System and method for high voltage protection of powered devices

• US 20070263333A1
• Filed: 06/23/2006
• Published: 11/15/2007
• Est. Priority Date: 05/11/2006
• Status: Active Grant

• Current Assignee: Skyworks Solutions Incorporated
• Original Assignee: Silicon Laboratories Incorporated
• Inventors: Apfel, Russell J.
• Granted Patent: US 7,511,930 B2
• Time in Patent Office: Days
• US Class Current: 361/91.100
• CPC Class Codes: H02H 9/041 using a short-circuiting device

Abstract

A powered device includes a rectifier circuit, a logic circuit, and a power protection element. The rectifier circuit includes two inputs to receive an input voltage from a powered network and includes two output terminals to provide a rectified power supply voltage in response to the input voltage. The logic circuit is coupled between the two inputs and adapted to receive data from the powered network. The power protection element is coupled between the two output terminals to protect to the logic circuitry from high power transients. In a first mode of operation, the power protection element presents a high impedance to the two output terminals. In a second mode of operation, the power protection element has a first power protection characteristic. In a third mode of operation, the power protection element has a second power protection characteristic.

Claims

1. A powered device comprising:

a rectifier circuit having two inputs to receive an input voltage from a powered network and having two output terminals to provide a rectified power supply voltage in response to the input voltage;

a logic circuit coupled between the two inputs and adapted to receive data from the powered network; and

a power protection element coupled between the two output terminals to protect to the logic circuitry from high power transients, wherein, in a first mode of operation, the power protection element presents a high impedance to the two output terminals, in a second mode of operation, the power protection element has a first power protection characteristic, and in a third mode of operation, the voltage protection element has a second power protection characteristic.

2. The powered device of claim 1, wherein the powered network comprises a Power over Ethernet (PoE) network, and wherein the powered device is adapted to derive power from the PoE network.

3. The powered device of claim 1, wherein the powered network comprises an electrical power network.

4. The powered device of claim 1, wherein the power protection element further comprises active logic to generate a fault protection signal to shut off power to the logic circuit when in the third mode of operation.

5. The powered device of claim 1, wherein the power protection element comprises two switches adapted to activate asynchronously in response to a signal to clamp the rectified power supply to a reduced level.

6. The powered device of claim 1, wherein the power protection element comprises a silicon controlled rectifier.

7. The integrated circuit of claim 1, wherein the power protection element is at a higher voltage in the second mode of operation than in the third mode of operation.

8. The integrated circuit of claim 7, wherein in the second mode of operation, the higher voltage is greater than 55 volts and wherein the power protection element has a current level less than one Ampere.

9. The integrated circuit of claim 7, wherein in the third mode of operation, the power protection element has a voltage level less than ten volts and a current level greater than half an Ampere.

10. The integrated circuit of claim 7, wherein the power protection element changes from the second mode of operation to the first mode of operation after a current level of the power protection element falls below a threshold current level.

11. The integrated circuit of claim 1, wherein the second power protection characteristic comprises a lower impedance than the first power protection characteristic.

12. A method comprising:

receiving an input voltage from a cable coupled to a powered network at a first input terminal and a second input terminal of an integrated circuit, the integrated circuit including a voltage protection element and at least one low-power element;

rectifying the input voltage using a diode bridge;

detecting, via the voltage protection element, an over-voltage condition when the rectified voltage exceeds a threshold voltage; and

shutting off power to the at least one low-power element in response to detecting the over-voltage condition.

13. The method of claim 12, further comprising:

shunting the rectified voltage between the first input terminal and the second input terminal after detecting the over-voltage condition.

14. The method of claim 13, wherein shunting the rectified voltage comprises clamping a voltage applied to the at least one low-power element to a voltage level that is below a voltage rating of the at least one low-power element.

15. The method of claim 13, wherein shunting the rectified voltage comprises drawing excess current through the voltage protection element.

16. The method of claim 12, wherein the powered network comprises a power over Ethernet (PoE) network.

17. The method of claim 12, wherein receiving the input voltage comprises:

receiving a first input voltage at the first input terminal of the integrated circuit; and

receiving a second input voltage at the second input terminal of the integrated circuit;

wherein the input voltage comprises a potential difference between the first input voltage and the second input voltage.

18. An integrated circuit of a powered device, the integrated circuit comprising:

a rectifier circuit having two input terminals to receive an input supply voltage from a powered network and having two output terminals to provide a rectified power supply voltage;

at least one low-voltage circuit element coupled between the two output terminals; and

a voltage protection element coupled between the two output terminals, wherein, in a first mode of operation, the voltage protection element presents a high impedance to the two output terminals, in a second mode of operation, the voltage protection element has a first over-voltage characteristic, and in a third mode of operation, the voltage protection element has a second over-voltage protection characteristic.

19. The integrated circuit of claim 18, wherein the voltage protection element comprises an over-voltage threshold component to detect an over-voltage condition and a switch coupled to the over-voltage threshold component to clamp the input voltage to a voltage level that is below a voltage level of the rectified power supply voltage in response to detecting the over-voltage condition.

20. The integrated circuit of claim 18, wherein the voltage protection element comprises two switches adapted to activate asynchronously in response to a control signal to clamp the supply voltage to a reduced voltage level.

21. The integrated circuit of claim 18, wherein the voltage protection element comprises a silicon controlled rectifier.

22. The integrated circuit of claim 18, wherein the voltage protection element further comprises active logic to generate a fault protection signal provided to the at least one low-voltage circuit element after detecting the over-voltage condition.

23. The integrated circuit of claim 22, wherein the fault protection signal comprises a shut down signal to deactivate the at least one low-voltage circuit element.

24. The integrated circuit of claim 18, wherein the voltage protection element is at a higher voltage in the second mode of operation than in the third mode of operation.

25. The integrated circuit of claim 24, wherein in the second mode of operation, the higher voltage is greater than 55 volts and wherein the voltage protection element has a current level less than one Ampere.

26. The integrated circuit of claim 24, wherein in the third mode of operation, the voltage protection element has a voltage level less than ten volts and a current level greater than half an Ampere.

27. The integrated circuit of claim 24, wherein the over-voltage protection element changes from the second mode of operation to the first mode of operation after a current level of the voltage protection element falls below a threshold level.