Method and apparatus for detecting and fixing faults in an inline-power capable ethernet system

• US 20060268898A1
• Filed: 05/25/2005
• Published: 11/30/2006
• Est. Priority Date: 05/25/2005
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Karam, Roger
• Granted Patent: US 7,586,840 B2
• Time in Patent Office: Days
• US Class Current: 370/401
• CPC Class Codes: H04L 12/10 Current supply arrangements
• CPC Class Codes: H04L 25/08 Modifications for reducing interference; Modifications for reducing effects due to line faults ; Receiver end arrangements for detecting or overcoming line faults
• CPC Class Codes: H04L 69/40 for recovering from a failure of a protocol instance or entity, e.g. service redundancy protocols, protocol state redundancy or protocol service redirection management of faults, events, alarms or notifications in data switching networks H04L41/06
• CPC Class Codes: Y10S 370/91 Carrier sense multiple access, e.g. ethernet, 10base-t

Abstract

The present disclosure provides for the sensing and detection of potential ground faults, and location of faulty ports. Circuitry is provided that utilizes the isolation resistor provided in the PSE. The present disclosure provides for temporarily breaking isolation to help improve the detection process disclosed herein.

Claims

1. An Ethernet system for detecting ground faults comprising:

an Ethernet switch configured to provide inline power to a plurality of ports;

each of said plurality of ports including a positive rail and a negative rail;

a power source operatively disposed in said Ethernet switch between said positive and negative rails;

a floating resistance disposed between said power source and said negative rails for providing isolation from ground for said plurality of said ports, the floating resistance including a voltage divider sensing node;

ground fault circuitry operatively coupled to voltage divider sensing node, the ground fault circuitry configured for sensing the current flowing through said floating resistance; and

wherein said ground fault circuitry is further configured to detect a ground fault in at least one of said plurality of ports of said Ethernet switch when the current detected at said voltage divider sensing node exceeds a predefined level.

2. The Ethernet system of claim 1, further comprising:

current sensing circuitry disposed in series within the positive and negative rails of said plurality of ports;

find-port circuitry disposed between said rails;

the find-port circuitry being configured to selectively couple a second power source in parallel with said floating resistance, thereby breaking ground isolation for said plurality of said ports; and

detect a current mismatch between the positive and negative rails of one or more of said plurality of ports.

3. The Ethernet system of claim 2, wherein all ports of said Ethernet switch have ground isolation broken simultaneously.

4. The Ethernet system of claim 2, wherein a selected one of said plurality of ports of said Ethernet switch has ground isolation broken.

5. The Ethernet system of claim 2, wherein a port undergoing the discovery process according to IEEE 802.3af is scanned for ground faults prior to powering up an Ethernet Powered Device (PD).

6. The Ethernet system of claim 5, wherein said scanned port is not powered up if a ground fault is detected.

7. An Ethernet apparatus for detecting ground faults comprising:

Ethernet switching means configured to provide inline power to a plurality of ports;

each of said plurality of ports including a positive rail and a negative rail;

power source means operatively disposed in said Ethernet switch between said positive and negative rails;

floating resistance means disposed between said power source and said negative rails for providing isolation from ground for said plurality of said ports, the floating resistance including a voltage divider sensing node;

ground fault circuitry means operatively coupled to voltage divider sensing node for sensing the current flowing through said floating resistance; and

said ground fault circuitry means further comprising means for detecting a ground fault in at least one of said plurality of ports of said Ethernet switch when the current detected at said voltage divider sensing node exceeds a predefined level.

8. The Ethernet apparatus of claim 7, further comprising:

current sensing circuitry disposed in series within the positive and negative rails of said plurality of ports;

find-port circuitry disposed between said rails;

the find-port circuitry being configured to selectively couple a second power source in parallel with said power source and said floating resistance, thereby breaking ground isolation for said plurality of said ports; and

detect a current mismatch between the positive and negative rails of one said plurality of ports.

9. The Ethernet apparatus of claim 8, wherein all ports of said Ethernet switching means further comprising means for breaking ground isolation simultaneously.

10. The Ethernet apparatus of claim 8, wherein a selected one of said plurality of ports of said Ethernet switching means has ground isolation broken.

11. The Ethernet apparatus of claim 8, further comprising means for scanning for ground faults prior to powering up an Ethernet Powered Device (PD).

12. The Ethernet apparatus of claim 11, further comprising means for power up a scanned port if a ground fault is detected.

13. A method for detecting ground faults in an Ethernet system comprising:

detecting a ground fault in an Ethernet system having a plurality of ports coupled to a power source;

locating a faulty one or more of said plurality of ports responsive to said detection; and

flagging one or more located ports as faulty.

14. The method of claim 13, further comprising the act of breaking isolation on said plurality of ports;

selectively switching in an inline power source; and

measuring the current drawn through each rail of a selected one of said plurality of ports.

15. The method of claim 14, further comprising the act comparing the current draw on each of rail of said selected one of said plurality of ports to determine if there is a mismatch.

16. The method of claim 15, wherein a fault is indicated if an increase is detected on the rail of a selected port that is substantially equal in magnitude to the current delivered in or out of by said inline power source.

17. The method of claim 14, wherein said method is used in conjunction with the discovery process of the IEEE 802.3af standard.

18. The method of claim 17, wherein at least one selected port is scanned for ground faults prior to powering the device.

19. The method of claim 18, wherein the discovery process is halted prior to the port being powered up if a ground fault is detected.

20. The method of claim 19, further comprising the acts of connecting the corresponding rails of a port one rail at a time after a successful discovery according to the IEEE 802.3af standard but before power is applied;

switching in an inline power source; and

scanning for ground faults.

21. The method of claim 20, wherein the scanned port is not powered up if a ground fault is detected.