High efficiency power converter

• US 7,558,083 B2
• Filed: 09/10/2007
• Issued: 07/07/2009
• Est. Priority Date: 01/24/1997
• Status: Expired due to Fees

• Current Assignee: SynQor Incorporated
• Original Assignee: SynQor Incorporated
• Inventors: Schlecht, Martin F.
• Primary Examiner(s): NGUYEN, MATTHEW VAN
• Application Number:
  US11/900,207
• Publication Number:
  US 20080151582A1
• Time in Patent Office: 666 Days
• Field of Search: 363 15- 18, 363/20, 363/21.01, 363/21.06, 363/21.14, 363/56.01, 363/56.02, 363/95, 363/97, 363/98, 363/125, 363/131, 363/132, 323/268, 323/271, 323/282
• US Class Current: 363/21.06
• CPC Class Codes: H02M 1/007 Plural converter units in cascade push-pull DC/DC converters with pre-regulator H02M3/3374; DC-AC converters following a DC-DC stage including a high frequency transformer H02M7/4807; DC-AC converters following a DC-DC conversion stage generating periodically varying voltages H02M7/4826
• CPC Class Codes: H02M 3/335 using semiconductor devices only
• CPC Class Codes: H02M 3/33546 with automatic control of the output voltage or current H02M3/33561 takes precedence
• CPC Class Codes: H02M 3/33553 with galvanic isolation between input and output of both the power stage and the feedback loop
• CPC Class Codes: H02M 3/33592 having a synchronous rectifier circuit or a synchronous freewheeling circuit at the secondary side of an isolation transformer
• CPC Class Codes: H02M 3/3372 of the parallel type
• CPC Class Codes: H02M 3/3374 with preregulator, e.g. current injected push-pull
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

A power converter nearly losslessly delivers energy and recovers energy from capacitors associated with controlled rectifiers in a secondary winding circuit, each controlled rectifier having a parallel uncontrolled rectifier. First and second primary switches in series with first and second primary windings, respectively, are turned on for a fixed duty cycle, each for approximately one half of the switching cycle. Switched transition times are short relative to the on-state and off-state times of the controlled rectifiers. The control inputs to the controlled rectifiers are cross-coupled from opposite secondary transformer windings.

Claims

1. A non-regulating isolating step-down DC-DC power converter that provides a non-regulated, isolated DC output having a non-regulated voltage, comprising:

i) at least one isolating step-down transformer that is not driven into saturation, the at least one transformer having plural windings including at least one primary winding and at least one secondary winding;

ii) plural power MOSFET switches in circuit with the at least one primary winding, the plural power MOSFET switches causing power from a DC input to flow into the at least one primary winding;

iii) control circuitry coupled to the plural power MOSFET switches, the control circuitry determining when the power MOSFET switches are turned on and off in a switching cycle at a switching frequency, the switching cycle substantially comprising two substantial portions, a first portion and a second portion; and

iv) plural controlled rectifiers in circuit with the at least one secondary winding, each having a parallel uncontrolled rectifier, each controlled rectifier being turned on for an on-state time and off for an off-state time in synchronization with a voltage waveform of the at least one primary winding to provide the non-regulated, isolated DC output having a non-regulated voltage, the voltage waveform of the at least one primary winding having a fixed duty cycle and transition times which are short relative to the on-state and the off-state times of the controlled rectifiers;

v) a first controlled rectifier of the plural controlled rectifiers being conductive during the first portion of the switching cycle and a second controlled rectifier of the plural controlled rectifiers being conductive during the second portion of the switching cycle, there being a short time, during a transition between the portions, when the first controlled rectifier and the second controlled rectifier are both off and their corresponding uncontrolled rectifiers are both conducting.

2. A DC-DC power converter as claimed in claim 1 wherein the at least one isolating step-down transformer comprises plural transformers that are each not driven into saturation, each having plural windings including at least one primary winding and at least one secondary winding, power flowing to the isolated DC output from a first of the plural transformers during the first portion of the switching cycle and from a second of the plural transformers during the second portion of the switching cycle.

3. A DC-DC power converter as claimed in claim 1 further comprising a first voltage divider circuit, having first voltage dividing capacitors, coupled to a gate of the first controlled rectifier and coupled to a first of the at least one secondary winding, and a second voltage divider circuit, having second voltage dividing capacitors, coupled to a gate of the second controlled rectifier and coupled to a second of the at least one secondary winding.

4. A DC-DC power converter as claimed in claim 3 wherein one of the capacitors in each of the voltage divider circuits is intrinsic parasitic capacitance.

5. A DC-DC power converter as claimed in claim 1 wherein each controlled rectifier is controlled by a signal derived from a voltage of the at least one secondary winding.

6. A DC-DC power converter as claimed in claim 1 wherein a gate of the first controlled rectifier is driven by a first signal derived from a voltage of a first of the at least one secondary winding, and a gate of the second controlled rectifier is driven by a second signal derived from a voltage of a second of the at least one secondary winding.

7. A DC-DC power converter as claimed in claim 6 further comprising a first voltage divider circuit, having first voltage dividing capacitors, coupled to the gate of the first controlled rectifier and coupled to the first of the at least one secondary winding, and a second voltage divider circuit, having second voltage dividing capacitors, coupled to the gate of the second controlled rectifier and coupled to the second of the at least one secondary winding.

8. A DC-DC power converter as claimed in claim 1 wherein the fixed duty cycle is approximately 50% of the switching cycle.

9. A DC-DC power converter as claimed in claim 1 further comprising a filter inductor directly connected to plural of the windings of the at least one transformer, all current that flows through the inductor flowing through a first of the plural windings during the first portion of the switching cycle and a second of the plural windings during the second portion of the switching cycle.

10. A DC-DC power converter as claimed in claim 9 further comprising a first voltage divider circuit, having first voltage dividing capacitors, coupled to a gate of the first controlled rectifier and coupled to a first of the at least one secondary winding, and a second voltage divider circuit, having second voltage dividing capacitors, coupled to a gate of the second controlled rectifier and coupled to a second of the at least one secondary winding.

11. A DC-DC power converter as claimed in claim 9 wherein a gate of the first controlled rectifier is driven by a signal derived from a voltage of a first of the at least one secondary winding, and a gate of the second controlled rectifier is driven by a signal derived from a voltage of a second of the at least one secondary winding.

12. A DC-DC power converter as claimed in claim 11 further comprising a first voltage divider circuit, having first voltage dividing capacitors, coupled to the gate of the first controlled rectifier and coupled to the first of the at least one secondary winding, and a second voltage divider circuit, having second voltage dividing capacitors, coupled to the gate of the second controlled rectifier and coupled to the second of the at least one secondary winding.

13. A DC-DC power converter as claimed in claim 1 wherein the non-regulated voltage of the non-regulated, isolated DC output is associated with an input voltage on the DC input according to a turns ratio of the at least one transformer.

14. A DC-DC power converter as claimed in claim 1 wherein the non-regulated voltage of the non-regulated, isolated DC output drops with increasing current flow through the non-regulating isolating step-down converter.

15. A DC-DC power converter as claimed in claim 1 wherein power flow through the non-regulating isolating step-down converter is substantially uninterrupted.

16. A DC-DC power converter as claimed in claim 1 wherein energy is nearly losslessly delivered to and recovered from capacitors associated with the controlled rectifiers during transition times of the power MOSFET switches.

17. A DC-DC power converter as claimed in claim 1 wherein each of the at least one transformer has only one primary winding.

18. A DC-DC power converter as claimed in claim 1 adapted to receive a wide range of voltages at the DC input.

19. A DC-DC power converter as claimed in claim 18 adapted to receive a range of about 36-75 volts at the DC input.

20. A DC-DC power converter as claimed in claim 1 adapted to provide a range of currents of about 1 to 25 amps at the non-regulated, isolated DC output.

21. A DC-DC power converter as claimed in claim 1 wherein the switching frequency is in the range of 100 kHz and above.

22. A non-regulating isolating step-down DC-DC power converter through which power flows from a DC input to provide a non-regulated, isolated DC output having a non-regulated voltage, comprising:

i) at least one isolating step-down transformer that is not driven into saturation, the at least one transformer having plural windings including at least one primary winding and at least one secondary winding;

ii) plural power MOSFET switches in circuit with the at least one primary winding, the plural power MOSFET switches causing power from the DC input to flow into the at least one primary winding;

iii) control circuitry coupled to the plural power MOSFET switches, the control circuitry determining when the power MOSFET switches are turned on and off in a switching cycle at a switching frequency, the switching cycle substantially comprising two substantial portions, a first portion and a second portion;

iv) plural controlled rectifiers in circuit with the at least one secondary winding, each having a parallel uncontrolled rectifier, each controlled rectifier being turned on for an on-state time and off for an off-state time in synchronization with a voltage waveform of the at least one primary winding to provide the non-regulated, isolated DC output having a non-regulated voltage, the voltage waveform of the at least one primary winding having a fixed duty cycle and transition times which are short relative to the on-state and the off-state times of the controlled rectifiers; and

v) a filter inductor directly connected to plural of the windings of the at least one transformer, all current that flows through the inductor flowing through a first of the plural windings during the first portion of the switching cycle, and a second of the plural windings during the second portion of the switching cycle.

23. A DC-DC power converter as claimed in claim 22 wherein the at least one isolating step-down transformer comprises plural transformers that are each not driven into saturation, each having plural windings including at least one primary winding and at least one secondary winding, power flowing to the isolated DC output from a first of the plural transformers during the first portion of the switching cycle and from a second of the plural transformers during the second portion of the switching cycle.

24. A DC-DC power converter as claimed in claim 22 further comprising a first voltage divider circuit, having first voltage dividing capacitors, coupled to a gate of the first controlled rectifier and coupled to a first of the at least one secondary winding, and a second voltage divider circuit, having second voltage dividing capacitors, coupled to a gate of the second controlled rectifier and coupled to a second of the at least one secondary winding.

25. A DC-DC power converter as claimed in claim 24 wherein one of the capacitors in each of the voltage divider circuits is intrinsic parasitic capacitance.

26. A DC-DC power converter as claimed in claim 22 wherein each controlled rectifier is controlled by a signal derived from a voltage of the at least one secondary winding.

27. A DC-DC power converter as claimed in claim 22 wherein a gate of the first controlled rectifier is driven by a first signal derived from a voltage of a first of the at least one secondary winding, and a gate of the second controlled rectifier is driven by a second signal derived from a voltage of a second of the at least one secondary winding.

28. A DC-DC power converter as claimed in claim 27 further comprising a first voltage divider circuit, having first voltage dividing capacitors, coupled to the gate of the first controlled rectifier and coupled to the first of the at least one secondary winding, and a second voltage divider circuit, having second voltage dividing capacitors, coupled to the gate of the second controlled rectifier and coupled to the second of the at least one secondary winding.

29. A DC-DC power converter as claimed in claim 22 wherein the fixed duty cycle is approximately 50% of the switching cycle.

30. A DC-DC power converter as claimed in claim 22 wherein the non-regulated voltage of the non-regulated, isolated DC output is associated with an input voltage on the DC input according to a turns ratio of the at least one transformer.

31. A DC-DC power converter as claimed in claim 22 wherein the non-regulated voltage of the non-regulated, isolated DC output drops with increasing current flow through the non-regulating isolating step-down converter.

32. A DC-DC power converter as claimed in claim 22 wherein power flow through the non-regulating isolating step-down converter is substantially uninterrupted.

33. A DC-DC power converter as claimed in claim 22 wherein energy is nearly losslessly delivered to and recovered from capacitors associated with the controlled rectifiers during transition times of the power MOSFET switches.

34. A DC-DC power converter as claimed in claim 22 wherein each of the at least one transformer has only one primary winding.

35. A DC-DC power converter as claimed in claim 22 adapted to receive a wide range of voltages at the DC input.

36. A DC-DC power converter as claimed in claim 35 adapted to receive a range of about 36-75 volts at the DC input.

37. A DC-DC power converter as claimed in claim 22 adapted to provide a range of currents of about 1 to 25 amps at the non-regulated, isolated DC output.

38. A DC-DC power converter as claimed in claim 22 wherein the switching frequency is in the range of 100 kHz and above.

39. A method of converting power from DC to DC to provide a non-regulated, isolated DC output having a non-regulated voltage, comprising:

flowing power from a DC input through a non-regulating isolating step-down converter, the non-regulating isolating step-down converter providing a non-regulated, isolated DC output having a non-regulated voltage, and in the isolating step-down converter;

i) causing plural power MOSFET switches to be turned on in a switching cycle at a switching frequency, the switching cycle substantially comprising two substantial portions, a first portion and a second portion, to cause power to flow into at least one isolating step-down transformer that is not driven into saturation, the at least one transformer having plural windings including at least one primary winding and at least one secondary winding; and

ii) turning plural controlled rectifiers on for an on-state time and off for an off-state time, the plural controlled rectifiers being in circuit with the at least one secondary winding, each controlled rectifier having a parallel uncontrolled rectifier, the plural controlled rectifiers being turned on and off in synchronization with a voltage waveform of the at least one primary winding to provide the non-regulated, isolated DC output, the voltage waveform of the at least one primary winding having a fixed duty cycle and transition times which are short relative to the on-state and the off-state times of the controlled rectifiers;

iii) a first controlled rectifier of the plural controlled rectifiers being conductive during the first portion of the switching cycle and a second controlled rectifier of the plural controlled rectifiers being conductive during the second portion of the switching cycle, there being a short time, during a transition between the portions, when the first controlled rectifier and the second controlled rectifier are both off and their corresponding uncontrolled rectifiers are both conducting.

40. A method as claimed in claim 39 further comprising flowing current through a filter inductor directly connected to plural of the windings of the at least one transformer, all current that flows through the inductor flowing through a first of the plural windings during the first portion of the switching cycle and flowing through a second of the plural winding during the second portion of the switching cycle.

41. A method as claimed in claim 40 further comprising gating the first controlled rectifier from a first voltage divider circuit, having first voltage dividing capacitors, that is coupled to a first of the at least one secondary winding and gating the second controlled rectifier from a second voltage divider circuit, having second voltage dividing capacitors, that is coupled to a second of the at least one secondary winding.

42. A method as claimed in claim 40 further comprising gating the first controlled rectifier by a signal derived from a voltage of a first of the at least one secondary winding and gating the second controlled rectifier by a signal derived from the voltage of a second of the at least one secondary winding.

43. A method as claimed in claim 42 further comprising gating the first controlled rectifier from a first voltage divider circuit, having first voltage dividing capacitors, that is coupled to the first of the at least one secondary winding, and gating the second controlled rectifier from a second voltage divider circuit, having second voltage dividing capacitors, that is coupled to the second of the at least one secondary winding.

44. A method as claimed in claim 39 wherein the at least one isolating step-down transformer comprises plural transformers that are each not driven into saturation, each having plural windings including at least one primary winding and at least one secondary winding, power flowing to the isolated DC output from a first of the plural transformers during the first portion of the switching cycle and from a second of the plural transformers during the second portion of the switching cycle.

45. A method as claimed in claim 39 wherein each controlled rectifier is controlled by a signal derived from a voltage of the at least one secondary winding.

46. A method as claimed in claim 39 wherein a gate of the first controlled rectifier is driven by a first signal derived from voltages of a first of the at least one secondary winding, and a gate of the second controlled rectifier is driven by a second signal derived from voltages of a second of the at least one secondary winding.

47. A method as claimed in claim 46 wherein the first controlled rectifier is gated from the first of the at least one secondary winding through a first voltage divider circuit, having first voltage dividing capacitors, and the second controlled rectifier is gated from the second of the at least one secondary winding through a second voltage divider circuit, having second voltage dividing capacitors.

48. A method as claimed in claim 39 wherein each of the at least one transformer has only one primary winding.

49. A method of converting power from DC to DC to provide a non-regulated, isolated DC output having a non-regulated voltage, comprising:

flowing power from a DC input through a non-regulating isolating step-down converter, the non-regulating isolating step-down converter providing a non-regulated, isolated DC output having a voltage, and in the isolating step-down converter;

i) causing plural power MOSFET switches to be turned on in a switching cycle at a switching frequency, the switching frequency substantially comprising two substantial portions, a first portion and a second portion, to cause power to flow into at least one isolating step-down transformer that is not driven into saturation, the at least one transformer having plural windings including at least one primary winding and at least one secondary winding;

ii) turning plural controlled rectifiers on for an on-state time and off for an off-state time, the plural controlled rectifiers being in circuit with the at least one secondary winding, each controlled rectifier having a parallel uncontrolled rectifier, the plural controlled rectifiers being turned on and off in synchronization with a voltage waveform of the at least one primary winding to provide the non-regulated, isolated DC output, the voltage waveform of the at least one primary winding having a fixed duty cycle and transition times which are short relative to the on-state and the off-state times of the controlled rectifiers;

iii) flowing current through a filter inductor directly connected to plural of the windings of the at least one transformer, all current that flows through the inductor flowing through a first of the plural windings during the first portion of the switching cycle and flowing through a second of the plural winding during the second portion of the switching cycle.

50. A method as claimed in claim 49 wherein the at least one isolating step-down transformer comprises plural transformers that are each not driven into saturation, each having plural windings including at least one primary winding and at least one secondary winding, power flowing to the isolated DC output from a first of the plural transformers during the first portion of the switching cycle and from a second of the plural transformers during the second portion of the switching cycle.

51. A method as claimed in claim 49 wherein each controlled rectifier is controlled by a signal derived from a voltage of the at least one secondary winding.

52. A method as claimed in claim 49 wherein a gate of the first controlled rectifier is driven by a first signal derived from voltages of a first of the at least one secondary winding, and a gate of the second controlled rectifier is driven by a second signal derived from voltages of a second of the at least one secondary winding.

53. A method as claimed in claim 52 wherein the first controlled rectifier is gated from the first of the at least one secondary winding through a first voltage divider circuit, having first voltage dividing capacitors, and the second controlled rectifier is gated from the second of the at least one secondary winding through a second voltage divider circuit, having second voltage dividing capacitors.

54. A method as claimed in claim 49 wherein each of the at least one transformer has only one primary winding.