Power management with over voltage protection

• US 8,836,166 B2
• Filed: 10/17/2011
• Issued: 09/16/2014
• Est. Priority Date: 10/15/2010
• Status: Expired

• Current Assignee: Semiconductor Components Industries LLC (ON Semiconductor Corporation)
• Original Assignee: Fairchild Semiconductor Corporation (ON Semiconductor Corporation)
• Inventors: Maher, Gregory A., Miske, Myron J.
• Primary Examiner(s): Barnie, Rexford
• Assistant Examiner(s): DHILLON, JAGDEEP S
• Application Number:
  US13/274,654
• Publication Number:
  US 20120126625A1
• Time in Patent Office: 1,065 Days
• Field of Search: 307/80, 307/43, 361/91.1, 361/111, 361/18, 361/100, 714/733, 325/22, 325/57, 325/21, 325/52, 320/134, 320/152, 320/157, 320/159, 323/282
• US Class Current: 307/80
• CPC Class Codes: G06F 1/263 Arrangements for using multiple switchable power supplies, e.g. battery and AC G06F1/30 takes precedence
• CPC Class Codes: G06F 1/30 Means for acting in the event of power-supply failure or interruption, e.g. power-supply fluctuations for resetting only G06F1/24
• CPC Class Codes: H02H 1/06 Arrangements for supplying operative power power supply arrangements in general G05F, H02M
• CPC Class Codes: H02H 3/20 responsive to excess voltage
• CPC Class Codes: H02H 7/20 for electronic equipment for converters H02H7/10; for electric measuring instruments G01R1/36; for dc voltage or current semiconductor regulators G05F1/569; for amplifiers H03F1/52; for electronic switching circuits H03K17/08
• CPC Class Codes: H02H 9/04 responsive to excess voltage lightning arrestors H01C7/12, H01C8/04, H01G9/18, H01T
• CPC Class Codes: H02J 9/061 for DC powered loads
• CPC Class Codes: H02J 9/068 Electronic means for switching from one power supply to another power supply, e.g. to avoid parallel connection

Abstract

This document discusses, among other things, systems and methods to provide an internal supply rail with over voltage protection using a host power source, an external power source, and a switch configured to receive indications of host and external power source validity. In an example, the switch can be configured to provide the internal supply rail using the host power source when the indication of host power source validity indicates a valid host power source and the external power source when the indication of host power source validity indicates an invalid host power source and the indication of external power source validity indicates a valid external power source.

Claims

1. A power management circuit, comprising:

a switch configured to receive a host power source, an external power source, an indication of host power source validity, and an indication of external power source validity;

wherein the switch is configured to provide an internal supply rail using (1) the host power source when the indication of host power source validity indicates a valid host power source, and (2) the external power source when the indication of host power source validity indicates an invalid host power source and the indication of external power source validity indicates a valid external power source; and

an over voltage protection circuit, including;

an over voltage detection circuit configured to detect an over voltage condition on the external power source; and

a clamp circuit configured to clamp the external power source when the over voltage detection circuit detects the over voltage condition on the external power source.

2. The power management circuit of claim 1, including:

a host power source detection circuit configured to validate the host power source and to provide the indication of host power source validity; and

an external power source detection circuit configured to validate the external power source and to provide the indication of external power source validity;

wherein the host power source includes a battery, and wherein the external power source includes an external bus voltage.

3. The power management circuit of claim 2, wherein the clamp circuit includes a clamp switch configured to selectively short the clamp circuit for an initial time period when the indication of external power source validity indicates a valid external power source.

4. The power management circuit of claim 2, including a bandgap reference circuit configured to provide a bandgap voltage reference;

wherein the host power source detection circuit includes a comparator configured to validate the host power source using the value of the host power source and the bandgap voltage reference; and

wherein the external power source detection circuit includes a comparator configured to validate the external power source using the value of the external power source and the bandgap voltage reference.

5. The power management circuit of claim 1, including a voltage regulator configured to provide a regulated external power source;

and

wherein the switch is configured to provide the internal supply rail using the regulated external power source when the indication of host power source validity indicates an invalid host power source and the indication of external power source validity indicates a valid external power source.

6. The power management circuit of claim 1, wherein the switch includes:

a first input configured to receive the host power source;

a second input configured to receive the external power source;

a first control input configured to receive the indication of the host power source validity;

a second control input configured to receive the indication of the external power source validity; and

an output configured to provide an internal supply rail.

7. The power management circuit of claim 1, wherein the clamp circuit includes a clamp switch configured to selectively short the clamp circuit when the over voltage detection circuit does not detect the over voltage condition on the external power source.

8. The power management circuit of claim 7, wherein the clamp switch includes a transistor;

wherein the clamp circuit includes a clamp control circuit including an oscillator, a counter, and a charge pump; and

wherein the clamp control circuit is configured to receive an indication of a detected over voltage condition and to control the clamp switch using the indication of over voltage detection circuit detects the over voltage condition on the external power source.

9. A power management method, comprising:

receiving indications of host and external power source validities;

providing an internal supply rail using a host power source when the indication of host power source validity indicates a valid host power source;

providing an internal supply rail using an external power source when the indication of host power source validity indicates an invalid host power source and the indication of external power source validity indicates a valid external power source;

detecting an over voltage condition on the external power source; and

clamping the external power source using a clamp circuit when the over voltage condition is detected on the external power source.

10. The method of claim 9, including:

validating the host power source and providing the indication of host power source validity; and

validating the external power source and providing the indication of external power source validity.

11. The method of claim 10, including selectively shorting the clamp circuit for an initial time period when the indication of external power source validity indicates a valid external power source.

12. The method of claim 10, including:

providing a bandgap voltage reference;

validating the host power source using the value of the host power source and the bandgap voltage reference; and

validating the external power source using the value of the external power source and the bandgap voltage reference.

13. The method of claim 9, including providing a regulated external power source;

and

wherein the providing the internal supply rail includes using the regulated external power source when the indication of host power source validity indicates an invalid host power source and the indication of external power source validity indicates a valid external power source.

14. The method of claim 9, including selectively shorting a clamp circuit when the over voltage detection circuit does not detect an over voltage condition on the external power source.

15. The method of claim 14, including:

receiving an indication of a detected over voltage condition on the external power source; and

controlling the clamp circuit using the indication of over voltage detection detects the over voltage condition on the external power source.

16. A power management system, comprising:

an electronic device, including a host power source and a universal serial bus (USB) port, the USB port configured to receive an external power source;

a switch configured to receive the host power source, the external power source, an indication of host power source validity, and an indication of external power source validity;

wherein the switch is configured to provide an internal supply rail using (1) the host power source when the indication of host power source validity indicates a valid host power source, and (2) the external power source when the indication of host power source validity indicates an invalid host power source and the indication of external power source validity indicates a valid external power source;

an over voltage protection circuit, including;

an over voltage detection circuit configured to detect an over voltage condition on the external power source; and

a clamp circuit configured to clamp the external power source when the over voltage detection circuit detects the over voltage condition on the external power source.

17. The power management system of claim 16, including:

a host power source detection circuit configured to validate the host power source and to provide the indication of host power source validity; and

an external power source detection circuit configured to validate the external power source and to provide the indication of external power source validity.

18. The power management system of claim 17, wherein the clamp circuit includes a clamp switch configured to selectively short the clamp circuit for an initial time period when the indication of external power source validity indicates a valid external power source.

19. The power management system of claim 17, including a bandgap reference circuit configured to provide a bandgap voltage reference;

wherein the host power source detection circuit includes a comparator configured to validate the host power source using the value of the host power source and the bandgap voltage reference; and

wherein the external power source detection circuit includes a comparator configured to validate the external power source using the value of the external power source and the bandgap voltage reference.

20. The power management circuit of claim 16, wherein the clamp circuit includes a clamp switch configured to selectively short the clamp circuit when the over voltage detection circuit does not detect the over voltage condition on the external power source.