Phy-based current imbalance compensation for magnetics in a wired data telecommunications network

• US 20060115007A1
• Filed: 11/03/2004
• Published: 06/01/2006
• Est. Priority Date: 11/03/2004
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Karam, Roger A., Wakerly, John F.
• Granted Patent: US 7,457,252 B2
• Time in Patent Office: Days
• US Class Current: 375/257
• CPC Class Codes: H04L 12/10 Current supply arrangements

Abstract

In a circuit delivering common mode inline power over a pair of conductors imbalance in the current carried by the first and second conductors of the pair of conductors is detected and compensated with a bias current applied to counter the imbalance.

Claims

1. A method for compensating for an effective current imbalance in a pair of conductors carrying common mode electrical power, the pair of conductors coupled between a first magnetic device and a second magnetic device, the first magnetic device having a primary winding and a secondary winding, and the second magnetic device having a primary winding and a secondary winding, said pair of conductors coupling said secondary windings of said first and second magnetic devices, the method comprising:

detecting the effective current imbalance in the pair of conductors;

applying, responsive to said detecting, a direct current bias to the circuit element comprising the pair of conductors and the secondaries of the first and second magnetic devices in a magnitude and direction to compensate for the effective current imbalance.

2. The method of claim 1, wherein said applying occurs through a third winding of the first magnetic device.

3. The method of claim 2, wherein the third winding is disposed on the primary side of the first magnetic device.

4. The method of claim 2, wherein the third winding is disposed on the secondary side of the first magnetic device.

5. The method of claim 1, wherein said detecting senses the effective current imbalance indirectly by monitoring data pulses received through the primary winding of the first magnetic device.

6. The method of claim 1, wherein said detecting senses the effective current imbalance indirectly by means of droop detection pulses transmitted by a PHY through the primary winding of the first magnetic device.

7. The method of claim 6, wherein a receiver attached to the PHY monitors the droop detection pulses as they are transmitted by a transmitter at the PHY.

8. The method of claim 1, wherein said detecting senses the current imbalance directly by measuring current flow through at least two locations of the circuit element and comparing the measurements to create an error signal to drive the magnitude and direction of the direct current bias.

9. The method of claim 1, wherein said applying occurs at a node disposed in the circuit element.

10. The method of claim 8, wherein said applying occurs at a node disposed in the circuit element.

11. The method of claim 2, wherein said detecting senses the effective current imbalance indirectly by monitoring pulses received through the primary winding of the first magnetic device.

12. The method of claim 3, wherein said detecting senses the effective current imbalance indirectly by monitoring pulses received through the primary winding of the first magnetic device.

13. The method of claim 4, wherein said detecting senses the effective current imbalance indirectly by monitoring pulses received through the primary winding of the first magnetic device.

14. The method of claim 2, wherein said detecting senses the effective current imbalance directly by measuring current flow through at least two locations of the circuit element and comparing the measurements to create an error signal to drive the magnitude and direction of the direct current bias.

15. The method of claim 3, wherein said detecting senses the effective current imbalance directly by measuring current flow through at least two locations of the circuit element and comparing the measurements to create an error signal to drive the magnitude and direction of the direct current bias.

16. The method of claim 4, wherein said detecting senses the effective current imbalance directly by measuring current flow through at least two locations of the circuit element and comparing the measurements to create an error signal to drive the magnitude and direction of the direct current bias.

17. An apparatus for compensating for an effective current imbalance in a pair of conductors carrying common mode electrical power, the pair of conductors coupled between a first magnetic device and a second magnetic device, the first magnetic device having a primary winding and a secondary winding, and the second magnetic device having a primary winding and a secondary winding, said pair of conductors coupling said secondary windings of said first and second magnetic devices, the apparatus comprising:

means for detecting the effective current imbalance in the pair of conductors;

means for applying, responsive to said means for detecting, a direct current bias to the circuit element comprising the pair of conductors and the secondaries of the first and second magnetic devices in a magnitude and direction to compensate for the effective current imbalance.

18. The apparatus of claim 17, wherein said means for applying utilizes a third winding of the first magnetic device.

19. The apparatus of claim 18, wherein the third winding is disposed on the primary side of the first magnetic device.

20. The apparatus of claim 18, wherein the third winding is disposed on the secondary side of the first magnetic device.

21. The apparatus of claim 17, wherein said means for detecting senses the effective current imbalance indirectly by monitoring data pulses received through the primary winding of the first magnetic device.

22. The apparatus of claim 17, wherein said means for detecting senses the effective current imbalance indirectly by means of droop detection pulses transmitted by a PHY through the primary winding of the first magnetic device.

23. The apparatus of claim 22, wherein a receiver attached to the PHY monitors the droop detection pulses as they are transmitted by a transmitter at the PHY.

24. The apparatus of claim 17, wherein said means for detecting senses the effective current imbalance directly by measuring current flow through at least two locations of the circuit element and compares the measurements to create an error signal to drive the magnitude and direction of the direct current bias.

25. The apparatus of claim 17, wherein said means for applying operates to inject a current at a node disposed in the circuit element.

26. The apparatus of claim 24, wherein said means for applying operates to inject a current at a node disposed in the circuit element.

27. The apparatus of claim 18, wherein said means for detecting senses the effective current imbalance indirectly by monitoring pulses received through the primary winding of the first magnetic device.

28. The apparatus of claim 19, wherein said means for detecting senses the effective current imbalance indirectly by monitoring pulses received through the primary winding of the first magnetic device.

29. The apparatus of claim 20, wherein said means for detecting senses the effective current imbalance indirectly by monitoring pulses received through the primary winding of the first magnetic device.

30. The apparatus of claim 18, wherein said means for detecting senses the effective current imbalance directly by measuring current flow through at least two locations of the circuit element and compares the measurements to create an error signal to drive the magnitude and direction of the direct current bias.

31. The apparatus of claim 19, wherein said means for detecting senses the effective current imbalance directly by measuring current flow through at least two locations of the circuit element and compares the measurements to create an error signal to drive the magnitude and direction of the direct current bias.

32. The apparatus of claim 20, wherein said means for detecting senses the effective current imbalance directly by measuring current flow through at least two locations of the circuit element and compares the measurements to create an error signal to drive the magnitude and direction of the direct current bias.

33. A system for compensating for an effective current imbalance in a pair of conductors carrying common mode electrical power, the pair of conductors coupled between a first magnetic device and a second magnetic device, the first magnetic device having a primary winding and a secondary winding, and the second magnetic device having a primary winding and a secondary winding, said pair of conductors coupling said secondary windings of said first and second magnetic devices, the system comprising:

circuitry for detecting the effective current imbalance in the pair of conductors;

circuitry for applying, responsive to said circuitry for detecting, a direct current bias to the circuit element comprising the pair of conductors and the secondaries of the first and second magnetic devices in a magnitude and direction to compensate for the effective current imbalance.

34. The system of claim 33, wherein said circuitry for applying utilizes a third winding of the first magnetic device.

35. The system of claim 34, wherein the third winding is disposed on the primary side of the first magnetic device.

36. The system of claim 34, wherein the third winding is disposed on the secondary side of the first magnetic device.

37. The system of claim 33, wherein said circuitry for detecting senses the effective current imbalance indirectly by monitoring data pulses received through the primary winding of the first magnetic device.

38. The system of claim 33, wherein said circuitry for detecting senses the effective current imbalance indirectly by means of droop detection pulses transmitted by a PHY through the primary winding of the first magnetic device.

39. The system of claim 38, wherein a receiver attached to the PHY monitors the droop detection pulses as they are transmitted by a transmitter at the PHY.

40. The system of claim 33, wherein said circuitry for detecting senses the effective current imbalance directly by measuring current flow through at least two locations of the circuit element and compares the measurements to create an error signal to drive the magnitude and direction of the direct current bias.

41. The system of claim 33, wherein said circuitry for applying operates to inject a current at a node disposed in the circuit element.

42. The system of claim 40, wherein said circuitry for applying operates to inject a current at a node disposed in the circuit element.

43. The system of claim 34, wherein said circuitry for detecting senses the effective current imbalance indirectly by monitoring pulses received through the primary winding of the first magnetic device.

44. The system of claim 35, wherein said circuitry for detecting senses the effective current imbalance indirectly by monitoring pulses received through the primary winding of the first magnetic device.

45. The system of claim 36, wherein said circuitry for detecting senses the effective current imbalance indirectly by monitoring pulses received through the primary winding of the first magnetic device.

46. The system of claim 34, wherein said circuitry for detecting senses the effective current imbalance directly by measuring current flow through at least two locations of the circuit element and compares the measurements to create an error signal to drive the magnitude and direction of the direct current bias.

47. The system of claim 35, wherein said circuitry for detecting senses the effective current imbalance directly by measuring current flow through at least two locations of the circuit element and compares the measurements to create an error signal to drive the magnitude and direction of the direct current bias.

48. The system of claim 36, wherein said circuitry for detecting senses the effective current imbalance directly by measuring current flow through at least two locations of the circuit element and compares the measurements to create an error signal to drive the magnitude and direction of the direct current bias.

49. A power sourcing equipment (PSE) apparatus, comprising:

a first magnetic device having a primary winding and a secondary winding;

a coupler for receiving a pair of conductors, the coupler coupled to the secondary winding of the first magnetic device;

power sourcing circuitry coupled to apply a common mode inline power voltage signal to the secondary of the first magnetic device;

circuitry for detecting an effective current imbalance in the pair of conductors; and

circuitry for applying, responsive to said circuitry for detecting, a direct current bias to a circuit element comprising the coupler and the secondary of the first magnetic device in a magnitude and direction to compensate for the current imbalance.

50. The PSE of claim 49, wherein said circuitry for applying utilizes a third winding of the first magnetic device.

51. The PSE of claim 50, wherein the third winding is disposed on the primary side of the first magnetic device.

52. The PSE of claim 50, wherein the third winding is disposed on the secondary side of the first magnetic device.

53. The PSE of claim 49, wherein said circuitry for detecting senses the effective current imbalance indirectly by monitoring data pulses received through the primary winding of the first magnetic device.

54. The PSE of claim 49, wherein said circuitry for detecting senses the effective current imbalance indirectly by means of droop detection pulses transmitted by a PHY through the primary winding of the first magnetic device.

55. The PSE of claim 54, wherein a receiver attached to the PHY monitors the droop detection pulses as they are transmitted by a transmitter at the PHY.

56. The PSE of claim 49, wherein said circuitry for detecting senses the effective current imbalance directly by measuring current flow through at least two locations of the circuit element and compares the measurements to create an error signal to drive the magnitude and direction of the direct current bias.

57. The PSE of claim 49, wherein said circuitry for applying operates to inject a current at a node disposed in the circuit element.

58. The PSE of claim 56, wherein said circuitry for applying operates to inject a current at a node disposed in the circuit element.

59. The PSE of claim 50, wherein said circuitry for detecting senses the effective current imbalance indirectly by monitoring pulses received through the primary winding of the first magnetic device.

60. The PSE of claim 51, wherein said circuitry for detecting senses the effective current imbalance indirectly by monitoring pulses received through the primary winding of the first magnetic device.

61. The PSE of claim 52, wherein said circuitry for detecting senses the effective current imbalance indirectly by monitoring pulses received through the primary winding of the first magnetic device.

62. The PSE of claim 50, wherein said circuitry for detecting senses the effective current imbalance directly by measuring current flow through at least two locations of the circuit element and compares the measurements to create an error signal to drive the magnitude and direction of the direct current bias.

63. The PSE of claim 51, wherein said circuitry for detecting senses the effective current imbalance directly by measuring current flow through at least two locations of the circuit element and compares the measurements to create an error signal to drive the magnitude and direction of the direct current bias.

64. The PSE of claim 52, wherein said circuitry for detecting senses the effective current imbalance directly by measuring current flow through at least two locations of the circuit element and compares the measurements to create an error signal to drive the magnitude and direction of the direct current bias.

65. A powered device (PD) apparatus, comprising:

a second magnetic device having a primary winding and a secondary winding;

a coupler for receiving a pair of conductors coupled to a secondary winding of a remote first magnetic device, the coupler coupled to the secondary winding of the second magnetic device;

powered device circuitry coupled to receive a common mode inline power voltage signal from the secondary of the second magnetic device;

circuitry for detecting an effective current imbalance in the pair of conductors; and

circuitry for applying, responsive to said circuitry for detecting, a direct current bias to a circuit element comprising the coupler and the secondary of the second magnetic device in a magnitude and direction to compensate for the effective current imbalance.

66. The PD of claim 65, wherein said circuitry for applying utilizes a third winding of the second magnetic device.

67. The PD of claim 66, wherein the third winding is disposed on the primary side of the second magnetic device.

68. The PD of claim 66, wherein the third winding is disposed on the secondary side of the second magnetic device.

69. The PD of claim 65, wherein said circuitry for detecting senses the effective current imbalance indirectly by monitoring data pulses received through the primary winding of the second magnetic device.

70. The PD of claim 65, wherein said circuitry for detecting senses the effective current imbalance indirectly by means of droop detection pulses transmitted by a PHY through the primary winding of the second magnetic device.

71. The PD of claim 70, wherein a receiver attached to the PHY monitors the droop detection pulses as they are transmitted by a transmitter at the PHY.

72. The PD of claim 65, wherein said circuitry for detecting senses the effective current imbalance directly by measuring current flow through at least two locations of the circuit element and compares the measurements to create an error signal to drive the magnitude and direction of the direct current bias.

73. The PD of claim 65, wherein said circuitry for applying operates to inject a current at a node disposed in the circuit element.

74. The PD of claim 72, wherein said circuitry for applying operates to inject a current at a node disposed in the circuit element.

75. The PD of claim 66, wherein said circuitry for detecting senses the effective current imbalance indirectly by monitoring pulses received through the primary winding of the second magnetic device.

76. The PD of claim 67, wherein said circuitry for detecting senses the effective current imbalance indirectly by monitoring pulses received through the primary winding of the second magnetic device.

77. The PD of claim 68, wherein said circuitry for detecting senses the effective current imbalance indirectly by monitoring pulses received through the primary winding of the second magnetic device.

78. The PD of claim 66, wherein said circuitry for detecting senses the effective current imbalance directly by measuring current flow through at least two locations of the circuit element and compares the measurements to create an error signal to drive the magnitude and direction of the direct current bias.

79. The PD of claim 67, wherein said circuitry for detecting senses the effective current imbalance directly by measuring current flow through at least two locations of the circuit element and compares the measurements to create an error signal to drive the magnitude and direction of the direct current bias.

80. The PD of claim 68, wherein said circuitry for detecting senses the effective current imbalance directly by measuring current flow through at least two locations of the circuit element and compares the measurements to create an error signal to drive the magnitude and direction of the direct current bias.

81. A method for compensating for an effective current imbalance in a pair of conductors carrying common mode electrical power, the pair of conductors coupled between a first magnetic device and a second magnetic device, the first magnetic device associated with power sourcing equipment (PSE) and having a primary winding and a secondary winding, and the second magnetic device associated with a powered device (PD) and having a primary winding and a secondary winding, said pair of conductors coupling said secondary windings of said first and second magnetic devices, the method comprising:

conducting an auto-negotiation between the PSE and the PD to select which of the PSE and the PD will current imbalance correct the current in the pair of conductors;

detecting at the selected one of the PSE and the PD the effective current imbalance in the pair of conductors;

applying at the selected one of the PSE and the PD, responsive to said detecting, a direct current bias to the circuit element comprising the pair of conductors and the secondaries of the first and second magnetic devices in a magnitude and direction to compensate for the effective current imbalance.

82. A method for compensating for an effective current imbalance in a pair of conductors carrying common mode electrical power, the pair of conductors coupled between a first magnetic device and a second magnetic device, the first magnetic device associated with power sourcing equipment (PSE) and having a primary winding and a secondary winding, and the second magnetic device associated with a powered device (PD) and having a primary winding and a secondary winding, said pair of conductors coupling said secondary windings of said first and second magnetic devices, the method comprising:

conducting a time domain reflectometer measurement to measure the length of the pair of conductors;

detecting (if the measured length is less than a predetermined length) the effective current imbalance in the pair of conductors;

applying (if the measured length is less than a predetermined length), responsive to said detecting, a direct current bias to the circuit element comprising the pair of conductors and the secondaries of the first and second magnetic devices in a magnitude and direction to compensate for the effective current imbalance.

83. A method for compensating for an effective current imbalance in a pair of conductors carrying common mode electrical power, the pair of conductors coupled between a first magnetic device and a second magnetic device, the first magnetic device having a primary winding and a secondary winding, and the second magnetic device having a primary winding and a secondary winding, said pair of conductors coupling said secondary windings of said first and second magnetic devices, the method comprising:

detecting the effective current imbalance;

applying, responsive to said detecting, a predistorted signal to a primary of the first magnetic device, predistortion in the applied predistorted signal compensating for the effective current imbalance.

84. The method of claim 83, wherein said detecting is performed with a receiver wired to receive a differential signal transmitted into the primary of the first magnetic device.

85. The method of claim 84, wherein said applying is performed with a digital signal processor (DSP) receiving an input from the receiver.

86. A method for compensating for an effective current imbalance in a pair of conductors carrying common mode electrical power, the pair of conductors coupled between a first magnetic device and a second magnetic device, the first magnetic device having a primary winding and a secondary winding, and the second magnetic device having a primary winding and a secondary winding, said pair of conductors coupling said secondary windings of said first and second magnetic devices, the method comprising:

detecting the effective current imbalance with first equipment coupled to the primary of the first magnetic device;

communicating between the first equipment and second equipment coupled to the primary of the second magnetic device; and

correcting for the imbalance at the primary of the first magnetic device responsive to said detecting and said communicating.

87. A method for compensating for an effective current imbalance in a pair of conductors carrying common mode electrical power, the pair of conductors coupled between a first magnetic device and a second magnetic device, the first magnetic device having a primary winding and a secondary winding, and the second magnetic device having a primary winding and a secondary winding, said pair of conductors coupling said secondary windings of said first and second magnetic devices, the method comprising:

detecting the effective current imbalance with first equipment coupled to the primary of the first magnetic device and with second equipment coupled to the primary of the second magnetic device;

communicating between the first equipment and the second equipment; and

correcting for the imbalance at one or both of the primary of the first magnetic device and the primary of the second magnetic device in response to said detecting and said communicating.