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D.
PRIMARY/TRANSFER
CORONA'
CURRENT AND GRID BIAS
VOLTAGE CONTROL SYSTEM
1. Outline
The circuit shown in Figure 3-19 con-
trols the primary/transfer coronal
current
and
the bias voltage of the grid of the
primary
corona.
Main
functions
are
as
follows.
:
(1) Switching primary/transfer corona cur-
rent ON/OFF
(2) Maintaining
primary/transfer
corona
current constant
(3) Switching
primary
corona
grid
bias
voltage
(4) Switching
primary
corona
grid
bias
ON/OFF
- In order to eliminate the influence of
changes in atmospheric conditions on the
effectiveness of the corona discharge, the
current to the primary corona wire is main-
tained constant.
The primary corona and transfer corona
current are switched ON and OFF by the
HIGH VOLTAGE ON command (HVTON).
The grid bias voltage is switched by the
GRID BIAS CONTROL signal (GRDON).
DC controller
- an
Variable
pulse
width
oscillator
Differential
amplifier
|
HVTON!
|
Limiter
2. Switching
Primary/Transfer
Corona
Current ON/OFF
(1) When AVTON = 1
Differential amplifier goes OFF.
~Variable pulse width oscillator goes
' OFF.
High-voltage
transformer
goes
OFF.
(2) When HVTON
= O
Differential amplifier goes ON.
Variable pulse width oscillator goes
_ ON.
High-voltage
transformer
goes
ON.
3. Maintaining Primary/Transfer Corona
Current Constant
_ If the primary corona current is greater
than the correct value due to changes in the
environment, the level (analog) of the feed-
back
signal
to the
differential
amplifier
circuit will increase and the output form the
differential
amplifier circuit will fall. As a
result, the primary/transfer coronal current
will fall. Similarly,
if the primary corona
current is too low, it will be increased.
If the output side of the high-vdltage
transformer supplying the primary corona
unit is ever over!caded, the current will be
limited to a certain maximum.
High-vottage transformer (HVT)
Primary corona unit
|
T3 drive
|
circuit
ss
High-voltage
transformer
Photosensitive!
drum
circuit
Transfer corona
Microprocessor
Comparator
Figure 3-19
COPYRIGHT © 1984 CAKOH Inc,
CANON NP-1215 REV.O MAR. 1988 PRINTED IN JAPAN (IMPRIME AU JAPON)
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