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

• US 7,586,840 B2
• Filed: 05/25/2005
• Issued: 09/08/2009
• 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
• Primary Examiner(s): Chan; Wing F
• Assistant Examiner(s): Tsegaye; Saba
• Application Number:
  US11/139,007
• Publication Number:
  US 20060268898A1
• Time in Patent Office: 1,567 Days
• Field of Search: 370/216, 370/217, 370/400, 370/910, 370/401, 370/908, 713/300, 713/324, 379/399.01
• US Class Current: 370/216
• 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 apparatus, comprising:

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

where members of the plurality of ports comprise a positive rail and a negative rail;

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

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

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

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

find port circuitry disposed between the rails,

the find port circuitry being configured to selectively couple a secondary power source in parallel with the floating resistance, thereby breaking ground isolation for the plurality of ports and increasing current flowing through the plurality of ports to facilitate detecting a fault in a member of the plurality of ports;

and to detect a current mismatch between the positive rails and the negative rails of one or more members of the plurality of ports; and

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

2. The apparatus of claim 1, where all ports of the Ethernet switch have ground isolation broken simultaneously.

3. The apparatus of claim 1, where a selected one of the plurality of ports has ground isolation broken.

4. The apparatus of claim 1, where 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).

5. The apparatus of claim 4, where the scanned port is not powered up if a ground fault is detected.