Low cast chopper inverter power supply and gating circuit therefor

• US 3,953,783 A
• Filed: 03/26/1974
• Issued: 04/27/1976
• Est. Priority Date: 04/06/1971
• Status: Expired due to Term

• Current Assignee: Environment/One Corporation
• Original Assignee: Environment/One Corporation
• Inventors: Peters, Philip H. Jr.
• Primary Examiner(s): Shoop, William M.
• Application Number:
  US05/454,787
• Time in Patent Office: 763 Days
• Field of Search: 307/240, 307/252 R, 307/252 M, 321/16, 321/18, 321/43-45, 321/45 C
• US Class Current: 363/124
• CPC Class Codes: F24C 7/02 using microwaves
• CPC Class Codes: G05D 23/19 characterised by the use of electric means G05D23/1393 takes precedence
• CPC Class Codes: G05D 23/1917 using digital means
• CPC Class Codes: G05D 23/24 the sensing element having a resistance varying with temperature, e.g. a thermistor
• CPC Class Codes: G05D 23/27 with sensing element responsive to radiation
• CPC Class Codes: G05F 1/56 using semiconductor devices in series with the load as final control devices G05F1/461 takes precedence
• CPC Class Codes: H02M 1/083 for the ignition at the zero crossing of the voltage or the current
• CPC Class Codes: H02M 3/135 using semiconductor devices only
• CPC Class Codes: H02M 5/45 using semiconductor devices only
• CPC Class Codes: H02M 7/515 using semiconductor devices only
• CPC Class Codes: H02M 7/525 with automatic control of output waveform or frequency H02M7/517 - H02M7/523 take precedence
• CPC Class Codes: H05B 2206/022 Special supports for the induction coils
• CPC Class Codes: H05B 6/062 for cooking plates or the like
• CPC Class Codes: H05B 6/1254 using conductive pieces to direct the induced magnetic field
• CPC Class Codes: Y02B 40/00 Technologies aiming at improving the efficiency of home appliances, e.g. induction cooking or efficient technologies for refrigerators, freezers or dish washers

Abstract

A metal based cookware induction heating apparatus having an improved power supply and control circuit comprised of a chopper inverter including a gate controlled power thyristor coupled to and supplying an induction heating coil with periodic energization currents. A full wave rectifier supplies rectified, unfiltered, unidirectional high voltage excitation potential to the chopper inverter which converts the excitation potential to a comparatively high frequency of the order of 20 kilohertz for supply to the induction heating coil. A gating circuit is provided for driving the chopper inverter directly from the rectified high voltage excitation potential supplied by the rectifier.

The gating circuit includes an additional low voltage, direct current excitation potential connected to supply to a timing circuit charging capacitor. A voltage responsive switch such as a SUS or PUT or their equivalents is rendered conductive upon the timing circuit reaching a present value and in turn rendered conductive a constant current high voltage switching transistor connected in series with the primary winding of a pulse transformer across the output of the additional low voltage derived from the main full wave rectifier. The pulse transformer in turn has its secondary winding connected to the control gate of the power thyristor included in the chopper inverter.

Claims

1. An improved power supply and control circuit comprising inverter circuit means having only a single bidirectional conducting gate controlled power thyristor coupled to and supplying load with periodic energization currents, rectifier means for supplying a rectified semi-filtered unidirectional high voltage excitation potential for said inverter circuit means and gating circuit means for periodically gating on said inverter circuit means, said gating circuit means including means for deriving a low voltage unidirectional self excitation potential from the high voltage rectified unfiltered undirectional excitation potential supplied from said rectifier means, timing circuit charging means supplied by said low voltage excitation potential, voltage responsive switching means connected to and controlled by said timing circuit charging means, said voltage responsive switching means being rendered conductive upon the voltage of said timing circuit charging means attaining a preset value, a semiconductor switching device having a relatively flat current vs voltage conducting characteristic and having its load terminals connected to the output from the rectifier means, the control gate of said constant current semiconductor switching device being connected to and supplied by the voltage responsive switching means and gating signal output circuit means connected in series circuit relationship with the constant current high voltage switching device and adapted for connection to the control gate of the gate controlled power thyristor comprising a part of the invertor circuit means.

2. An improved power supply and control circuit according to claim 1 further including means for varying the charging time constant of said timing circuit charging means to thereby control the power output of the inverter circuit means.

3. An improved power supply circuit and control according to claim 2 wherein the voltage responsive switching means comprises a silicon unilateral switch device, the constant current high voltage semiconductor device comprises a high voltage switching transistor, and the gating signal output means comprises an isolating transformer having its primary winding connected in the emitter-collector circuit of the high voltage switching transistor and having its secondary winding adapted to be connected to the control gate of the large power rated thyristor in the inverter circuit means.

4. An improved power supply circuit and control according to claim 3 further including soft-starting zero point energization switching means connected intermediate the output of the rectifier means and the inverter circuit means, and zero point sensing and turn-on circuit means coupled to and controlling said soft starting zero point energization switching means for rendering the same conductive only near the beginning of each cycle of the rectified unfiltered unidirectional excitation potential.

5. An improved power supply circuit and control according to claim 4 further including inhibit control means for inhibiting operation of said zero point sensing and turn-on circuit means, and load condition sensing means for sensing the operating condition of a load supplied by the inverter circuit means and deriving an on-off control signal in response to the load condition for controlling operation of said inhibit control means.

6. An improved power supply circuit and control according to claim 1 further including capacitor switching means operable during non-conducting intervals of the inverter circuit means to switch different values of commutating capacitance into effective circuit relationship in the inverter circuit means to thereby control the power generated by the circuit.

7. An improved power supply circuit and control according to claim 1 further including dv/dt sensing means comprising a series connected resistor and capacitor connected across a switching thyristor comprising a part of the inverter circuit means, said series connected resistor and capacitor serving to limit the rate of rise of reapplied forward voltage across the switching thyristor, signal rectifying and shaping circuit means coupled to said series connected resistor and capacitor for deriving an output dv/dt control signal therefrom representative of the rate of reapplied forward voltage across the switching thyristor, and means for applying the dv/dt control signal back to the gating circuit means for modifying operation of the inverter circuit means in a direction to provide a lesser dv/dt value.

8. An improved power supply circuit and control according to claim 1 further including means for sensing the operating condition of the load comprising an opto-electronic sensing circuit connected across the output of said rectifier means for deriving a ripple factor control voltage representative of the ripple present in the output from said rectifier means and indicative of the loading conditions on the power supply circuit, and means for automatically modifying the operation of the inverter to cut back the power output in response to a sensed predetermined magnitude of ripple.

9. An improved power supply circuit and control according to claim 1 wherein the inverter circuit means is a chopper inverter comprised by a filter inductor having an inductance L₂, a bidirectional conducting gate control semiconductor thryristor switching device connected in series circuit relationship with the filter inductor across the output from said rectifier means with the filter inductor interposed between the thyristor switching device and the rectifier means, a commutating inductor having an inductance L₁ and commutating capacitor having a capacitance C₁ connected in series circuit relationship across the thyristor switching device and tuned to series resonance at a desired commutating frequency that provides a combined thyristor conduction and commutating period t₁ during each cycle of operation, means for deriving output power coupled to at least one of the commutating components, the gating circuit means being coupled to the control gate of the thyristor switching device for rendering the device conductive at a controlled frequency of operation that provides an operating period T for the chopper inverter including a quiescent charging period t₂ in each cycle of operation where T = t₁ +t₂ such that the value ω

₂ t₂ equals substantially π

/2 radians or greater and where ω

₂ = 1/√

L₂ C₁ whereby the reapplied forward voltage across the semiconductor thyristor switching device following each conduction interval is maintained substantially independent of load.

10. An improved power supply circuit and control according to claim 9 wherein the gating circuit means further includes means for varying the charging time constant of said timing circuit charging means, on-off control circuit means for turning said gating circuit means on and off in in accordance with the power demands on the circuit, said on-off control circuit means comprising soft starting zero point energization switching means connected intermediate the output from the rectifier means and the chopper inverter circuit means, zero point sensing and turn-on circuit means coupled to said soft start zero point energization switching means for switching said means only at or near the beginning of each half cycle of the rectified, unfiltered unidirectional excitation potential, inhibit control means for inhibiting operation of said zero point sensing and gating circuit means, and load condition sensing means for sensing the operating condition of the load in response to the output from the chopper inverter circuit means and deriving on-off control signal in response to the load condition for controlling operation of the inhibit circuit means, and capacitor switching means operable during non-conducting intervals of the inverter circuit means to switch different values of commutating capacitance into effective circuit relationship in the inverter circuit means to thereby control the rate of power production by the circuit.

11. An improved power supply circuit and control according to claim 9 wherein said gating circuit means is a variable frequency gating circuit means for varying the frequency of operation of the chopper inverter circuit means to control the output power with the instantaneous frequency output being controllable over a range of frequencies that satisfies substantially the relation ω

₂ t₂ equals substantially π

/2 radians or greater, and further including means for sensing substantial changes in loading of the power supply circuit, and means for automatically reducing the frequency of operation of the chopper inverter circuit means in response to the sensed sudden change in loading.

12. An improved power supply circuit and control according to claim 1 wherein the inverter circuit means comprises a chopper inverter circuit that produces periodic pulsed currents having radio frequency interference emission effects and the circuit further includes a smoothing inductor and a smoothing capacitor connected in circuit relationship across the chopper inverter circut which serve to shape the output current supplied by the chopper inverter circuit to the load to substantially a sinusoidal wave shape having little or no radio frequency interference effects.

13. An improved power supply circuit and control according to claim 9 further including a smoothing inductor having an inductance L₃ and smoothing capacitor having a capacitance C₃ connected in series circuit relationship across at least one of the commutating components and having impedance values such that the combined impedance of the commutating capacitor, the smoothing inductor and the smoothing capacitor is capacitive in nature and series resonates with the commutating inductor to establish the commutating period t₁, and wherein the smoothing inductor and capacitor shape the output current flowing through the smoothing inductor to substantially a sinusoidal waveshape having little or no radio frequency interference emission effects, and the load is coupled to and derives output power from the smoothing inductor.

14. An improved power supply circuit and opto-electronic control comprising power supply terminal means connected to and supplying a power supply circuit, a ripple sensing device connected in said power supply means for deriving an output ripple signal only in response to and indicative of the presence and magnitude of a ripple in the current supplied through said power supply terminal means, a control circuit for controlling operation of said power supply circuit, a ripple signal sensitive device connected in said control circuit for sensing the ripple signal derived by said ripple sensing device under conditions where a substantial ripple is present in the power being supplied by said power supply terminal means, and means utilizing the ripple produced output signal developed by said ripple signal sensitive device for controlling operation of said control circuit means and hence of said power supply circuit to maintain the ripple signal within predetermined limits.

15. A chopper inverter power supply circuit including in combination supply terminal means adapted to be connected to a source of electric energy for energizing the chopper inverter, a filter inductor having an inductance L₂, a bidirectional conducting gate controlled semiconductor thyristor switching device connected in series circuit relationship with the filter inductor across said supply terminal means with the filter inductor interposed between the thyristor switching device and the supply terminal means, a commutating inductor having an inductance L₁ and commutating capacitor having a capacitance C₁ connected in series circuit relationship across the thyristor switching device and tuned to series resonance at a desired commutating frequency that provides a combined thyristor conduction and commutating period t₁ during each cycle of operation, means for deriving output power coupled across at least one of said commutating components, and gating circuit means coupled to the control gate of said thyristor switching device for rendering the device conductive at a controlled frequency of operation that provides an operating period T for the chopper inverter including a quiescent charging period t₂ in each cycle of operation where T = t₁ + t₂ such that the value ω

₂ t₂ equals substantially π

/2 radians or greater and where ω

₂ = 1/√

L₂ C₁ whereby the reapplied forward voltage across the semiconductor thyristor switching device following each conduction interval is substantially independent of load.

16. A chopper inverter power supply circuit according to claim 15 further including a filter capacitor having a capacitance C₂ connected across the series connected filter inductor and thyristor switching device.

17. A chopper inverter power supply circuit according to claim 15 further including rectifier means connected across said supply terminal means intermediate a source of alternating current supply and said thyristor switching device for supplying rectified semi-filtered unidirectional excitation potentials to said thyristor switching device across said supply terminal means from an alternating current supply.

18. A chopper inverter power supply circuit according to claim 15 further including on-off control circuit means for rendering said gating circuit means effective to control turn-on of the thyristor switching device in accordance with the power demands on the circuit.

19. A chopper inverter power supply circuit according to claim 18 wherein said on-off control circuit means includes soft starting zero point energization switching means connected intermediate the supply terminal means and the thyristor switching device, and zero point sensing and control circuit means coupled to said soft start zero point switching means for switching said soft start switching means on only at the beginning of each half cycle of the input supply rectified, unfiltered unidirectional excitation potential.

20. A chopper inverter power supply circuit according to claim 19 wherein said on-off control means includes inhibit control means for inhibiting operation of said zero point sensing and control circuit means, and load condition sensing means for sensing the operating condition of the load in response to the output from the chopper inverter power supply circuit and deriving an on-off control signal in response to the load condition for controlling operation of said inhibit control means.

21. A chopper inverter power supply circuit according to claim 15 wherein said gating circuit means is a variable frequency gating circuit means for varying the frequency of operation of the chopper inverter power supply circuit to control the output power with the instantaneous frequency output being controllable over a range of frequencies that satisfies substantially the relation ω

₂ t₂ = π

/2 radians or greater.

22. A chopper inverter power supply circuit according to claim 21 further including means for sensing a substantial change in the loading of the power supply circuit from a substantially full load to a no load condition, and means for automatically reducing the frequency of operation of the circuit in response to the sensed change in loading.

23. A chopper inverter power supply circuit according to claim 15 further including a smoothing inductor having an inductance L₃ and a smoothing capacitor having a capacitance C₃ connected in series circuit relationship across at least one of said commutating components, the combined impedance of the commutating capacitor, the smoothing inductor and the smoothing capacitor being capacitive in nature and series resonant with the commutating inductor to establish the commutating period t₁, and wherein the smoothing inductor and capacitor shape the output current flowing through the smoothing inductor to substantially a sinusoidal waveshape having little or no radio frequency interference emission effects.

24. A chopper inverter power supply circuit according to claim 15 wherein said commutating capacitor comprises a plurality of parallel connected capacitors and power rate controlling switching means for switching selected ones of said parallel connected capacitors into effective circuit relationship in accordance with a desired rate of power production.

25. An improved power supply and control circuit according to claim 17 wherein the position of the rectifier means and the filter inductor are interchanged, and the thyristor switching device is unidirectional conducting whereby the circuit is adapted for excitation from an alternating current supply and the rectifier means functions in the dual capacity of a rectifier and feedback diode.

26. An improved regulated power supply circuit including in combination power supply terminal means for connection across a source of alternating current electric energy, rectifier means coupled to and supplied by said power supply terminal means for converting the alternating current energy to undirectional current energy, high frequency inverter circuit means coupled to and supplied by said rectifier means for converting the undirectional current energy to high frequency pulsed currents of energy for supplying a load, output power control switching means interconnected in said regulated power supply circuit intermediate the power supply terminal means and the high frequency inverter circuit means for controlling the output power developed by the high frequency inverter circuit means, said high frequency inverter circuit means including commutating capacitor means and means for varying the value of said commutating capacitor means for thereby additionally controlling the average output power developed by the high frequency inverter circuit means.

27. An improved regulated power supply circuit according to claim 26 wherein the output power control switching means is interconnected intermediate the output from the rectifier means and the energization input terminals of the high frequency inverter circuit means and comprises and on-off zero point switching means for on-off controlling the output power developed by the high frequency inverter circuit means.

28. An improved power supply circuit according to claim 26 wherein the output power control switching means is interconnected intermediate the power supply terminal means and the rectifier means and comprises an on-off zero point switching means for on-off controlling the output power developed by the high frequency inverter circuit means.

29. An improved power supply and control circuit comprising inverter circuit means including a gate controlled power thyristor coupled to and supplying a load with periodic energization currents, rectifier means for supplying a rectified unfiltered unidirectional high voltage excitation potential for said inverter circuit means and gating circuit means for periodically gating on said inverter circuit means, said gating circuit means including means for deriving a low voltage unidirectional self excitation potential from the high voltage rectified unfiltered unidirectional excitation potential supplied from said rectifier means, timing circuit charging means supplied by said low voltage excitation potential, voltage responsive switching means connected to and controlled by said timing circuit charging means, said voltage responsive switching means being rendered conductive upon the voltage of said timing circuit charging means attaining a preset value, a semiconductor switching device having a relatively flat current vs voltage conducting characteristic and having its load terminals connected to the output from the rectifier means, the control gate of said constant current semiconductor switching device being connected to and supplied by the voltage responsive switching means and gating signal output circuit means connected in series circuit relationship with the constant current high voltage switching device and adapted for connection to the control gate of the gate controlled power thyristor comprising a part of inverter circuit means, selectively operable inhibit circuit means coupled across said gating circuit means for selectively inhibiting operation of said gating circuit means, and delay means for introducing a delay period intermediate selective operation of the inhibit means in a direction to remove the inhibit and enable operation of the gating circuit means.

30. An improved power supply and control circuit according to claim 29 further including means for varying the charging time constant of said timing circuit charging means to thereby control the power output of the inverter circuit means.

31. An improved power supply circuit and control according to claim 29 wherein the voltage responsive switching means comprises a silicon unilateral switch device, the semiconductor switching device comprises a high voltage switching transistor, and the gating signal output means comprises a load resistor connected in the emitter-collector circuit of the high voltage switching transistor and that in turn is connected to the control gate of the large power rated thyristor in the inverter circuit means.

32. An improved power supply circuit and control according to claim 29 wherein said selectively operable inhibit circuit means comprises an inhibiting thyristor device coupled across the means for deriving the low voltage self excitation potential for selectively clamping off the excitation potential to the timing circuit charging means to thereby inhibit operation thereof, and zero point sensing and turn-on control circuit means coupled to and controlled by said inhibiting thyristor device for readering the same non-conductive and thereby enable the timing circuit charging means only at or near the beginning of each cycle of the rectified unfiltered unidirectional excitation potential.

33. An improved power supply circuit and control according to claim 32 further including inhibit control means for inhibiting operation of said zero point sensing and turn-on circuit means, and operating condition sensing means for sensing the operating condition of the inverter circuit means and deriving an on-off control signal in response to the load condition for controlling operation of said inhibit control means.

34. An improved power supply circuit and control according to claim 29 further including capacitor switching means operable during non-conducting intervals of the inverter circuit means to switch different values of commutating capacitance into effective circuit relationship in the inverter circuit means to thereby control the power generated by the circuit.

35. An improved power supply circuit and control according to claim 29 wherein said rectifier means is comprised by a fast recovery diode bridge that serves simultaneously as a full wave rectifier of the supply alternating current potential and to provide feedback of reverse currents in the inverter circuit means.

36. An improved power supply circuit and control according to claim 29 wherein the inverter circuit means is a chopper inverter comprised by a filter inductor having an inductance L₂, a bidirectional conducting gate control semiconductor thyristor switching device connected in series circuit relationship with the filter inductor across the output from said rectifier means with the filter inductor interposed between the thyristor switching device and the rectifier means, a commutating inductor having an inductance L₁ and commutating capacitor having a capacitance C₁ connected in series circuit relationship across the thyristor switching device and tuned to series resonance at a desired commutating frequency that provides a combined thryistor conduction and commutating period t₁ during each cycle of operation, means for deriving output power coupled to at least one of the commutating components, the gating circuit means being coupled to the control gate of the thyristor switching device for rendering the device conductive at a controlled frequency of operation that provides an operating period T for the chopper inverter including a quiescent charging period t₂ in each cycle of operation where T = t₁ + t₂ such that the value ω

₂ t₂ equals substantially π

/2 radiant or greater where ω

₂ = 1/√

L₂ C₁ whereby the reapplied forward voltage across the semiconductor thyristor switching device following each conduction interval is maintained substantially independent of load.

37. An improved power supply circuit and control according to claim 36 wherein the gating circuit means further includes means for varying the charging time constant of said timing circuit charging means, on-off control circuit means for turning said gating circuit means on and off in accordance with the power demands on the circuit, said on-off control circuit means comprising an inhibiting thyristor device coupled across the means for deriving the low voltage self excitation potential for selectively clamping-off the excitation potential to the timing circuit charging means to thereby inhibit operation thereof, zero point sensing and turn-on circuit means coupled to and controlling said inhibiting thyristor device for switching said device off to thereby enable the timing circuit charging means only at or near the beginning of each half cycle of the rectified, unfiltered unidirectional excitation potential, inhibit control means for inhibiting operation of said zero point sensing and turn-on circuit means, and operating condition sensing means for sensing the operating condition of the chopper-inverter and deriving on-off control signal in response to the operating condition for controlling operation of the inhibit control means, and capacitor switching means operable during non-conducting intervals of the inverter circuit means to switch different values of commutating capacitance into effective circuit relationship in the inverter circuit means to thereby control the rate of power production by the circuit.

38. An improved power supply and control circuit according to claim 33 further including means for varying the charging time constant of said timing circuit charging means to thereby control the power output of the inverter circuit means.

39. An improved power supply circuit and control according to claim 33 further including capacitor switching means operable during non-conducting intervals of the inverter circuit means to switch different values of commutating capacitance into effective circuit relationship in the inverter circuit means to thereby control the power generated by the circuit.

40. An improved power supply circuit and control according to claim 38 further including capacitor switching means operable during non-conducting intervals of the inverter circuit means to switch different values of commutating capacitance into effective circuit relationship in the inverter circuit means to thereby control the power generated by the circuit.

41. An improved power supply circuit and control according to claim 40 wherein said rectifier means is comprised by a fast recovery diode bridge that serves simultaneously as a full wave rectifier of the supply alternating current potential and to provide feedback of reverse currents in the inverter circuit means.

42. An improved power supply circuit and control according to claim 41 wherein the inverter circuit means is a chopper inverter comprised by a filter inductor having an inductance L₂ , a bidirectional conducting gate control semiconductor thyristor switching device connected in series circuit relationship with the filter inductor across the output from said rectifier means with the filter inductor interposed between the thyristor switching device and the rectifier means, a commuating inductor having an inductance L₁ and commutating capacitor having a capacitance C₁ connected in series circuit relationship across the thyristor switching device and tuned to series resonance at a desired commutating frequency that provides a combined thyristor conduction and a commutating period t₁ during each cycle of operation, means for deriving output power coupled to at least one of the commutating components, the gating circuit means being coupled to the control gate of the thyristor switching device for rendering the device conductive at a controlled frequency of operation that provides an operating period T for the chopper inverter including a quiescent charging period t₂ in each cycle of operation where T = t.sub. 1 + t₂ such that the value ω

₂ t₂ equals substantially π

/2 radians or greater where ω

_t2 = 1/√

L₂ C₁ whereby the reapplied forward voltage across the semiconductor thyristor switching device following each conduction interval is maintained substantially independent of load.

43. A chopper inverter power supply circuit including in combination supply terminal means adapted to be connected to a source of electric energy for energizing the chopper inverter, a filter inductor having an inductance L₂, a bidirectional conducting gate controlled semiconductor thyristor switching device connected in series circuit relationship with the filter inductor across said supply terminal means with the filter inductor interposed between the thyristor switching device and the supply terminal means, a commutating inductor having an inductance L₁ and commutating capacitor having a capacitance C₁ connected in series circuit relationship across the thyristor switching device and tuned to series resonance at a desired commutating frequency that provides a combined thyristor conduction and commutating period t₁ during each cycle of operation, gating circuit means coupled to the control gate of said thyristor switching device for rendering the device conductive at a controlled frequency of operation, a smoothing inductor having an inductance L₃ and a smoothing capacitor having a capacitance C₃ connected in series circuit relationship across at least one of said commutating components, the combined impedance of the commutating capacitor, the smoothing inductor and the smoothing capacitor being capacitive in nature and series resonant with the commutating inductor to establish the commutating period t₁, wherein the smoothing inductor and capacitor shape the output current flowing through the smoothing inductor to substantially a sinusoidal waveshape having little or no radio frequency interference emission effects and improved power coupling, and means for deriving output power from across said smoothing inductor.

44. A chopper inverter power supply circuit according to claim 43 further including a filter capacitor having a capacitance C₂ connected across the series connected filter inductor and thyristor switching device.

45. A chopper inverter power supply circuit according to claim 44 further including rectifier means connected across said supply terminal means intermediate a source of alternating current supply and said thyristor switching device for supplying rectified semi-filtered unidirectional excitation potentials to said thyristor switching device across said supply terminal means from an alternating current supply.

46. A chopper inverter power supply circuit according to claim 45 further including on-off control circuit means for rendering said gating circuit means effective to control turn-on of the thyristor switching device in accordance with the power demands on the circuit.

47. A chopper inverter power supply circuit according to claim 46 wherein said on-off control circuit means includes soft starting zero point energization switching means connected intermediate the supply terminal means and the thyristor switching device, and zero point sensing and control circuit means coupled to said soft start zero point switching means for switching said soft start switching means on only at the beginning of each half cycle of the input supply rectified, semi-filtered unidirectional excitation potential.

48. A chopper inverter power supply circuit according to claim 47 wherein said on-off control means includes inhibit control means for inhibiting operation of said zero point sensing and control circuit means, and load condition sensing means for sensing the operating condition of the load in response to the output from the chopper inverter power supply circuit and deriving an on-off control signal in response to the load condition for controlling operation of said inhibit control means.

49. A chopper inverter power supply circuit according to claim 43 wherein the gating circuit means coupled to the control gate of the thyristor switching device renders the device conductive at a controlled frequency of operation that provides an operating period T for the chopper inverter including a quiescent charging period t.sub. 2 in each cycle of operation where T= t.sub. 1 + t₂ such that the value ω

₂ t₂ equals substantially π

/2 radians or greater and where ω

₂ = 1/√

L₂ C₁ whereby the reapplied forward voltage across the semiconductor thyristor switching device following each conduction interval is maintained substantially independent of load and the storage of adequate commutating energy for the thyristor switching device intermediate each conductor interval, is assured.

50. A chopper inverter power supply circuit according to claim 43 wherein said commutating capacitor comprises a plurality of parallel connected capacitors and power rate controlling switching means for switching selected ones of said parallel connected capacitors into effective circuit relationship in accordance with a desired rate of power production.

51. A chopper inverter power supply circuit according to claim 50 further including on-off control circuit means for controlling turn-on and turn-off of said thyristor switching device and said on-off control circuit means includes soft starting zero point energization switching means connected to control the on-off control circuit means and the thyristor switching device, zero point sensing and control circuit means coupled to said soft start zero point switching means for switching said soft start switching means on only at the beginning of each half cycle of an input supply rectified, semi-filtered unidirectional excitation potential, inhibit control means for inhibiting operation of said zero point sensing and control circuit means, and delay means controlling operation of said inhibit control means intermediate each operation of said power rate controlling switching means.

52. An improved power supply and control circuit according to claim 45 wherein the position of the rectifier means and the filter inductor are interchanged, and the thyristor switching device is unidirectional conducting whereby the circuit is adapted for excitation from an alternating current supply and the rectifier means functions in the dual capacity of a rectifier and feedback diode.

53. An improved power supply and control circuit according to claim 43 further including rectifier means for supplying a rectified semi-filtered unidirectional high voltage excitation potential for said inverter circuit means and wherein said gating circuit means for periodically gating on said inverter circuit means includes means for deriving a low voltage unidirectional excitation potential, timing circuit charging means supplied by said low voltage excitation potential, voltage responsive switching means connected to and controlled by said timing circuit charging means, said voltage responsive switching means being rendered conductive upon the voltage of said timing circuit means attaining a preset value, a semiconductor switching device having a relatively flat current vs. voltage conducting characteristic and having its load terminals connected to gating signal output circuit means connected in series circuit relationship with the constant current high voltage switching device, the gating signal output circuit means being adapted for connection to the control gate of the gate controlled power thyristor comprising a part of inverter circuit means.

54. An improved power supply circuit and control according to claim 53 wherein the semiconductor switching device comprises a high voltage switching transistor, and the gating signal output means comprises a load resistor connected in the emitter-collector circuit of the high voltage switching transistor and that in turn is connected to the control gate of the large power rated thyristor in the inverter circuit means.

55. An improved power supply circuit and control according to claim 53 further including selectively operable inhibit circuit means comprising an inhibiting thyristor device coupled across the means for deriving the low voltage excitation potential for selectively clamping off the excitation potential to the timing circuit charging means to thereby inhibit operation thereof, and zero point sensing and turn-on control circuit means coupled to and controlled by said inhibiting thyristor device for rendering the same non-conductive and thereby enable the timing circuit charging means only at or near the beginning of each cycle of the rectified semi-filtered unidirectional excitation potential.

56. An improved power supply circuit and control according to claim 55 further including inhibit control means for inhibiting operation of said zero point sensing and turn-on circuit means, and operating condition sensing means for sensing the operating condition of the inverter circuit means and deriving an on-off control signal in response to the load condition for controlling operation of said inhibit control means.

57. An improved power supply circuit control according to claim 53 further including capacitor switching means operable during non-conducting intervals of the inverter circuit means to switch different values of commutating capacitance into effective circuit relationship in the inverter circuit means to thereby control the power generated by the circuit.

58. An improved power supply circuit and control according to claim 53 wherein said rectifier means is comprised by a fast recovery diode bridge that serves simultaneously as a full wave rectifier of the supply alternating current potential and to provide feedback of reverse currents in the inverter circuit means.

59. An improved power supply circuit and control according to claim 53 wherein the gating circuit means coupled to the control gate of the thyristor switching device renders the device conductive at a controlled frequency of operation that provides an operating T for the chopper inverter including a quiescent charging period t₂ in each cycle of operation where T = t₁ + t₂ such that the value ω

₂ t₂ equals substantially π

/2 radiant or greater where ω

₂ = 1/√

L₂ C₁ whereby the reapplied forward voltage across the semiconductor thyristor switching device following each conduction interval is maintained substantially independent of load and the storage of adequate commutating energy for the thyristor switching device intermediate each conduction interval, is assured.

60. An improved power supply and control circuit comprising inverter circuit means having only a single bidirectional conducting gate controlled power thyristor for supplying a load with periodic energization currents, rectifier means for supplying a rectified, semi-filtered unidirectional high voltage excitation potential for said inverter circuit means, gating circuit means for periodically gating on said inverter circuit means, means for deriving a low voltage unidirectional excitation potential, said gating circuit means comprising timing circuit means supplied by said low voltage excitation potential, low voltage switching means connected to and controlled by said timing circuit means, said low voltage switching means being rendered conductive upon said timing circuit means attaining a preset value, a power rated semiconductor switching device having a relatively flat current vs. voltage conducting characteristic and having its load terminals connected across the output from said rectifier means as a source of excitation potential, the control gate of said constant current semiconductor switching device being responsive to the low voltage switching means, and gating signal output circuit means connected in series circuit relationship with the constant current power rated semiconductor switching device and adapted for connection to the control gate of the gate controlled power thyristor comprising a part of the inverter circuit means.

61. An improved power supply circuit and control according to claim 60, wherein the constant current high voltage semiconductor device comprises a high voltage switching transistor and the gating signal output means comprises an isolating transformer having its primary winding connected in the emitter-collector circuit of the high voltage switching transistor and having its secondary winding adapted to be connected to the control gate of the large power rated thyristor in the inverter circuit means.

62. An improved power supply circuit and control according to claim 60 further including soft-starting zero point energization switching means controlling the operation of said gating circuit means, and zero point sensing and turn-on circuit means coupled to and controlling said soft starting zero point energization switching means for rendering the same conductive only near the beginning of each cycle of the rectified semi-filtered unidirectional excitation potential.

63. An improved power supply circuit and control according to claim 62 further including inhibit control means for inhibiting operation of said zero point sensing and turn-on circuit means to assure the storage of adequate commutating energy in the inverter circuit means during initial start-up.

64. An improved power supply circuit and control according to claim 63 further including means for sensing the operating condition of a load supplied by the inverter circuit means and deriving an on-off control signal in response to the load condition for controlling operation of said inhibit control means.

65. An improved power supply circuit and control according to claim 63 further including capacitor switching means coupled to the inverter circuit means and to the inhibit control means and operable during non-conducting intervals of the inverter circuit means to switch different values of commutating capacitance into effective circuit relationship in the inverter circuit means to thereby control the power generated by the circuit, said inhibit control means inhibiting operation of the inverter circuit means during the switching operation.

66. An improved power supply circuit and control according to claim 60 futher including dv/dt sensing means comprising a series connected resistor and capacitor connected across the switching thyristor comprising a part of the inverter circuit means, said series connected resistor and capacitor serving to limit the rate of rise of reapplied forward voltage across the switching thyristor, signal rectifying and shaping circuit means coupled to said series connected resistor and capacitor for deriving an output dv/dt control signal therefrom representative of the rate of reapplied forward voltage across the switching thyristor, and means for applying the dv/dt control signal back to the gating circuit means for modifying operation of the inverter circuit means in a direction to provide a lesser dv/dt value.

67. An improved power supply circuit and control according to claim 60 further including means for sensing the operating condition of the load comprising an opto-electronic sensing circuit connected across the output of said rectifier means for deriving a ripple factor control voltage representative of the ripple present in the output from said rectifier means and indicative of the loading conditions on the power supply circuit, and means for automatically modifying the operation of the inverter to cut back the power output in response to a sensed predetermined magnitude of ripple.

68. An improved power supply circuit and control according to claim 60 wherein the gating circuit means coupled to the control gate of the thyristor switching device renders the device conductive at a controlled frequency of operation that provides an operating period T for the chopper inverter including a quiescent charging period t₂ in each cycle of operation where T = t₁ + t₂, the value t is determined by the commutating frequency of the inverter circuit means, and the value ω

₂ t₂ equals substantially π

/2 radians or greater at the operating frequency 1/T where ω

₂ = 1/√

L₂ C₁ whereby the reapplied forward voltage across the semiconductor thyristor switching device following each conduction interval is maintained substantially independent of load and the storage of adequate commutating energy for the thyristor switching device intermediate each conduction interval, is assured.

69. An improved power supply circuit and control according to claim 68 further including a smoothing inductor having an inductance L₃ and smoothing capacitor having a capacitance C₃ connected in series circuit relationship across at least one of the commutating components of the inverter circuit means and having impedance values such that the combined impedance of the commutating components, the smoothing inductor and the smoothing capacitor series resonates to establish the commutating period t₁, and wherein the smoothing inductor and capacitor shape the output current flowing through the smoothing inductor to substantially a sinusoidal waveshape having little or no radio frequency interference emission effects, and improved power coupling, and the load is coupled to and derives output power from the smoothing inductor.