| 摘要 |
PURPOSE:To quickly detect the non-electrified state with a simple constitution by detecting the voltage between terminals of a capacitor, which is charged with a charging characteristic lower than the detection temperature characteristic of a fixing heater, as a reference voltage. CONSTITUTION:The time constant for charging of a capacitor 8 is so set that the increase curve of the voltage between terminals of the capacitor 8 is slower than that of the temperature detection signal at a connection point 3 between a thermistor 1 and a variable resistance 2. If disconnection or the like of the fixing heater or the like occurs, the temperature detection signal at the connection point 3, namely, the output signal from an amplifier 4 is kept at a certain value, and therefore, magnitude relations between signals supplied to a comparator 7 are inverted in a relatively short time after making of a power switch, and the signal indicating that the output signal from the amplifier 4 is smaller, namely, the signal indicating the non-conduction state of the fixing heater is supplied from the comparator 7 to a fixing heater control part 6. Consequently, the feeding operation to the fixing heater by the control part 6 is stopped.
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