Controlling The Primary Corona Current - Canon 1000 Service Manual

3. OPERATION AND TIMING

2. Controlling the Primary Corona Current

Figure 3-521 shows the current that controls the primary corona current, and the circuit has the following
functions:
• Turns ON/OFF the primary corona current.
• Executes constant current control.
The primary corona current is turned on and off by the primary corona current drive signal (HVPR), and
the mechanism is as follows:
HVPR=1
The variable width pulse oscillator circuit turns on, sending pulse output to the transformer.
The output of the primary corona current is monitored with reference to its current, and the data is fed
back to the variable width pulse oscillator, thereby ensuring that the primary corona current remains
constant. If an overcurrent, because of leakage or example, is detected, the OC signal forces off the pulse
output. When such occurs, the primary corona current will remain OFF for 20 ms and then will return
automatically.
Feedback
3-98
COPYRIGHT © 2001 CANON INC.
The transformer is driven.
Corona current sent to the primary charging assembly.
DC controller
24V
Variable width pulse
oscillator circuit
oc
Overcurrent
detection circuit
Figure 3-521
CANON CLC1000/1000S/3100 REV.2 MAY 2001 PRINTED IN JAPAN (IMPRIME AU JAPON)
HVT2-1
Corona current
Transformer
Current
detection circuit
Primary charging
assembly