Current imbalance compensation for magnetics in a wired data telecommunications network

• US 7,577,104 B2
• Filed: 12/07/2005
• Issued: 08/18/2009
• 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.
• Primary Examiner(s): Nguyen; Brian D
• Application Number:
  US11/297,230
• Publication Number:
  US 20060119478A1
• Time in Patent Office: 1,350 Days
• Field of Search: 370/252, 370/200, 340/538, 340/531, 340/533, 340/310.11, 375/258
• US Class Current: 370/252
• 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 conductors coupled to power sourcing equipment (PSE) and a powered device (PD) via a first magnetic device and a second magnetic device, the first and second magnetic devices each having a primary and secondary winding, the method comprising:

sending a signal between the PSE and the PD;

detecting an effective current imbalance between the PSE and the PD from the signal; and

applying a direct current bias at a desired point between the PSE and the PD in response to the detected current imbalance, the direct current bias having a magnitude and direction to compensate for the effective current imbalance;

wherein a receiver circuit is coupled to the pair of conductors carrying the common mode electrical power, the receiver circuit being constructed and arranged to receive the signal between the PSE and the PD;

wherein a processor circuit is coupled to the receiver circuit;

wherein detecting the effective current imbalance between the PSE and the PD from the signal includes generating, from the processor circuit, a difference error signal indicating a magnitude of droop present on the first and second magnetic devices based on a comparison between (i) waveform characteristics of the signal, when received by the receiver circuit, and (ii) waveform characteristics of an ideal signal; and

wherein applying the direct current bias at the desired point between the PSE and the PD in response to the detected current imbalance includes injecting current at an node coupled to the pair of conductors in response to the difference error signal.

2. The method of claim 1, wherein the detecting occurs at the primary winding of at least one of the first and second magnetic device.

3. The method of claim 1, wherein the detecting occurs at the secondary winding of at least one of the first and second magnetic device.

4. The method of claim 1, wherein the desired point is at the primary winding of at least one of the first and second magnetic device.

5. The method of claim 1, wherein the desired point is at the secondary winding of the first magnetic device.

6. The method of claim 1, wherein the desired point is at the primary winding of second magnetic device.

7. The method of claim 1, wherein the desired point is at the secondary winding of first magnetic device.

8. The method of claim 1, wherein the signal is a test signal.

9. The method of claim 1, wherein the signal is a data signal.

10. The method of claim 1, wherein the detecting further comprises measuring current flow through at least two further comprising locations between the PSE and the PD.

11. The method of claim 1 wherein injecting current at the node coupled to the pair of conductors in response to the difference error signal include:

applying, responsive to the detecting, a predistorted signal to the primary winding of the first magnetic device, wherein a predistortion characteristic in the applied predistorted signal compensates the effective current imbalance.

12. The method of claim 1, further comprising performing an auto-negotiation process between the PSE and the PD, wherein the PSE and PD selectively apply the direct current bias.

13. The method of claim 1 wherein the signal between the PSE and the PD includes a pulse;

wherein generating the difference error signal from the processor circuit includes (i) measuring a peak amplitude of the pulse at a predefined point of the pulse, (ii) comparing the peak amplitude of the pulse to a predefined amplitude value, and (iii) outputting the difference error signal to represent a magnitude of difference between the peak amplitude of the pulse at the predefined point and the predefined amplitude value; and

wherein injecting the current at the node provides a feedback loop to subsequently bring both magnitude of the droop and the magnitude represented by the difference error signal to zero.

14. A system comprising:

first equipment having a first magnetic device, the first magnetic device having a primary winding and a secondary winding;

second equipment having a second magnetic device, the second magnetic device having a primary winding and a secondary winding;

at least one pair of conductors carrying common mode electrical power and coupling the secondary windings of the first and second magnetic devices;

means for transmitting a test signal in the conductors;

means for detecting an effective current imbalance between the first equipment and the second equipment from the test signal, the means for detecting including a receiver circuit and a processor circuit coupled to the receiver circuit; and

means for correcting the effective current imbalance at a desired point between the first and second equipment in response to the detected current imbalance;

wherein the receiver circuit is coupled to the at least one pair of conductors carrying the common mode electrical power, the receiver circuit being constructed and arranged to receive the test signal between the first equipment and the second equipment;

wherein the means for detecting an effective current imbalance between the first equipment and the second equipment from the test signal includes means for generating, from the processor circuit, a difference error signal indicating a magnitude of droop present on the first and second magnetic devices based on a comparison between (i) waveform characteristics of the signal, when received by the receiver circuit, and (ii) waveform characteristics of an ideal signal; and

wherein the means for correcting the effective current imbalance at a desired point between the first and second equipment in response to the detected current imbalance includes means for injecting current at an node coupled to the at least one pair of conductors in response to the difference error signal.

15. The system of claim 14, wherein the desired point is at the primary winding of at least one of the first and second magnetic devices.

16. The system of claim 14, wherein the desired point is at the secondary winding of at least one of the first and second magnetic devices.

17. The system of claim 14, wherein the means for transmitting transmits the test signal when data signals are not sent between the first and second equipment.

18. The system of claim 14, wherein the means for correcting corrects the current imbalance of at least one of the first equipment, the first magnetic device, the second magnetic device and the second equipment.

19. The system of claim 14, wherein the means for correcting provides a current bias at the desired point to correct the current imbalance.

20. A system comprising:

first equipment having a first magnetic device, the first magnetic device having a primary winding and a secondary winding;

second equipment having a second magnetic device, the second magnetic device having a primary winding and a secondary winding;

at least one pair of conductors carrying common mode electrical power and coupling the secondary windings of the first and second magnetic devices;

circuitry configured to transmit a test signal between the first equipment and the second equipment;

circuitry configured to detect an effective current imbalance between the first equipment and the second equipment from the test signal, the circuitry configured to detect the effective current imbalance including a receiver circuit and a processor circuit coupled to the receiver circuit; and

circuitry configured to correct the effective current imbalance at a desired point between the first and second equipment in response to the detected current imbalance;

wherein the receiver circuit is coupled to the at least one pair of conductors carrying the common mode electrical power, the receiver circuit being constructed and arranged to receive the test signal between the first equipment and the second equipment;

wherein the circuitry configured to detect an effective current imbalance between the first equipment and the second equipment from the test signal includes circuitry configured to generate, from the processor circuit, a difference error signal indicating a magnitude of droop present on the first and second magnetic devices based on a comparison between (i) waveform characteristics of the signal, when received by the receiver circuit, and (ii) waveform characteristics of an ideal signal; and

wherein the circuitry configured to correct the effective current imbalance at a desired point between the first and second equipment in response to the detected current imbalance includes circuitry configured to inject current at an node coupled to the at least one pair of conductors in response to the difference error signal.