Apparatus and method for classifying a powered device (PD) in a power source equipment (PSE) controller

• US 20070206774A1
• Filed: 04/30/2007
• Published: 09/06/2007
• Est. Priority Date: 01/17/2006
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: Chin, David, Vorenkamp, Pieter, Woo, Agnes, Perzow, John, Fujimori, Ichiro, Tammineedi, Anil
• Granted Patent: US 7,936,546 B2
• Time in Patent Office: Days
• US Class Current: 379/310
• CPC Class Codes: G06F 1/26 Power supply means, e.g. regulation thereof for memories G11C
• 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: H04B 3/44 Arrangements for feeding power to a repeater along the transmission line
• CPC Class Codes: H04L 12/10 Current supply arrangements
• CPC Class Codes: H04L 12/40045 Details regarding the feeding of energy to the node from the bus
• CPC Class Codes: H04L 25/02 Details ; arrangements for supplying electrical power along data transmission lines systems for transmitting signals via power distribution lines H04B3/54
• CPC Class Codes: Y10S 370/91 Carrier sense multiple access, e.g. ethernet, 10base-t

Abstract

Power over Ethernet (PoE) communication systems provide power and data communications over the same communications link, where a power source device (PSE) provides DC power (for example, 48 volts DC) to a powered device (PD). The DC power is transmitted simultaneously over the same communications medium with the high speed data from one node to the other node. The PSE typically includes a controller that controls the DC power provided to the PD at the second node of the communications link. The PSE controller measures the voltage, current, and temperature of the outgoing and incoming DC supply lines to characterize the power requirements of the PD. In addition, the PSE controller may detect and validate a compatible PD, determine a power classification signature for the validated PD, supply power to the PD, monitor the power, and reduce or remove the power from the PD when the power is no longer requested or required. During detection, if the PSE finds the PD to be non-compatible, the PSE can prevent the application of power to that PD device, protecting the PD from possible damage.

Claims

1. In a Power Source Equipment (PSE) Controller, an apparatus for classifying a powered device (PD), the apparatus comprising of:

a preamplifier configured to receive a differential input voltage from the PD, wherein the preamplifier converts the input differential voltage to a single ended output; and

a classification module to compare the single ended output to a classification reference voltage to produce a classification current, wherein the PSE controller classifies the PD based on the classification current.

2. The apparatus of claim 1, wherein the preamplifier converts the differential input voltage to the single ended output using an operational amplifier.

3. The apparatus of claim 2, wherein the gain of the operational amplifier is substantially equal to one.

4. The apparatus of claim 2, wherein a shunt resistor is coupled to an inverting input of the operational amplifier, a first series resistor coupled between the inverting input of the operational amplifier and the PD, a feedback resistor coupled between a non-inverting input of the operational amplifier and an output of the operational amplifier, and a second series resistor coupled between the non-inverting input of the operational amplifier and the PD.

5. The apparatus of claim 4, wherein the shunt resistor, the feedback resistor, the first series resistor, and the second series resistor are implemented using a material with a sheet Rho approximately 1 kohm/square.

6. The apparatus of claim 1, wherein the classification module includes a comparator to compare the single ended output to the classification reference voltage.

7. The apparatus of claim 6, wherein the classification module includes a main driver switch to produce the classification current based upon an output of the comparator.

8. The apparatus of claim 1, wherein the classification module includes a main driver switch to produce the classification current.

9. The apparatus of claim 1, further comprising:

a current measurement system to measure the classification current.

10. The apparatus of claim 9, wherein the PSE controller classifies the PD as a Class 0 when a measured classification current is between 0 mA to 5 mA, a Class 1 when the measured classification current is between 8 mA and 13 mA, a Class 2 when the measured classification current is between 16 mA and 21 mA, a Class 3 when the measured classification current is between 25 mA and 31 mA, and a Class 4 when the measured classification current is between 35 mA and 45 mA.

11. A Power over Ethernet (PoE) system, the system comprising of:

a powered device (PD) configured to output a differential voltage;

a preamplifier to convert the input differential voltage to a single ended output;

a classification module to compare the single ended output to a classification reference voltage to produce a classification current; and

a PSE controller to classify the PD based on the classification current.

12. The system of claim 11, wherein the preamplifier converts the differential input voltage to the single ended output using an operational amplifier.

13. The system of claim 12, wherein the gain of the operational amplifier is substantially equal to one.

14. The system of claim 12, wherein a shunt resistor is coupled to an inverting input of the operational amplifier, a first series resistor coupled between the inverting input of the operational amplifier and the PD, a feedback resistor coupled between a non-inverting input of the operational amplifier and an output of the operational amplifier, and a second series resistor coupled between the non-inverting input of the operational amplifier and the PD.

15. The system of claim 14, wherein the shunt resistor, the feedback resistor, the first series resistor, and the second series resistor are implemented using a material with a sheet Rho approximately 1 kohm/square.

16. The system of claim 11, wherein the classification module includes a comparator to compare the single ended output to the classification reference voltage.

17. The system of claim 16, wherein the classification module includes a main driver switch to produce the classification current based upon an output of the comparator.

18. The system of claim 11, wherein the classification module includes a main driver switch to produce the classification current.

19. The system of claim 11, further comprising:

a current measurement system to measure the classification current.

20. The system of claim 19, wherein the PSE controller classifies the PD as a Class 0 when a measured classification current is between 0 mA to 5 mA, a Class 1 when the measured classification current is between 8 mA and 13 mA, a Class 2 when the measured classification current is between 16 mA and 21 mA, a Class 3 when the measured classification current is between 25 mA and 31 mA, and a Class 4 when the measured classification current is between 35 mA and 45 mA.

21. A method for classifying a powered device (PD) in a Power over Ethernet (PoE) system, the method comprises the steps of:

receiving a differential input voltage from the PD;

converting the differential input voltage to a single ended output;

comparing the single ended output to a classification reference voltage to produce a classification current; and

classifying the PD based on the classification current.

22. The method of claim 21, further comprising the step of:

applying a classification voltage to the PD to generate the differential input voltage.

23. The method of claim 22, wherein the classification voltage is from 15.5V to 20.5V.

24. The method of claim 21, wherein the step of converting the differential input voltage to a single ended output is performed by an operational amplifier.

25. The method of claim 21, wherein the step of comparing the single ended output to a classification reference voltage is performed by a comparator.

26. The method of claim 21, wherein the classification current is produced by a main driver switch.

27. The method of claim 21, wherein the step of classifying the PD based on the classification current further comprises:

classifying the PD as a Class 0 when a measured classification current is between 0 mA to 5 mA, a Class 1 when the measured classification current is between 8 mA and 13 mA, a Class 2 when the measured classification current is between 16 mA and 21 mA, a Class 3 when the measured classification current is between 25 mA and 31 mA, and a Class 4 when the measured classification current is between 35 mA and 45 mA.