Techniques for measuring network channel resistive loss between a power-sourcing apparatus and a powered device

• US 20080252307A1
• Filed: 04/11/2007
• Published: 10/16/2008
• Est. Priority Date: 04/11/2007
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Schindler, Frederick R.
• Granted Patent: US 7,818,591 B2
• Time in Patent Office: Days
• US Class Current: 324/713
• CPC Class Codes: G06F 1/266 Arrangements to supply power to external peripherals either directly from the computer or under computer control, e.g. supply of power through the communication port, computer controlled power-strips
• CPC Class Codes: H04L 12/10 Current supply arrangements

Abstract

A method and apparatus are provided for determining resistive power loss through a channel between Power Sourcing Equipment (PSE) and a Powered Device (PD). The method includes (1) receiving indication that a PSE signal measurement is available from the PSE or a PD signal measurement is available from the PD, (2) selecting, as an input parameter to a processing operation, at least one of the PSE signal measurement or the PD signal measurement, (3) performing the processing operation to calculate a resistance value indicative of the resistive power loss through the channel between the PSE and PD based on the input parameter, and (4) outputting the resistive power loss value as a result of carrying out the processing operation.

Claims

1. A method for determining resistive power loss through a channel between Power Sourcing Equipment (PSE) and a Powered Device (PD), the method comprising:

receiving indication that a PSE signal measurement is available from the PSE or a PD signal measurement is available from the PD;

selecting, as an input parameter to a processing operation, at least one of the PSE signal measurement or the PD signal measurement; and

performing the processing operation to calculate a resistance value indicative of the resistive power loss through the channel between the PSE and PD based on the input parameter.

2. A method as in claim 1 wherein receiving includes:

obtaining the PD signal measurement from the PD, the PD signal measurement being based on (i) a first signal value read at a connection interface of the PD while a first load is applied by the PD to the channel and (ii) a second signal value read at the connection interface of the PD while a second load is applied by the PD to the channel in place of the first load.

3. A method as in claim 2 wherein:

the first signal value comprises a first voltage measurement and a first current measurement;

the second signal value comprises a second voltage measurement and a second current measurement; and

performing the processing operation comprises calculating a voltage difference as the difference between the first and second voltage measurements, calculating a current difference as the difference between the second and first current measurements, and dividing the voltage difference by the current difference.

4. A method as in claim 1 wherein selecting comprises choosing a method for calculating resistive power loss based on the availability of the PSE signal measurement and the PD signal measurement and picking an input parameter associated with the chosen method.

5. A method as in claim 4 wherein selecting further includes choosing a method that is most accurate among a variety of methods.

6. A method as in claim 5 wherein choosing a method further includes:

if a PD signal measurement is available and if the PD is capable of measuring local voltage and current for two different load values, then selecting as the input parameter the PD signal measurement.

7. A method as in claim 6 wherein receiving includes:

obtaining the PD signal measurement from the PD, the PD signal measurement being based on (i) a first signal value read at a connection interface of the PD while a first load is applied by the PD to the channel and (ii) a second signal value read at the connection interface of the PD while a second load is applied by the PD to the channel in place of the first load.

8. A method as in claim 7 wherein:

the first signal value comprises a first voltage measurement and a first current measurement;

the second signal value comprises a second voltage measurement and a second current measurement; and

performing the processing operation comprises subtracting the second voltage measurement from the first voltage measurement and dividing the difference by the first current measurement minus the second current measurement.

9. A method as in claim 5 wherein selecting further includes:

if a PD signal measurement is not available or if the PD is not capable of measuring local voltage and current for two different load values then;

if the PSE is capable of measuring local voltage and current for two different load values, then selecting as the input parameter the PSE signal measurement;

otherwise

if the PSE is capable of measuring local voltage and current for one load value and the PD is capable of reporting its power load, then selecting as the input parameter the PSE signal measurement and the PD signal measurement;

otherwise

selecting as the input parameter the PSE signal measurement.

10. A method as in claim 9 wherein receiving includes:

if the PD signal measurement is selected, obtaining the PD signal measurement from the PD, the PD signal measurement being based on a plurality of measurements taken at different loads, the plurality of measurements being used to eliminate any offset or gain errors.

11. A method as in claim 4 wherein selecting further includes choosing a method that is fastest among a variety of methods.

12. A method as in claim 1 wherein the method further comprises:

if the resistance is higher than a pre-determined value, instructing the PSE to cease applying power to the PD.

13. An apparatus comprising;

memory;

a network interface; and

a controller, the controller configured to;

receive indication that a Power Sourcing Equipment (PSE) signal measurement is available from a PSE or a Powered Device (PD) signal measurement is available from a PD;

select, as an input parameter to a processing operation, at least one of the PSE signal measurement or the PD signal measurement; and

perform the processing operation to calculate a resistance value indicative of a resistive power loss through the channel between the PSE and PD based on the input parameter.

14. An apparatus as in claim 13 wherein the controller is configured such that when it receives indication that the PSE signal measurement or PD signal measurement is available it is configured to:

obtain the PD signal measurement from the PD, the PD signal measurement being based on (i) a first signal value read at a connection interface of the PD while a first load is applied by the PD to the channel and (ii) a second signal value read at the connection interface of the PD while a second load is applied by the PD to the channel in place of the first load.

15. An apparatus as in claim 14 wherein:

the first signal value comprises a first voltage measurement and a first current measurement;

the second signal value comprises a second voltage measurement and a second current measurement; and

the controller is configured such that when it performs the processing operation it is configured to calculate a voltage difference as the difference between the first and second voltage measurements, calculate a current difference as the difference between the second and first current measurements, and divide the voltage difference by the current difference.

16. An apparatus as in claim 13 wherein the controller is configured such that when it selects it is configured to choose a method for calculating resistance based on the availability of the PSE signal measurement and the PD signal measurement and pick an input parameter associated with the chosen method.

17. An apparatus as in claim 16 wherein the controller is configured such that when it selects it is further configured to choose a method that is most accurate among a variety of methods.

18. An apparatus as in claim 17 wherein the controller is configured such that when it chooses a method, if a PD signal measurement is available and if the PD is capable of measuring local voltage and current for two different load values, it is further configured to:

select as the input parameter the PD signal measurement.

19. An apparatus as in claim 18 wherein the controller is configured such that when it receives indication that the PSE signal measurement or PD signal measurement is available it is configured to:

obtain the PD signal measurement from the PD, the PD signal measurement being based on (i) a first signal value read at a connection interface of the PD while a first load is applied by the PD to the channel and (ii) a second signal value read at the connection interface of the PD while a second load is applied by the PD to the channel in place of the first load.

20. An apparatus as in claim 19 wherein:

the first signal value comprises a first voltage measurement and a first current measurement;

the second signal value comprises a second voltage measurement and a second current measurement; and

the controller is configured such that when it performs the processing operation it is configured to subtract the second voltage measurement from the first voltage measurement and divide the difference by the first current measurement minus the second current measurement.

21. An apparatus as in claim 17 wherein the controller is configured such that when it chooses a method, if a PD signal measurement is not available or if the PD is not capable of measuring local voltage and current for two different load values, it is further configured to:

if the PSE is capable of measuring local voltage and current for two different load values, then select as the input parameter the PSE signal measurement;

otherwise

if the PSE is capable of measuring local voltage and current for one load value and the PD is capable of reporting its power load, then select as the input parameter the PSE signal measurement and the PD signal measurement;

otherwise

select as the input parameter the PSE signal measurement.

22. An apparatus as in claim 21 wherein:

if the PD signal measurement is selected, the PD signal measurement is based on a plurality of measurements taken at different loads, the plurality of measurements being used to eliminate any offset or gain errors.

23. An apparatus as in claim 16 wherein the controller is configured such that when it selects it is further configured to choose a method that is fastest among a variety of methods.

24. An apparatus as in claim 13 wherein the controller is further configured to:

if the resistance is higher than a pre-determined value, instruct the PSE to cease applying power to the PD.

25. An apparatus comprising;

memory;

a network controller; and

means for;

receiving indication that a Power Sourcing Equipment (PSE) signal measurement is available from a PSE or a Powered Device (PD) signal measurement is available from a PD;

selecting, as an input parameter to a processing operation, at least one of the PSE signal measurement or the PD signal measurement; and

performing the processing operation to calculate a resistance value indicative of a resistive power loss through the channel between the PSE and PD based on the input parameter.