According to an embodiment, a circuit comprising includes a first switching circuit coupled to a power supply input, a second switching circuit coupled to an output of the first switching circuit, a supply capacitor coupled to the second switching circuit, and a startup cell coupled to the power supply input and the supply capacitor. The startup cell is configured to electrically couple the power supply input to the supply capacitor when the second switching circuit is not actively switching. The startup cell is also configured to electrically decouple the power supply input from the supply capacitor when the second switching circuit is actively switching.