A power supply circuit includes a power amplifier that receives a direct current (DC) voltage from a first power source. A control signal applied to the power amplifier causes the power amplifier to convert the DC voltage to an alternating current (AC) output signal. The AC output signal is applied to a transformer that includes a first winding, a second winding, and a third winding. The first winding receives the AC output signal and the second winding receives an output current that varies in accordance with the AC output signal to apply current to a load. A rectifier includes a plurality of diodes configured to rectify a voltage across the third winding and clamp the voltage at the load. Return power from the third winding may be returned to the first power source.