth switch is connected,
　said first capacitor It is a first switch, connected between the first DC terminal and the second DC terminal,
　wherein between the first DC terminal and the second DC terminal is connected to a DC power source,
　the inductive load , which is connected between the first AC terminal and the second AC terminal,
　said second capacitor, said inductive load during said first AC terminal and the second AC terminal are connected in series for,
　the control device, the conductive state from the positive terminal of said first switch and said fourth switch to the negative electrode terminal is a state in which current can flow, and wherein second switch and the third conductive state from the positive terminal of the switch to the negative electrode terminal, time and the state in which no current can flow through the first switch and the cathode of said fourth switch conduction from the terminal to the negative terminal State is a state where no current can flow, and, the conductive state from the positive terminal of the second switch and the third switch to the negative terminal is a state in which current can flow time preparative power supply system according to any one of claims 1 to 7, wherein the controller controls based on the output frequency set by the frequency setting device.
[Claim 9]
　The magnetic energy recovery switches, the first wheel elements, the second wheel elements, further comprising a first AC terminal, a second AC terminal, a first DC terminal, and a second DC terminal,
　said first 1 of the capacitor, there are two,
　the plurality of switches are two switches of the first switch and the second switch,
　each of the two switches, and a positive terminal and a negative terminal,
　wherein two conductive state from each of the negative terminal of the switch to the positive terminal is always a state in which current can flow,
　the conductive state from each of the positive terminal of the two switches to the negative terminal, the on-off of the switch by a signal from the control unit, in one of the states of a state that can not be a state in which current can flow,
　said first wheel elements and the second Each wheel elements has a positive and negative terminals,
　wherein each of the conductive state of the to the positive terminal from the negative terminal of the first wheel elements and the second wheel elements is that the current always flows a state where it is,
　the respective conduction state of the positive terminal to the negative terminal of the first wheel elements and the second wheel elements is always in a state in which no current can flow,
　said first wherein the negative terminal of the switch, and the positive terminal of the second switch is connected to each other,
　the negative terminal of the first wheel elements, the positive electrode terminal and is connected to each of said second wheel elements is,
　said positive terminal of the first switch, wherein the first wheel elements and the positive terminal is connected to each other,
　and the negative terminal of the second switch, the negative electrode of said second wheel elements and the terminal Are mutually connected,
　wherein one of the two said first capacitor, a connection point of the first switch and the connection point of the first wheel elements, the first wheel elements and the second wheel elements connected between,
　the other of said two of said first capacitor, a connection point of the second switch and the second wheel elements, of the first wheel elements and the second wheel elements is connected between the connection point,
　the first AC terminal, wherein the first switch is connected to a connection point between the second switch,
　the second AC terminal, said first wheel elements It is connected to a connection point between said second wheel elements,
　the first DC terminal, said positive terminal of said first switch is connected to the positive terminal of the first wheel elements,
　the first second DC terminals, and the negative terminal of the second switch, the first Is connected to the negative terminal of the second wheel elements,
　said between said first DC terminal second DC terminal is connected to a DC power source,
　the inductive load, the said first AC terminal is connected between the second AC terminal,
　said second capacitor is connected in series with the inductive load between the first AC terminal and the second AC terminal,
　the control device, the conductive state from the positive terminal of the first switch to the negative electrode terminal is a state in which current can flow, and conduction to the negative terminal from the positive terminal of the second switch state, time and a state where no current can flow, the conductive state from the positive terminal of the first switch to the negative terminal is a state in which no current can flow, and the second the negative from the positive terminal of the switch Conductive state to the terminal, the time and is a state in which current can flow, any one of claims 1 to 7, wherein the controller controls based on the output frequency set by the frequency setting device the power supply system according to.
[Claim 10]
　The inductive load, the power supply according to any one of claims 1 to 9, characterized in that it comprises at least one object to be heated is a coil or a conductive heating for heating induces an object to be heated system.