| 摘要 |
PURPOSE:To automatically adjust a control basic voltage value to a set voltage value by comparing the control basic voltage value for determining a developing bias voltage with the set voltage value and changing the control basic voltage based on its deviation output to adjust the developing bias voltage. CONSTITUTION:A scanning exposure lamp 101 is turned on and the reference voltage value VO of the control basic voltage applied from an amplifier circuit 104 through an adjusting circuit 2 is inputted to a central processing unit (CPU) 305 through an A/D converter 304 and compared with the set voltage value VS. In case of VOnot equal to VS, the deviation (e) of both values is calculated, the variation DELTAT in the time width of a clock pulse TP outputted from a PWM timer 302 is calculated by multiplying the deviation (e) by a constant of proportion K and a new TP is written in the PWM timer 302. Thus, the voltage is controlled by executing the loop operation so that VO=VS is formed. Consequently, the control basic voltage VO outputted from the amplifier circuit 104 is controlled in accordance with an original ground density (OD) and the developing bias voltage value VB is adjusted.
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