PURPOSE: To prevent memory effect from being generated by connecting + terminal of a secondary battery connected to a charger to the middle terminal of a coil, connecting one terminal of a coil to the charger via a switcher, regenerating energy with a circuit connected to the other terminal of the coil when the switcher is turned off.

CONSTITUTION: A battery 3 is charged with a charger 2 for rectifying an input power supply 1. The middle tap of a choke coil 10 is accurately connected to the positive pole of the battery 3 and one terminal of the coil 10 is connected to the charger 2 via a charge control switcher SW. The other terminal of the coil 10 is connected to an energy regeneration circuit 11 which is constituted of a diode D for commutation. When the switcher SW is turned off, a battery discharge current flows to an energy regeneration circuit 11 owing to back electromotive force induced at the choke coil 10 when the switcher SW is turned off, thus preventing memory effect from being generated with a simple configuration where the need for a special synchronization circuit is eliminated and preventing energy from being consumed.