Patent ID: 7843670

Claim:
A method for monitoring a line-side electrical current provided by a power sourcing equipment (PSE) port to a powered device (PD), the PSE port having a power-isolation transformer comprising a primary coil on an isolated side and a secondary coil on a line side, the method comprising: (a) determining a value for an electrical current on the isolated side of the power-isolation transformer; (b) indirectly monitoring the line-side electrical current based on the determined isolated-side electrical current value; (c) sampling the voltage at a voltage-sensing node on the isolated side and holding a resulting analog sampled voltage value; (d) generating an isolated-side-current-based voltage value based on the electrical current through the primary coil; and (e) converting the analog sampled voltage value into a digital sampled voltage value and using the digital sampled voltage value and the isolated-side-current-based voltage value to control a switching signal, wherein: the primary coil is connected between a voltage source having a first voltage value and a transistor, wherein the transistor: (i) is connected to a reference node, and (ii) is adapted to be driven by the switching signal having a switching period and a duty cycle; and the secondary coil is connected to the PD.