Power supply via Ethernet using a single shielded twisted pair of wires.

Abstract

Power-over-Ethernet (PoE) system, comprising: a power source equipment (PSE) to be coupled to a powered device (PD) via a single wire pair and a shield conductor surrounding the wire pair, the PSE being configured to transmit differential or symmetrical data signals over the wire pair; first AC coupling components connected between a first digital communication circuit in the PSE and the wire pair; a first inductor having a first terminal coupled to a first wire in the wire pair; a second inductor having a first terminal coupled to a second wire in the wire pair;wherein the first inductor has a second terminal which is coupled to a second terminal of the second inductor at a first common node; wherein the PSE comprises a PSE control device, wherein the PSE control device is configured to perform a low-power handshaking routine or low-current acknowledgment routine over the wire pair and the shield conductor to determine PoE requirements of the PD, wherein the first wire and the second wire carry handshaking and acknowledgment signals respectively over the first inductor and the second inductor in parallel;and a first mains switch in the PSE, wherein the PSE control device is configured to close the first mains switch after the acknowledgement routine, resulting in a first terminal of a DC voltage source being coupled to the first common node and a second terminal of the voltage source being coupled to the shield conductor, so that a DC voltage is supplied to the PD to power the PD; wherein the system further comprises the powered device (PD), the PD comprising: a second AC coupling component connected between the second digital communication circuit in the PD and the wire pair; a third inductor having a first terminal coupled to the first wire in the wire pair; a fourth inductor having a first terminal coupled to the second wire in the wire pair;wherein the third inductor has a second terminal coupled to a second terminal of the fourth inductor at a second common node; and the PD comprises a PD control device, wherein the PD control device is configured to perform the low-current acknowledgment routine associated with the PSE control device by means of the wire pair and the shield conductor to determine the PoE requirements of the PD, wherein the first wire and the second wire carry the acknowledgment signals in parallel by means of the third inductor and the fourth inductor; wherein the system further comprises a second switch in the PD coupled between the second common node and a PD load to supply the DC voltage to the PD load when the second switch is closed.

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