Current sensing in a power converter

• US 7,683,593 B2
• Filed: 11/30/2006
• Issued: 03/23/2010
• Est. Priority Date: 11/30/2006
• Status: Expired due to Fees

• Current Assignee: Fairchild Semiconductor Corporation (ON Semiconductor Corporation)
• Original Assignee: Fairchild Semiconductor Corporation (ON Semiconductor Corporation)
• Inventors: Tao, Hai
• Primary Examiner(s): HAN, YOUNGHUIE JESSICA
• Application Number:
  US11/606,449
• Publication Number:
  US 20080130330A1
• Time in Patent Office: 1,209 Days
• Field of Search: 323/313, 323/314, 323/316, 323274-280, 323/282, 323/284
• US Class Current: 323/277
• CPC Class Codes: G01R 19/0092 measuring current only all subgroups of G01R19/00 take precedence
• CPC Class Codes: H02M 1/0009 Devices or circuits for detecting current in a converter

Abstract

In one embodiment, a power converter system includes a power device coupled between a first node and second node. The power device is operable to be turned on and off by a control signal. Current flows through the power device when the power device is turned on for delivering power to a load. A sensing circuit is coupled in parallel to the power device between the first node and the second node. The sensing circuit is operable to develop a signal indicative of the current flowing through the power device and is further operable to be turned on and off by the same control signal as for the power device. The sensing circuit turns on when the power device turns on and turns off when the power device turns off.

Claims

1. A power converter system comprising:

a power device coupled between a first node and second node, the power device operable to be turned on and off by a control signal, wherein current flows through the power device when the power device is turned on for delivering power to a load; and

a sensing circuit coupled in parallel to the power device between the first node and the second node, the sensing circuit operable to develop a signal indicative of the current flowing through the power device and further operable to be turned on and off by the same control signal as for the power device, wherein the sensing circuit turns on when the power device turns on and turns off when the power device turns off.

2. The power converter system of claim 1, wherein the sensing circuit comprises:

a first switching device coupled between the first node and a third node, wherein the first switching device remains turned on during operation of the power converter system; and

a second switching device coupled in series with the first switching device between the third node and the second node, the second switching device turned on and off by the same control signal as for the switching device.

3. The power converter system of claim 2, wherein the power device, the first switching device, and the second switching device are in triode mode when the power device and the sensing circuit are turned on.

4. The power converter system of claim 2, wherein a size ratio between each of the first and second switching and the power device is predetermined.

5. The power converter system of claim 2, wherein the signal indicative of the current flowing through the power device comprises a current flowing through the first and second switching devices.

6. The power converter system of claim 1, wherein the sensing circuit is implemented on an integrated circuit device.

7. The power converter system of claim 1, wherein the power device and the sensing circuit are implemented on an integrated circuit device.

8. The power converter system of claim 1, wherein the sensing circuit comprises a switching device, wherein a size ratio between the switching device of the sensing circuit and the power device is predetermined.

9. The power converter system of claim 8, wherein the power device and the switching device are geometrically matched.

10. In a power converter system having a power device operable to be turned on and off by a control signal for delivering power to a load, a method for sensing current flow through the power device, the method comprising:

providing a sensing circuit coupled in parallel to the power device;

turning on the sensing circuit when the power device turns on;

developing a signal indicative of the current flowing through the power device using the sensing circuit when the power device is turned on; and

turning off the sensing circuit when the power device turns off.

11. The method of claim 10 wherein the power device is coupled between a first node and second node, and wherein the sensing circuit comprises:

a first switching device coupled between the first node and a third node, wherein the first switching device remains turned on during operation of the power converter system;

a second switching device coupled in series with the first switching device between the third node and the second node, the second switching device turned on and off by the same control signal as for the switching device.

12. The method of claim 11, comprising maintaining the power device, the first switching device, and the second switching device in triode mode when the power device and the sensing circuit are turned on.

13. The method of claim 11, wherein the signal indicative of the current flowing through the power device comprises a current flowing through the first and second switching devices.

14. The method of claim 10, wherein at least one of the power device and the sensing circuit are implemented on an integrated circuit device.

15. The method of claim 10, wherein the sensing circuit comprises a switching device, wherein a size ratio between the switching device of the sensing circuit and the power device is predetermined.

16. The method of claim 10, wherein the power device and the switching device are geometrically matched.

17. A power converter system for providing power to a load, the power converter system comprising:

a regulated output terminal at which the load can be connected;

a power device operable to be turned on and off with a control signal, the power device coupled between a first node and a second node;

an inductor coupled between the second node and the output terminal through which current flows to the regulated output terminal; and

a sensing circuit coupled in parallel to the power device between the first node and the second node, the sensing circuit operable to develop a signal indicative of the current flowing through the power device and further operable to be turned on and off by the same control signal as for the power device, wherein the sensing circuit turns on when the power device turns on and turns off when the power device turns off.

18. The power converter system of claim 17 comprising a synchronous rectifier coupled to the power device at the second node.

19. The power convener system of claim 17, wherein the sensing circuit comprises:

a first switching device coupled between the first node and a third node, wherein the first switching device remains turned on during operation of the power converter system; and

a second switching device coupled in series with the first switching device between the third node and the second node, the second switching device turned on and off by the same control signal as for the switching device.

20. The power converter system of claim 19, wherein the power device, the first switching device, and the second switching device are in triode mode when the power device and the sensing circuit are turned on.

21. The power converter system of claim 19, wherein a size ration between each of the first and second switching devices and the power device is predetermined.

22. The power converter system of claim 19, wherein the signal indicative of the current flowing through the power device comprises a current flowing through the first and second switching devices.

23. The power converter system of claim 19, wherein the power device and the sensing circuit are implemented on an integrated circuit device.

24. The power converter system of claim 19, wherein the sensing circuit comprises a switching device, wherein a size ration between the switching device of the sensing circuit and the power device is predetermined.

25. The power converter system of claim 24, wherein the power device and the switching device are geometrically matched.