System and method of detection of power loss in powered ethernet devices

• US 20070283173A1
• Filed: 06/06/2006
• Published: 12/06/2007
• Est. Priority Date: 06/06/2006
• Status: Active Grant

• Current Assignee: Skyworks Solutions Incorporated
• Original Assignee: Silicon Laboratories Incorporated
• Inventors: Webb, Richard B., Landry, D. Matthew
• Granted Patent: US 7,511,388 B2
• Time in Patent Office: Days
• US Class Current: 713/300
• CPC Class Codes: G06F 1/305 in the event of power-supply fluctuations
• CPC Class Codes: H04L 12/10 Current supply arrangements
• CPC Class Codes: H04L 12/66 Arrangements for connecting between networks having differing types of switching systems, e.g. gateways

Abstract

A powered device includes a power supply input, a diode bridge, and a power loss detector. The power supply input is responsive to an external power source. The diode bridge has an input to receive at least one power supply input. The power loss detector includes an input responsive to the power supply input. The power loss detector is adapted to detect a power loss event and to initiate a power shutdown. In one embodiment, the powered device includes a load circuit to receive a power supply voltage from the diode bridge. The load circuit is responsive to the power loss detector to perform a power shutdown operation.

Claims

1. A powered device comprising:

at least one power supply input responsive to an external power source;

a diode bridge having an input to receive the at least one power supply input; and

a power loss detector having an input responsive to the at least one power supply input, the power loss detector to detect a power loss event and to initiate a power shutdown.

2. The powered device of claim 1, further comprising a load circuit to receive a power supply voltage from the diode bridge, the load circuit responsive to the power loss detector, the load circuit to perform a shutdown operation after the power loss detector initiates the power shutdown.

3. The powered device of claim 1, wherein the power shutdown includes backup operations to store data before shutting down.

4. The powered device of claim 1, wherein the power loss detector generates a power loss indicator in response to detection of the power loss event.

5. The powered device of claim 1, wherein the powered device comprises an integrated circuit.

6. The powered device of claim 1, wherein the external power source comprises power source equipment coupled to the at least one power supply input via an Ethernet cable.

7. The powered device of claim 1, wherein the power loss detector comprises:

at least one blocking diode responsive to the at least one power supply input;

a zener diode circuit having an input coupled to the at least one blocking diode and an output, the zener diode circuit having a breakdown voltage characteristic that defines a voltage level related to the power loss event; and

a comparator coupled to the output of the zener diode circuit, the comparator to generate an output signal related to a voltage level of the at least one power supply input.

8. The powered device of claim 7, wherein the zener diode circuit comprises a plurality of zener diodes in series, wherein the breakdown voltage characteristic includes a sum of breakdown voltage characteristics of each of the plurality of zener diodes.

9. The powered device of claim 1, wherein the power loss detector comprises:

a thermal input to receive a signal related to a thermal event, wherein the power loss detector initiates the power shutdown in response to the signal related to the thermal event.

10. The powered device of claim 1, wherein the power loss detector comprises:

an initialization input to receive a signal related to an initialization mode, the initialization input to selectively disable the power loss detector based on the initial mode.

11. A powered device coupled to a network to receive power and data from the network via a cable, the powered device comprising:

at least one power supply input responsive to a wire of the cable, the cable to provide data and power;

a first supply terminal and a second supply terminal;

a diode bridge having an input to receive the at least one power supply input and having an output to provide a rectified supply voltage to the first and the second supply terminals;

an input filter capacitor coupled between the first supply terminal and the second supply terminal; and

a power loss detector having an input responsive to the at least one power supply input, the power loss detector to detect a power loss event and to automatically initiate a power shutdown when a voltage level of the at least one power supply input falls below a threshold level.

12. The powered device of claim 11, wherein the power loss detector comprises:

at least one diode responsive to the at least one power supply input;

a diode circuit coupled to the at least one diode, the diode circuit defining a breakdown voltage level related to the power loss event; and

a comparator responsive to the diode circuit, the comparator to generate an indictor of the power loss event when the voltage level falls below the threshold voltage level.

13. The powered device of claim 11, wherein the power loss detector generates a power loss indicator when the voltage level is less than the threshold level.

14. The powered device of claim 13, further comprising a load circuit coupled to the first and second supply terminals, the load circuit to receive the power loss indicator and to perform a controlled power shutdown in response to the power loss indicator.

15. The powered device of claim 11, wherein the power loss detector is coupled to the first and second supply terminals, the power loss detector to shunt a voltage between the first supply terminal and the second supply terminal to produce a step voltage, wherein a falling edge of the step voltage comprises a power loss indicator.

16. The powered device of claim 11, wherein the power loss detector includes a thermal protection switch to initiate the power shutdown in response to a thermal overload event.

17. The powered device of claim 11, wherein the power loss detector includes an initialization switch to disable the power loss detector from initiating the power shutdown during an initialization mode.

18. A method comprising:

monitoring an input voltage at an input port of a powered device, the powered device including power circuitry responsive to the input port to rectify the input voltage to produce a rectified voltage supply;

comparing the input voltage to a threshold voltage level; and

detecting a power loss event to initiate a power shutdown when the input voltage falls below the threshold voltage level;

wherein the power loss event is detected concurrently while the rectified voltage supply of the associated input voltage is being produced.

19. The method of claim 18, wherein the power loss event is detected before a rectified voltage level falls below the threshold voltage level.

20. The method of claim 18, wherein the power loss event is detected in parallel with production of the rectified voltage supply.

21. The method of claim 18, wherein monitoring the input voltage comprises:

transferring the input voltage from the input port to a node;

level-shifting the input voltage from the node to an input of a comparator using a diode circuit comprising a plurality of diodes in series, wherein a breakdown voltage of the diode circuit defines the threshold voltage level; and

producing a comparator output responsive to the input to drive a voltage level of a power loss output pin, the comparator input relating to the input voltage;

wherein the method further comprises shunting the rectified voltage supply between a first voltage supply terminal and a second voltage supply terminal to produce a step signal on the first and second voltage supply terminals.

22. An electronic device coupled to a network to receive power and data;

the electronic device comprising;

a rectifier circuit including a power supply input to receive a power supply via a network cable and to provide a rectified power supply to a first power supply terminal and to a second power supply terminal, the network cable to carry power and data;

a capacitor coupled between the first and the second power supply terminals to filter the rectified power supply; and

logic responsive to the power supply input to generate a power loss indication when the power supply is less than a threshold voltage level.

23. The electronic device of claim 22, wherein the logic includes an initialization input to receive an initialization indicator to prohibit generation of the power loss indication during an initialization mode.

24. The electronic device of claim 22, wherein the logic includes a thermal event input to receive a thermal indicator to initiate a power shutdown in response to detection of a thermal event.

25. The electronic device of claim 22, wherein the threshold voltage level comprises a power on voltage level and a power off voltage level, and wherein the logic includes a hysteresis between the power on voltage level and the power off voltage level.