Bias Control - Canon GP160F Service Manual

B.

Bias control

The transfer charging roller bias is controlled by the DC controller PCB's CPU
(IC301). When a positive bias drive signal (TRPWM) is output from CPU, the positive
bias generation circuit comes into operation.
Also, when a negative bias signal (TRNFOT) is output, the negative bias generation
circuit comes into operation.
As mentioned before, 4 types of bias are applied to the transfer charging roller at
designated times.
Furthermore, the transfer bias to the transfer charging roller is switched, depending
on the print resolution (1200dpi equivalent and 600dpi equivalent) of this unit.
By means of the bias switching signal (1200DPI) from the CPU, the output voltage
from the positive bias generation circuit and negative bias generation circuit switches
over.
Photo-
sensitive
drum
Transfer charging roller
[1] TRPWM: Positive bias drive signal
[2] 1200DPI: Bias switching signal
[3] TRNFOT: Negative bias switching signal
COPYRIGHT © 1999 CANON INC.
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Positive bias
JH403
Super-
generation
impose
circuit
Figure 6-301
CANON GP160 REV.0 FEB. 1999 PRINTED IN JAPAN (IMPRIME AU JAPON)
CHAPTER 6 IMAGE FORMATION SYSTEM
Fixed voltage
control
+24V
Comparison
circuit
Bias switching
Negative
bias
generation
DC controller PCB
[1] TRPWM
CPU
(IC301)
[2] 1200DPI
[3] TRNFOT
6-5