Device and method for powering Ethernet midspan device and endspan device

1. A midspan device for connecting an Ethernet one-pair power sourcing equipment (PSE) to a two-pair powered device (PD) comprising:

a path for direct current coupling the PSE to the PD;

a power supply configured to provide a supply voltage in response to a power voltage from the PSE; and

a converter powered by the supply voltage and configured to convert one-pair data from the PSE into two-pair data for the PD.

2. The midspan device of claim 1 , wherein the power supply is a switched mode power supply.

3. The midspan device of claim 1 , further comprising an under voltage lock out circuit configured to prevent input voltages below a threshold voltage from activating the power supply.

4. The midspan device of claim 1 , further comprising transformers with center taps configured to couple the power voltage of the PSE to a common mode power voltage on two pairs coupled to the PD.

5. The midspan device of claim 1 , further comprising a timing circuit configured to prevent a probe voltage from the PSE from activating the power supply.

6. The midspan device of claim 1 , further comprising a current detector configured to monitor current of the one pair and deactivate the power supply when the current is below a threshold value.

7. The midspan device of claim 1 , further comprising a diode bridge configured to couple the supply voltage to the power supply.

8. The midspan device of claim 1 , wherein data from the PSE is blocked from flowing on the path.

9. A midspan device for providing data communication between an Ethernet one-pair power sourcing equipment (PSE) and a two-pair powered device (PD), the midspan device comprising:

a converter for converting one-pair data from the PSE to two pair data for the PD, wherein power for powering the converter is provided by the PSE; and

a DC path between the PSE and the PD.

10. The midspan device of claim 9 , wherein a power voltage from the PSE is coupled to a power supply that provides a supply voltage for the converter.

11. The midspan device of claim 10 , further comprising a lock out circuit configured to prohibit voltages from the PSE below a threshold voltage from activating the power supply.

12. The midspan device of claim 9 , further comprising a time-voltage circuit configured to block a probe voltage from the PSE from activating the power supply.

13. The midspan device of claim 10 , wherein the path comprises a plurality of conductors extending between a one-pair port and a two-pair port.

14. The midspan device of claim 13 , further comprising a current sensor for measuring a current in one of the plurality of conductors, the current sensor configured to cause a shut down of the power supply when the measured current is less than a threshold value.

15. The midspan device of claim 9 , further comprising blocking inductors configured to prohibit data flow on the DC path.

16. A method for providing a data communication link between an Ethernet power sourcing equipment (PSE) and a powered device (PD), the method comprising:

transforming a power voltage of the PSE to a common mode power voltage for the PD;

applying to a converter a converter supply voltage from the power voltage of the PSE;

converting one-pair data of the PSE to two-pair data for the PD; and

transferring data via the converter between the PSE and the PD.

17. The method of claim 16 , further comprising:

receiving a probe signal from the PSE; and

preventing the probe signal from generating a supply voltage for the converter.

18. The method of claim 16 , further comprising removing the converter supply voltage from the converter if current from the PSE drops below a threshold value.

19. A midspan device comprising:

a DC path for connecting a differential mode power voltage on a one-pair port to a common mode power voltage on the two-pair port; and

a converter for converting one-pair data from the PSE to two-pair data for the PD, wherein the converter is configured to receive power from the one-pair port.

20. The device of claim 19 , further comprising a current detector configured to measure current in the DC path and cause removal of power to the converter when the measured current is below a threshold value.