Canon PC430 - Primary Charging Control Circuit; Outline

COPYRIGHT © 1998 CANON INC. CANON PC400/420/430,FC200/220 REV.0 JAN.1998 PRINTED IN JAPAN (IMPRIME AU JAPON)
CHPTER 4 IMAGE FORMATION SYSTEM
4-3
C. Primary Charging Control Circuit
1. Outline
Figure 4-101C shows the circuit that controls the primary charging, and the circuit
has the following functions:
• Turns the DC bias ON and OFF.
• Turns the AC bias ON and OFF.
• Controls the DC bias voltage
(constant).
• Controls the AC bias current
(constant).
A DC bias (-625 V/-230 V) and an AC bias are applied to the primary charging roller
to maintain the surface potential of the photosensitive drum uniform.
During document exposure (-625 V) and non-exposure periods (-230 V) DC bias is
switched by the DC bias high output command (HVPHO).
The DC bias and AC bias are turned ON and OFF by the DC bias ON command
(HVPDC) and AC bias ON command (HVPAC), respectively.
Reference:
Unless the document is being illuminated, the DC bias is switched to -230V to
prevent adhesion of toner on the photosensitive drum.