Claims:
1. An adaptivepower supply circuit comprising a rectifying circuit connected to directly receive varying AC electrical source, wherein the rectifying circuit is operatively coupled with one of the phase-angle controlled thyristors(T1)and (T2)that is triggered to control output phase of the rectifying circuit.
2. The adaptivepower supply circuit of claim 1, wherein the power supply circuit is configured in a Changeover switch disconnector (COSD).
3. The adaptivepower supply circuit of claim 1, wherein the power supply circuit further comprises a gating circuit (DZ2 + C3) having a reference Zener diode (DZ2) across the power supply feeding an R-C circuit (R3 and C1) coupled to the thyristor(T1) gate, wherein the capacitor (C1) of the R-C circuit is coupled to the thyristor (T1) cathode and provides a source of output current, and wherein a second Zener diode (DZ1) is configured to limit the output voltage.
4. The adaptivepower supply circuit of claim 3, wherein the thyristor (T1) is gated on when output voltage across capacitor (C2) is less than a first reference voltage such thatas the output voltage rises, conduction angle of the thyristor (T1) decreases, and as the output voltage decreases, conduction angle increases in a manner such that firing angle of the thyristor (T1) is caused to vary automatically as an inverse function of the output voltage that maintains the output voltage at a stable level.
5. The adaptive power supply circuit of claim 4, wherein gating voltage required to fire thyristor (T1)is a function of voltage across the capacitor (C3), and wherein the capacitor (C3) serves as reference voltage for the reference Zener diode (DZ2).
6. The adaptive power supply circuit of claim 4, wherein when the circuit commences operation, voltage across the capacitor (C2) is relatively small, and a relatively low gating voltage at the capacitor (C3) is required to cause thyristor (T1) to conduct, and wherein once the thyristor (T1)is gated ON, the thyristor (T1) continues to conduct for balance of the waveform.
7. The adaptive power supply circuit of claim 4, wherein the thyristor (T1)is triggered at the start of every half cycle by the reference voltage capacitor (C3) such that once the capacitor (C2) is charged to the first reference voltage, the thyristor (T1)is turned OFF till the time capacitor (C2) voltage is less than the first reference voltage.
8. The adaptive power supply circuit of claim 4, the circuit further comprises a thyristor (T2) connected across the resistor (R2) and the thyristor (T1) to bypass during starting and during sudden load changes, wherein the thyristor (T2)is triggered by a second reference voltage zener diode (DZ3) whose voltage is less than DZ2 voltage.
9. The adaptive power supply circuit of claim 8, wherein voltage is impressed across series combination of the resistor(R1) and the capacitor (C2) when the Thyristor (T2) is switched ON, wherein gating voltage necessary to cause Thyristor (T2) to fire is a function of the voltage across the capacitor (C4), and wherein the capacitor(C2) starts charging till the time its voltage is equal to the second reference voltage (DZ3), and wherein the thyristor (T2) is turned OFF when C2 voltages reaches to DZ3 reference voltage.
10. The adaptive power supply circuit of claim 9, wherein the full wave rectified voltage is impressed across the series combination of the resistor(R1), the resistor (R2), and the capacitor (C2) when the Thyristor (T1) is switched ON, which charges the capacitor (C2) from the second (DZ3) reference voltage till the time its voltage is equal to the first (DZ2) reference voltage where resistor (R1) and resistor (R2) act as current limiting resistors, and where voltage across the capacitor (C2) is limited by the zener diode (DZ1).
, Description:TECHNICAL FIELD

[0001] This present disclosure generally pertains to changeover switch disconnectors (COSD), and more particularly to power supply circuit for an electrically operated mechanism (EOM) of changeover switch disconnector for obtaining a low voltage, stable DC signal from a variable alternating current electrical source.

BACKGROUND

[0002] Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
[0003] Electrical distribution systems employ a variety of devices for controlling and managing distribution of electrical power, including changeover switch disconnectors (COSD). COSD is also commonly referred to as open transition transfer switch, and is generally used at the incoming side of load and has three stable positions called mains, generator, and OFF. Depending on the availability of power supply, load will be connected to either mains or generator and during maintenance it will be in OFF position.
[0004] COSDs are employed in a wide variety of residential and commercial structures to allow an electrical load therein to be supplied with power from an alternate power source in the event of instability and/or loss of power from a main power source. In such installations, user has to change the position of the COSD manually using handle. Due to changing system requirements, there is a need of some electrically operated mechanism (EOM) to perform the same operation, wherein EOM is an accessory of COSD and is basically a motor driven mechanism that, based on the input command, changes the position of the COSD. A power transfer from a “normal” power source to an alternate “emergency” power source is initiated by the electronic controller energizing the motor operated mechanism. The motor operated mechanism is energized until the switching mechanism is moved to a desired position and the control contacts cut off power to the motor. Accordingly, a need remains for quickly, inexpensively and reliably converting manual COSD into motorized COSD without a significant power outage.
[0005] As it is commonly known, available AC input voltage varies from area to area. Presently, the usual AC electrical source used in Korea and Japan is 100 V and 220 V. In some countries, including Australia, 250 V of AC power is used, and AC power from 100V-250V is usually used worldwide. Therefore, when electronic appliances are exported to other countries where the AC electrical source has a different voltage, a power supply using a fixed voltage specification, depending on the area where it is going to be exported, is usually necessary. This variation in AC power from country to country causes inconvenience in making electronic appliances and thereby results in both increase of production costs and other additional problems.
[0006] Most control circuits derive their operating voltage from power lines which carry relatively high voltages. For commercial reasons the devices must be usable with a broad range of voltages, often from 85 to 500 volts. The voltage of the control power supply, however, must remain within a closely-regulated band of the order of 10 to 24V. At the same time the power supply must be simple, rugged and relatively inexpensive.
[0007] In some industrial field conditions because of unskilled workers, by mistake there are possibilities of applying 440V line voltage from 3-phase supply to the electronic appliances which are rated for 240V, will result in catastrophic failure. It will therefore be appreciated that it would be highly desirable to provide an improved power supply circuit operation in a “fail-safe” manner, and to provide a voltage supply stage which is relatively inexpensive but is capable of accepting applied voltages whose values vary over a wide range.
[0008] Prior art US4456871 discloses a method to achieve above goals using Thyristor based power supply circuit. Because of half wave rectification, this circuit cannot be used for higher load currents and the problem associated with current limiting resistor is delayed power up which will lead to delayed command execution in case of automatic transfer switch application.
[0009] Accordingly, in order to overcome the disadvantages and problems as mentioned above in the prior art systems, there is need for simple, fast response and inexpensive power supply that automatically converts a wide range of available line voltages into a single, low-level voltage suitable for use with digital control equipment.
[0010] All publications herein are incorporated by reference to the same extent as if each individual publication or patent application were specifically and individually indicated to be incorporated by reference. Where a definition or use of a term in an incorporated reference is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply.
[0011] In some embodiments, the numbers expressing quantities of ingredients, properties such as concentration, reaction conditions, and so forth, used to describe and claim certain embodiments of the invention are to be understood as being modified in some instances by the term “about.” Accordingly, in some embodiments, the numerical parameters set forth in the written description and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by a particular embodiment. In some embodiments, the numerical parameters should be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of some embodiments of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as practicable. The numerical values presented in some embodiments of the invention may contain certain errors necessarily resulting from the standard deviation found in their respective testing measurements.
[0012] As used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.
[0013] The recitation of ranges of values herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range. Unless otherwise indicated herein, each individual value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g. “such as”) provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.
[0014] Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member can be referred to and claimed individually or in any combination with other members of the group or other elements found herein. One or more members of a group can be included in, or deleted from, a group for reasons of convenience and/or patentability. When any such inclusion or deletion occurs, the specification is herein deemed to contain the group as modified thus fulfilling the written description of all groups used in the appended claims.

OBJECTS OF THE INVENTION

[0015] An object of the present disclosure is to overcome above-mentioned disadvantages and problems in the prior art systems.
[0016] Another object of the present disclosure is to provide a simple, fast response and inexpensive power supply that automatically converts a wide range of available line voltages into a single, low-level voltage suitable for use with digital control equipment.

SUMMARY

[0017] In an aspect, the present disclosure relates to changeover switch disconnectors (COSD), and more particularly, to power supply circuit for an electrically operated mechanism (EOM) of changeover switch disconnector for obtaining a low voltage, stable DC signal from a variable alternating current electrical source. In an exemplary and non-limiting aspect, such variable alternating current electrical source can have a broad range from 85 to 500 V, wherein the proposed power supply circuit can be configured without use of a step-down transformer, tap-switch, or complicated high frequency MOSFET switching, so that circuits of electronic appliances can be protected in fail safe manner.
[0018] In an aspect, the present disclosure relates to an adaptive power supply circuit comprising a rectifying circuit connected to directly receive varying AC electrical source, wherein the rectifying circuit is operatively coupled with a phase-angle controlled thyristor (T1) that is triggered to control output phase of the rectifying circuit.
[0019] In an aspect, the proposed power supply circuit can be configured in a Changeover switch disconnector (COSD).
[0020] In another aspect, thepower supply circuit can further include a gating circuit (DZ2 + C3) having a reference Zener diode (DZ2) across the power supply feeding an R-C circuit (R3 and C1) coupled to the thyristor (T1) gate, wherein the capacitor (C1) of the R-C circuit is coupled to the thyristor (T1) cathode and provides a source of output current, and wherein a second Zener diode (DZ1) is configured to limitthe output voltage.
[0021] In an aspect, the thyristor (T1) can be gated on when output voltage across capacitor (C2) is less than a first reference voltage such thatas the output voltage rises, conduction angle of the thyristor (T1) decreases, and as the output voltage decreases, conduction angle increases in a manner such that firing angle of the thyristor (T1) is caused to vary automatically as an inverse function of the output voltage that maintains the output voltage at a stable level.
[0022] In another aspect, gating voltage required to fire thyristor (T1)can be a function of voltage across the capacitor (C3), and wherein the capacitor (C3) serves as reference voltage for the reference Zener diode (DZ2).
[0023] In another aspect, when the circuit commences operation, voltage across the capacitor (C2) is relatively small, and a relatively low gating voltage at the capacitor (C3) is required to cause thyristor (T1) to conduct, and wherein once the thyristor (T1)is gated ON, the thyristor (T1) continues to conduct for balance of the waveform. In an exemplary implementation, the thyristor (T1)can be triggered at the start of every half cycle by the reference voltage capacitor (C3) such that once the capacitor (C2) is charged to the first reference voltage, the thyristor (T1)is turned OFF till the time capacitor (C2) voltage is less than the first reference voltage.
[0024] In another aspect, the proposed circuit can further include a thyristor (T2) connected across the resistor (R2) and the thyristor (T1) to bypass during starting and during sudden load changes, wherein the thyristor (T2)is triggered by a second reference voltage Zener diode (DZ3) whose voltage is less than DZ2 voltage. In an aspect, voltage can be impressed across series combination of the resistor (R1) and the capacitor (C2) when the Thyristor (T2) is switched ON, wherein gating voltage necessary to cause Thyristor (T2) to fire is a function of the voltage across the capacitor (C4), and wherein the capacitor (C2) starts charging till the time its voltage is equal to the second reference voltage (DZ3), and wherein the thyristor (T2) is turned OFF when C2 voltages reaches to DZ3 reference voltage in which situation, full wave rectified voltage is impressed across the series combination of the resistor (R1), the resistor (R2), and the capacitor (C2) when the Thyristor (T1) is switched ON, which charges the capacitor (C2) from the second (DZ3) reference voltage till the time its voltage is equal to the first (DZ2) reference voltage where resistor (R1) and resistor (R2) act as current limiting resistors, and where voltage across the capacitor (C2) is limited by the Zener diode (DZ1).
[0025] Various objects, features, aspects and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components.
BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The accompanying drawings are included to provide a further understanding of the present disclosure, and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the present disclosure and, together with the description, serve to explain the principles of the present disclosure.
[0027] FIG.1 is an exemplary block diagram of the proposed system.
[0028] FIG.2 is an exemplary block diagram in schematic form of a control circuit in accordance with an embodiment of the present invention.
[0029] FIGs.3A-3Cillustrate exemplary simulation waveforms of the present invention.

DETAILED DESCRIPTION

[0030] The following is a detailed description of embodiments of the disclosure depicted in the accompanying drawings. The embodiments are in such detail as to clearly communicate the disclosure. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims.
[0031] Each of the appended claims defines a separate invention, which for infringement purposes is recognized as including equivalents to the various elements or limitations specified in the claims. Depending on the context, all references below to the "invention" may in some cases refer to certain specific embodiments only. In other cases it will be recognized that references to the "invention" will refer to subject matter recited in one or more, but not necessarily all, of the claims.
[0032] Various terms as used herein are shown below. To the extent a term used in a claim is not defined below, it should be given the broadest definition persons in the pertinent art have given that term as reflected in printed publications and issued patents at the time of filing.
[0033] In an aspect, the present disclosure relates to changeover switch disconnectors (COSD), and more particularly, to power supply circuit for an electrically operated mechanism (EOM) of changeover switch disconnector for obtaining a low voltage, stable DC signal from a variable alternating current electrical source. In an exemplary and non-limiting aspect, such variable alternating current electrical source can have a broad range from 85 to 500 V, wherein the proposed power supply circuit can be configured without use of a step-down transformer, tap-switch, or complicated high frequency MOSFET switching, so that circuits of electronic appliances can be protected in fail safe manner.
[0034] In an aspect, the present disclosure relates to an adaptive power supply circuit comprising a rectifying circuit connected to directly receive varying AC electrical source, wherein the rectifying circuit is operatively coupled with a phase-angle controlled thyristor (T1) that is triggered to control output phase of the rectifying circuit.
[0035] In an aspect, the proposed power supply circuit can be configured in a Changeover switch disconnector (COSD).
[0036] In another aspect, the power supply circuit can further include a gating circuit (DZ2 + C3) having a reference Zener diode (DZ2) across the power supply feeding an R-C circuit (R3 and C1) coupled to the thyristor (T1) gate, wherein the capacitor (C1) of the R-C circuit is coupled to the thyristor (T1) cathode and provides a source of output current, and wherein a second Zener diode (DZ1) is configured to limit the output voltage.
[0037] In an aspect, the thyristor (T1) can be gated on when output voltage across capacitor (C2) is less than a first reference voltage such thatas the output voltage rises, conduction angle of the thyristor (T1) decreases, and as the output voltage decreases, conduction angle increases in a manner such that firing angle of the thyristor (T1) is caused to vary automatically as an inverse function of the output voltage that maintains the output voltage at a stable level.
[0038] In another aspect, gating voltage required to fire thyristor (T1)can be a function of voltage across the capacitor (C3), and wherein the capacitor (C3) serves as reference voltage for the reference Zener diode (DZ2).
[0039] In another aspect, when the circuit commences operation, voltage across the capacitor (C2) is relatively small, and a relatively low gating voltage at the capacitor (C3) is required to cause thyristor (T1) to conduct, and wherein once the thyristor (T1)is gated ON, the thyristor (T1) continues to conduct for balance of the waveform. In an exemplary implementation, the thyristor (T1)can be triggered at the start of every half cycle by the reference voltage capacitor (C3) such that once the capacitor (C2) is charged to the first reference voltage, the thyristor (T1)is turned OFF till the time capacitor (C2) voltage is less than the first reference voltage.
[0040] In another aspect, the proposed circuit can further include a thyristor (T2) connected across the resistor (R2) and the thyristor (T1) to bypass during starting and during sudden load changes, wherein the thyristor (T2)is triggered by a second reference voltage Zener diode (DZ3) whose voltage is less than DZ2 voltage. In an aspect, voltage can be impressed across series combination of the resistor (R1) and the capacitor (C2) when the Thyristor (T2) is switched ON, wherein gating voltage necessary to cause Thyristor (T2) to fire is a function of the voltage across the capacitor (C4), and wherein the capacitor (C2) starts charging till the time its voltage is equal to the second reference voltage (DZ3), and wherein the thyristor (T2) is turned OFF when C2 voltages reaches to DZ3 reference voltage in which situation, full wave rectified voltage is impressed across the series combination of the resistor (R1), the resistor (R2), and the capacitor (C2) when the Thyristor (T1) is switched ON, which charges the capacitor (C2) from the second (DZ3) reference voltage till the time its voltage is equal to the first (DZ2) reference voltage where resistor (R1) and resistor (R2) act as current limiting resistors, and where voltage across the capacitor (C2) is limited by the Zener diode (DZ1).
[0041] Changeover switch disconnector (COSD), also referred to as open transition transfer switch, is generally used at incoming side of load and it has three stable positions called mains, generator and OFF as shown in FIG.1, wherein depending on availability of power supply, load 106 will be connected to either mains 102 or generator 104, and during maintenance, it will be in OFF position. The motorized COSD can include a switch configured to connect one of two sources 102/104 to a load 106 or disconnect the load 106, and further include a mechanical drive, an actuator, a microcontroller, and a solid state switch, wherein the mechanical drive can be configured to drive the switch to either first position, or second position, or to OFF position. The first position connects the switch to the first source, and the second position connects the switch to the second source. The actuator can be in mechanical communication with the mechanical drive to cause the mechanical drive to move on command.
[0042] In an aspect, power supply for systems of the present type is of particular interest as it presents a substantial design challenge due to the fact that devices such as the industrial motorized COSD shown in FIG. 1 should be adaptable for use with AC power of from 85 to 500 volts and for frequencies of both 50 and 60 Hz, while producing a constant low-voltage regulated output. At the same time, due to relatively low price of such devices, cost of the power supply must be low, ruling out complex regulation systems of conventional design.
[0043] In an aspect of the present disclosure, a phase-angle controlled thyristor arrangement can be utilized without the need for complex firing and commutation circuits or elaborate gate-timing systems. In such a proposed configuration/arrangement, power supply can include a rectifying circuit connected to directly receive an AC electrical source of anywhere from 85V AC to 500V AC of alternating current, wherein thyristor can be used for controlling output phase of the rectifying circuit. The arrangement can further include a circuit for generating a trigger signal for controlling phase for triggering the thyristor.
[0044] In an aspect, in accordance with one aspect of the invention, foregoing objects are achieved by providing a power supply incorporating a thyristor in series with a source of high potential, and a gating circuit comprising a reference Zener diode across the power supply feeding an R-C circuit coupled to the thyristor gate. A capacitor coupled to the thyristor cathode provides a source of output current, and zener diode is configured to limit the output voltage. The thyristor can be gated on when the output capacitor voltage is less than reference voltage. As output voltage rises, conduction angle of the thyristor decreases and visa-versa in a manner such that firing angle of the thyristor is caused to vary automatically as an inverse function of output voltage, which maintains the output voltage at a relatively stable level.
[0045] With reference to FIG. 2, in an aspect, gating voltage necessary to cause Thyristor T1 to fire can be a function of voltage across capacitor C3, which serves as reference voltage DZ2. When the circuit commences operation, voltage across capacitor C2 is relatively small, and a relatively low gating voltage at C3 is required to cause Thyristor T1 to conduct. Once gated ON, the Thyristor T1 can continue to conduct for the balance of the waveform, that is, up to 180°. Thyristor T1 can be triggered at the start of every half cycle by the reference voltage capacitor C3 such that once Capacitor C2 is charged to the reference voltage level, Thyristor T1 will be turned OFF till the time C2 voltage is less than reference voltage by D2 voltage drop and Thyristor T1 gate to cathode voltage drop.
[0046] In applications where quick power built up is required, time constant of the power supply has to be reduced. However, because of lower time constant i.e. lower resistance, charging current increases to higher value leading to increased size of the resistor to accommodate heat dissipation. In an aspect, as shown in FIG. 2, Thyristor T2 can be connected across R2 and T1 to bypass them during starting and sudden load changes. Thyristor T2 can be triggered by separate reference voltage zener diode DZ3 whose voltage can be less than DZ2 voltage by 3V. In this circuit, reference voltage can be built up by connecting R8, C4, and DZ3 across R7 and C3 combination. Diode D3 can be connected between reference voltage generated by C4 capacitor and Thyristor T2 gate to isolate the high input voltage present at gate terminal when Thyristor T2 is conducting. To avoid triggering caused by thermally generated carriers at the gate junction of Thyristor T2, a resistor R9 can be connected across gate and cathode terminals of Thyristor T2, which increases dv/dt capability of the Thyristor T2. To remove high frequency noise and increase dv/dt capability, capacitor C5 can be connected across gate and cathode of Thyristor T2.
[0047] Constant load condition is represented using RL1 whereas transient load condition is represented using RL2, wherein transient load condition can be simulated using switches SW1 and SW2. As shown in FIG.2, transient load RL2 can be switched ON at t=1.5 sec by closing SW1 switch and switched OFF at t=2 sec by opening SW2 switch. Here, the load can include, in a non-limiting manner, microcontroller, capacitors, relay coils or solid state switches and LED. To avoid back feeding of capacitive load to C2, a diode D1 is connected in between.
[0048] Full wave rectified voltage can be impressed across the series combination of resistors R1 and capacitor C2 when the Thyristor T2 is switched ON. The gating voltage necessary to cause Thyristor T2 to fire is a function of the voltage across capacitor C4, which serves as reference voltage DZ3. C2 capacitor starts charging till the time its voltage is equal to the reference voltage DZ3, where R1 acts as current limiting resistor. Thyristor T1 will be turned OFF when C2 voltages reaches to DZ3 reference voltage. Now full wave rectified voltage can be impressed across the series combination of resistors R1, R2, and capacitor C2 when the Thyristor T1 is switched ON. C2 capacitor starts charging from DZ3 reference voltage till the time its voltage is equal to the reference voltage DZ2, where R1 and R2 acts as current limiting resistors. Here, the voltage across the capacitor C2 is limited by the Zener diode DZ1. In order to gate Thyristor T1 ON, the voltage at the gate terminal thereof must be sufficiently greater than the voltage at the cathode i.e. C2, to allow the necessary gating current to flow.
[0049] It would be appreciated that the voltages and references thresholds/cut-off of 10V and 13V are completely exemplary and have been discloses only to help explain the inventive step of the application, and the values should not be construed to be limiting the scope of the invention in any manner whatsoever.
[0050] In an exemplary aspect, resistors R4-R6 along with Zener diodes DZ2 and DZ3 can be used for voltage build up, wherein, during initialization,T2 stops working when voltage across C2 is above the reference voltage defined by DZ3 (say of 10V), in which scenario, T1 starts working through voltage buildup taking place across C3 in which scenario, T1 stops working when voltage across C2 is greater than the reference voltage defined by DZ2 (say of 13V), in which scenario C2 starts using its charge to operate the load.
[0051] As shown in FIG. 3A, based on capacitor discharge rate, conduction time of Thyristor T1 changes. It will now be appreciated that, depending upon the load and therefore the rate at which current is drained from capacitor C2, firing angle of Thyristor T1 will automatically vary, resulting in a greater or lesser conduction time for Thyristor T1. As shown in FIG.3B, the proposed circuit charges quickly and responds to load changes i.e., good load regulation. As shown in FIG. 3C, the proposed circuit responds quickly to sudden load changes, wherein when the Voltage across C2 capacitor falls less than DZ2 reference voltage by 3V, the Thyristor T2 can come into conduction, which can help achieve quick charging of Capacitor C2. In this manner, a predetermined voltage level is automatically maintained upon capacitor C2 without the necessity for complex gating or control apparatus.
[0052] It would be appreciated that the present invention comprises an economical yet accurate voltage regulator that is adaptable for use over a broad range of input voltages, for quick charging of storage capacitor during higher load conditions which exhibits a self-limiting function without the need for special sensing or timing circuits. The present invention further enables automatic conversion of a wide range (85 -500V AC) of available line voltages into a single, low-level voltage suitable for use with digital control equipment. The proposed arrangement is also simple, rugged and relatively inexpensive thyristor based power supply circuit having a self-limiting function that does not need special sensing or timing circuits, and enables quick power up to help reduce changeover switch transfer time and improve response to sudden load changes.
[0053] In another aspect, the proposed construction helps power larger electronic loads, and does not require bulk capacitance to hold charge. Also, as the proposed adaptive power supply circuit does not have high supply time constant, it can be used for quick power up applications and has a good load regulation. The proposed invention proposes an adaptive power supply circuit for variable input voltages.
[0054] While the foregoing describes various embodiments of the invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof. The scope of the invention is determined by the claims that follow. The invention is not limited to the described embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person having ordinary skill in the art.

ADVANTAGES OF THE INVENTION

[0055] The present invention provides a simple, fast response and inexpensive power supply that automatically converts a wide range of available line voltages into a single, low-level voltage suitable for use with digital control equipment.
[0056] The present invention helps power larger electronic loads, and does not require bulk capacitance to hold charge.
[0057] The present invention proposes an adaptive power supply circuit that does not have high supply time constant and therefore can be used for quick power up applications and has a good load regulation.
[0058] The present invention further proposes an adaptive power supply circuit for variable input voltages.