PURPOSE: To drive a motor stably, by constituting a charge circuit such that a cell to be charged is separated from the output of a transistor inverter and a load during AC drive mode.

CONSTITUTION: A switch (Sw) 6 is connected to the side of contact (a) during AC drive mode where a transistor inverter (Tin) 4 is oscillating. An electromagnetic Sw 5 is at a contact (b) because a power source is turned on, but a cell 1 to be charged is separated from the output of the Tin 4 because the contact (c) of the Sw 6 is open. Consequently, the output is fed through the contact (d) of the Sw 6 only to a motor 3 thus driving the motor 3. A Sw 7 is at the contact (f), at this time, and the emitter resistance of a transistor Q1 equals to the parallel resistance of resistors R4, R5 thus increasing output current. Consequently, fluctuation of cell voltage has no influence on the rotation of the motor 3.