| 摘要 |
PROBLEM TO BE SOLVED: To permit load current to flow so as to improve power factor of a power source over the whole cycle of an A.C. power source by controlling the conductor rate of a switch device and restricting the conductive rate when load current flowing in a heater is larger than a prescribed value. SOLUTION: When a main control circuit 33 outputs a heater temp. setting signal TagHT to a heater control circuit 29, the switch device 23 starts switching and the heater 19 is conducted. The switch device 23 repeats on and off by a higher frequency in comparison with that of the A.C. power source 1. When the heater 19 and a surrounding fixing roller are heated, the temp. of the roller is detected by a terminator 27 and the conductive rate of the switch device 23 is controller to the prescribed value corresponding to the heater temp. setting signal TagHT by a heater control circuit 29. That is, the energizing quantity of the heater 19 increases when the conductive rate becomes larger and the temp. of the roller ascends. Thus, the temp. of the roller is directly fed-back to the heater control circuit 29 and constant temp. control is attained to permit the roller temp. to be the prescribed value. |
