Importance

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Abstract

Embodiments of the present invention provide a power feed circuit operable to supply an Ethernet power signal to a coupled Ethernet network. This power feed circuit includes a number of input nodes, differential transistor pairs, active control circuits, insertion loss control limit circuits and output nodes. The input nodes receive a first power signal such as that provided by an isolated 48 volt power supply. Each transistor of the differential transistor pairs couples to one input node. These differential transistor pairs draw currents which combine to produce a power signal component of the Ethernet power signal. The active control circuits sense the currents drawn by each transistor and are operable to apply a feedback signal to the differential transistor pairs based on the second circuit. Additionally, the insertion loss control limit circuit may sense the power and/or data rate associated with the data signal component of the Ethernet power signal. This then enables the power signal component to be adjusted. By considering the power of both the power signal component and data signal component, the overall power may be limited to prevent damage to downstream power devices. At least one twisted pair couples to each differential transistor pair's output node and is operable to pass the Ethernet power signal.

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First Claim