Circuit and method for controlling a synchronous rectifier converter

• US 6,038,154 A
• Filed: 07/02/1999
• Issued: 03/14/2000
• 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: Rozman, Allen Frank, Boylan, Jeffrey J.
• Primary Examiner(s): Wong, Peter S.
• Assistant Examiner(s): Vu, Bao Q.
• Application Number:
  US09/346,848
• Time in Patent Office: 256 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: 363/127
• 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 transitions 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. A method of operating a power supply having an independently selectable output setpoint and parallel-coupled to a second power supply with independently selectable output setpoint, comprising:

rectifying substantially alternating current to produce substantially direct current with switching circuitry including at least one synchronous rectifier device and adapted to operate in an active bi-directional mode of operation;

sensing an output current of said power supply and developing a signal when said output current is negative; and

adjusting said output setpoint of said power supply based on said signal to prevent substantially large negative currents from flowing from an output of said second power supply into an output of said power supply.

2. The method as recited in claim 1 wherein said output current comprises negative instantaneous currents.

3. The method as recited in claim 1 wherein said output current comprises negative average currents.

4. The method as recited in claim 1 wherein said adjusting comprises adjusting a duty ratio of a switch associated with said power supply.

5. The method as recited in claim 1 wherein said adjusting occurs during a startup period of said power supply.

6. The method as recited in claim 1 wherein said adjusting comprises substantially equalizing said output setpoints of said power supply and said second power supply.

7. A power supply having an independently selectable output setpoint and parallel-couplable to a second power supply having an independently selectable output setpoint, comprising:

switching circuitry including at least one synchronous rectifier device and adapted to operate in an active bi-directional mode of operation thereby rectifying substantially alternating current to produce substantially direct current; and

a sensor capable of sensing an output current of said power supply and developing a signal when said output current is negative; and

synchronous rectifier control circuitry, coupled to said sensor, capable of adjusting an output setpoint of said power supply based on said signal to prevent substantially large negative currents from flowing from an output of said second power supply into an output of said power supply.

8. The power supply as recited in claim 7 wherein said output current comprises negative instantaneous currents.

9. The power supply as recited in claim 7 wherein said output current comprises negative average currents.

10. The power supply as recited in claim 7 wherein said synchronous rectifier control circuitry adjusts a duty ratio of a switch associated with said power supply.

11. The power supply as recited in claim 7 wherein said synchronous rectifier control circuitry adjusts said output setpoint during a startup period of said power supply.

12. The power supply as recited in claim 7 further comprising an active load sharing circuit adapted to substantially equalize said output setpoints of said power supply and said second power supply.

13. The power supply as recited in claim 7, further comprising:

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

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

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. A method of operating a power system, comprising:

providing first and second power supplies having switching circuitry with at least one synchronous rectifier device and independently selectable output setpoints, each of said first and second power supplies adapted to;

operate said switching circuitry in a selected one of (a) an active bi-directional mode of operation when enabled and (b) an inactive unidirectional mode of operation when disabled, thereby rectifying substantially alternating current to produce substantially direct current,

sense an operating characteristic thereof, and

enable or disable said switching circuitry as a function of said characteristic to prevent substantial reverse power flow therethrough; and

coupling at least one conduction device to said first and second power supplies adapted to prevent outputs of said first and second power supplies from diverging by more than about a forward drop associated with said at least one conduction device.

15. The method as recited in claim 14 wherein said conduction device is a diode.

16. The method as recited in claim 14 wherein said switching circuitry of said first and second power supplies comprises discrete diodes to allow said switching circuitry to operate in said inactive unidirectional mode of operation.

17. The method as recited in claim 14 wherein said switching circuitry of said first and second power supplies is disabled during a startup period of said power system.

18. The method as recited in claim 14 further comprising detecting when said first and second power supplies are operating in parallel.

19. The method as recited in claim 14 wherein said at least one conduction device is non-conductive during steady state operation of the power system.

20. The method as recited in claim 14 wherein said switching circuitry of said first and second power supplies comprise a plurality of synchronous rectifier devices.

21. A power system, comprising:

first and second power supplies having independently selectable output setpoints and including;

switching circuitry having at least one synchronous rectifier device and adapted to operate in a selected one of (a) an active bi-directional mode of operation when enabled and (b) an inactive unidirectional mode of operation when disabled, thereby rectifying substantially alternating current to produce substantially direct current,

a sensor capable of sensing an operating characteristic thereof, and

synchronous rectifier control circuitry capable of enabling or disabling said switching circuitry as a function of said characteristic to prevent substantial reverse power flow therethrough; and

at least one conduction device coupled to said first and second power supplies adapted to prevent outputs of said first and second power supplies from diverging by more than about a forward drop associated with said at least one conduction device.

22. The power system as recited in claim 21 wherein said conduction device is a diode.

23. The power system as recited in claim 21 wherein said switching circuitry of said first and second power supplies comprises discrete diodes to allow said switching circuitry to operate in said inactive unidirectional mode of operation.

24. The power system as recited in claim 21 wherein said switching circuitry of said first and second power supplies is disabled during a startup period of said power system.

25. The power system as recited in claim 21 further comprising detection circuitry adapted to detect parallel operation between said first and second power supplies.

26. The power system as recited in claim 21 wherein said at least one conduction device is non-conductive during steady state operation of the power system.

27. The power system as recited in claim 21 wherein said switching circuitry ofsaid first and second power supplies comprise a plurality of synchronous rectifier devices.

28. The power system as recited in claim 21 wherein said first and second power supplies further include:

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

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

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.