An apparatus for controlling power efficiency of an information processing device is disclosed. The apparatus includes a voltage converter that converts a selected input voltage into a predetermined output voltage, an information processing device that uses power supplied by the voltage converter; and a controller that determines the selected input voltage based on an operating state of the information processing device where the operating state includes one or more parameters selected from fan speed, power consumption, power consumption fluctuation, processor usage, processor usage fluctuation, system temperature, sensor-specific temperature, mobility, and acceleration. A method and a system also perform various functions of the apparatus.