An electronic device operable from one of an external power supply and a battery. The electronic device includes a display part, a power converter, an inverter generating an operating voltage for the display part, a system part generating information to be displayed on the display part and operable from an output of the power converter, a battery, an input power detector, and a switching controller. The switching controller controls power to the inverter so that where the input power detector detects availability of an external power, the switching controller supplies the external power to the power converter and the power converter supplies power to the inverter to generate the operating voltage for the display part; and where the input power detector detects the external power is not available, the switching system supplies battery power to the power converter and the inverter independently.