| 摘要 |
PURPOSE:To hold the temperature of a heat development photosensitive material constant by providing a deviation detecting circuit for the deviation of the resistance value of the heat development photosensitive material from a specific resistance value and a control circuit for electric power supplied to a feed heating body according to the output of said circuit. CONSTITUTION:When the temperature of the feed heating body 1 is low and its resistance value Rt is smaller than a desired value, a phase control circuit 8 increases the firing angle of a triac 3 to increase the level of a current which flows through the feed heating body 1. When the temperature of the feed heating body 1 is high and its resistance value Rt is larger than the desired value, on the other hand, the firing angle of the triac 3 is decreased to decrease the current level. When an AC power source 2 is determined,a voltage V1 is constant, so when the resistance value Rt of the feed heating body 1 is held constant, a voltage V2 is also constant, and consequently the output voltage Vf of an operational amplifier 5 is held nearly as high as a reference voltage Vr.
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