Abstract: A DC-DC converter of simple arrangement that effectively utilizes a negative voltage to improve loss of power. This DC-DC converter is suitable as a dc power source for an electronic flash of a camera.

Abstract: A battery rapid charging circuit is disclosed which includes a DC power source supplying a DC voltage across first and second terminals between which a battery to be charged is connected, a circuit element for short-circuiting the first and second terminals in a short period of time during a charging period of the battery, a comparator for comparing a terminal voltage of the battery upon the above short-circuiting period with a reference voltage, and a circuit element for stopping the supply of the DC voltage across the first and second terminals in response to the output of the comparator.