Methods and apparatus for provisioning phantom power to remote devices

• US 20050262364A1
• Filed: 05/20/2004
• Published: 11/24/2005
• Est. Priority Date: 05/20/2004
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Schindler, Frederick R., Diab, Wael William
• Granted Patent: US 7,353,407 B2
• Time in Patent Office: Days
• US Class Current: 713/300
• CPC Class Codes: H04L 12/10 Current supply arrangements
• CPC Class Codes: H04L 41/0806 for initial configuration or provisioning, e.g. plug-and-play
• CPC Class Codes: H04M 9/08 Two-way loud-speaking telephone systems with means for conditioning the signal, e.g. for suppressing echoes for one or both directions of traffic

Abstract

An apparatus provisions power from a power budget to remote devices configured to obtain phantom power. The apparatus includes, among other things, a controller which is configured to identify a power demand for a remote device (e.g., a power demand based on an actual cable loss), and generate a comparison between the power demand for the remote device and the power budget of the apparatus. The controller is further configured to allocate power from the power budget provided by the power supply to the remote device when the comparison indicates that the power budget supports the power demand for the remote device, and reject allocation of power from the power budget to the remote device when the comparison indicates that the power budget does not support the power demand for the remote device.

Claims

1. A method for provisioning power from a power budget of an apparatus which is configured to provide phantom power to a set of remote devices, the method comprising:

identifying a power demand for a remote device;

generating a comparison between the power demand for the remote device and the power budget of the apparatus; and

allocating power from the power budget to the remote device when the comparison indicates that the power budget supports the power demand for the remote device, and rejecting allocation of power from the power budget to the remote device when the comparison indicates that the power budget does not support the power demand for the remote device.

2. The method of claim 1 wherein identifying the power demand for the remote device includes:

directing a time domain reflectometry circuit to send a signal through a cable leading from the apparatus to the remote device to determine a cable distance between the apparatus and the remote device; and

calculating a cable dissipation power value based on the cable distance; and

providing, as the power demand for the remote device, a total power value based on a power rating for the remote device and the calculated cable dissipation power value.

3. The method of claim 2 wherein calculating the cable dissipation power value includes:

determining a total resistance of the cable based on the cable distance;

determining a maximum current through the cable based on the power rating of the remote device; and

generating, as the cable dissipation power value, an amount based on the total resistance of the cable and the maximum current through the cable.

4. The method of claim 1 wherein identifying the power demand for the remote device includes:

measuring a voltage drop from the apparatus to the remote device through a cable leading from the apparatus to the remote device;

measuring a current through the cable;

calculating a cable dissipation power value based on the measured voltage drop and the measured current; and

providing, as the power demand for the remote device, a total power value based on a power rating for the remote device and the calculated cable dissipation power value.

5. The method of claim 4 wherein calculating the cable dissipation power value includes:

determining a total resistance of the cable based on the measured voltage drop and the measure current;

determining a maximum current through the cable based on the power rating of the remote device; and

generating, as the cable dissipation power value, an amount based on the total resistance of the cable and the maximum current through the cable.

6. The method of claim 4 wherein each of (i) measuring the voltage drop and the current through the cable, (ii) calculating the cable dissipation power value based on the measured voltage drop and the measured current, and (iii) providing, as the power demand for the remote device, the total power value based on a power rating for the remote device and the calculated cable dissipation power value, is repeated while the remote device operates in a startup low power mode and a normal high power mode in order to obtain a worst case power demand for the remote device and an actual power demand for the remote device.

7. The method of claim 4 wherein measuring the voltage drop from the apparatus to the remote device through the cable includes:

sensing a first voltage applied by the apparatus to the cable leading from the apparatus to the remote device;

receiving a message from the remote device, the message indicating a second voltage sensed by the remote device from the cable; and

subtracting the second voltage from the first voltage to obtain the voltage drop from the apparatus to the remote device through the cable.

8. The method of claim 1, further comprising:

after power is allocated from the power budget to the remote device, determining an actual power demand for the remote device based on an actual loss between the apparatus and the remote device; and

adjusting the power budget of the apparatus based on the actual power demand.

9. The method of claim 1, further comprising:

subtracting the power demand from the power budget in response to allocating power from the power budget to the remote device.

10. The method of claim 1 wherein the apparatus is Ethernet data communications equipment, wherein the remote device is a remote Voice-over-IP telephone, and wherein the method further comprises:

exchanging Voice-over-IP telephone signals through a cable extending between the Ethernet data communications equipment and the Voice-over-IP telephone, the cable being configured to deliver phantom power from the Ethernet data communications equipment to the remote Voice-over-IP telephone in response to allocating power from the power budget to the remote device.

11. An electronic system, comprising:

a cable;

a remote device coupled to one end of the cable; and

an apparatus coupled to another end of the cable, the apparatus being configured to provision power from a power budget to a set of remote devices, the apparatus comprising;

a set of ports configured to connect to the set of remote devices through a set of cables, one of the ports coupling to the cable;

a power supply configured to provide power within the power budget; and

a controller coupled to the set of ports and to the power supply, the controller being configured to;

identify, through a port of the set of ports, a power demand for a remote device;

generate a comparison between the power demand for the remote device and the power budget of the apparatus; and

allocate power from the power budget provided by the power supply to the remote device through the port of the set of ports when the comparison indicates that the power budget supports the power demand for the remote device, and reject allocation of power from the power budget to the remote device when the comparison indicates that the power budget does not support the power demand for the remote device.

12. The electronic system of claim 11 wherein the controller of the apparatus is further configured to:

subtract the power demand from the power budget in response to allocating power from the power budget to the remote device.

13. An apparatus for provisioning power from a power budget to a set of remote devices configured to obtain phantom power from the apparatus, the apparatus comprising:

a set of ports configured to connect to the set of remote devices through a set of cables;

a power supply configured to provide power within the power budget; and

a controller coupled to the set of ports and to the power supply, the controller being configured to;

identify, through a port of the set of ports, a power demand for a remote device;

generate a comparison between the power demand for the remote device and the power budget of the apparatus; and

allocate power from the power budget provided by the power supply to the remote device through the port of the set of ports when the comparison indicates that the power budget supports the power demand for the remote device, and reject allocation of power from the power budget to the remote device when the comparison indicates that the power budget does not support the power demand for the remote device.

14. The apparatus of claim 13 wherein the controller, when identifying the power demand for the remote device, is configured to:

direct a time domain reflectometry circuit to send a signal through a cable leading from the apparatus to the remote device to determine a cable distance between the apparatus and the remote device; and

calculating a cable dissipation power value based on the cable distance; and

providing, as the power demand for the remote device, a total power value based on a power rating for the remote device and the calculated cable dissipation power value.

15. The apparatus of claim 14 wherein the controller, when calculating the cable dissipation power value, is configured to:

determine a total resistance of the cable based on the cable distance;

determine a maximum current through the cable based on the power rating of the remote device; and

generate, as the cable dissipation power value, an amount based on the total resistance of the cable and the maximum current through the cable.

16. The apparatus of claim 13 wherein the controller, when identifying the power demand for the remote device, is configured to:

measure a voltage drop from the apparatus to the remote device through a cable leading from the apparatus to the remote device;

measure a current through the cable;

calculate a cable dissipation power value based on the measured voltage drop and the measured current; and

provide, as the power demand for the remote device, a total power value based on a power rating for the remote device and the calculated cable dissipation power value.

17. The apparatus of claim 16 wherein the controller, when calculating the cable dissipation power value, is configured to:

determine a total resistance of the cable based on the measured voltage drop and the measure current;

determine a maximum current through the cable based on the power rating of the remote device; and

generate, as the cable dissipation power value, an amount based on the total resistance of the cable and the maximum current through the cable.

18. The apparatus of claim 16 wherein the controller, when measuring the voltage drop from the apparatus to the remote device through the cable, is configured to:

sense a first voltage applied by the apparatus to the cable leading from the apparatus to the remote device;

receive a message from the remote device, the message indicating a second voltage sensed by the remote device from the cable; and

subtract the second voltage from the first voltage to obtain the voltage drop from the apparatus to the remote device through the cable.

19. The apparatus of claim 13 wherein the controller is further configured to:

subtract the power demand from the power budget in response to allocating power from the power budget to the remote device.

20. The apparatus of claim 13 wherein the apparatus is Ethernet data communications equipment, wherein the remote device is a remote Voice-over-IP telephone, and wherein the controller is further configured to:

exchange Voice-over-IP telephone signals through a cable extending between the Ethernet data communications equipment and the Voice-over-IP telephone, the cable being configured to deliver phantom power from the Ethernet data communications equipment to the remote Voice-over-IP telephone in response to allocating power from the power budget to the remote device.

21. An apparatus for provisioning power from a power budget to a set of remote devices configured to obtain phantom power from the apparatus, the apparatus comprising:

a set of ports configured to connect to the set of remote devices through a set of cables;

a power supply configured to provide power within the power budget; and

a controller coupled to the set of ports and to the power supply, the controller including;

means for identifying, through a port of the set of ports, a power demand for a remote device;

means for generating a comparison between the power demand for the remote device and the power budget of the apparatus; and

means for allocating power from the power budget provided by the power supply to the remote device through the port of the set of ports when the comparison indicates that the power budget supports the power demand for the remote device, and rejecting allocation of power from the power budget to the remote device when the comparison indicates that the power budget does not support the power demand for the remote device.

22. The apparatus of claim 21 wherein the controller further includes:

means for subtracting the power demand from the power budget in response to allocating power from the power budget to the remote device.