In accordance with an embodiment, a method of operating a switched-mode power supply includes receiving power from an input node via a first transistor, providing a first portion of the received power to a load via a switching transistor having a first terminal coupled to the first transistor and a second terminal coupled to the load via a series resistor and a series inductor, measuring a current through the load, measuring comprising monitoring a voltage across the series resistor; and controlling an average current through the load by switching on and switching off the switching transistor according to the measured current.