PSE controller in PoE system detects different PDs on data pairs and spare pairs

1. A method performed by a Power over Ethernet (PoE) system comprising data wire pairs and spare wire pairs, the system comprising a Power Sourcing Equipment (PSE) controller having an OUT 1 terminal connected to a data wire pair, an OUT 2 terminal connected to a spare wire pair, and a SENSE terminal connected to the OUT 1 terminal via a first resistor and connected to the OUT 2 terminal via a second resistor, the system further comprising a switch controlled by the PSE controller coupled between a PoE voltage source and the SENSE terminal, the method comprising:

supplying a first current to the OUT 1 terminal and measuring a V 1 1 voltage at the OUT 1 terminal by the PSE controller;

supplying a second current to the OUT 1 terminal and measuring a V 1 2 voltage at the OUT 1 terminal by the PSE controller;

by using V 1 1 and V 1 2 , detecting whether there is a signature resistance of a PoE-compatible Powered Device (PD) connected to the data wire pair;

supplying the first current to the OUT 2 terminal and measuring a V 2 1 voltage at the OUT 2 terminal by the PSE controller;

supplying the second current to the OUT 2 terminal and measuring a V 2 2 voltage at the OUT 2 terminal by the PSE controller;

by using V 2 1 and V 2 2 , detecting whether there is a signature resistance of a PoE-compatible PD connected to the spare wire pair;

supplying the first current to the SENSE terminal and measuring a VSENSE 1 voltage at the SENSE terminal by the PSE controller;

supplying the second current to the SENSE terminal and measuring a VSENSE 2 voltage at the SENSE terminal by the PSE controller;

by using VSENSE 1 and VSENSE 2 , detecting whether there is zero, one, or two PoE-compatible PDs connected to the data wire pair and the spare wire pair; and

based on the detection of voltages at the OUT 1 , OUT 2 , and SENSE terminals, determining, by the PSE controller, whether to control the switch to couple the PoE voltage source to the data wire pair and spare wire pair.

2. The method of claim 1 wherein:

the step of using V 1 1 and V 1 2 to detect whether there is a signature resistance of a PoE-compatible PD connected to the data wire pair comprises detecting a resistance of the PD as ΔV/ΔI=(V 1 1 −V 1 2 )/(I DET1 −I DET2 ), where I DET1 is the first current and I DET2 is the second current; wherein

the step of using V 2 1 and V 2 2 to detect whether there is a signature resistance of a PoE-compatible PD connected to the spare wire pair comprises detecting a resistance of the PD as ΔV/ΔI=(V 2 1 −V 2 2 )/(I DET1 −I DET2 ), where I DET1 is the first current and I DET2 is the second current; and wherein

the step of using VSENSE 1 and VSENSE 2 to detect whether there is zero, one, or two PoE-compatible PDs connected to the data wire pair and the spare wire pair comprises detecting a resistance of the PD as ΔV/ΔI=(VSENSE 1 −VSENSE 2 )/(I DET1 −I DET2 ), where I DET1 is the first current and I DET2 is the second current.

3. A Power over Ethernet (PoE) system comprising:

a Power Sourcing Equipment (PSE) controller having an OUT 1 terminal connected to a data wire pair, an OUT 2 terminal connected to a spare wire pair, and a SENSE terminal connected to the OUT 1 terminal via a first resistor and connected to the OUT 2 terminal via a second resistor;

a switch controlled by the PSE controller coupled between a PoE voltage source and the SENSE terminal;

the PSE controller being configured to supply currents to the OUT 1 terminal, the OUT 2 terminal, and the SENSE terminal, during a handshaking phase, to detect signature resistances of zero, one, or two Powered Devices (PDs) connected to the data wire pair and the spare wire pair; and

the PSE controller being configured to close the switch after it has been determined that at least one PoE-compatible PD is connected to the data wire pair and/or spare wire pair.

4. The system of claim 3 wherein the PSE controller is configured for:

supplying a first current to the OUT 1 terminal and measuring a V 1 1 voltage at the OUT 1 terminal by the PSE controller;

supplying a second current to the OUT 1 terminal and measuring a V 1 2 voltage at the OUT 1 terminal by the PSE controller;

by using V 1 1 and V 1 2 , detecting whether there is a signature resistance of a PoE-compatible Powered Device (PD) connected to the data wire pair;

supplying the first current to the OUT 2 terminal and measuring a V 2 1 voltage at the OUT 2 terminal by the PSE controller;

supplying the second current to the OUT 2 terminal and measuring a V 2 2 voltage at the OUT 2 terminal by the PSE controller;

by using V 2 1 and V 2 2 , detecting whether there is a signature resistance of a PoE-compatible PD connected to the spare wire pair;

supplying the first current to the SENSE terminal and measuring a VSENSE 1 voltage at the SENSE terminal by the PSE controller;

supplying the second current to the SENSE terminal and measuring a VSENSE 2 voltage at the SENSE terminal by the PSE controller;

by using VSENSE 1 and VSENSE 2 , detecting whether there is zero, one, or two PoE-compatible PDs connected to the data wire pair and the spare wire pair; and

based on the detection of voltages at the OUT 1 , OUT 2 , and SENSE terminals, determining, by the PSE controller, whether to control the switch to couple the PoE voltage source to the data wire pair and spare wire pair.

5. The system of claim 3 wherein resistances of the first resistor and second resistor are less than 1 Ohm.

6. The system of claim 3 wherein one PD is connected to the data wire pair.

7. The system of claim 3 wherein one PD is connected to the spare wire pair.

8. The system of claim 3 wherein one PD is connected to both the data wire pair and the spare wire pair.

9. The system of claim 3 wherein one PD is connected to the data wire pair and another PD is connected to the spare wire pair.

10. The system of claim 3 wherein the signature resistance of the at least one PoE-compatible PD is approximately 25 kOhms.