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4. Controlling the Pre-Primary Charging
Figure 3-524 shows the circuit that controls pre-primary charging current, and the circuit has the fol-
lowing functions:
1 Turns ON/OFF the pre-primary corona current.
2 Executes constant current control,
The pre-primary corona current is turned off and on by the pre-primary corona current drive signal
(HVPPR) as follows:
Input in the range of HVPPR+OV to 12V
An output voltage suited to voltage of HVGR is generated by the transformer.
The pulse output drives the transformer.
Corona current that suits the voltage of HVPPR is generated.
The output of the pre-primary current is monitored with reference to its current value, and the data is
fed back to the variable pulse oscillator circuit. The feedback signal is used to ensure a specific level of
pre-primary corona current. If overcurrent, because of leakage for example, is detected, the pulse output
is forced off; the pre-primary corona current will remain OFF for 20 ms and thereafter will return auto-
matically.
executed
(Correction is
data
from the environment sensor.)
DC controller PCB
detection circuit
Figure 3-524
CANON CLClOOO REV.1 MAY 1997 PRINTED IN JAPAN (IMPRIME AU
each time the Copy Start key is pressed
HVTP-1
Corona current
based on
r
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