Power supplies for electronic devices (e.g., portable ultrasound devices) are disclosed herein. In one embodiment, a stack of batteries and one or more switches between the batteries can change a voltage provided to a terminal that is connectable to a load. A charge pump comprising a number of capacitors are connected by switches. In one configuration, the switches are set so that each capacitor is charged from a common voltage source. In another mode, the switches are connected such that capacitors can be connected in series to provide a multiple of the charging voltage to the load.