Circuit and method for controlling a synchronous rectifier converter

• US 6,191,964 B1
• Filed: 12/27/1999
• Issued: 02/20/2001
• Est. Priority Date: 05/04/1995
• Status: Expired due to Term

• Current Assignee: Lineage Power Corporation (GE Aerospace)
• Original Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: Boylan, Jeffrey J., Rozman, Allen Frank
• Primary Examiner(s): Wong, Peter S.
• Assistant Examiner(s): Vu, Bao Q.
• Application Number:
  US09/472,617
• Time in Patent Office: 421 Days
• Field of Search: 363/127, 363/89, 363/20, 363/21, 363/53, 363/71, 363/65, 363/97, 363/81, 363/84, 323/239
• US Class Current: 363/89
• CPC Class Codes: H02J 1/001 Hot plugging or unplugging of load or power modules to or from power distribution networks
• CPC Class Codes: H02J 1/102 being switching converters H02J1/108, H02J1/12 take precedence
• CPC Class Codes: H02M 3/1563 without using an external clock H02M3/158 takes precedence
• CPC Class Codes: H02M 3/33584 Bidirectional converters
• 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: 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

For use in a power system having a power train, a rectifier having an input and an output and a method of controlling the rectifier. The rectifier comprises: (1) switching circuitry coupled between the input and the output, the switching, circuitry adapted to operate in selected one of (a) a bidirectional mode of operation and (b) an unidirectional mode of operation to rectify substantially alternating current at the input to produce substantially direct current at the output; and (2) control circuitry coupled to a control input of the switching circuitry, the control circuitry capable of sensing a characteristic of the power system and transitioning the switching circuitry between the bidirectional mode and the unidirectional mode as a function of the characteristic thereby to prevent substantial reverse power flow through the rectifier.

Claims

1. For use with a power converter including a synchronous rectifier circuit having switching circuitry with at least one synchronous rectifier device and adapted to rectify substantially alternating current to produce substantially direct current, a control circuit, comprising:

a sensor capable of sensing a characteristic of said power converter;

comparison circuitry capable of comparing said characteristic with a reference and developing a control signal in accordance therewith; and

synchronous rectifier control circuitry, coupled to said comparison circuitry, adapted to disable said at least one synchronous rectifier device as a function of said control signal to thereby prevent substantial reverse power flow through said power converter.

2. The control circuit as recited in claim 1 wherein said power converter, further comprises:

a power transformer having primary and secondary windings, said secondary winding being coupled to said switching circuitry; and

at least one power switch occasionally coupling said primary winding to a source of electrical power.

3. The control circuit as recited in claim 2 wherein said power converter further comprises a clamping circuit, coupled to said power transformer, adapted to limit a voltage across said transformer during at least a portion of a non-conduction interval of said at least one power switch.

4. The control circuit as recited in claim 1 wherein said synchronous rectifier control circuitry is adapted to disable said at least one synchronous rectifier device during one of a start-up and shut-down period of said power converter.

5. The control circuit as recited in claim 1 wherein said power converter is parallel-coupled to a second power converter, said synchronous rectifier control circuitry adapted to disable said at least one synchronous rectifier device thereby preventing said second power converter from causing said substantial reverse power flow.

6. The control circuit as recited in claim 5 further comprising an active load-sharing circuit adapted to effect load sharing between said power converter and said second power converter.

7. The control circuit as recited in claim 1 wherein said switching circuitry comprises at least one discrete diode.

8. The control circuit as recited in claim 1 wherein said sensor is selected from the group consisting of:

a current transformer in electrical communication with an output of said power converter;

a resistor in electrical communication with said output; and

a Hall effect current sense device coupled in series with said output.

9. The control circuit as recited in claim 1 wherein said switching circuitry comprises a plurality of synchronous rectifier devices, said synchronous rectifier control circuitry adapted to disable all of said plurality of synchronous rectifier devices.

10. The control circuit as recited in claim 1 further comprising detection circuitry capable of detecting parallel operation between said power converter and a second power converter, said detection circuitry allowing said synchronous rectifier control circuitry to disable said at least one synchronous rectifier device only when said power converter is parallel-coupled to said second power converter.

11. For use with a power converter including a synchronous rectifier circuit having switching circuitry with at least one synchronous rectifier device and adapted to rectify substantially alternating current to produce substantially direct current, a method for controlling said synchronous rectifier circuit, comprising:

sensing a characteristic of said power converter;

comparing said characteristic with a reference and developing a control signal in accordance therewith; and

disabling said at least one synchronous rectifier device as a function of said control signal to thereby prevent substantial reverse power flow through said power converter.

12. The method as recited in claim 11 wherein said power converter, further comprises:

a power transformer having primary and secondary windings, said secondary winding being coupled to said switching circuitry; and

at least one power switch occasionally coupling said primary winding to a source of electrical power.

13. The method as recited in claim 12 wherein said power converter further comprises a clamping circuit, coupled to said power transformer, adapted to limit a voltage across said power transformer during at least a portion of a non-conduction interval of said at least one power switch.

14. The method as recited in claim 11 wherein said disabling said at least one synchronous rectifier device occurs during one of a start-up and shut-down period of said power converter.

15. The method as recited in claim 11 wherein said power converter is parallel-coupled to a second power converter, said disabling said at least one synchronous rectifier device thereby preventing said second power converter from causing said substantial reverse power flow.

16. The method as recited in claim 15 wherein said power converter further comprises an active load-sharing circuit that effects load sharing between said power converter and said second power converter.

17. The method as recited in claim 11 wherein said switching circuitry comprises at least one discrete diode.

18. The method as recited in claim 11 wherein said sensing is performed by a sensor selected from the group consisting of:

a current transformer in electrical communication with an output of said power converter;

a resistor in electrical communication with said output; and

a Hall effect current sense device coupled in series with said output.

19. The method as recited in claim 11 wherein said switching circuitry comprises a plurality of synchronous rectifier devices, said disabling further disabling all of said plurality of synchronous rectifier devices as said function of said control signal.

20. The method as recited in claim 11 wherein said power converter further comprises detection circuitry capable of detecting parallel operation between said power converter and a second power converter.

21. A power converter having an input and an output, comprising:

at least one power switch coupled to said input;

a power transformer having primary and secondary windings, said primary winding coupled to said at least one power switch;

a synchronous rectifier circuit, interposed between said secondary winding and said output, including switching circuitry with at least one synchronous rectifier device and adapted to rectify substantially alternating current to produce substantially direct current; and

a control circuit, coupled to said synchronous rectifier circuit, including;

a sensor capable of sensing a characteristic of said power converter,

comparison circuitry capable of comparing said characteristic with a reference and developing a control signal in accordance therewith, and

synchronous rectifier control circuitry, coupled to said comparison circuitry, adapted to disable said at least one synchronous rectifier device as a function of said control signal to thereby prevent substantial reverse power flow through said power converter.

22. The power converter as recited in claim 21 further comprising a clamping circuit, coupled to said power transformer, adapted to limit a voltage across said power transformer during at least a portion of a non-conduction interval of said at least one power switch.

23. The power converter as recited in claim 21 wherein said synchronous rectifier control circuitry is adapted to disable said at least one synchronous rectifier device during one of a start-up and shut-down period of said power converter.

24. The power converter as recited in claim 21 wherein said power converter is parallel-coupled to a second power converter, said synchronous rectifier control circuitry adapted to disable said at least one synchronous rectifier device thereby preventing said second power converter from causing said substantial reverse power flow.

25. The power converter as recited in claim 21 wherein said control circuit further comprises an active load-sharing circuit adapted to effect load sharing between said power converter and said second power converter.

26. The power converter as recited in claim 21 wherein said switching circuitry comprises at least one discrete diode.

27. The power converter as recited in claim 21 wherein said sensor is selected from the group consisting of:

a current transformer in electrical communication with said output;

a resistor in electrical communication with said output; and

a Hall effect current sense device coupled in series with said output.

28. The power converter as recited in claim 21 wherein said switching circuitry comprises a plurality of synchronous rectifier devices, said synchronous rectifier control circuitry adapted to disable all of said plurality of synchronous rectifier devices.

29. The power converter as recited in claim 21 wherein said control circuit further comprises detection circuitry capable of detecting parallel operation between said power converter and a second power converter, said detection circuitry allowing said synchronous rectifier control circuitry to disable said at least one synchronous rectifier device only when said power converter is parallel-coupled to said second power converter.

30. The power converter as recited in claim 21 further comprising an output capacitor and inductor interposed between said synchronous rectifier circuit and said output.

31. A power system having first and second power converters, each of said first and second converters, comprising:

a synchronous rectifier circuit including switching circuitry having at least one synchronous rectifier device and adapted to rectify substantially alternating current to produce substantially direct current;

a control circuit, coupled to said switching circuitry, adapted to control said at least one synchronous rectifier device as a function of a characteristic of said power system thereby to prevent one of said first and second power converters from creating substantial reverse power flow through another of said first and second power converters; and

an active load-sharing circuit coupled to said first and second power converters adapted to effect load sharing therebetween.

32. The power system as recited in claim 31 wherein each of said first and second power converters, further comprises:

a power transformer having primary and secondary windings, said secondary winding being coupled to said switching circuitry; and

at least one power switch occasionally coupling said primary winding to a source of electrical power.

33. The power system as recited in claim 32 wherein each of said first and second power converters further comprises a clamping circuit, coupled to said power transformer, adapted to limit a voltage across said transformer during at least a portion of a non-conduction interval of said at least one power switch.

34. The power system as recited in claim 31 wherein said control circuit is adapted to disable said at least one synchronous rectifier device during one of a start-up and shut-down period of said power system.

35. The power system as recited in claim 31 wherein said first power converter is parallel-coupled to said second power converter, said control circuit adapted to control said at least one synchronous rectifier device thereby preventing said second power converter from causing said substantial reverse power flow.

36. The power system as recited in claim 31 said at least one synchronous rectifier device is a metal oxide semiconductor field effect transistor (MOSFET).

37. The power system as recited in claim 31 wherein said switching circuitry comprises at least one discrete diode.

38. The power system as recited in claim 31 wherein said control circuit includes a sensor adapted to measure said characteristic of said power system selected from the group consisting of:

a current transformer in electrical communication with an output of said power system;

a resistor in electrical communication with said output; and

a Hall effect current sense device coupled in series with said output.

39. The power system as recited in claim 31 wherein said switching circuitry comprises a plurality of synchronous rectifier devices, said control circuit adapted to control all of said plurality of synchronous rectifier devices.

40. The power system as recited in claim 31 further comprising detection circuitry capable of detecting parallel operation between said first and second power converters, said detection circuitry allowing said control circuit to control said at least one synchronous rectifier device only when said first power converter is parallel-coupled to said second power converter.