Abstract: Dynamic insertion insertion loss for an ethernet power on differential cable pairs is shown in a power feed circuit that supplies power to a network attached device (PD). An insertion loss control circuit limits power loss in a coupled power feed circuit. determines an insertion loss limit, and senses an average power of the power signals to produce a common mode feedback signal to the power feed circuit.

Abstract: The present invention provides for dynamic insertion loss control for a 10/100/1000 megahertz Ethernet power on differential cable pairs. A power feed circuit supplies power to a network attached device (PD). An insertion loss control circuit limits power loss in a coupled power feed circuit. The insertion loss control circuit determines an insertion loss limit and senses an average power of the power signals to produce a common mode feedback signal to the power feed circuit. The insertion loss limit is determined for the received signals based on a differential RMS of the received Ethernet power signals as seen by a differential transistor pair. Alternatively, the insertion loss limit may be determined logically by the higher layers of the network protocol based on the AC differential portion of the network power signal.