Description:Complete Specification:
The following specification describes and ascertains the nature of this invention and the manner in which it is to be performed.

Field of the invention:
[0001] The present invention relates to a circuit to regulate inrush current and a method for the same

Background of the invention:
[0002] Pre-charging is a widely used concept in power electronics which involves large DC link capacitors or capacitive loads. The purpose is to limit the large charging current during the initialization of circuit/ or Electronic Control Units (ECU). If the ECU system or circuitry is exposed to these high currents for a prolonged duration, it might damage the system. The widely used method to achieve pre-charging is the use of a separate bypass channel for carryout the pre-charging process. Once the capacitor reaches the sufficient voltage level, the bypass channel is disabled. The current limiting in this channel is done by using multiple resistors with high heat dissipation capability. Another widely used method is the use of NTC resistors in the circuit. But the disadvantage of NTC resistor is that it is having a high power loss.

[0003] The conventional pre-charging systems are having the following common traits. Majority of the current limiting techniques are using current limiting elements like resistors, varistors or thermistors. All the topologies are using a dedicated parallel path or individual circuit for achieving the control. The solutions which are using active devices (in linear mode) are either using an additional path during the inrush condition or using current limiting elements in the path or using an uncontrolled/ unmonitored path or only limiting the AC current. Some applications are solving the problem by using clocks for periodical On/Off of the switches which is causing a discontinuous current flow and switching losses. All topologies are on the current limiting in a single direction. The major disadvantages with conventional topologies are need of separate circuit and monitoring/ control mechanisms, need of large resistors, higher power loss and slow pre-charging, as the current carrying capability is limited in most cases.

[0004] According to state of the art US6225797, a circuit for limiting inrush current through a transistor is provided. The power transistor switched power supply connecting a power source to a capacitive load, including a circuit and method for limiting the inrush surge current through the power transistor. The control gate of a junction field effect transistor (JFET) is coupled between the conductive path of the power transistor and the load to sense voltage drop across the power transistor. The conductive controlled path of the JFET is connected to control the impedance of the power transistor. The JFET shunts some of the power transistor control terminal current during the on transition allowing the power transistor to only turn partially on for a period of time, thus limiting the current through the power transistor from the power source to the load. Because the inrush surge current is limited, the accompanying transient power source voltage drop is reduced with less impact to other circuits connected to the power source.

Brief description of the accompanying drawings:
[0005] An embodiment of the disclosure is described with reference to the following accompanying drawings,
[0006] Fig. 1 illustrates circuits to regulate inrush current, according to an embodiment of the present invention;
[0007] Fig. 2 illustrates a controller to regulate the inrush current, according to an embodiment of the present invention, and
[0008] Fig. 3 illustrates a method for regulating inrush current in the circuit, according to the present invention.

Detailed description of the embodiments:
[0009] Fig. 1 illustrates circuits to regulate inrush current, according to an embodiment of the present invention. The circuit 100, 130 comprises a power supply line 104 between a power source 102 and a load 110 through at least one semiconductor switch 106, 108, and a current sensor 112 to measure current through said power supply line 104, characterized in that, the at least one semiconductor switch 106, 108 is operated based on measured current 122 through the power supply line 104 and a measured voltage 128 across the load 110 in a manner to regulate/control both of the inrush current/pre-charging current and load current or controlling dual operation of managing the inrush current/pre-charging current and the load current through the same power supply line 104, without the need of conventional and additional current limiting elements and parallel paths. The load current refers to the current which is required by the load under normal/regular operating/working conditions. The load current may also be referred to as power supply or supplying power.

[0010] According to the present invention, a variable voltage source 116 connected to a control terminal of each of the semiconductor switch 106, 108 via a driver circuit 114. The at least one semiconductor switch 106, 108 is operated through the driver circuit 114 in dependence of the variable voltage source 116 based on measurement from the current sensor 112 and a voltage measured across the load 110.

[0011] According to an embodiment of the present invention, a controller 120 is configured to receive input signals comprising the measured current 122 and measured voltage 128 of the load 110, control the variable voltage source 116 based on received input signals, and operate the control terminal of the at least one semiconductor switch 106, 108 to regulate the inrush current or surge current or pre-charging current.

[0012] According to the present invention, the controller 120 is provided with necessary signal detection, acquisition, and processing circuits. The controller 120 is the control unit which comprises input/output interfaces having pins or ports, a memory element 118 such as Random Access Memory (RAM) and/or Read Only Memory (ROM), Analog-to-Digital Converter (ADC) and a Digital-to-Analog Convertor (DAC), clocks, timers, counters and at least one processor (capable of implementing machine learning) connected with each other and to other components through communication bus channels. The memory element 118 is pre-stored with logics or instructions or programs or applications or modules/models and/or threshold/safe limit values/ranges, which is/are accessed by the at least one processor as per the defined routines. The internal components of the controller 120 are not explained for being state of the art, and the same must not be understood in a limiting manner. The controller 120 may also comprise communication units to communicate with ECU of the vehicle 100 through wireless or wired means such as Global System for Mobile Communications (GSM), 3G, 4G, 5G, Wi-Fi, Bluetooth, Ethernet, serial networks, Controller Area Network (CAN), and the like. The controller 120 is implementable in the form of System-in-Package (SiP) or System-on-Chip (SOC) or any other known types.

[0013] According to the present invention, the controller 120 is configured to operate the variable voltage source 116 based on safe operating limit of the at least one semiconductor switch 106, 108 in terms of the maximum current and maximum voltage for the at least one semiconductor switch 106, 108. In accordance to an embodiment, the controller 120 is adapted to regulate bidirectional inrush current between the power source 102 and the load 110. The power source 102 is at least one of a rotating machine such as an alternator, a generator, and a battery, and the load 110 is at least one of a capacitive load, the rotating machine, the battery, and electrical and electronic accessories. In an embodiment, the circuit 100, 130 is applied/used for pre-charging requirements.

[0014] In Fig. 1, two circuits, a first circuit 100 and a second circuit 130 are shown. The working of the circuits 100, 130 is explained below. The first circuit 100 comprises the battery as the power source 102, the current sensor 112 having a resistor with negligible resistance, two semiconductor switches 106, 108 and the electric motor as the load 110, all of which are connected through the power supply line 104. The first circuit 100 further comprises driver circuit 114 connected to control terminal of each of the two semiconductor switches 106, 108. Further, the variable voltage source 116 is connected to the driver circuit 114. Both of the driver circuit 114 and the variable voltage source 116 are connected to the output pin/ports of the controller 120. The input pin/ports of the controller 120 are connected to the current sensor 112 and receives the measured voltage 128 across the load 110 or measures the voltage. Now consider a first case, where due to parasitic capacitance or a capacitive load 110, there is a chance of large inrush current in the direction from power source 102 to the load 110. The semiconductor switches 106, 108 are in open condition that is open circuit. In other words, the output voltage of the driver circuit 114 is limited during the initial condition, such a way that the current flow through the power supply path 104 is limited. By this way by using the same path/line/topology, a fast pre-charging/current limitation is achieved without any additional space consumption. However, as the power source 102 starts supplying power, the controller 120 starts measuring the voltage across the load 110 along with measuring current through the power supply line 104 using the current sensor 112. The controller 120 compares the measured current 122 and the measured voltage 128 with safe operating limits of current and voltage for the semiconductor switches 106, 108 and the capacitor or load respectively. The safe limit or safe operating limit of current and voltage is stored in the memory element 118. If the measured current 122 and the measured voltage 128 are within any one of the safe operating limits for the current or voltage, the controller 120 sends a command to the variable voltage source 116 to change the duty cycle in incremental manner thereby allowing flow of more current through the two semiconductor switches 106, 108 to the load 110. The controller 120 keeps incrementing the duty cycle in a loop, until the safety limit is reached, after which the controller 120 directly sets the maximum duty cycle to keep the semiconductor switches 106, 108 in closed condition for continuous supply of power to the load 110. An output of the variable voltage source 116 is connected to the input of the driver circuit 114.

[0015] Within the variable voltage source 116, a low voltage regulator 212 (shown in Fig. 2) and a main boost converter 214 (shown in Fig. 2) are provided with associate circuitry known in the art such as protection, control, and bootstrap, etc. The low voltage regulator 208 is controlled by the controller 120 to provide variable output voltage to the driver circuit 114 to operate the control terminal of the semiconductor switch 106, 108, such as a gate terminal of the MOSFETs. The main boost converter 210 is used when the semiconductor switches 106, 108 are in close condition, i.e. the pre-charging phase is completed, or the inrush current is controlled, and the steady current is required using the signal 124. The driver circuit 114 then operates the semiconductor switches 106, 108 as per the voltage commanded by the controller 120. The above working is applicable even for the current flow from the load 110 to the power source 102. Thus, without any parallel paths, and using the same power supply line 104, the inrush current or pre-charging current is regulated/controlled.

[0016] Similarly, in the Fig. 1 the second circuit 130 comprises the alternator/generator as the power source 102 which is connected to AC/DC converter (as required), the current sensor 112, the two semiconductor switches 106, 108 and the battery as the load 110 through the power supply line 104. Consider a second case, where the battery is completely discharged, and when the power source 102 is activated, there is a tendency to draw large current which might damage the components in the power supply line 104. Hence, the controller 120 as explained for the first circuit 100, controls the operation of the variable voltage source 116 based on the measured current 122 through the power supply line 104 and the measured voltage 128 across the battery (the load 110) and controls the amount of current flow through the two semiconductor switches 106, 108. Further, the battery may act as power source 102 and start supplying current to another load 110 in the same second circuit 130 and the same circuit 100, 130 still applies if installed in the correct manner.

[0017] According to an embodiment of the present invention, a pre-charge circuit 100 or mechanism is provided. The pre-charge circuit 100 comprises the power supply line 104 between the power source 102 and the load 110 through the at least one semiconductor switch 106, 108, and the current sensor 112 to measure current through the power supply line 104, characterized in that, the at least one semiconductor switch 106, 108 is operated based on measured current 122 through the power supply line 104 and the measured voltage 128 across the load 110 in the manner to control both of the inrush current and power supply through the same power supply line 104, without the need of conventional and additional current limiting elements and parallel paths. The pre-charging is bidirectional, i.e. in the direction from power source 102 to the load 110 and from load 110 to the power source 102. In an embodiment, the inrush current is the pre-charge current. In another embodiment, the inrush current is surge current. According to the type of circuit 100, 130 being used, the current in the power supply line is either the pre-charge current or the surge current or the inrush current.

[0018] According to the present invention, the variable voltage source 116 connected to the control terminal of each of the at least one semiconductor switch 106, 108 via the driver circuit 114. The at least one semiconductor switch 106, 108 is operated through the variable voltage source 116 based on measurement from the current sensor 112 and the voltage measured across the load 110. The controller 120 receives input from the current sensor 112 and the measured voltage 128 and adapted to control the variable voltage source 116 based on the measured current 122 and measured voltage 128, and operate the control terminal of each of the at least one semiconductor switch 106, 108 to regulate the inrush current/ pre-charging current. The at least one semiconductor switch 106, 108 is operated through the driver circuit 114.

[0019] Fig. 2 illustrates a controller to regulate the inrush current, according to an embodiment of the present invention. The controller 120 for regulating inrush current in the circuit 100, 130 is provided. The circuit 100, 130 comprises the power supply line 104 between the power source 102 and the load 110 through at least one semiconductor switch 106, 108, and the current sensor 112 to measure current through the power supply line 104, characterized in that, the controller 120 configured to receive input signals comprising measured current 122 and measured voltage 128, compare the received input signals with safe limits of the at least one semiconductor switch 106, 108, and control the variable voltage source 116 based on the comparison. An output of the variable voltage source 116 is connected to and is used to operate the at least one semiconductor switch 106, 108 through the driver circuit 114 and regulate the inrush current. In Fig. 2, the driver circuit 114 is considered to be part of voltage variable source 116 and explained as a single body for simplicity. Although the working of the controller 120 is already explained above, but the same has been explained using block diagram below to provide more clarity. A working of the controller is envisaged using the block diagram of the controller 120.

[0020] In the Fig. 2, a block diagram of the controller 120 is illustrated with internal blocks representing the flow of control. The controller 120 receives the input signal comprising the measured current 122 from the current sensor 112 and the measured voltage 128 across the load 110. The measured voltage 128 is compared against the critical safe limit set in the memory element 118 in the first block 202. If the measured voltage 128 is greater than the set voltage limit, then the control flow moves to next block otherwise the controller 120 sets the duty cycle to maximum allowable safe limit as shown in block 210 which does not damage but operates the semiconductor switch 106, 108 as per normal operation, indicating that the pre-charging phase, or the in-rush current phase is over. For example, in case of the pre-charging, the measured voltage 128 being greater than the set voltage limit indicates that the voltage at the capacitor is charged and pre-charging is completed. The controller 120 sets the duty cycle of the semiconductor switch 106, 108 to a value to effect a normal operation as indicated in the block 210. Once the duty cycle is set, the same signal is sent to the main boost converter 214 to provide the voltage for normal operation through a signal 126. In the case when the measured voltage 128 is less than the set voltage limit, the controller 120 checks the measured current 122 with set current safe limit in block 204. If the measured current 122 is less than the safe limit, than the duty cycle of the semiconductor switch 106, 108 is increased/incremented to increase the current flow through the power supply line 104 as shown in block 206. If the measured current 122 is more than the safe limit than the duty cycle of the semiconductor switch 106, 108 is decreased to reduce/decremented the current flow through the power supply line 104 as shown on block 208. The set duty cycle by the controller 120 is translated to the selection of control voltage through the low voltage regulator 212 which then drives the driver circuit 114 and operates the semiconductor switch 106, 108.

[0021] Although the variable voltage source 116 is explained with low volage converter 212 and the main boost converter 214, but any voltage means which is able to provide the same output as described by variable voltage source 116 is covered by the present invention.

[0022] According to the present invention, the circuit 100, 130 makes use of a single path for main power delivery and pre-charging/current limitation without any current limiting elements in the power supply line 104. Further, both the power delivery and the pre-charging are done in positive and negative directions using the same cognate path, i.e. the power supply line 104. In the Fig. 1, the pre-charging is achieved in both directions by the linear mode operation of two back to back connected MOSFETs in the power supply line 104. The current sensor 112 with negligible resistance is used for monitoring the current flow in both directions. So using a cognate path, both pre-charging and power delivery is achieved bidirectionally. The MOSFETs are operating in a controlled linear mode through a variable voltage converter mechanism.

[0023] According to an embodiment of the present invention, the semiconductor switch 106, 108 is selected from a group comprising a Bipolar Junction Transistor (BJT), a Metal–Oxide–Semiconductor Field-Effect Transistor (MOSFET), an Insulated Gate Bipolar Transistor (IGBT), a Gate turn-off Thyristor (GTO) etc.

[0024] Fig. 3 illustrates a method for regulating inrush current in the circuit, according to the present invention. The circuit 100, 130 comprises the power supply line 104 between the power source 102 and the load 110 through at least one semiconductor switch 106, 108. The circuit 100, 130 also comprises the current sensor 112 to measure current through the power supply line 104. The method is characterized by plurality of steps of which a step 302 comprises detecting load current flowing through the power supply line 104 connected to the load 110. A step 304 comprises measuring voltage across the load 110. A step 306 comprises operating the at least one semiconductor switch 106, 108 based on the measured current 122 through the power supply line 104 and measured volage across the load 110 and accordingly performing dual operations of regulating the inrush current and supplying the power to the load 110 through the same power supply line 104, without the need or use of conventional parallel paths or current limiting electrical components.

[0025] The step 306 comprises a step 308, which comprises applying varying voltage to the control terminal of each of the at least one semiconductor switch 106, 108 based on the measured current 122 and the measured voltage 128 through the driver circuit 114. According to the present invention, the controller 120 is configured for performing the steps and controlling the inrush current in the circuit 100, 130 in following manner. A step 310 of receiving input signals by the controller 120 comprising the measured current 122 and the measured voltage 128. A step 312 comprises controlling, by the controller 120, the variable voltage source 116 based on the measured current 122 and measured voltage 128. A step 314 comprises operating, by the controller 120, the control terminal of each of the at least one semiconductor switch 106, 108 to regulate the inrush current or the pre-charging current.

[0026] According to the present invention, the method comprises controlling the at least one semiconductor switch 106, 108 within respective safe operating limit with respect to critical/threshold current and voltage. The method comprises regulating bidirectional inrush current between the power source 102 and the load 110. The power source 102 is at least one of the rotating machine such as the alternator, the generator, and the battery, and the load 110 is at least one of the capacitive load, the rotating machines, the battery, and electrical and electronic accessories. According to the present invention, the method is applied for pre-charging requirements of the circuit 100, 130.

[0027] According to an embodiment of the present invention, a cognate channel based bidirectional pre-charging/limiting inrush current and power delivery mechanism is provided for safety critical automotive applications. In the present invention, the pre-charging is achieved in both directions by the linear mode operation of two back to back connected semiconductor switches 106, 108 in the power supply line 104 or power delivery path. The current sensor 112 with the resistor with negligible resistance is used for monitoring the current flow in both directions. So using a cognate/same path, both pre-charging/inrush current limitation and power delivery is achieved bidirectionally. The semiconductor switches 106, 108 are operating in a controlled linear mode through a variable voltage converter mechanism. The present invention is applicable for power distribution channels involving semiconductor switches 106, 108 such as High side MOSFET configuration (example Intelligent Electronic Power Distributor (IPDM)). Further, MOSFETs are operated in linear mode, if the Vgs voltage is varied properly. By choosing a fixed Vgs, the current flow through MOSFETs is controlled. The present invention enables limiting the inrush current or pre-charging current control without using additional path or circuitry in the main power flow channel, i.e. the power supply line 104. The inrush current is controlled in both directions. The current flow path is inherently controlled and protected. Further, the present invention does not use any clocks to mask the operation, which ensures a continuous working. There is no separate circuit, no additional Integrated Circuits (ICs) or passive elements in the power supply line 104.

[0028] According to the present invention, a circuit to regulate pre-charge current and inrush current with cognative power supply line 104 and a method for the same. In brief, no additional current carrying channels or dedicated circuits are used for achieving the current control, hence reduced cost/size. No current limiting elements are used, which prevents the use of additional heat dissipation mechanisms. No clock pulses are used. The current flow in the power supply line 104 is continuous. The power supply line 104 is well monitored. The inrush current limiting is achieved in both directions (bidirectional current limiting), hence improves safety. The circuit 100, 130 provides fast pre-charging (high current carrying capability) which improves performance and efficiency. The circuit 100, 130 enables flow of high current in the pre-charging phase, which help the application to reach steady state with a short period of time. The circuit 100, 130 is able to regulate the pre-charging current, and also achieves main current flow and pre-charge current flow/inrush current regulation in the same channel (cognatively).

[0029] It should be understood that the embodiments explained in the description above are only illustrative and do not limit the scope of this invention. Many such embodiments and other modifications and changes in the embodiment explained in the description are envisaged. The scope of the invention is only limited by the scope of the claims.
 
, Claims:We claim:
1. A circuit (100, 130) to regulate inrush current, said circuit (100, 130) comprises
a power supply line (104) between a power source (102) and a load (110) through at least one semiconductor switch (106, 108), and
a current sensor (112) to measure current through said power supply line (104), characterized in that,
said at least one semiconductor switch (106, 108) is operated based on measured current (122) through said power supply line (104) and a measured voltage (128) across said load (110) in a manner to control both of said inrush current and supply of load current through said same power supply line (104).

2. The circuit (100, 130) as claimed in claim 1, wherein a variable voltage source (116) connected to a control terminal of each of said semiconductor switch (106, 108) via a driver circuit (114), wherein said at least one semiconductor switch (106, 108) is operated through said driver circuit (114) in dependence of said variable voltage source (116) based on said measured current (122) and said measured voltage (128).

3. The circuit (100, 130) as claimed in claim 1 is applied for pre-charging requirements.

4. A controller (120) for regulating inrush current in a circuit, said circuit (100, 130) comprises a power supply line (104) between a power source (102) and a load (110) through at least one semiconductor switch (106, 108), and a current sensor (112) to measure current through said power supply line (104), characterized in that, said controller (120) configured to
receive input signals comprising measured current (122) and measured voltage (128),
compare said received input signals with safe limits of said at least one semiconductor switch (106, 108),
control a variable voltage source (116) based on said comparison, an output of said variable voltage source (116) is connected to and is used to operate said at least one semiconductor switch (106, 108) through a driver circuit (116) and regulate said inrush current.

5. The circuit (100, 130) as claimed in claim 1 is adapted to regulate bidirectional inrush current between said voltage source (102) and said load (110), wherein said voltage source (102) is at least one of an alternator, a generator, and a battery, and said load (110) is at least one of a capacitive load, a rotating machine, said battery and electrical and electronic accessories.

6. A method for regulating inrush current in a circuit (100, 130), said circuit (100, 130) comprises a power supply line (104) between a power source (102) and a load (110) through at least one semiconductor switch (106, 108), and a current sensor (112) to measure current through said power supply line (104), characterized by, said method comprises the steps of
detecting load current flowing through said power supply line (104) connected to said load (110);
measuring voltage across said load (110), and
operating said at least one semiconductor switch (106, 108) based on measured current (122) through said power supply line (104) and measured voltage (128) across said load (110) and accordingly performing dual operations of regulating said inrush current and supplying said load current through said same power supply line (104).

7. The method as claimed in claim 6, comprises varying voltage applied to a control terminal of each of said at least one semiconductor switch (106, 108) based on said measured current (122) and said measured voltage (128) through a driver circuit (114).

8. The method as claimed in claim 7, wherein a controller (120) is configured for performing said steps and controlling said inrush current in said circuit (100, 130), by
receiving input signals, by a controller (120), comprising said measured current (122) and said measured voltage (128);
controlling, by said controller (120), said variable voltage source (116) based on said measured current (122) and measured voltage (128), and
operating, by said controller (120), said control terminal of each of said at least one semiconductor switch (106, 108) through a driver circuit (114) to regulate said inrush current.

9. The method as claimed in claim 6, comprises regulating a bidirectional inrush current between said voltage source (102) and said load (110), wherein said voltage source (102) is at least one of an alternator, a generator, and a battery, and said load (110) is at least one of a capacitive load, a rotating machine, said battery and electrical and electronic accessories.

10. The method as claimed in claim 6 is applied for pre-charging requirements of said circuit (100, 130).