Canon NP7161 D. Controlling the Primary/Transfer Bias

CHAPTER 4 IMAGE FORMATION SYSTEM
4–6
COPYRIGHT © 1998 CANON INC. CANON NP7161/NP7160 REV.0 AUG. 1998 PRINTED IN JAPAN (IMPRIME AU JAPON)
Figure 4-108
2. Turning On/Off the Primary/Transfer Bias
a. When the primary/transfer bias is off,
• When HVT_DR is 0,
Oscillation control circuit turns off
Primary/transfer high-voltage transformer turns off
b. When the primary/transfer bias is on,
• When HVT_DR is 1,
Oscillation control circuit turns on
Primary/transfer high-voltage transformer turns on
HVT
Tr
Pr
J301
-8
Oscillation
control circuit
Transformer
Current
detection circuit
Reference
voltage circuit
Short circuit/no load
detection circuit
DC controller
PCB Power supply PCB
J212
-10
J106
-15 J210 -3
HVT_DR
D. Controlling the Primary/Transfer Bias
1. Outline
Figure 4-108 shows the circuit used to control the primary/transfer bias, and the circuit has
the following functions:
1. Turning on/off the primary/transfer bias
2. Controlling the grid bias to a specific voltage
3. Controlling the primary shield current to a specific current
To eliminate the effects of changes in the environment to corona charging, the output to the
primary charging assembly is controlled by controlling the shield current to a specific current.
The primary/transfer bias is turned on/off using the following signal from the DC controller
PCB.
• HVT_DR (HVT drive command)