ADC-to-DC converter which is configured to provide a main DC supply and an auxiliary DC supply from a single energy source such as a fuel cell. The main supply voltage may be greater than the voltage provided by the energy source, and the auxiliary supply voltage may be less than the voltage provided by the energy source. In some embodiments boost and buck conversion are provided by a single switching bridge, such as an inverter. Such an inverter may comprise three-legs connected between a main output voltage and a reference or ground voltage. Each leg of such an inverter may comprise two switches connected in series. These legs may share a common DC voltage link, for example a common ground and positive rail.