Abstract: In the present invention, after a motor is electrically disconnected from a power source by a safety switch, said motor is electrically disconnected from a circuit connected thereto by means of a diode. Therefore, the effects of a regenerative electric force generated by said motor in a circuit connected to said motor are eliminated, and the voltage of said circuit connected to said motor is less than a standard safety voltage level.

Abstract: A heater driving device for supplying AC power to a heater of a fixing device of an image forming apparatus. The heater driving device has self arc suppression type elements between an AC power source and the heater for controlling supply of AC power to the heater in accordance with a control signal supplied to the self arc suppression type elements. The control signal is obtained by modifying signal voltage corresponding to the temperature of the heater in accordance with an absolute value signal which is generated by reducing AC power and converting the reduced AC power to an absolute value, and then comparing the modified signal voltage and a pulse signal generated by a triangular wave oscillator.