Multimode power converter

• US 5,900,722 A
• Filed: 08/12/1996
• Issued: 05/04/1999
• Est. Priority Date: 09/14/1994
• Status: Expired due to Fees

• Current Assignee: Pramac America LLC
• Original Assignee: Coleman Company Incorporated (Newell Brands Inc.)
• Inventors: Anderson, William, Scott, Harold C., Sun, Chiping, Pandya, Kandarp I.
• Primary Examiner(s): Stephan, Steven L.
• Assistant Examiner(s): Ponomarenko, Nicholas
• Application Number:
  US08/695,558
• Time in Patent Office: 995 Days
• Field of Search: 322/46, 322/29, 290/49
• US Class Current: 322/46
• CPC Class Codes: B23K 9/1062 with computing means
• CPC Class Codes: F02B 2063/045 Frames for generator-engine sets
• CPC Class Codes: F02B 2063/046 Handles adapted therefor, e.g. handles or grips for movable units
• CPC Class Codes: F02B 63/04 for electric generators
• CPC Class Codes: F02B 63/044 the engine-generator unit being placed on a frame or in an housing
• CPC Class Codes: F02B 75/16 Engines characterised by number of cylinders, e.g. single-cylinder engines F02B75/26 takes precedence
• CPC Class Codes: F05C 2201/021 Aluminium
• CPC Class Codes: H02K 1/278 Surface mounted magnets; Inset magnets
• CPC Class Codes: H02K 1/2786 Outer rotors
• CPC Class Codes: H02K 21/48 Generators with two or more outputs
• CPC Class Codes: H02K 3/28 Layout of windings or of connections between windings windings for pole-changing H02K17/06, H02K17/14, H02K19/12, H02K19/32
• CPC Class Codes: H02K 7/1815 structurally associated with reciprocating piston engines general aspects of generating sets, e.g. housing, F02B63/04
• CPC Class Codes: H02M 7/00 Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
• CPC Class Codes: H02M 7/483 Converters with outputs that each can have more than two voltages levels
• CPC Class Codes: H02P 2101/45 for motor vehicles, e.g. car alternators
• CPC Class Codes: H02P 25/188 wherein the motor windings are switched from series to parallel or vice versa to control speed or torque
• CPC Class Codes: H02P 9/04 Control effected upon non-electric prime mover and dependent upon electric output value of the generator
• CPC Class Codes: H02P 9/107 for limiting effects of overloads
• CPC Class Codes: H02P 9/14 by variation of field H02P9/08, H02P9/10 take precedence
• CPC Class Codes: H02P 9/30 using semiconductor devices
• CPC Class Codes: H02P 9/48 : Arrangements for obtaining a constant output value at varying speed of the generator, e.g. on vehicle H02P9/04 - H02P9/46 take precedence

Abstract

A particularly advantageous power converter, suitable for use in an engine powered generator system. A signal simulating a desired AC waveform is produced by a converter circuit at first and second converter output terminals. The converter circuit, responsive to respective switching signals applied thereto, selectively effects current paths between a juncture node and one of the first and second converter output terminals and between a common rail and the other of the first and second converter output terminals. A controller selectively generates control signals to the converter circuit and to a mechanism for varying the magnitude of the juncture node voltage, to create a predetermined waveform at the converter output terminals simulating the desired AC waveform. A number of alternative embodiments for producing a simulated sine wave are described, as well as accommodations for inductive loads, and mechanisms for minimizing power dissipation during the switching interval.

Claims

1. Apparatus for producing a signal simulating a desired AC waveform having a sloped rising edge, comprising:

first and second converter output terminals;

a juncture node, at a voltage of predetermined polarity and variable magnitude relative to a common rail;

a converter circuit, responsive to control signals applied thereto, for selectively effecting current paths between the juncture node and one of the first and second converter output terminals and between the common rail and the other of the first and second converter output terminals;

means, responsive to control signals applied thereto, for controllably varying the magnitude of the juncture node voltage; and

a controller for selectively generating the control signals to the converter circuit and means for varying the magnitude of the juncture node voltage, to create a predetermined waveform having a sloped rising edge at the converter output terminals, simulating the desired AC waveform.

2. The apparatus of claim 1, wherein the controller comprises a programmed microcomputer.

3. The apparatus of claim 1, wherein the controller generates, in sequence:

a first control signal to the converter to cause the converter to effect a current path between the juncture node and the first converter output terminal and between the common rail and the second converter output terminal, the magnitude of the juncture node voltage initially being at a first level;

a second control signal to the means for varying the magnitude of the juncture node voltage, to initiate a change in the magnitude of the juncture node voltage to a second level, greater than the first level;

a third control signal to the means for varying the magnitude of the juncture node voltage, to initiate a change in the magnitude of the juncture node voltage back to the first level;

a fourth control signal to the converter to cause the converter to effectively break at least one of the current paths between the juncture node and the first converter output terminal and between the common rail and the second converter output terminal; and

a fifth control signal to the converter to cause the converter to effect a current path between the juncture node and the second converter output terminal and between the common rail and the first converter output terminal.

4. The apparatus of claim 3, wherein:

the fourth control signal to the converter causes the converter to effectively break the current path between the juncture node and the first converter output terminal, and

the controller generates, after the fourth control signal but before the fifth control signal, a further control signal to the converter to cause the converter to effectively break the current path between the common rail and the second converter output terminal.

5. The apparatus of claim 1, wherein the converter circuit comprises:

a first power switch circuit, electrically connected to the juncture node, and to the first converter output terminal, disposed to, responsive to control signals applied thereto, selectively effect a current path between the juncture node and the first converter output terminal; and

a second power switch circuit, electrically connected to the juncture node, and to the second converter output terminal, disposed to, responsive to control signals applied thereto, selectively effect a current path between the juncture node, and the second converter output terminal;

a third power switch circuit, electrically connected to the common rail, and to the first converter output terminal, disposed to, responsive to control signals applied thereto, selectively effect a current path between the common rail and the first converter output terminal;

a fourth power switch circuit, electrically connected to the common rail, and to the second converter output terminal, disposed to, responsive to control signals applied thereto, selectively effect a current path between the common rail and the second converter output terminal.

6. The apparatus of claim 5, wherein the controller generates, in sequence:

first control signals to first and fourth power switch circuits to initiate current paths between the juncture node and the first converter output terminal and between the common rail and the second converter output terminal, the magnitude of the juncture node voltage initially being at a first level;

a second control signal to the means for varying the magnitude of the juncture node voltage, to initiate a change in the magnitude of the juncture node voltage to a second level, greater than the first level;

a third control signal to the means for varying the magnitude of the juncture node voltage, to initiate a change in the magnitude of the juncture node voltage back to the first level;

fourth control signals to at least one of the first and fourth power switch circuits to cause the converter to effectively break at least one of the current paths between the juncture node and the first converter output terminal and between the common rail and the second converter output terminal; and

a fifth control signal to the converter to cause the converter to effect a current path between the juncture node and the second converter output terminal and between the common rail and the first converter output terminal.

7. The apparatus of claim 6, wherein:

the fourth control signal to the converter causes the converter to effectively break the current path between the juncture node and the first converter output terminal, and

the controller generates, after the fourth control signal but before the fifth control signal, a further control signal to the converter to cause the converter to effectively break the current path between the common rail and the second converter output terminal.

8. The apparatus of claim 5 wherein each power switch circuit comprises a power switching device and a firing circuit for turning the power device on and off in accordance with the control signals;

and

the firing circuits for the first and second power switch circuits comprise means for quickly driving the associated power switching device into a saturated state when the associated control signal changes state to minimize power dissipation during the switching interval.

9. The apparatus of claim 5 wherein each power switch circuit comprises a power switching device and a firing circuit for generating actuating signals to turn the power device on and off in accordance with the control signals;

and the firing circuits for the first and second power switch circuits comprise;

a capacitor;

a resistance cooperating with the capacitor to produce a predetermined discharge time constant;

a switching circuit disposed to selectively effect connections to develop a voltage on the capacitor in excess of that required to render the power switching device fully conductive during periods when the switching device is non-conductive, and

provide a discharge path for the capacitor to provide the actuating signal to the switching device in response to the control signal;

the discharge time constant of the capacitor being such that the charge on the capacitor is only slightly above the threshold value required to render the power switching device fully conductive at the time the switching device is rendered non-conductive.

10. The apparatus of claim 1 wherein the means for controllably varying the magnitude of the juncture node voltage comprises:

a capacitor; and

a switching circuit, for, responsive to control signals applied thereto, selectively effecting a charging path to the capacitor during dead time periods when no connection is effected by the converter, and selectively effecting a discharge path from the capacitor to the juncture node during a predetermined portion of the periods when the converter effects a current path between the juncture node and one of the first and second converter output terminals.

11. The apparatus of claim 5 wherein the means for controllably varying the magnitude of the juncture node voltage comprises:

a capacitor; and

a switching circuit, for, responsive to control signals applied thereto, selectively effecting a charging path to the capacitor during dead time periods when none of the power switch circuits is conducting, and selectively effecting a discharge path from the capacitor to the juncture node during a predetermined portion of the periods when one of the power switch circuits effect a current path between the juncture node and one of the first and second converter output terminals.

12. The apparatus of claim 1 wherein the means for controllably varying the magnitude of the juncture node voltage comprises:

a capacitance, and

a switching circuit, electrically connected to the capacitance, disposed to, responsive to control signals applied thereto, selectively effect a current path between the juncture node and the common rail through the capacitance.

13. The apparatus of claim 12, wherein the controller for selectively generating the control signals to the converter circuit and means for varying the magnitude of the juncture node voltage, generates:

a first control signal to the converter to cause the converter to effect a current path between the juncture node and the first converter output terminal and between the common rail and the second converter output terminal, the magnitude of the juncture node voltage initially being at a first level;

a second control signal to the means for varying the magnitude of the juncture node voltage, to initiate a change in the magnitude of the juncture node voltage to a second level, greater than the first level;

a third control signal to the means for varying the magnitude of the juncture node voltage, to initiate a change in the magnitude of the juncture node voltage back to the first level;

a fourth control signal to the converter to cause the converter to effectively break at least one of the current paths between the juncture node and the first converter output terminal and between the common rail and the second converter output terminal; and

a fifth control signal to the converter to cause the converter to effect a current path between the juncture node and the second converter output terminal and between the common rail and the first converter output terminal.

14. The apparatus of claim 13, wherein:

the fourth control signal to the converter causes the converter to effectively break the current path between the juncture node and the first converter output terminal, and

the controller generates, after the fourth control signal but before the fifth control signal, a further control signal to the converter to cause the converter to effectively break the current path between the common rail and the second converter output terminal.

15. The apparatus of claim 13, wherein:

the second control signal comprises a control signal to the switching circuit, electrically connected to the capacitance, to effect a current path between the juncture node and the common rail through the capacitance;

the third control signal comprises a control signal to the switching circuit, electrically connected to the capacitance, to effectively break the current path between the juncture node and the common rail through the capacitance.

16. The apparatus of claim 12 further including means for controllably discharging the capacitance, to facilitate generation of a relatively low voltage across the converter output terminals.

17. The apparatus of claim 12, wherein the converter circuit comprises:

a first power switch circuit, electrically connected to the juncture node, and to the first converter output terminal, disposed to, responsive to control signals applied thereto, selectively effect a current path between the juncture node and the first converter output terminal; and

a second power switch circuit, electrically connected to the juncture node, and to the second converter output terminal, disposed to, responsive to control signals applied thereto, selectively effect a current path between the juncture node, and the second converter output terminal;

a third power switch circuit, electrically connected to the common rail, and to the first converter output terminal, disposed to, responsive to control signals applied thereto, selectively effect a current path between the common rail and the first converter output terminal;

a fourth power switch circuit, electrically connected to the common rail, and to the second converter output terminal, disposed to, responsive to control signals applied thereto, selectively effect a current path between the common rail and the second converter output terminal.

18. The apparatus of claim 17 including means for selectively rendering at least one of the third or fourth power switch circuits partially conductive whereby the capacitance is controllably discharged through a resistance.

19. The apparatus of claim 17 wherein at least one of the third or fourth power switch circuits comprises:

a switching device which is rendered fully conductive by application thereto of a control signal of a first predetermined magnitude, and rendered into a linear mode of operation by application thereto of a control signal of a second predetermined magnitude; and

driver circuits for selectively applying respective control signals of said first and second magnitudes.

20. The apparatus of claim 5 wherein at least one of the third or fourth power switch circuits comprises:

a switching device which is rendered fully conductive by application thereto of a control signal of a first predetermined magnitude, and rendered into a linear mode of operation by application thereto of a control signal of a second predetermined magnitude; and

driver circuits for selectively applying respective control signals of said first and second magnitudes.

21. The apparatus of claim 5 wherein:

the first and fourth power switch circuits are independently controlled; and

the second and third power switch circuits are independently controlled.

22. The apparatus of claim 5 wherein:

the control signals applied to the first and fourth power switch circuits are of different duration; and

the control signals applied to the second and third power switch circuits are of different duration.

23. The apparatus of claim 1 wherein the means for controllably varying the magnitude of the juncture node voltage comprises:

a generator with a rotor and a stator, and

an auxiliary winding disposed such that relative movement between rotor and stator induces a current therein; and

a switching circuit, for, responsive to control signals applied thereto, selectively effecting a connection to the auxiliary winding during a predetermined portion of the periods when one of the power switch circuits effect a current path between the juncture node and one of the converter output terminals.

42. The apparatus of claim 1, wherein the means for controllably varying the magnitude of the juncture node voltage comprises:

a rotor, adapted for selective rotation;

a stator, including at least one stator winding disposed such that rotation of the rotor induces current in the stator winding; and

a switching circuit, responsive to control signals applied thereto, selectively applying a voltage developed from the current induced in the stator winding between the juncture node and common rail.

43. The apparatus of claim 42 wherein the means for controllably varying the magnitude of the juncture node voltage further comprises a capacitance disposed to develop a voltage from the current induced in the stator winding.

44. The apparatus of claim 43, further comprising means for rotating the rotor.

45. The apparatus of claim 43 wherein the means for controllably varying the magnitude of the juncture node voltage further comprises a further switching circuit disposed to selectively connect and disconnect the capacitance between the juncture node and the common rail.

46. The apparatus of claim 1, wherein the means for controllably varying the magnitude of the juncture node voltage comprises:

a rotor, adapted for selective rotation;

a stator, including a plurality of stator windings disposed such that rotation of the rotor induces current in the stator windings; and

a switching circuit, responsive to control signals applied thereto, selectively completing current paths between individual stator windings and the juncture node.

48. The apparatus of claim 46, wherein the means for generating the unipolar rail voltage comprises:

a rotor, adapted for selective rotation;

a stator, including at least one stator winding disposed such that rotation of the rotor induces current in the stator winding; and

a switching circuit, responsive to control signals applied thereto, selectively applying a voltage developed from the current induced in the stator winding between the juncture node and common rail.

50. The apparatus of claim 48 wherein the means for generating the unipolar rail voltage further comprises a further switching circuit disposed to selectively connect and disconnect the capacitance between the juncture node and the common rail.

52. The apparatus of claim 50, wherein the means for generating the junction node signal comprises:

a rotor, adapted for selective rotation;

a stator, including at least one stator winding disposed such that rotation of the rotor induces current in the stator winding; and

a switching circuit, responsive to control signals applied thereto, selectively effecting a current path between the stator winding and the juncture node.

79. The apparatus of claim 5, wherein the controller generates, in sequence:

first control signals to first and fourth power switch circuits to initiate current paths between the juncture node and the first converter output terminal and between the common rail and the second converter output terminal, the magnitude of the juncture node voltage initially being at a first level;

a second control signal to the means for varying the magnitude of the juncture node voltage, to initiate a change in the magnitude of the juncture node voltage to a second level, greater than the first level;

a third control signal to the means for varying the magnitude of the juncture node voltage, to initiate a change in the magnitude of the juncture node voltage back to the first level;

fourth control signals to at least one of the first and fourth power switch circuits to cause the converter to effectively break at least one of the current paths between the juncture node and the first converter output terminal and between the common rail and the second converter output terminal; and

a fifth control signal to the converter to cause the converter to effect a current path between the juncture node and the second converter output terminal and between the common rail and the first converter output terminal.

80. The apparatus of claim 79, wherein:

the fourth control signal to the converter causes the converter to effectively break the current path between the juncture node and the first converter output terminal; and

the controller generates, after the fourth control signal but before the fifth control signal, a further control signal to the converter to cause the converter to effectively break the current path between the common rail and the second converter output terminal.

24. Apparatus comprising:

first and second rails, adapted to have a rectified rail voltage applied therebetween;

first and second converter output terminals;

a first power switch circuit, electrically connected to the first rail, and to the first converter output terminal, disposed to, responsive to control signals applied thereto, selectively effect a current path between the first rail and the first converter output terminal; and

a second power switch circuit, electrically connected to the first rail, and to the second converter output terminal, disposed to, responsive to control signals applied thereto, selectively effect a current path between the first rail, and the second converter output terminal;

a third power switch circuit, electrically connected to the second rail, and to the first converter output terminal, disposed to, responsive to control signals applied thereto, selectively effect a current path between the second rail and the first converter output terminal; and

a fourth power switch circuit, electrically connected to the second rail, and to the second converter output terminal, disposed to, responsive to control signals applied thereto, selectively effect a current path between the second rail and the second converter output terminal; and

a controller for selectively generating the control signals to the power switch circuits to create a predetermined waveform having a sloped rising edge at the converter output terminals simulating a desired AC waveform;

wherein

each power switch circuit comprises a power switching device and a firing circuit for turning the power switching device on and off in accordance with the control signals; and

the firing circuits for the first and second power switch circuits comprise means for quickly driving the associated power switching device into a saturated state when the associated control signal changes state to minimize power dissipation during the switching interval.

25. The system of claim 24 wherein the first and second power switch circuits are isolated power switch circuits and the third and fourth power switch circuits are non-isolated power switch circuits.

26. The system of claim 24 wherein the power switching device is a power transistor.

27. The system of claim 24, further comprising means for varying the magnitude of the rail voltage, wherein the controller generates, in sequence:

first control signals to first and fourth power switch circuits to initiate current paths between the first rail and the first converter output terminal and between the second rail and the second converter output terminal, the magnitude of the rail voltage initially being at a first level;

a second control signal to the means for varying the magnitude of the rail voltage, to initiate a change in the magnitude of the rail voltage to a second level, greater than the first level;

a third control signal to the means for varying the magnitude of the rail voltage, to initiate a change in the magnitude of the rail voltage back to the first level;

fourth control signals to at least one of the first and fourth power switch circuits to cause the converter to effectively break at least one of the current paths between the first rail and the first converter output terminal and between the second rail and the second converter output terminal; and

fifth control signals to the first and fourth power switch circuits to cause the converter to effect a current path between the first rail and the second converter output terminal and between the second rail and the first converter output terminal.

28. The apparatus of claim 27, wherein:

the fourth control signal to the converter causes the converter to effectively break the current path between the juncture node and the first converter output terminal, and

the controller generates, after the fourth control signal but before the fifth control signal, a further control signal to the converter to cause the converter to effectively break the current path between the common rail and the second converter output terminal.

29. The apparatus of claim 24 wherein:

the first and fourth power switch circuits are independently controlled; and

the second and third power switch circuits are independently controlled.

30. The apparatus of claim 24 wherein:

the control signals applied to the first and fourth power switch circuits are of different duration; and

the control signals applied to the second and third power switch circuits are of different duration.

47. The apparatus of claim 24 further comprising means for generating the unipolar rail voltage.

49. The apparatus of claim 47 wherein the means for generating the unipolar rail voltage further comprises a capacitance disposed to develop a voltage from the current induced in the stator winding.

31. Apparatus comprising:

first and second converter output terminals;

a juncture node, receptive of a rectified signal relative to a common rail;

a first power switch circuit, electrically connected to the juncture node, and to the first converter output terminal, disposed to, responsive to control signals applied thereto, selectively effect a current path between the juncture node and the first converter output terminal; and

a second power switch circuit, electrically connected to the juncture node, and to the second converter output terminal, disposed to, responsive to control signals applied thereto, selectively effect a current path between the juncture node, and the second converter output terminal;

a third power switch circuit, electrically connected to the common rail, and to the first converter output terminal, disposed to, responsive to control signals applied thereto, selectively effect a current path between the common rail and the first converter output terminal;

a fourth power switch circuit, electrically connected to the common rail, and to the second converter output terminal, disposed to, responsive to control signals applied thereto, selectively effect a current path between the common rail and the second converter output terminal;

a capacitance;

a fifth power switch circuit, electrically connected to the capacitance, disposed to, responsive to control signals applied thereto, selectively effect a current path between the juncture node and the common rail through the capacitance; and

a controller for selectively generating the control signals to the power switch circuits to create a predetermined waveform having a sloped rising edge at the converter output terminals simulating a desired AC waveform.

32. The apparatus of claim 31 further including means for controllably discharging the capacitance, to facilitate generation of a relatively low voltage across the converter output terminals.

33. The apparatus of claim 31 including means for selectively rendering at least one of the third or fourth power switch circuits partially conductive whereby the capacitance is controllably discharged through a resistance.

34. The apparatus of claim 31 wherein at least one of the third or fourth power switch circuits comprises:

a switching device which is rendered fully conductive by application thereto of a control signal of a first predetermined magnitude, and rendered into a linear mode of operation by application thereto of a control signal of a second predetermined magnitude; and

driver circuits for selectively applying respective control signals of said first and second magnitudes.

35. The apparatus of claim 31 wherein:

the first and fourth power switch circuits are independently controlled; and

the second and third power switch circuits are independently controlled.

36. The apparatus of claim 31 wherein:

the control signals applied to the first and fourth power switch circuits are of different duration; and

the control signals applied to the second and third power switch circuits are of different duration.

51. The apparatus of claim 31 further comprising means for generating the junction node signal.

53. The apparatus of claim 51, further comprising means for rotating the rotor.

55. The apparatus of claim 53, wherein the controller generates, in sequence:

a first control signal to the converter to cause the converter to effect a current path between the juncture node and the first converter output terminal and between the common rail and the second converter output terminal, the magnitude of the juncture node voltage initially being at a first level;

a second control signal to the means for varying the magnitude of the juncture node voltage, to initiate a change in the magnitude of the juncture node voltage to a second level, greater than the first level;

a third control signal to the means for varying the magnitude of the juncture node voltage, to initiate a change in the magnitude of the juncture node voltage back to the first level;

a fourth control signal to the converter to cause the converter to effectively break at least one of the current paths between the juncture node and the first converter output terminal and between the common rail and the second converter output terminal; and

a fifth control signal to the converter to cause the converter to effect a current path between the juncture node and the second converter output terminal and between the common rail and the first converter output terminal.

57. The apparatus of claim 53, wherein the converter circuit comprises:

a first power switch circuit, electrically connected to the juncture node, and to the first converter output terminal, disposed to, responsive to control signals applied thereto, selectively effect a current path between the juncture node and the first converter output terminal;

a second power switch circuit, electrically connected to the juncture node, and to the second converter output terminal, disposed to, responsive to control signals applied thereto, selectively effect a current path between the juncture node, and the second converter output terminal;

a third power switch circuit, electrically connected to the common rail, and to the first converter output terminal, disposed to, responsive to control signals applied thereto, selectively effect a current path between the common rail and the first converter output terminal; and

a fourth power switch circuit, electrically connected to the common rail, and to the second converter output terminal, disposed to, responsive to control signals applied thereto, selectively effect a current path between the common rail and the second converter output terminal.

59. The apparatus of claim 57, wherein:

the fourth control signal to the converter causes the converter to effectively break the current path between the juncture node and the first converter output terminal; and

the controller generates, after the fourth control signal but before the fifth control signal, a further control signal to the converter to cause the converter to effectively break the current path between the common rail and the second converter output terminal.

62. The apparatus of claim 53 wherein the means for controllably varying the magnitude of the juncture node voltage comprises:

a capacitor; and

a switching circuit, for, responsive to control signals applied thereto, selectively effecting a charging path to the capacitor during dead time periods when no connection is effected by the converter, and selectively effecting a discharge path from the capacitor to the juncture node during a predetermined portion of the periods when the converter effects a current path between the juncture node and one of the first and second converter output terminals.

64. The apparatus of claim 53 wherein the means for controllably varying the magnitude of the juncture node voltage comprises:

a capacitance; and

a switching circuit, electrically connected to the capacitance, disposed to, responsive to control signals applied thereto, selectively effect a current path between the juncture node and the common rail through the capacitance.

66. The apparatus of claim 64, wherein:

the fourth control signal to the converter causes the converter to effectively break the current path between the juncture node and the first converter output terminal; and

the controller generates, after the fourth control signal but before the fifth control signal, a further control signal to the converter to cause the converter to effectively break the current path between the common rail and the second converter output terminal.

67. The apparatus of claim 64, wherein:

the second control signal comprises a control signal to the switching circuit, electrically connected to the capacitance, to effect a current path between the juncture node and the common rail through the capacitance; and

the third control signal comprises a control signal to the switching circuit, electrically connected to the capacitance, to effectively break the current path between the juncture node and the common rail through the capacitance.

75. The apparatus of claim 53 wherein the means for controllably varying the magnitude of the juncture node voltage comprises:

a generator with a rotor and a stator;

an auxiliary winding disposed such that relative movement between rotor and stator induces a current therein; and

a switching circuit, for, responsive to control signals applied thereto, selectively effecting a connection to the auxiliary winding during a predetermined portion of the periods when one of the power switch circuits effect a current path between the juncture node and one of the converter output terminals.

77. The apparatus of claim 75, wherein:

the fourth control signal to the converter causes the converter to effectively break the current path between the juncture node and the first converter output terminal; and

the controller generates, after the fourth control signal but before the fifth control signal, a further control signal to the converter to cause the converter to effectively break the current path between the common rail and the second converter output terminal.

81. The apparatus of claim 77 wherein each power switch circuit comprises a power switching device and a firing circuit for turning the power device on and off in accordance with the control signals;

and

the firing circuits for the first and second power switch circuits comprise means for quickly driving the associated power switching device into a saturated state when the associated control signal changes state to minimize power dissipation during the switching interval.

82. The apparatus of claim 77 wherein each power switch circuit comprises a power switching device and a firing circuit for generating actuating signals to turn the power device on and off in accordance with the control signals;

and the firing circuits for the first and second power switch circuits comprise;

a capacitor;

a resistance cooperating with the capacitor to produce a predetermined discharge time constant; and

a switching circuit disposed to selectively effect connections to develop a voltage on the capacitor in excess of that required to render the power switching device fully conductive during periods when the switching device is non-conductive, and

provide a discharge path for the capacitor to provide the actuating signal to the switching device in response to the control signal

the discharge time constant of the capacitor being such that the charge on the capacitor is only slightly above the threshold value required to render the power switching device fully conductive at the time the switching device is rendered non-conductive.

83. The apparatus of claim 77 wherein the means for controllably varying the magnitude of the juncture node voltage comprises:

a capacitor; and

a switching circuit, for, responsive to control signals applied thereto, selectively effecting a charging path to the capacitor during dead time periods when none of power switch circuits are conducting, and selectively effecting a discharge path from the capacitor to the juncture node during a predetermined portion of the periods when one of the power switch circuits effect a current path between the juncture node and one of the first and second converter output terminals.

84. The apparatus of claim 77 wherein the means for controllably varying the magnitude of the juncture node voltage comprises:

a capacitance; and

a switching circuit, electrically connected to the capacitance, disposed to, responsive to control signals applied thereto, selectively effect a current path between the juncture node and the common rail through the capacitance.

85. The apparatus of claim 83 further including means for controllably discharging the capacitance, to facilitate generation of a relatively low voltage across the converter output terminals.

86. The apparatus of claim 77 wherein at least one of the third or fourth power switch circuits comprises:

a switching device which is rendered fully conductive by application thereto of a control signal of a first predetermined magnitude, and rendered into a linear mode of operation by application thereto of a control signal of a second predetermined magnitude; and

driver circuits for selectively applying respective control signals of said first and second magnitudes.

87. The apparatus of claim 77 wherein:

the first and fourth power switch circuits are independently controlled; and

the second and third power switch circuits are independently controlled.

88. The apparatus of claim 77 wherein:

the control signals applied to the first and fourth power switch circuits are of different duration; and

the control signals applied to the second and third power switch circuits are of different duration.

90. The apparatus of claim 88, wherein the controller for selectively generating the control signals to the converter circuit and means for varying the magnitude of the juncture node voltage, generates:

a first control signal to the converter to cause the converter to effect a current path between the juncture node and the first converter output terminal and between the common rail and the second converter output terminal, the magnitude of the juncture node voltage initially being at a first level;

a second control signal to the means for varying the magnitude of the juncture node voltage, to initiate a change in the magnitude of the juncture node voltage to a second level, greater than the first level;

a third control signal to the means for varying the magnitude of the juncture node voltage, to initiate a change in the magnitude of the juncture node voltage back to the first level;

a fourth control signal to the converter to cause the converter to effectively break at least one of the current paths between the juncture node and the first converter output terminal and between the common rail and the second converter output terminal; and

a fifth control signal to the converter to cause the converter to effect a current path between the juncture node and the second converter output terminal and between the common rail and the first converter output terminal.

93. The apparatus of claim 88 further including means for controllably discharging the capacitance, to facilitate generation of a relatively low voltage across the converter output terminals.

37. Apparatus comprising:

high, intermediate, and common DC rails, an intermediate DC rail signal being applied between the intermediate and common rails, and a high DC rail signal being applied between the high and common rails;

first and second converter output terminals;

a juncture node, receptive of the intermediate DC rail signal;

a first power switch circuit, electrically connected to the juncture node, and to the first converter output terminal, disposed to, responsive to control signals applied thereto, selectively effect a current path between the juncture node and the first converter output terminal; and

a second power switch circuit, electrically connected to the juncture node, and to the second converter output terminal, disposed to, responsive to control signals applied thereto, selectively effect a current path between the juncture node, and the second converter output terminal;

a third power switch circuit, electrically connected to the juncture node, and to the high DC rail, disposed to, responsive to control signals applied thereto, selectively effect a current path between the high DC rail and the juncture node;

a fourth power switch circuit, electrically connected to the common DC rail, and to the first converter output terminal, disposed to, responsive to control signals applied thereto, selectively effect a current path between the common DC rail and the first converter output terminal;

a fifth power switch circuit, electrically connected to the common DC rail, and to the second converter output terminal, disposed to, responsive to control signals applied thereto, selectively effect a current path between the common DC rail and the second converter output terminal; and

a controller for selectively generating the control signals to the power switch circuits to create a predetermined waveform having a sloped rising edge at the converter output terminals simulating a desired AC signal.

38. The system of claim 37 wherein the first and second power switch circuits are isolated power switch circuits and the third and fourth power switch circuits are non-isolated power switch circuits.

39. The system of claim 37 wherein each power switch circuit comprises a power switching device and a firing circuit for turning the power switching device on and off in accordance with the control signals.

40. The system of claim 39 wherein the power switching device is a power transistor.

41. The system of claim 39 wherein the firing circuits for the first, second and third power switch circuits comprise means for quickly driving the associated power switching device into a saturated state when the associated control signal changes state to minimize power dissipation during the switching interval.

54. Apparatus for producing a signal simulating a desired AC waveform having a sloped rising edge, comprising:

first and second converter output terminals;

a juncture node, at a voltage of variable magnitude relative to a common rail;

a converter circuit, responsive to respective control signals applied thereto, for selectively effecting current paths between the juncture node and one of the first and second converter output terminals and between the common rail and the other of the first and second converter output terminals;

means, responsive to control signals applied thereto, for controllably varying the magnitude of the juncture node voltage; and

means, for selectively generating the control signals to the converter circuit and to the means for varying the magnitude of the juncture node voltage, to create a predetermined waveform at the converter output terminals simulating the desired AC waveform.

56. The apparatus of claim 54, wherein:

the fourth control signal to the converter causes the converter to effectively break the current path between the juncture node and the first converter output terminal; and

the controller generates, after the fourth control signal but before the fifth control signal, a further control signal to the converter to cause the converter to effectively break the current path between the common rail and the second converter output terminal.

58. The apparatus of claim 56, wherein the controller generates, in sequence:

first control signals to first and fourth power switch circuits to initiate current paths between the juncture node and the first converter output terminal and between the common rail and the second converter output terminal, the magnitude of the juncture node voltage initially being at a first level;

a second control signal to the means for varying the magnitude of the juncture node voltage, to initiate a change in the magnitude of the juncture node voltage to a second level, greater than the first level;

a third control signal to the means for varying the magnitude of the juncture node voltage, to initiate a change in the magnitude of the juncture node voltage back to the first level;

fourth control signals to at least one of the first and fourth power switch circuits to cause the converter to effectively break at least one of the current paths between the juncture node and the first converter output terminal and between the common rail and the second converter output terminal; and

a fifth control signal to the converter to cause the converter to effect a current path between the juncture node and the second converter output terminal and between the common rail and the first converter output terminal.

60. The apparatus of claim 56 wherein each power switch circuit comprises a power switching device and a firing circuit for turning the power device on and off in accordance with the control signals;

and

the firing circuits for the first and second power switch circuits comprise means for quickly driving the associated power switching device into a saturated state when the associated control signal changes state to minimize power dissipation during the switching interval.

61. The apparatus of claim 56 wherein each power switch circuit comprises a power switching device and a firing circuit for generating actuating signals to turn the power device on and off in accordance with the control signals;

and the firing circuits for the first and second power switch circuits comprise;

a capacitor;

a resistance cooperating with the capacitor to produce a predetermined discharge time constant; and

a switching circuit disposed to selectively effect connections to develop a voltage on the capacitor in excess of that required to render the power switching device fully conductive during periods when the switching device is non-conductive, and

provide a discharge path for the capacitor to provide the actuating signal to the switching device in response to the control signal,

the discharge time constant of the capacitor being such that the charge on the capacitor is only slightly above the threshold value required to render the power switching device fully conductive at the time the switching device is rendered non-conductive.

63. The apparatus of claim 56 wherein the means for controllably varying the magnitude of the juncture node voltage comprises:

a capacitor; and

a switching circuit, for, responsive to control signals applied thereto, selectively effecting a charging path to the capacitor during dead time periods when none of power switch circuits are during a predetermined portion of the periods when one of the power switch circuits effect a current path between the juncture node and one of the first and second converter output terminals.

65. The apparatus of claim 63, wherein the controller for selectively generating the control signals to the converter circuit and means for varying the magnitude of the juncture node voltage, generates:

a first control signal to the converter to cause the converter to effect a current path between the juncture node and the first converter output terminal and between the common rail and the second converter output terminal, the magnitude of the juncture node voltage initially being at a first level;

a second control signal to the means for varying the magnitude of the juncture node voltage, to initiate a change in the magnitude of the juncture node voltage to a second level, greater than the first level;

a third control signal to the means for varying the magnitude of the juncture node voltage, to initiate a change in the magnitude of the juncture node voltage back to the first level;

a fourth control signal to the converter to cause the converter to effectively break at least one of the current paths between the juncture node and the first converter output terminal and between the common rail and the second converter output terminal; and

a fifth control signal to the converter to cause the converter to effect a current path between the juncture node and the second converter output terminal and between the common rail and the first converter output terminal.

68. The apparatus of claim 63 further including means for controllably discharging the capacitance, to facilitate generation of a relatively low voltage across the converter output terminals.

69. The apparatus of claim 63, wherein the converter circuit comprises:

a first power switch circuit, electrically connected to the juncture node, and to the first converter output terminal, disposed to, responsive to control signals applied thereto, selectively effect a current path between the juncture node and the first converter output terminal;

a second power switch circuit, electrically connected to the juncture node, and to the second converter output terminal, disposed to, responsive to control signals applied thereto, selectively effect a current path between the juncture node, and the second converter output terminal;

a third power switch circuit, electrically connected to the common rail, and to the first converter output terminal, disposed to, responsive to control signals applied thereto, selectively effect a current path between the common rail and the first converter output terminal; and

a fourth power switch circuit, electrically connected to the common rail, and to the second converter output terminal, disposed to, responsive to control signals applied thereto, selectively effect a current path between the common rail and the second converter output terminal.

70. The apparatus of claim 68 including means for selectively rendering at least one of the third or fourth power switch circuits partially conductive whereby the capacitance is controllably discharged through a resistance.

71. The apparatus of claim 68 wherein at least one of the third or fourth power switch circuits comprises:

a switching device which is rendered fully conductive by application thereto of a control signal of a first predetermined magnitude, and rendered into a linear mode of operation by application thereto of a control signal of a second predetermined magnitude; and

driver circuits for selectively applying respective control signals of said first and second magnitudes.

72. The apparatus of claim 56 wherein at least one of the third or fourth power switch circuits comprises:

a switching device which is rendered fully conductive by application thereto of a control signal of a first predetermined magnitude, and rendered into a linear mode of operation by application thereto of a control signal of a second predetermined magnitude; and

driver circuits for selectively applying respective control signals of said first and second magnitudes.

73. The apparatus of claim 56 wherein:

the first and fourth power switch circuits are independently controlled; and

the second and third power switch circuits are independently controlled.

74. The apparatus of claim 56 wherein:

the control signals applied to the first and fourth power switch circuits are of different duration; and

the control signals applied to the second and third power switch circuits are of different duration.

76. Apparatus for a producing a signal simulating a desired AC waveform, comprising:

first and second converter output terminals;

a juncture node, at a voltage of variable magnitude relative to a common rail;

a converter circuit, responsive to respective control signals applied thereto, for selectively effecting current paths between the juncture node and one of the first and second converter output terminals and between the common rail and the other of the first and second converter output terminals;

means, responsive to control signals applied thereto, for controllably varying the magnitude of the juncture node voltage;

a controller for selectively generating, in sequence;

a first control signal to the converter to cause the converter to effect a current path between the juncture node and the first converter output terminal and between the common rail and the second converter output terminal, the magnitude of the juncture node voltage initially being at a first level;

a second control signal to the means for varying the magnitude of the juncture node voltage, to initiate a change in the magnitude of the juncture node voltage to a second level;

greater than the first level;

a third control signal to the means for varying the magnitude of the juncture node voltage, to initiate a change in the magnitude of the juncture node voltage back to the first level;

a fourth control signal to the converter to cause the converter to effectively break at least one of the current paths between the juncture node and the first converter output terminal and between the common rail and the second converter output terminal;

a fifth control signal to the converter to cause the converter to effect a current path between the juncture node and the second converter output terminal and between the common rail and the first converter output terminal; and

the control signals to the converter circuit and means for varying the magnitude of the juncture node voltage, effecting a predetermined waveform at the converter output terminals simulating the desired AC waveform.

78. Apparatus for producing a signal simulating a desired periodic AC waveform comprising:

first and second converter output terminals;

a juncture node, at a voltage of variable magnitude relative to a common rail;

a converter circuit comprising;

a first power switch circuit, electrically connected to the juncture node, and to the first converter output terminal, disposed to, responsive to control signals applied thereto, selectively effect a current path between the juncture node, and the first converter output terminal;

a second power switch circuit, electrically connected to the juncture node, and to the second converter output terminal, disposed to, responsive to control signals applied thereto, selectively effect a current path between the juncture node, and the second converter output terminal;

a third power switch circuit, electrically connected to the common rail, and to the first converter output terminal, disposed to, responsive to control signals applied thereto, selectively effect a current path between the common rail and the first converter output terminal;

a fourth power switch circuit, electrically connected to the common rail, and to the second converter output terminal, disposed to, responsive to control signals applied thereto, selectively effect a current path between the common rail and the second converter output terminal;

means, responsive to control signals applied thereto, for controllably varying the magnitude of the juncture node voltage; and

a controller for selectively generating control signals at periodic predetermined times in the desired AC waveform to the converter circuit and to the means for varying the magnitude of the juncture node voltage, to create a predetermined waveform at the converter output terminals simulating the desired AC waveform.

89. Apparatus for producing a signal simulating a desired periodic AC waveform comprising:

first and second converter output terminals;

a juncture node, at a voltage of variable magnitude relative to a common rail;

a converter circuit, responsive to respective control signals applied thereto, for selectively effecting current paths between the juncture node and one of the first and second converter output terminals and between the common rail and the other of the first and second converter output terminals;

a capacitance;

a switching circuit, electrically connected to the capacitance, disposed to, responsive to control signals applied thereto, selectively effect a current path between the juncture node and the common rail through the capacitance; and

a controller for selectively generating control signals at periodic times in the desired AC waveform to the converter circuit and to the switching circuit, to create a predetermined waveform at the converter output terminals simulating the desired AC waveform.

91. The apparatus of claim 89, wherein:

the fourth control signal to the converter causes the converter to effectively break the current path between the juncture node and the first converter output terminal; and

the controller generates, after the fourth control signal but before the fifth control signal, a further control signal to the converter to cause the converter to effectively break the current path between the common rail and the second converter output terminal.

92. The apparatus of claim 89, wherein:

the second control signal comprises a control signal to the switching circuit, electrically connected to the capacitance, to effect a current path between the juncture node and the common rail through the capacitance; and

the third control signal comprises a control signal to the switching circuit, electrically connected to the capacitance, to effectively break the current path between the juncture node and the common rail through the capacitance.

94. The apparatus of claim 89 wherein said periodic times a rising edge and a falling edge of the predetermined waveform.

95. The apparatus of claim 89 wherein a present half-cycle of the predetermined waveform includes a pulse having a leading portion, an internal portion, and a trailing portion, the pulse being between the first and third portion, wherein the control signals are generated to the switching circuit such that the current path between the juncture node and the common rail is not effected during the leading portion and the trailing portion of the pulse.

96. The apparatus of claim 95 wherein the desired waveform includes a dead time between the trailing portion of the present half-cycle and a successive leading portion of the pulse of a successive half-cycle, the successive leading portion having the same position in the next successive half-cycle as the leading portion of the successive half-cycle.