To prevent the fault of a power unit at voltage drop of commercial power and besides, suppress the production cost of the device, in an electric apparatus such as an image maker or the like.

A current within a power unit is increased to operate a protective circuit against overcurrent, by driving a drive system such as a motor, etc., (#3) in case that it is judged that the power has dropped during waiting to a specified voltage level a2 or under (YES in #2). Hereby, the supply of power is stopped (#4) to prevent the fault of the power unit.