A flat display employs at least one high voltage different from logic voltages. The display has a voltage detection unit and a drive control signal control unit. The voltage detection unit is used to detect the high voltage. The drive control signal control unit is used to control drive control signals of the flat display in accordance with the detected high voltage. This arrangement eliminates charging currents that are applied to a display panel but have nothing to do on the actual displaying of data, or reactive currents due to unnecessary switching operations, thereby reducing power consumption.