A control circuit includes a first input coupled to a power source, a second input coupled to an output of a power supply, and an output coupled to an input of the power supply. The control circuit senses current at the power supply output. If the sensed current exceeds a threshold, the control circuit connects the power supply input to the power source. If sensed current does not exceed the threshold, the control circuit disconnects the power supply input from the power source and applies a voltage to the power supply output. If the sensed current exceeds the threshold while the power supply input is disconnected from the power source and while the control circuit is applying voltage to the power supply output, the control circuit discontinues application of voltage to the power supply output and connects the power supply input to the power source.