Power electronic circuits with ripple current cancellation

• US 6,437,999 B1
• Filed: 05/12/2001
• Issued: 08/20/2002
• Est. Priority Date: 05/12/2001
• Status: Expired due to Fees

• Current Assignee: Technical Witts Incorporated
• Original Assignee: Technical Witts Incorporated
• Inventors: Wittenbreder, Ernest H.
• Primary Examiner(s): BERHANE, ADOLF D
• Application Number:
  US09/853,561
• Time in Patent Office: 465 Days
• Field of Search: 363/39, 363/40, 363/41, 363/42, 363/43, 363/16, 363/17
• US Class Current: 363/39
• CPC Class Codes: H02M 3/158 including plural semiconductor devices as final control devices for a single load

Abstract

PWM DC to DC converter circuits which accomplish ripple cancellation at one or more terminals are revealed. Four or more inductors are required in each case, however, in all cases multiple inductors can be combined into a single simple coupled inductor to accomplish the ripple cancellation. Some of the circuits revealed accomplish ripple cancellation at all terminals and some also provide zero voltage switching and galvanic load isolation. The non-isolated DC to DC converter networks revealed accomplish buck, boost, buck boost (flyback), buck complement, boost complement, or flyback complement conversion using a simple circuit requiring only two switches, one of which may be a simple diode rectifier, two or more capacitors, and four or more inductors, which may be co-located on a single common magnetic core. The isolated converters revealed provide continuous and discontinuous forward converter and continuous flyback converter transfer functions. Also revealed are techniques to accomplish isolation, high order (quadrature) transfer functions, zero ripple tapped inductor topologies, and methodology for generalizing the process of changing three terminal networks with pulsating terminal currents into three terminal networks with zero ripple terminal currents.

Claims

1. A three terminal power conversion network comprising,

a first network terminal,

a first inductor having first and second terminals with said first terminal of said first inductor connected to said first network terminal,

first switch means having first and second terminals with said first terminal of said first switch means connected to said second terminal of said first inductor,

a first capacitor having first and second terminals with said first terminal of said first capacitor connected to said first terminal of said first switch means and to said second terminal of said first inductor,

a second capacitor having first and second terminals with said first terminal of said second capacitor connected to said second terminal of said first capacitor,

second switch means having first and second terminals with said first terminal of said second switch means connected to said second terminal of said first switch means and with said second terminal of said second switch means connected to said second terminal of said second capacitor, operable substantially in anti-synchronization to said first switch means,

a second inductor having first and second terminals with said second terminal of said second inductor connected to said second terminal of said second capacitor and to said second terminal of said second switch means,

a second network terminal connected to said first terminal of said second inductor,

a third inductor having first and second terminals with said first terminal of said third inductor connected to said second terminal of said first switch means and to said first terminal of said second switch means,

a third network terminal connected to said second terminal of said third inductor,

a fourth inductor having first and second terminals with said second terminal of said fourth inductor connected to said first network terminal and to said first terminal of said first inductor,

a third capacitor having first and second terminals with said first terminal of said third capacitor connected to said first terminal of said fourth inductor and with said second terminal of said third capacitor connected to said second terminal of said first switch means, to said first terminal of said second switch means, and to said first terminal of said third inductor,

a fifth inductor having first and second terminals with said second terminal of said fifth switch means connected to said second network terminal and to said first terminal of said second inductor,

a fourth capacitor having first and second terminals with said first terminal of said fourth capacitor connected to said second terminal of said first switch means, to said first terminal of said second switch means, to said second terminal of said third capacitor, and to said first terminal of said third inductor and with said second terminal of said fourth capacitor connected to said first terminal of said fifth inductor,

a sixth inductor having first and second terminals with said first terminal of said sixth inductor connected to said third network terminal and to said second terminal of said third inductor and with said second terminal of said sixth inductor connected to said second terminal of said first capacitor and to said first terminal of said second capacitor,

whereby one of said first, said second, or said third network terminals is connected to a load and the remaining two of said first, said second, and said third network terminals are connected to substantially DC voltage sources, one of which sources may be ground or common, thereby forming a complete power converter circuit in which two inductors are connected at each network terminal such that the ripple current of an inductor connected to a network terminal substantially cancels the ripple current of the other inductor connected to the same network terminal.

2. The network of claim 1 wherein said switch means comprise semiconductor switch means.

3. The network of claim 2 wherein said first, said second, said third, said fourth, said fifth, and said sixth inductors are integrated on a single common core.

4. A three terminal power conversion network comprising,

a first network terminal,

a first inductor having first and second terminals with said first terminal of said first inductor connected to said first network terminal,

first switch means having first and second terminals with said first terminal of said first switch means connected to said second terminal of said first inductor,

a first capacitor having first and second terminals with said first terminal of said first capacitor connected to said second terminal of said first inductor and to said first terminal of said first switch means,

a second inductor having first and second terminals with said first terminal of said second inductor connected to said second terminal of said first switch means and with said second terminal of said second inductor connected to said second terminal of said first capacitor,

a third inductor having first and second terminals with said first terminal of said third inductor connected to said second terminal of said first switch means and to said first terminal of said second inductor,

a second network terminal connected to said second terminal of said third inductor,

second switch means having first and second terminals with said first terminal of said second switch means connected to said second terminal of said first capacitor and to said second terminal of said second inductor, operable substantially in anti-synchronization to said first switch means,

a second capacitor having first and second terminals with said first terminal of said second capacitor connected to said second terminal of said first switch means, to said first terminal of said second inductor, and to said first terminal of said third inductor and with said second terminal of said second capacitor connected to said second terminal of said second switch means,

a fourth inductor having first and second terminals with said first terminal of said fourth inductor connected to said second terminal of said second switch means and to said second terminal of said second capacitor,

a third network terminal connected to said second terminal of said fourth inductor,

a fifth inductor having first and second terminals with said second terminal of said fifth inductor connected to said first network terminal and to said first terminal of said first inductor,

a third capacitor having first and second terminals with said first terminal of said third capacitor connected to said first terminal of said

fifth inductor and with said second terminal of said third capacitor connected to said first terminal of said fourth inductor, to said second terminal of said second switch means, and to said second terminal of said second capacitor,

a sixth inductor having first and second terminals with said first terminal of said sixth inductor connected to said second network terminal and to said second terminal of said third inductor,

a fourth capacitor having first and second terminals with said first terminal of said fourth capacitor connected to said second terminal of said sixth inductor and with said second terminal of said fourth capacitor connected to said second terminal of said second inductor, to said second terminal of said first capacitor, and to said first terminal of said second switch means,

a seventh inductor having first and second terminals with said first terminal of said seventh inductor connected to said third network terminal and to said second terminal of said fourth inductor,

a fifth capacitor having first and second terminals with said first terminal of said fifth capacitor connected to said second terminal of said seventh inductor and with said second terminal of said fifth capacitor connected to said second terminal of said first inductor, to said first terminal of said first switch means, and to said first terminal of said first capacitor,

whereby one of said first, said second, or said third network terminals is connected to a load and the remaining two of said first, said second, and said third network terminals are connected to substantially DC voltage sources, one of which sources may be ground or common, thereby forming a complete power converter circuit in which two inductors are connected at each network terminal such that the ripple current of an inductor connected to a network terminal substantially cancels the ripple current of the other inductor connected to the same network terminal.

5. The network of claim 4 wherein said switch means comprise semiconductor switch means.

6. The network of claim 5 wherein said first, said second, said third, said fourth, said fifth, said sixth, and said seventh inductors are integrated on a single common core.

7. A three terminal power conversion network comprising,

a first network terminal,

a coupled inductor comprising,

a first winding having first and second terminals with said first terminal of said first winding connected to said first network terminal,

a second winding having first and second terminals,

a third winding having first and second terminals,

a fourth winding having first and second terminals with said second terminal of said fourth winding connected to said first terminal of said third winding,

a fifth winding having first and second terminals with said second terminal of said fifth winding connected to said first network terminal and to said first terminal of said first winding,

a sixth winding having first and second terminals with said second terminal of said sixth winding connected to said first terminal of said second winding,

a seventh winding having first and second terminals with said first terminal of said seventh winding connected to said second terminal of said third winding,

first switch means having first and second terminals with said first terminal of said first switch means connected to said second terminal of said first winding of said coupled inductor and with said second terminal of said first switch means connected to said first terminal of said fourth winding of said coupled inductor,

second switch means having first and second terminals with said first terminal of said second switch means connected to said first terminal of said third winding of said coupled inductor and to said second terminal of said fourth winding of said coupled inductor and with said second terminal of said second switch means connected to said second terminal of said second winding of said coupled inductor, operable substantially in anti-synchronization to said first switch means,

a first capacitor having first and second terminals with said first terminal of said first capacitor connected to said second terminal of said first winding of said coupled inductor and to said first terminal of said first switch means and with said second terminal of said first capacitor connected to said second terminal of said seventh winding of said coupled inductor,

a second capacitor having first and second terminals with said first terminal of said second capacitor connected to said second terminal of said first capacitor and to said second terminal of said seventh winding of said coupled inductor and with said second terminal of said second capacitor connected to said second terminal of said second winding of said coupled inductor and to said second terminal of said second switch means,

third capacitor having first and second terminals with said first terminal of said third capacitor connected to said first terminal of said fifth winding of said coupled inductor and with said second terminal of said third capacitor connected to said first terminal of said second switch means, to said first terminal of said third winding of said coupled inductor, and to said second terminal of said fourth winding of said coupled inductor,

a fourth capacitor having first and second terminals with said first terminal of said fourth capacitor connected to said first terminal of said second switch means, to said first terminal of said third winding of said coupled inductor, to said second terminal of said fourth winding of said coupled inductor, and to said second terminal of said third capacitor and with said second terminal of said fourth capacitor connected to said first terminal of said sixth winding of said coupled inductor,

whereby one of said first, said second, or said third network terminals is connected to a load and the remaining two of said first, said second, and said third network terminals are connected to substantially DC voltage sources, one of which sources may be ground or common, thereby forming a complete power converter circuit in which two coupled inductor windings are connected at each network terminal such that the ripple current of a winding connected to a network terminal substantially cancels the ripple current of the other winding connected to the same network terminal.

8. The network of claim 7 wherein said switch means comprise semiconductor switch means.

9. The network of claim 8 further comprising,

a second inductor connected in series with said first switch means,

an active reset network connected to said first switch means and to said second inductor comprising,

a fifth capacitor,

third switch means connected in series with said fifth capacitor operable substantially in anti-synchronization to said first switch means,

whereby said active reset network provides a means to reverse the current in said second inductor during the off time of said first switch means such that energy is available and current in said second inductor is directed to provide a zero voltage turn on transition for said first switch means.

10. A three terminal power conversion network comprising,

a first network terminal,

a first inductor having first and second network terminals with said first terminal of said first inductor connected to said first network terminal,

first switch means having first and second terminals with said first terminal of said first switch means connected to said second terminal of said first inductor,

a first capacitor having first and second terminals with said first terminal of said first capacitor connected to said second terminal of said first inductor and to said first terminal of said first switch means,

a second inductor having first and second terminals with said second terminal of said second inductor connected to said second terminal of said first capacitor,

a second network terminal connected to said first terminal of said second inductor,

second switch means having first and second terminals with said first terminal of said second switch means connected to said second terminal of said first capacitor and to said second terminal of said second inductor,

a second capacitor having first and second terminals with said first terminal of said second capacitor connected to said second terminal of said second switch means and with said second terminal of said second capacitor connected to said second terminal of said first switch means,

a third inductor having first and second terminals with said first terminal of said third inductor connected to said second terminal of said first switch means and to said second terminal of said second capacitor and with said second terminal of said third inductor connected to said first terminal of said second inductor and to said second network terminal,

a fourth inductor having first and second terminals with said first terminal of said fourth inductor connected to said first terminal of said second capacitor and to said second terminal of said second switch means,

a third network terminal connected to said second terminal of said fourth inductor,

whereby one of said first, said second, or said third network terminals is connected to a load and the remaining two of said first, said second, and said third network terminals are connected to substantially DC voltage sources, one of which sources may be ground or common, thereby forming a complete power converter circuit in which two inductors are connected at said second network terminal such that the ripple current of said second inductor substantially cancels the ripple current of said third inductor at said second network terminal.

11. The network of claim 10 wherein said switch means comprise semiconductor switch means.

12. The network of claim 10 in which all four inductors are coupled on a single common magnetic core.

13. The network of claim 10 further comprising,

a fifth inductor having first and second terminals with said second terminal of said fifth inductor connected to said first network terminal and to said first terminal of said first inductor,

a third capacitor having first and second terminals with said first terminal of said third capacitor connected to said first terminal of said fifth inductor and with said second terminal of said third capacitor connected to said first terminal of said second capacitor and to said second terminal of said second switch means,

a sixth inductor having first and second terminals with said first terminal of said sixth inductor connected to said third network terminal and to said second terminal of said fourth inductor,

a fourth capacitor having first and second terminals with said first terminal of said fourth capacitor connected to said second terminal of said sixth inductor and with said second terminal of said fourth capacitor connected to said first terminal of said first switch means, to said first terminal of said first capacitor, and to said second terminal of said first inductor,

whereby one of said first, said second, or said third network terminals is connected to a load and the remaining two of said first, said second, and said third network terminals are connected to substantially DC voltage sources, one of which sources may be ground or common, thereby forming a complete power converter circuit in which two inductors are connected at each network terminal such that the ripple current of an inductor connected to a network terminal substantially cancels the ripple current of the other inductor connected to the same network terminal.

14. An active reset flyback converter comprising,

an input having first and second terminals coupleable to a source of substantially DC potential,

a first inductor having first and second terminals with said first terminal of said first inductor connected to said first terminal of said input,

a second inductor having first and second terminals with said second terminal of said second inductor connected to said first terminal of said input,

a third inductor having first and second terminals with said first terminal of said third inductor connected to said second terminal of said input,

a fourth inductor having first and second terminals with said second terminal of said fourth inductor connected to said second terminal of said input,

a first capacitor having first and second terminals with said first terminal of said first capacitor connected to said second terminal of said first inductor and with said second terminal of said first capacitor connected to said second terminal of said third inductor,

a second capacitor having first and second terminals with said first terminal of said second capacitor connected to said first terminal of said second inductor and with said second terminal of said second capacitor connected to said second terminal of said fourth inductor,

a coupled inductor having a primary winding with first and second terminals and a secondary winding having first and second terminals with said second terminal of said primary winding of said coupled inductor connected to said first terminal of said second inductor and to said first terminal of said second capacitor,

first switch means having first and second terminals with said first terminal of said first switch means connected to said first terminal of said primary winding of said coupled inductor and with said second terminal connected to said second terminal of said third inductor and to said second terminal of said first capacitor,

second switch means having first and second terminals with said first terminal of said second switch means connected to said first terminal of said first switch means and to said first terminal of said primary winding of said coupled inductor, operable substantially in anti-synchronization to said first switch means,

a third capacitor having first and second terminals with said first terminal of said third capacitor connected to said second terminal of said second switch means and with said second terminal of said third capacitor connected to said second terminal of said first switch means, to said second terminal of said first capacitor, and to said second terminal of said third inductor,

third switch means having first and second terminals, operable substantially in anti-synchronization to said first switch means, with said first terminal of said third switch means connected to said second terminal of said secondary winding of said coupled inductor,

an output, coupleable to a load, having first and second terminals with said first terminal of said output connected to said first terminal of said secondary winding of said coupled inductor and with said second terminal of said output connected to said second terminal of said third switch means,

whereby the AC current component of said first inductor is substantially equal in magnitude and opposite in sign to said AC current component of said second inductor thereby substantially canceling said AC current components of said first and said second inductors at said first terminal of said input and thereby providing substantially DC current load to said input, whereby the AC current component of said third inductor is substantially equal in magnitude and opposite in sign to said AC current component of said fourth inductor thereby substantially canceling said AC current components of said third and said fourth inductors at said second input terminal and thereby providing substantially DC current load to said input, and whereby the energy in said first, said second, said third, and said fourth inductors is used to drive a zero voltage turn on transition of said first switch means.

15. The converter of claim 14 wherein said switch means comprise semiconductor switch means.

16. The converter of claim 14 in which all four inductors are coupled on a single common magnetic core.

17. The converter of claim 16 further comprising,

a first diode having a cathode terminal and an anode terminal with said cathode terminal connected to said first terminal of said first switch means and with said anode terminal of said diode connected to said first terminal of said third inductor,

whereby said first diode clamps ringing associated with said first, said second, said third, and said fourth inductors and circuit parasitic capacitances such as intrinsic capacitance of said third switch means and inter-winding and intra-winding capacitance of said coupled inductor.

18. An active reset coupled inductor buck converter comprising,

an input having first and second terminals coupleable to a source of substantially DC potential,

a first inductor having first and second terminals with said first terminal of said first inductor connected to said first terminal of said input,

a second inductor having first and second terminals with said second terminal of said second inductor connected to said first terminal of said input,

a third inductor having first and second terminals with said first terminal of said third inductor connected to said second terminal of said input,

a fourth inductor having first and second terminals with said second terminal of said fourth inductor connected to said second terminal of said input,

a first capacitor having first and second terminals with said first terminal of said first capacitor connected to said second terminal of said first inductor,

a second capacitor having first and second terminals with said first terminal of said second capacitor connected to said first terminal of said second inductor and with said second terminal of said second capacitor connected to said second terminal of said fourth inductor,

a third capacitor having first and second terminals with said first terminal of said third capacitor connected to said second terminal of said third inductor and with said second terminal of said third capacitor connected to said second terminal of said first capacitor,

a coupled inductor having a primary winding with first and second terminals and a secondary winding having first and second terminals with said second terminal of said primary winding of said coupled inductor connected to said second terminal of said third capacitor and to said second terminal of said first capacitor,

first switch means having first and second terminals with said first terminal of said first switch means connected to said first terminal of said primary winding of said coupled inductor and with said second terminal connected to said first terminal of said second inductor and to said first terminal of said second capacitor,

second switch means having first and second terminals with said first terminal of said second switch means connected to said first terminal of said first switch means and to said first terminal of said primary winding of said coupled inductor and with said second terminal of said second switch means connected to said second terminal of said second capacitor and to said first terminal of said fourth inductor, operable substantially in anti-synchronization to said first switch means,

third switch means having first and second terminals, operable substantially in anti-synchronization to said first switch means, with said first terminal of said third switch means connected to said first terminal of said secondary winding of said coupled inductor,

an output, coupleable to a load, having first and second terminals with said first terminal of said output connected to said second terminal of said secondary winding of said coupled inductor and with said second terminal of said output connected to said second terminal of said third switch means,

whereby the AC current component of said first inductor is substantially equal in magnitude and opposite in sign to said AC current component of said second inductor thereby substantially canceling said AC current components of said first and said second inductors at said first terminal of said input and thereby providing substantially DC current load to said input, whereby the AC current component of said third inductor is substantially equal in magnitude and opposite in sign to said AC current component of said fourth inductor thereby substantially canceling said AC current components of said third and said fourth inductors at said second input terminal and thereby providing substantially DC current load to said input, and whereby the energy in said first, said second, said third, and said fourth inductors is used to drive a zero voltage turn on transition of said first switch means.

19. The converter of claim 18 wherein said switch means comprise semiconductor switch means.

20. The converter of claim 19 in which all four inductors are coupled on a single common magnetic core.

21. The converter of claim 20 further comprising,

a first diode having a cathode terminal and an anode terminal with said cathode terminal connected to said first terminal of said primary winding of said coupled inductor and with said anode terminal connected to said second terminal of said first switch means,

whereby said first diode clamps ringing associated with said first, said second, said third, and said fourth inductors and circuit parasitic capacitances such as intrinsic capacitance of said third switch means and inter-winding and intra-winding capacitance of said coupled inductor.

22. An active reset interleaved coupled inductor buck converter comprising,

an input having first and second terminals coupleable to a source of substantially DC potential,

a first inductor having first and second terminals with said first terminal of said first inductor connected to said first terminal of said input,

a second inductor having first and second terminals with said second terminal of said second inductor connected to said first terminal of said input,

a third inductor having first and second terminals with said first terminal of said third inductor connected to said second terminal of said input,

a fourth inductor having first and second terminals with said second terminal of said fourth inductor connected to said second terminal of said input,

a first capacitor having first and second terminals with said first terminal of said first capacitor connected to said second terminal of said first inductor and with said second terminal of said first capacitor connected to said second terminal of said third inductor,

a second capacitor having first and second terminals with said first terminal of said second capacitor connected to said first terminal of said second inductor and with said second terminal of said second capacitor connected to said first terminal of said fourth inductor,

a first coupled inductor having a primary winding with first and second terminals and a secondary winding having first and second terminals with said second terminal of said primary winding of said first coupled inductor connected to said first terminal of said second inductor and to said first terminal of said second capacitor,

a second coupled inductor having a primary winding with first and second terminals and a secondary winding having first and second terminals with said second terminal of said primary winding of said second coupled inductor connected to said first terminal of said primary winding of said first coupled inductor and with said first terminal of said secondary winding of said second coupled inductor connected to said second terminal of said secondary winding of said first coupled inductor,

first switch means having first and second terminals with said first terminal of said first switch means connected to said first terminal of said primary winding of said second coupled inductor and with said second terminal connected to said second terminal of said third inductor and to said second terminal of said first capacitor,

second switch means having first and second terminals with said first terminal of said second switch means connected to said first terminal of said first switch means and to said first terminal of said primary winding of said second coupled inductor, operable substantially in anti-synchronization to said first switch means,

a third capacitor having first and second terminals with said first terminal of said third capacitor connected to said second terminal of said second switch means and with said second terminal of said third capacitor connected to said second terminal of said first switch means, to said second terminal of said first capacitor, and to said second terminal of said third inductor,

third switch means having first and second terminals, operable substantially in anti-synchronization to said first switch means, with said first terminal of said third switch means connected to said second terminal of said secondary winding of said second coupled inductor,

fourth switch means having first and second terminals, operable substantially in synchronization with said first switch means, with said first terminal of said fourth switch means connected to said first terminal of said secondary winding of said first coupled inductor and with said second terminal of said fourth switch means connected to said second terminal of said third switch means,

an output, coupleable to a load, having first and second terminals with said first terminal of said output connected to said first terminal of said secondary winding of said second coupled inductor and to said second terminal of said secondary winding of said first coupled inductor and with said second terminal of said output connected to said second terminal of said third switch means and to said second terminal of said fourth switch means,

whereby the AC current component of said first inductor is substantially equal in magnitude and opposite in sign to said AC current component of said second inductor thereby substantially canceling said AC current components of said first and said second inductors at said first terminal of said input and thereby providing substantially DC current load to said input, whereby the AC current component of said third inductor is substantially equal in magnitude and opposite in sign to said AC current component of said fourth inductor thereby substantially canceling said AC current components of said third and said fourth inductors at said second input terminal and thereby providing substantially DC current load to said input, and whereby the energy in said first, said second, said third, and said fourth inductors is used to drive a zero voltage turn on transition of said first switch means.

23. The converter of claim 22 wherein said switch means comprise semiconductor switch means.

24. The converter of claim 22 in which all four inductors are coupled on a single common magnetic core.

25. The converter of claim 24 further comprising,

a first diode having a cathode terminal and an anode terminal with said cathode terminal connected to said first terminal of said first switch means and with said anode terminal of said diode connected to said first terminal of said third inductor, whereby said first diode clamps ringing associated with said first, said second, said third, and s aid fourth inductors and circuit parasitic capacitances such as intrinsic capacitance of said third switch means and inter-winding and intra-winding capacitance of said coupled inductors.

26. An active reset forward converter comprising,

an input having first and second terminals coupleable to a source of substantially DC potential,

a first inductor having first and second terminals with said first terminal of said first inductor connected to said first terminal of said input,

a second inductor having first and second terminals with said second terminal of said second inductor connected to said first terminal of said input,

a third inductor having first and second terminals with said first terminal of said third inductor connected to said second terminal of said input,

a fourth inductor having first and second terminals with said second terminal of said fourth inductor connected to said second terminal of said input,

a first capacitor having first and second terminals with said first terminal of said first capacitor connected to said second terminal of said first inductor and with said second terminal of said first capacitor connected to said second terminal of said third inductor,

a second capacitor having first and second terminals with said first terminal of said second capacitor connected to said first terminal of said second inductor and with said second terminal of said second capacitor connected to said first terminal of said fourth inductor,

a transformer having a primary winding with first and second terminals and a secondary winding having first and second terminals with said second terminal of said primary winding of said transformer connected to said first terminal of said second inductor and to said first terminal of said second capacitor,

first switch means having first and second terminals with said first terminal of said first switch means connected to said first terminal of said primary winding of said transformer and with said second terminal connected to said second terminal of said third inductor and to said second terminal of said first capacitor,

second switch means having first and second terminals with said first terminal of said second switch means connected to said first terminal of said first switch means and to said first terminal of said primary winding of said transformer, operable substantially in anti-synchronization to said first switch means,

a third capacitor having first and second terminals with said first terminal of said third capacitor connected to said second terminal of said second switch means and with said second terminal of said third capacitor connected to said second terminal of said first switch means, to said second terminal of said first capacitor, and to said second terminal of said third inductor,

third switch means having first and second terminals, operable substantially in anti-synchronization to said first switch means, with said first terminal of said third switch means connected to said second terminal of said secondary winding of said transformer,

fourth switch means having first and second terminals, operable substantially in synchronization with said first switch means, with said first terminal of said fourth switch means connected to said first terminal of said secondary winding of said transformer and with said second terminal of said fourth switch means connected to said second terminal of said third switch means,

a fifth inductor having first and second terminals with said second terminal of said fifth inductor connected to said second terminal of said secondary winding of said transformer and to said first terminal of said third switch means,

an output, coupleable to a load, having first and second terminals with said first terminal of said output connected to said first terminal of said fifth inductor and with said second terminal of said output connected to said second terminal of said third switch means and to said second terminal of said fourth switch means,

whereby the AC current component of said first inductor is substantially equal in magnitude and opposite in sign to said AC current component of said second inductor thereby substantially canceling said AC current components of said first and said second inductors at said first terminal of said input and thereby providing substantially DC current load to said input, whereby the AC current component of said third inductor is substantially equal in magnitude and opposite in sign to said AC current component of said fourth inductor thereby substantially canceling said AC current components of said third and said fourth inductors at said second input terminal and thereby providing substantially DC current load to said input, and whereby the energy in said first, said second, said third, and said fourth inductors is used to drive a zero voltage turn on transition of said first switch means.

27. The converter of claim 26 wherein said switch means comprise semiconductor switch means.

28. The converter of claim 26 in which all four primary side inductors are coupled on a single common magnetic core.

29. The converter of claim 28 further comprising,

a first diode having a cathode terminal and an anode terminal with said cathode terminal connected to said first terminal of said first switch means and with said anode terminal of said diode connected to said first terminal of said third inductor,

whereby said first diode clamps ringing associated with said first, said second, said third, and said fourth inductors and circuit parasitic capacitances such as intrinsic capacitance of said third switch means and inter-winding and intra-winding capacitance of said transformer.

30. An active reset discontinuous forward converter comprising,

an input having first and second terminals coupleable to a source of substantially DC potential,

a first inductor having first and second terminals with said first terminal of said first inductor connected to said first terminal of said input,

a second inductor having first and second terminals with said second terminal of said second inductor connected to said first terminal of said input,

a third inductor having first and second terminals with said first terminal of said third inductor connected to said second terminal of said input,

a fourth inductor having first and second terminals with said second terminal of said fourth inductor connected to said second terminal of said input,

a first capacitor having first and second terminals with said first terminal of said first capacitor connected to said second terminal of said first inductor and with said second terminal of said first capacitor connected to said second terminal of said third inductor,

a second capacitor having first and second terminals with said first terminal of said second capacitor connected to said first terminal of said second inductor and with said second terminal of said second capacitor connected to said first terminal of said fourth inductor,

a transformer having a primary winding with first and second terminals and a secondary winding with first and second terminals with said second terminal of said primary winding of said transformer connected to said first terminal of said second inductor and to said first terminal of said second capacitor,

first switch means having first and second terminals with said first terminal of said first switch means connected to said first terminal of said primary winding of said transformer and with said second terminal connected to said second terminal of said third inductor and to said second terminal of said first capacitor,

second switch means having first and second terminals with said first terminal of said second switch means connected to said first terminal of said first switch means and to said first terminal of said primary winding of said transformer, operable substantially in anti-synchronization to said first switch means,

a third capacitor having first and second terminals with said first terminal of said third capacitor connected to said second terminal of said second switch means and with said second terminal of said third capacitor connected to said second terminal of said first switch means, to said second terminal of said first capacitor, and to said second terminal of said third inductor,

third switch means having first and second terminals, operable substantially in synchronization with said first switch means, with said first terminal of said third switch means connected to said first terminal of said secondary winding of said transformer,

an output, coupleable to a load, having first and second terminals with said first terminal of said output connected to said second terminal of said secondary winding of said transformer and with said second terminal of said output connected to said second terminal of said third switch means,

whereby the AC current component of said first inductor is substantially equal in magnitude and opposite in sign to said AC current component of said second inductor thereby substantially canceling said AC current components of said first and said second inductors at said first terminal of said input and thereby providing substantially DC current load to said input, whereby the AC current component of said third inductor is substantially equal in magnitude and opposite in sign to said AC current component of said fourth inductor thereby substantially canceling said AC current components of said third and said fourth inductors at said second input terminal and thereby providing substantially DC current load to said input, and whereby the energy in said first, said second, said third, and said fourth inductors is used to drive a zero voltage turn on transition of said first switch means.

31. The converter of claim 30 wherein said switch means comprise semiconductor switch means.

32. The converter of claim 30 in which all four inductors are coupled