PURPOSE: To extend the service life of a charging battery and to reduce a danger of occurrence of a voltage drop below a minimum voltage required for an image pickup device by detecting a residual voltage of a main capacitor and controlling optimally a current supplied to the main capacitor based on the detected residual voltage.

CONSTITUTION: A residual voltage of a main capacitor 64 is obtained by residual voltage detection means 72, 73. Then a system controller 66 obtains a minimum current at which the charging is finished within a charging period based on the residual voltage. Then a desired setting voltage is selected from a data table in a memory 70 in which setting voltages for controlling a minimum current are stored and the selected setting voltage is outputted to a noninverting input terminal of a comparator 71 in a current limit circuit 63 via a D/A converter 68 as a comparison voltage VCP. Thus, the charging is made complete within a prescribed period regardless of charging with a minimum current.