| 摘要 |
PURPOSE:To preform constant-temperature control with high precision through simple constitution by controlling the closing of a switch circuit which synchronizes with the zero crossing of an AC source voltage according to a halt rate correlative to the variation rate of the AC voltage, and correcting the halt rate according to the temperature of a heat fixing devie. CONSTITUTION:A halogen lamp 21 as a heating body is connected to a power surce 23 through the switch circuit 22 which is triggered with a trigger pulse PT in accompanying with the zero crossing of the voltage of the AC power source 23. The voltage of this power source 23 is detected through a voltage detector 24 and an A/D converter 25, and the arithmetic processing circuit 26A of a control cricuit 26 calculates the halt rate correlative with the variation rate of the AC voltage and also corrects the halt rate on the basis of the result of the comparison between the heating temperature of the lamp 21 which is detected by a temperature detector 28 at every specific period and a reference temperature. Then, the pulse output PT from a gate circuit 26B which is opened through a pulse generator 27 is controlled in the zero crossing of the AC voltage. Consequently, the constant-temperature control over the heat fixing temperature of the electrophotographic copying machine is carried out through the simple constitution with high precision. |
