Controller for a synchronous rectifier and power converter employing the same

• US 5,940,287 A
• Filed: 07/14/1998
• Issued: 08/17/1999
• Est. Priority Date: 07/14/1998
• Status: Expired due to Term

• Current Assignee: ABB Power Electronics Inc. (ABB Ltd.)
• Original Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: Brkovic, Milivoje Slobodan
• Primary Examiner(s): Wong, Peter S.
• Assistant Examiner(s): Patel, Rajnikant B.
• Application Number:
  US09/115,487
• Time in Patent Office: 399 Days
• Field of Search: 363/127, 323/283, 323/224, 323/285, 323/284, 323/286, 323/287
• US Class Current: 363/127
• CPC Class Codes: G05F 1/618 using semiconductor devices in series and in parallel with the load as final control devices G05F1/461 takes precedence
• CPC Class Codes: H02M 3/1588 comprising at least one synchronous rectifier element H02M3/1582, H02M3/1584 take precedence
• 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 converter having a power switch and a synchronous rectifier device coupled between an input and an output thereof, a transient response network, method of disabling a synchronous rectifier device and power converter employing the network and method. In one embodiment, the transient response network includes a synchronous rectifier controller, coupled to the power switch and the synchronous rectifier device, that senses a state of the power switch and disables the synchronous rectifier device when the power switch has remained in a nonconducting state for at least a specified period of time.

Claims

1. For use in a power converter having a power switch and a synchronous rectifier device coupled between an input and an output thereof, a transient response network, comprising:

a synchronous rectifier controller, coupled to said power switch and said synchronous rectifier device, that senses a drive signal to said power switch and disables said synchronous rectifier device when said drive signal is missing for at least a specified period of time.

2. The network as recited in claim 1 wherein said synchronous rectifier device is located in a discharge path between an inductor and an output capacitor of said power converter.

3. The network as recited in claim 1 wherein said power converter further comprises a plurality of synchronous rectifier devices, said synchronous rectifier controller adapted to disable at least one of said plurality of synchronous rectifier devices.

4. The network as recited in claim 1 wherein said power converter further comprises a plurality of power switches, said synchronous rectifier controller adapted to disable said synchronous rectifier device when at least one of said plurality of power switches has remained in said nonconducting state for at least said specified period of time.

5. The network as recited in claim 1 wherein said specified period of time is greater than one switching cycle of said power switch.

6. The network as recited in claim 1 wherein said synchronous rectifier controller comprises a logic AND gate and a resistor-capacitor circuit, said resistor-capacitor circuit and said logic AND gate cooperating to allow said synchronous rectifier controller to disable said synchronous rectifier device when said power switch has remained in said nonconducting state for at least said specified period of time.

7. The network as recited in claim 1 wherein said synchronous rectifier controller comprises a circuit adapted to enable said synchronous rectifier device when said synchronous rectifier device has been disabled for a selected period of time.

8. The network as recited in claim 1 wherein said power switch and said synchronous rectifier device are selected from the group consisting of:

a field-effect transistor (FET), and

a bipolar transistor.

9. The network as recited in claim 1 wherein said power converter further comprises a pulse-width modulation controller coupled between said power switch and said output.

10. For use in a power converter having a power switch and a synchronous rectifier device coupled between an input and an output thereof, a method of disabling said synchronous rectifier device, comprising:

sensing a drive signal to said power switch; and

disabling said synchronous rectifier device when said drive signal is missing for at least a specified period of time.

11. The method as recited in claim 10 further comprising positioning said synchronous rectifier device in a discharge path between an inductor and an output capacitor of said power converter.

12. The method as recited in claim 10 wherein said power converter further comprises a plurality of synchronous rectifier devices, the method further comprising disabling at least one of said plurality of synchronous rectifier devices.

13. The method as recited in claim 10 wherein said power converter further comprises a plurality of power switches, the method further comprising disabling said synchronous rectifier device when at least one of said plurality of power switches has remained in said nonconducting state for at least said specified period of time.

14. The method as recited in claim 10 wherein said specified period of time is greater than one switching cycle of said power switch.

15. The method as recited in claim 10 wherein the act of disabling is performed by a synchronous rectifier controller comprising a logic AND gate and a resistor-capacitor circuit.

16. The method as recited in claim 10 further comprising enabling said synchronous rectifier device in a selected period of time following the act of disabling.

17. The method as recited in claim 10 wherein said power switch and said synchronous rectifier device are selected from the group consisting of:

a field-effect transistor (FET), and

a bipolar transistor.

18. The method as recited in claim 10 further comprising controlling said power switch with a pulse-width modulation controller.

19. A power converter, comprising:

a power switch coupled to an input of said power converter;

an inductor coupled to said power switch;

an output capacitor coupled to an output of said power converter;

a synchronous rectifier device located in a discharge path between said inductor and said output capacitor; and

a transient response network, comprising;

a synchronous rectifier controller, coupled to said power switch and said synchronous rectifier device, that senses a drive signal to said power switch and disables said synchronous rectifier device when said drive signal is missing for at least a specified period of time.

20. The power converter as recited in claim 19 further comprising a plurality of synchronous rectifier devices, said synchronous rectifier controller adapted to disable at least one of said plurality of synchronous rectifier devices.

21. The power converter as recited in claim 19 further comprising a plurality of power switches, said synchronous rectifier controller adapted to disable said synchronous rectifier device when at least one of said plurality of power switches has remained in said nonconducting state for at least said specified period of time.

22. The power converter as recited in claim 19 wherein said specified period of time is greater than one switching cycle of said power switch.

23. The power converter as recited in claim 19 wherein said synchronous rectifier controller comprises a logic AND gate and a resistor-capacitor circuit, said resistor-capacitor circuit and said logic AND gate cooperating to allow said synchronous rectifier controller to disable said synchronous rectifier device when said power switch has remained in said nonconducting state for at least said specified period of time.

24. The power converter as recited in claim 19 wherein said synchronous rectifier controller comprises a circuit adapted to enable said synchronous rectifier device when said synchronous rectifier device has been disabled for a selected period of time.

25. The power converter as recited in claim 19 wherein said power switch and said synchronous rectifier device are selected from the group consisting of:

a field-effect transistor (FET), and

a bipolar transistor.

26. The power converter as recited in claim 19 further comprising a pulse-width modulation controller coupled between said power switch and said output.