Detecting network power connection status using AC signals

• US 6,986,071 B2
• Filed: 10/24/2002
• Issued: 01/10/2006
• Est. Priority Date: 02/01/2002
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: PowerDsine Limited (Microchip Technology Incorporated)
• Inventors: Darshan, Yair, Ferentz, Alon, Korcheraz, Dror
• Primary Examiner(s): Browne, Lynne H.
• Assistant Examiner(s): Patel, Anand B.
• Application Number:
  US10/279,269
• Publication Number:
  US 20030146765A1
• Time in Patent Office: 1,174 Days
• Field of Search: 713/330
• US Class Current: 713/330
• CPC Class Codes: H04L 12/10 Current supply arrangements
• CPC Class Codes: H04L 12/28 characterised by path configuration, e.g. LAN [Local Area Networks] or WAN [Wide Area Networks] wireless communication networks H04W ; arrangements for dividing the transmission path H04W40/00
• CPC Class Codes: H04L 49/351 for local area network [LAN], e.g. Ethernet switches
• CPC Class Codes: H04L 49/40 Constructional details, e.g. power supply, mechanical construction or backplane

Abstract

A power supply subsystem for use in a local area network (LAN) includes a direct current (DC) power source, which supplies DC power to at least one of the nodes via at least one of the wire pairs used in communication cabling of the LAN, substantially without interfering with data communications. A signal generator generates a periodic time-varying signal and couples the time-varying signal into the at least one of the wire pairs. A control unit senses a time-varying voltage on the at least one of the wire pairs due to the time-varying signal generated by the signal generator, and responsive to the sensed time-varying voltage, controls the DC power supplied to the at least one of the nodes by the DC power source.

Claims

1. A power supply subsystem for use in a local area network (LAN), which includes a plurality of LAN nodes coupled to a LAN switch by communication cabling, the cabling including multiple twisted wire pairs connecting the plurality of nodes to the switch for providing data communication among the nodes, the power supply subsystem comprising:

a direct current (DC) power source, which is operative to supply DC power to at least one of the nodes via the communication cabling over at least one of the wire pairs substantially without interfering with the data communication;

a signal generator, which is operative to generate a periodic time-varying signal and to couple the time-varying signal into the at least one of the wire pairs superimposed onto said supplied DC power;

and a control unit, which is operative to sense a time-varying voltage on the at least one of the wire pairs due to the time-varying signal generated by the signal generator, and which is further operative, responsive to the sensed time-varying voltage, to control the DC power supplied to the at least one of the nodes by the DC power source.

2. A subsystem according to claim 1, wherein the control unit is operative to detect a disconnection of the at least one of the nodes from the cabling responsive to the time-varying voltage.

3. A subsystem according to claim 2, wherein the control unit is operative, upon detecting the disconnection, to cut off the DC power supplied to the at least one of the nodes.

4. A subsystem according to claim 1, wherein the control unit is operative to determine, responsive to the time-varying voltage, that the at least one of the nodes is connected to the at least one of the wire pairs.

5. A subsystem according to claim 4, wherein the control unit is further operative to make a determination, based on the time-varying voltage, that the at least one of the nodes is capable of receiving the DC power over the at least one of the wire pairs, and to turn on the DC power to the at least one of the nodes responsive to the determination.

6. A subsystem according to claim 5, wherein the control unit is operative to identify an operating mode of the at least one of the nodes based on the time-varying voltage, and to turn on the DC power to the at least one of the nodes responsive to the operating mode.

7. A subsystem according to claim 1, wherein the control unit is operative to determine an impedance characteristic of the at least one of the nodes based on the time-varying voltage.

8. A subsystem according to claim 7, wherein the control unit is operative to detect a change in the impedance characteristic by measuring a change in an amplitude of the time-varying voltage.

9. A subsystem according to claim 7, wherein the control unit is operative to detect a change in the impedance characteristic by measuring a change in a phase of the time-varying voltage.

10. A subsystem according to claim 7, wherein the impedance characteristic determined by the control unit is a complex impedance characteristic.

11. A subsystem according to claim 1, wherein the signal generator is coupled in parallel with the DC power source.

12. A subsystem according to claim 1, wherein the DC power source is adapted to be connected to the LAN in an end-span configuration.

13. A subsystem according to claim 1, wherein the DC power source is adapted to be connected to the LAN in a mid-span configuration.

14. A subsystem according to claim 1, wherein the DC power source is operative to generate a DC current over the at least one of the wire pairs, and wherein the controller is operative to sense the time-varying voltage and to control the DC power responsive thereto substantially independently of the DC current flowing over the at least one of the wire pairs.

15. A local area network (LAN), comprising:

a plurality of LAN nodes;

a LAN switch;

communication cabling comprising multiple twisted wire pairs connecting the plurality of nodes to the switch for providing data communication among the nodes;

and a power supply subsystem, which is operative to supply DC power to at least one of the nodes via the communication cabling over at least one of the wire pairs, substantially without interfering with the data communication, while coupling a periodic time-varying signal superimposed onto said supplied DC power into the at least one of the wire pairs, and which is further operative to sense a time-varying voltage on the at least one of the wire pairs due to the time-varying signal and, responsive to the sensed time-varying voltage, to control the DC power supplied to the at least one of the nodes.

16. A LAN according to claim 15, wherein the power supply subsystem is operative to detect a disconnection of the at least one of the nodes from the cabling responsive to the time-varying voltage.

17. A LAN according to claim 16, wherein the power supply subsystem is operative, upon detecting the disconnection, to cut off the DC power supplied to the at least one of the nodes.

18. A LAN according to claim 15, wherein the power supply subsystem is operative to determine, responsive to the time-varying voltage, that the at least one of the nodes is connected to the at least one of the wire pairs.

19. A LAN according to claim 18, wherein the power supply subsystem is further operative to make a determination, based on the time-varying voltage, that the at least one of the nodes is capable of receiving the DC power over the at least one of the wire pairs, and to turn on the DC power to the at least one of the nodes responsive to the determination.

20. A LAN according to claim 19, wherein the power supply subsystem is operative to identify an operating mode of the at least one of the nodes based on the time-varying voltage, and to turn on the DC power to the at least one of the nodes responsive to the operating mode.

21. A LAN according to claim 15, wherein the power supply subsystem is operative to determine an impedance characteristic of the at least one of the nodes based on the time-varying voltage.

22. A LAN according to claim 21, wherein the power supply subsystem is operative to detect a change in the impedance characteristic by measuring a change in an amplitude of the time-varying voltage.

23. A LAN according to claim 22, wherein the power supply subsystem is operative to detect a change in the impedance characteristic by measuring a change in a phase of the time-varying voltage.

24. A LAN according to claim 22, wherein the impedance characteristic determined by the power supply subsystem is a complex impedance characteristic.

25. A LAN according to claim 15, wherein the power supply subsystem is connected to the LAN in an end-span configuration.

26. A LAN according to claim 15, wherein the power supply subsystem is connected to the LAN in a mid-span configuration.

27. A LAN according to claim 15, wherein the power supply subsystem is operative to generate a DC current over the at least one of the wire pairs, and to sense the time-varying voltage and to control the DC power responsive thereto substantially independently of the DC current flowing over the at least one of the wire pairs.

28. A method for supplying power over a local area network (LAN), in which a plurality of LAN nodes are coupled to a LAN switch by communication cabling, the cabling including multiple twisted wire pairs connecting the plurality of nodes to the switch for providing data communication among the nodes, the method comprising:

supplying DC power to at least one of the nodes via the communication cabling over at least one of the wire pairs substantially without interfering with the data communication;

coupling a time-varying signal superimposed onto said supplied DC power into the at least one of the wire pairs;

sensing a time-varying voltage on the at least one of the wire pairs due to the time-varying signal generated by the signal generator; and

responsive to the sensed time-varying voltage, controlling the DC power supplied to the at least one of the nodes.

29. A method according to claim 28, wherein sensing the time-varying voltage comprises detecting a disconnection of the at least one of the nodes from the cabling responsive to the time-varying voltage.

30. A method according to claim 29, wherein controlling the DC power comprises, upon detecting the disconnection, cutting off the DC power supplied to the at least one of the nodes.

31. A method according to claim 28, wherein sensing the time-varying voltage comprises determining, responsive to the time-varying voltage, that the at least one of the nodes is connected to the at least one of the wire pairs.

32. A method according to claim 31, wherein controlling the DC power comprises making a determination, based on the time-varying voltage, that the at least one of the nodes is capable of receiving the DC power over the at least one of the wire pairs, and turning on the DC power to the at least one of the nodes responsive to the determination.

33. A method according to claim 32, wherein controlling the DC power further comprises identifying an operating mode of the at least one of the nodes based on the time-varying voltage, and controlling the DC power to the at least one of the nodes responsive to the operating mode.

34. A method according to claim 28, wherein sensing the time-varying voltage comprises determining an impedance characteristic of the at least one of the nodes based on the time-varying voltage.

35. A method according to claim 34, wherein determining the impedance characteristic comprises detecting a change in the impedance characteristic by measuring a change in an amplitude of the time-varying voltage.

36. A method according to claim 34, wherein determining the impedance characteristic comprises detecting a change in the impedance characteristic by measuring a change in a phase of the time-varying voltage.

37. A method according to claim 34, wherein determining the impedance characteristic comprises determining a complex impedance characteristic.

38. A method according to claim 28, wherein supplying the DC power comprises generating a DC current over the at least one of the wire pairs, and wherein sensing the time-varying voltage and controlling the DC power comprise sensing the time-varying voltage and controlling the DC power responsive thereto substantially independently of the DC current flowing over the at least one of the wire pairs.

39. A control unit for a power supply subsystem for use in a local area network (LAN), the LAN including a plurality of LAN nodes coupled to a LAN switch by communication cabling, the cabling including multiple twisted wire pairs connecting the plurality of nodes to the switch for providing data communication among the nodes, the power supply subsystem including a direct current (DC) power source, which is operative to supply DC power to at least one of the nodes via the communication cabling over at least one of the wire pairs substantially without interfering with the data communication, and a signal generator, which is operative to generate a periodic time-varying signal and to couple the time-varying signal superimposed onto said supplied DC power into the at least one of the wire pairs,

wherein the control unit is operative to sense a time-varying voltage on the at least one of the wire pairs due to the time-varying signal generated by the signal generator, and is further operative, responsive to the sensed time-varying voltage, to control the DC power supplied to the at least one of the nodes by the DC power source.

40. A control unit according to claim 39, wherein the control unit is operative to detect a disconnection of the at least one of the nodes from the cabling responsive to the time-varying voltage.

41. A control unit according to claim 40, wherein the control unit is operative, upon detecting the disconnection, to cut off the DC power supplied to the at least one of the nodes.

42. A control unit according to claim 39, wherein the control unit is operative to determine, responsive to the time-varying voltage, that the at least one of the nodes is connected to the at least one of the wire pairs.

43. A control unit according to claim 42, wherein the control unit is further operative to make a determination, based on the time-varying voltage, that the at least one of the nodes is capable of receiving the DC power over the at least one of the wire pairs, and to turn on the DC power to the at least one of the nodes responsive to the determination.

44. A control unit according to claim 43, wherein the control unit is operative to identify an operating mode of the at least one of the nodes based on the time-varying voltage, and to turn on the DC power to the at least one of the nodes responsive to the operating mode.

45. A control unit according to claim 39, wherein the control unit is operative to determine an impedance characteristic of the at least one of the nodes based on the time-varying voltage.

46. A control unit according to claim 45, wherein the control unit is operative to detect a change in the impedance characteristic by measuring a change in an amplitude of the time-varying voltage.

47. A control unit according to claim 45, wherein the control unit is operative to detect a change in the impedance characteristic by measuring a change in a phase of the time-varying voltage.

48. A control unit according to claim 45, wherein the impedance characteristic determined by the control unit is a complex impedance characteristic.

49. A control unit according to claim 39, wherein the DC power source is operative to generate a DC current over the at least one of the wire pairs, and wherein the controller is operative to sense the time-varying voltage and to control the DC power responsive thereto substantially independently of the DC current flowing over the at least one of the wire pairs.