PURPOSE: To facilitate detection of trouble such as degradation of the performance of an AC load or disconnection of wire by comparing a signal fed from an AC load current detecting means with a specific level determined based on the magnitude of AC voltage.
CONSTITUTION: The temperature of a fixing heater 4 is detected through a thermister 5 and fed to the A/D input port P1 of a control means 17. Since the resistance of the thermister 5 increases as the temperature increases, the voltage to be fed to the input port P1 increases as the temperature of the fixing heater 4 increases. When the voltage fed to the input port P1 drops below a threshold voltage VTH, HTD to be fed from the output port P2 of the control means 17 is brought to Low level and a solid state relay 7 is turned ON to apply an AC voltage onto the fixing heater 4. When the input voltage of the input port P1 exceeds over VTH, HTD is brought to High level and the solid state relay 7 is turned OFF.
KIMIZUKA JUNICHI
INUYAMA SATOHIKO
ITO TOSHIYUKI
