| 摘要 |
PURPOSE:To improve responsiveness and to stabilize good drum surface potential by controlling DC high voltage to be applied to a corona wire so as to maintain always constant the ratio of corona current flowing from the corona wire to the surface of a photosensitive drum to corona current flowing through a grid. CONSTITUTION:A corona current ig through a grid wire 10 is converted into an operational amplifier 17 into voltage Vg. Vg=igXRf1. Corona current id flowing to a photosensitive drum 2 is also converted into voltage Vd likewise with an operational amplifier 18. Vd=idXif2. An operational amplifier 20 inverts the polarity of the voltage Vd with an inverting amplifier and feeds it to an operational amplifier 19. Its output voltage Vo is fed to the control terminal C of a DC high voltage power supply 11, and its output voltage HVC is controlled so as to always equalize the abstract value of the voltage Vg to that of the voltage Vd. Charging voltage is controlled so as to render always constant a ratio of the corona current id flowing from a corona wire 9 to the photosensitive drum to the corona current ig flowing through a grid wire 10. |
