| 摘要 |
PURPOSE:To reduce an overshoot and a temperature ripple without extending a rising time by stepping down a duty cycle abruptly when proportional control is performed by varying the duty cycle, and to eliminate deterioration in fixation state during successive copying by switching decision temperature automatically between a stand-by state and a copying state, and preventing a temperature drop during the copying operation. CONSTITUTION:The output of a temperature detecting element 1 is inputted to a variable duty cycle circuit 2 which varies in duty cycle with temperature to be converted in frequency, and further inputted to a comparator 3. The comparator 3 detects decision temperature and falls in output level from High to Low. The variable cycle circuit 2 uses a pulse-width modulator or V/F converter. The outputs of the variable cycle circuit 2 and converter 3 are ORed by an OR circuit 4, whose output is inputted to an SSR5 to control a heater 6. Further, the comparator 3 inputs a copy signal 7 indicating that copying operation is in process, and consequently the reference voltage of the comparator 3 is varied to switch the decision temperature. |
