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Low loss synchronous rectifier for application to clamped-mode power converters

Imported: 23 Feb '17 | Published: 22 Oct '02

Allen Frank Rozman

USPTO - Reissues

Abstract

A synchronous rectifier for use with a clamped-mode power converter uses in one embodiment a hybrid rectifier with a MOSFET rectifying device active in one first cyclic interval or the conduction/nonconduction sequence of the power switch and a second rectifying device embodied in one illustrative embodiment as a low voltage bipolar diode rectifying device active during an alternative interval to the first conduction/nonconduction interval. The gate drive to the MOSFET device is continuous at a constant level for substantially all of the second interval which enhances efficiency of the rectifier. The bipolar rectifier device may also be embodied as a MOSFET deice. The subject rectifier may be used in both forward and flyback power converters.

Description

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic of a forward converter, of the prior are, having a synchronous rectifier;

FIG. 2 is a voltage waveform of the secondary transformer winding of the converter of FIG. 1;

FIG. 3 is a schematic of a clamped-mode forward converter with a synchronous rectifier embodying the principles of the invention;

FIG. 4 is a voltage waveform of the secondary transformer winding of the converter of FIG. 3;

FIG. 5 is a schematic of another version of a clamped-mode forward converter with a synchronous rectifier embodying the principles of the invention;

FIG. 6 is a schematic of another version of a clamper-mode forward converter with a synchronous rectifier and a center tapped secondary winding embodying the principles of the invention;

FIG. 7 is a schematic of a clamped-mode flyback converter with a synchronous rectifier embodying the principles or the invention; and

FIG. 8 is a schematic of another version of a clamped-mode forward converter with a synchronous rectifier and a center tapped secondary winding embodying the principles of the invention.

Claims

1. In a power converter, comprising:

2. In a power converter, comprising

3. In a power converter as claimed in claim 1 or 2, comprising:

4. In a power converter as claimed in claim 1 or 2, comprising:

5. A switching mode power converter, comprising:

6. A switching mode power converter as claimed in claim 5, further comprising:

7. A switching mode power converter as claimed in claim 5, further comprising:

8. A switching mode power converter as claimed in claim 6 or 7, further comprising:

9. A switching mode power converter as claimed in claim 6 or 7, further comprising:

10. A switching mode power converter as claimed in claim 6 or 7, further comprising:

11. A method of operating a power converter, comprising:

12. The method as claimed in claim 11 wherein said clamping circuit is directly connected to said power transformer.

13. The method as claimed in claim 11 wherein said clamping circuit is coupled to a primary winding of said power transformer.

14. The method as claimed in claim 11 wherein said power transformer has a center-

tapped secondary winding.

15. The method as claimed in claim 11 further comprising connecting a primary winding of said power transformer to an input of said power converter during a first cyclic interval of said power converter.

16. The method as claimed in claim 11 further comprising a further synchronous rectification device, coupled to said power transformer, that is active during a first cyclic interval of said power converter.

17. The method as claimed in claim 11 further comprising a rectification device, coupled to said power transformer, that is active during a first cyclic interval of said power converter.

18. The method as claimed in claim 11 wherein said clamping circuit comprises a switching device connected in series with a capacitor.

19. The method as claimed in claim 18 further comprising controlling said switching device with a control circuit.

20. The method as claimed in claim 11 wherein said power converter operates in one of:

21. A method of operating a power converter, comprising:

22. The method as claimed in claim 21 wherein said clamping circuit is directly connected to said power transformer.

23. The method as claimed in claim 21 wherein said clamping circuit is coupled to a primary winding of said power transformer.

24. The method as claimed in claim 21 wherein said power transformer has a center-

tapped secondary winding.

25. The method as claimed in claim 21 further comprising connecting a primary winding of said power transformer to an input of said power converter during a first cyclic interval of said power converter.

26. The method as claimed in claim 21 further comprising a further synchronous rectification device, coupled to said power transformer, that is active during a first cyclic interval of said power converter.

27. The method as claimed in claim 21 further comprising a rectification device, coupled to said power transformer, that is active during a first cyclic interval of said power converter.

28. The method as claimed in claim 21 wherein said clamping, circuit comprises a switching device connected in series with a capacitor.

29. The method as claimed in claim 28 further comprising controlling said switching device with a control circuit.

30. The method as claimed in claim 21 wherein said power converter operates in one of:

31. A method of operating a power converter, comprising:

32. The method as claimed in claim 31 wherein said clamping circuit is directly connected to said power transformer.

33. The method as claimed in claim 31 wherein said clamping circuit is coupled to a primary winding of said power transformer.

34. The method as claimed in claim 31 wherein said power transformer has a center-

tapped secondary winding.

35. The method as claimed in claim 31 further comprising connecting a primary winding of said power transformer to an input of said power converter during a first cyclic interval of said power converter.

36. The method as claimed in claim 31 further comprising a further synchronous rectification device, coupled to said power transformer, that is active during a first cyclic interval of said power converter.

37. The method as claimed in claim 31 further comprising a rectification device, coupled to said power transformer, that is active during a first cyclic interval of said power converter.

38. The method as claimed in claim 31 wherein said clamping circuit comprises a switching device connected in series with a capacitor.

39. The method as claimed in claim 38 further comprising controlling said switching device with a control circuit.

40. The method as claimed in claim 31 wherein said power converter operates in one of:

41. A method of operating a power converter, comprising:

42. The method as claimed in claim 41 wherein said clamping circuit is directly connected to said power transformer.

43. The method as claimed in claim 41 wherein said clamping circuit is coupled to a primary winding of said power transformer.

44. The method as claimed in claim 41 wherein said power transformer has a center-

tapped secondary winding.

45. The method as claimed in claim 41 further comprising connecting a primary winding of said power transformer to an input of said power converter during a first cyclic interval of said power converter.

46. The method as claimed in claim 41 further comprising a further synchronous rectification device, coupled to said power transformer, that is active during a first cyclic interval of said power converter.

47. The method as claimed in claim 41 further comprising a rectification device, coupled to said power transformer, that is active during a first cyclic interval of said power converter.

48. The method as claimed in claim 41 wherein said clamping circuit comprises a switching device connected in series with a capacitor.

49. The method as claimed in claim 48 further comprising controlling said switching device with a control circuit.

50. The method as claimed in claim 41 wherein said power converter operates in one of:

51. A method of operating a power converter, comprising:

52. The method as claimed in claim 51 wherein said clamping circuit is directly connected to said power transformer.

53. The method as claimed in claim 51 wherein said clamping circuit is coupled to said at least one primary winding of said power transformer.

54. The method as claimed in claim 51 wherein said at least one secondary winding has a center-

tap.

55. The method as claimed in claim 51 further comprising a voltage limiting device coupled to said synchronous rectification device.

56. The method as claimed in claim 51 further comprising a further synchronous rectification device, coupled to said power transformer, that is active during a first cyclic interval of said power converter.

57. The method as claimed in claim 51 further comprising rectification device, coupled to said power transformer, that is active during a first cyclic interval of said power converter.

58. The method as claimed in claim 51 wherein said clamping circuit comprises a switching device connected in series with a capacitor.

59. The method as claimed in claim 58 further comprising controlling said switching device with a control circuit.

60. The method as claimed in claim 51 wherein said power converter operates in one of: