Reverse current protection for power converters having synchronous rectifiers

Abstract

A power supply includes an input, an output, a reverse current protection circuit, a synchronous rectifier and an output choke. The reverse current protection circuit is configured for detecting a flyback voltage indicative of reverse current, and for deactivating the synchronous rectifier in response to detecting the flyback voltage. The flyback voltage can be detected a variety of ways, including across the output choke, across a switch in the synchronous rectifier, across the secondary winding of a power transformer, etc.

Description

DRAWINGS

The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.

FIG. 1 is a block diagram of a power converter according to one embodiment of the present disclosure.

FIG. 2 is a block diagram of the reverse current protection circuit shown in FIG. 1 according to another embodiment of the present disclosure.

FIG. 3 is a circuit diagram of a power converter having a reverse current protection circuit according to another embodiment of the present disclosure.

FIG. 4A is a circuit diagram of a reverse current protection circuit according to another embodiment of the present disclosure.

FIG. 4B is a circuit diagram of an alternative reverse current protection circuit.

FIG. 5A is a circuit diagram of a reverse current protection circuit according to still another embodiment of the present disclosure.

FIG. 5B is a circuit diagram of the reverse current protection circuit of FIG. 5A having an alternative output choke.

FIG. 6A is a circuit diagram of a power converter according to another embodiment of the present disclosure.

FIG. 6B is a circuit diagram of a power converter according to yet another embodiment of the present disclosure.

FIG. 7A is a circuit diagram of a power converter according to still another embodiment of the present disclosure.

FIG. 7B is a circuit diagram of a power converter according to another embodiment of the present disclosure.

FIG. 8A is a block diagram of a power converter according to yet another embodiment of the present disclosure.

FIG. 8B is a block diagram of a power converter according to another embodiment of the present disclosure.

Claims

1. A power supply comprising: a plurality of interconnected power supply modules for supplying power to an output load,at least one of the power supply modules including a synchronous rectifier, an output choke, and a reverse current protection circuit,the reverse current protection circuit configured for detecting a flyback voltage across the output choke, the flyback voltage being indicative of reverse current in the power supply module, and for deactivating the synchronous rectifier in response to detecting the flyback voltage.

2. The power supply of claim 2 wherein the at least one power supply module further includes an ORing MOSFET.

3. The power supply of claim 1 wherein the reverse current protection circuit includes at least a first comparator for comparing a voltage across the output choke with a reference voltage to detect the flyback voltage.

4. The power supply of claim 3 wherein the reverse current protection circuit is configured for deactivating the synchronous rectifier when the voltage across the output choke is greater than the reference voltage.

5. The power supply of claim 3 wherein the power supply module includes a current transformer and the reverse current protection includes a second comparator for comparing a voltage from the current transformer with a reference voltage to determine whether a turn-on condition exists.

6. The power supply of claim 5 wherein the reverse current protection circuit is configured to activate the synchronous rectifier when the load current in the power supply module is greater than ten percent (10%) of a full rated load current.

7. The power supply of claim 1 wherein the plurality of power supply modules each include a reverse current protection circuit.

8. The power supply of claim 7 wherein the plurality of power supply modules are connected in a parallel configuration.

9. A power supply comprising: a plurality of interconnected power supply modules for supplying power to an output load,at least one of the power supply modules including a synchronous rectifier, an output choke, and a reverse current protection circuit,the reverse current protection circuit configured for detecting a flyback voltage indicative of reverse current in the power supply module, and for deactivating the synchronous rectifier in response to detecting the flyback voltage.

10. The power supply of claim 9 wherein the reverse current protection circuit is configured for detecting the flyback voltage across the output choke.

11. The power supply of claim 10 wherein the reverse current protection circuit includes an auxiliary winding coupled to the output choke for reflecting a voltage across the output choke to the reverse current protection circuit.

12. The power supply of claim 11 wherein the reverse current protection circuit includes a comparator coupled to the auxiliary winding for comparing the reflected voltage with a reference voltage to detect the flyback voltage.

13. The power supply of claim 9 wherein the synchronous rectifier includes at least one switch and the reverse current protection circuit is configured for detecting the flyback voltage across said switch.

14. The power supply of claim 13 wherein the switch is a MOSFET having a drain and a source and the reverse current protection circuit is configured for detecting the flyback voltage across the drain to source of said MOSFET.

15. The power supply of claim 9 wherein the power supply module includes a transformer having a secondary winding and the reverse current protection circuit is configured for detecting the flyback voltage across the secondary winding of the transformer.

16. The power supply of claim 9 wherein the reverse current protection circuit includes one or more latch elements for holding the synchronous rectifier in the deactivated state.

17. The power supply of claim 16 wherein the reverse current protection circuit includes a reset circuit for activating the synchronous rectifier in response to detecting a turn-on condition.

18. The power supply of claim 17 wherein the reset circuit includes a current transformer for monitoring load current, and is configured to detect the turn-on condition by comparing a voltage signal from the current transformer with a reference voltage.

19. The power supply of claim 18 wherein the reset circuit is configured to activate the synchronous rectifier when the load current is greater than approximately ten percent (10%) of the rated load.

20. The power supply of claim 9 wherein the plurality of power supply modules are interconnected via a bus.

21. A power supply comprising: at least one power supply module including a synchronous rectifier, an output choke, and a reverse current protection circuit,the reverse current protection circuit configured for detecting a flyback voltage indicative of reverse current in the power supply module, and for deactivating the synchronous rectifier in response to detecting the flyback voltage.