Combination of high-side and low-side current control in system for providing power over communication link

• US 7,702,302 B1
• Filed: 08/21/2006
• Issued: 04/20/2010
• Est. Priority Date: 12/12/2005
• Status: Active Grant

• Current Assignee: Analog Devices International Unlimited Company (Analog Devices, Inc.)
• Original Assignee: Linear Technology Corporation (Analog Devices, Inc.)
• Inventors: Stineman, John Arthur Jr.
• Primary Examiner(s): Harper; Vincent P
• Assistant Examiner(s): OBAYANJU, OMONIYI
• Application Number:
  US11/506,779
• Time in Patent Office: 1,338 Days
• Field of Search: 455/572, 455/127
• US Class Current: 455/127.1
• CPC Class Codes: H04L 12/10 Current supply arrangements

Abstract

A novel system for supplying power to a powered device over a communication link, such as an Ethernet link, has a current control mechanism that combines low-side current control circuitry with high-side current control circuitry. The low-side current control circuitry is coupled to a low-side power supply line for controlling low-side current flowing in the low-side power supply line. The high-side current control circuitry is coupled to a high-side power supply line for controlling high-side current in the high-side power supply line.

Claims

1. A system for supplying power over a communication link, comprising:

a power supply device for delivering power to an output port coupled to the communication link,

a low-side power supply line provided between the output port and a more negative power supply lead of a pair of leads for supplying power to the power supply device,

a high-side power supply line provided between the output port and a more positive power supply lead of the pair of leads,

low-side current control circuitry coupled to the low-side power supply line for controlling low-side current in the low-side power supply line when the low-side current exceeds a first prescribed value, and

high-side current control circuitry coupled to the high-side power supply line for controlling high-side current in the high-side power supply line when the high-side current exceeds a second prescribed value.

2. The system of claim 1, wherein the communication link includes an Ethernet link.

3. The system of claim 1, wherein the high-side current control circuitry includes a high-side current limiting circuit for limiting the high-side current to a first prescribed value.

4. The system of claim 1, wherein the high-side current control circuitry includes a high-side circuit breaker for disconnecting the more positive power supply lead from the output port in response to an event.

5. The system of claim 4, wherein the high-side circuit breaker is configured to disconnect the more positive power supply lead from the output port when the high-side current exceeds a second prescribed value.

6. The system of claim 3, wherein the low-side side current control circuitry includes a low-side current limiting circuit for limiting the low-side current to the first prescribed value.

7. The system of claim 5, wherein the low-side current control circuitry includes a low-side circuit breaker for disconnecting the more negative power supply lead from the output port when the low-side current exceeds the second prescribed value.

8. The system of claim 1, wherein the high-side power supply line includes a high-side impedance for sensing the high-side current.

9. The system of claim 8, wherein the low-side power supply line includes a low-side impedance for sensing the low-side current.

10. The system of claim 1, wherein the high-side power supply line includes a high-side transistor device controlled by the high-side current control circuitry.

11. The system of claim 10, wherein the transistor device includes a MOSFET transistor.

12. The system of claim 10, wherein the low-side power supply line includes a low-side transistor device controlled by the low-side current control circuitry.

22. The system of claim 1, wherein the first prescribed value coincides with the second prescribed value.

23. The system of claim 1, wherein the first prescribed value differs from the second prescribed value.

13. A Power over Ethernet (PoE) system comprising:

Power Sourcing Equipment (PSE) for providing power to a PoE port,

a low-side power supply line provided between the PoE port and a more negative power supply lead of a pair of leads for supplying power to the PSE,

a high-side power supply line provided between the PoE port and a more positive power supply lead of the pair of the leads,

low-side current control circuitry coupled to the low-side power supply line for controlling low-side current in the low-side power supply line when the low-side current exceeds a first prescribed value, and

high-side current control circuitry coupled to the high-side power supply line for controlling high-side current in the high-side power supply line when the high-side current exceeds a second prescribed value.

14. The system of claim 13, wherein the high-side current control circuitry includes a high-side current limiting circuit for limiting the high-side current to a prescribed maximum current of the PSE at a short circuit condition.

15. The system of claim 13, wherein the high-side current control circuitry includes a high-side circuit breaker for disconnecting the more positive power supply lead from the PoE port when the high-side current exceeds a prescribed overload current detection range.

16. The system of claim 14, wherein the low-side side current control circuitry includes a low-side current limiting circuit for limiting the low-side current to the prescribed maximum current of the PSE at a short circuit condition.

17. The system of claim 15, wherein the low-side current control circuitry includes a low-side circuit breaker for disconnecting the more negative power supply lead from the output port when the low-side current exceeds the prescribed overload current detection range.

18. A method of providing power over a communication link, comprising:

controlling by first current control circuitry, first current flowing between an output power supply port and a first lead of a pair of power supply leads, in accordance with prescribed conditions, and

controlling by second current control circuitry, second current flowing between the output power supply port and a second lead of the pair of power supply leads, if the first current control circuitry fails.

19. The method of claim 18, wherein the step of controlling the second current includes limiting the second current to a first prescribed value.

20. The method of claim 18, wherein the step of controlling the second current includes disconnecting the second lead from the output power supply port when the second current exceeds a second prescribed value.

21. A local area network comprising:

at least a pair of network nodes,

a network hub, and

communication cabling for connecting the network nodes to the network hub to provide data communications,

the network hub including;

a power supply device for providing power to an output port coupled to the communication cabling,

a low-side power supply line provided between the output port and a more negative power supply lead of a pair of leads for supplying power to the power supply device,

a high-side power supply line provided between the output port and a more positive power supply lead of the pair of leads,

low-side current control circuitry coupled to the low-side power supply line for controlling low-side current in the low-side power supply line if the low-side current exceeds a first prescribed value, and

high-side current control circuitry coupled to the high-side power supply line for controlling high-side current in the high-side power supply line if the high-side current exceeds a second prescribed value.