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D.
PRIMARY/TRANSFER
CORONA
CURRENT
AND GRID BIAS
VOLTAGE
CONTROL
SYSTEM
1. Outline
The circuit shown in Figure 3-17
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
(4) ri!$pg
primary
corona
grid
bias
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).
2. Switching
Primary/Transfer
Corona
Current
ON/OFF
(1) When HVTON = 1
L
Differential
amplifier goes OFF.
L
Variable pulse width oscillator goes
CFF.
L.
_
;;gFh voltage
transformer
goes
(2) yen
HVTON = 0
Drfferential amplifier goes ON.
'L
Vanable pulse width oscillator goes
ON.
'L
_
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-voltage
transformer
supplying the primary corona
unit is ever over!oaded, the current will be
limited to a certain maximum.
HVTOI\
High-voltage
transformer
(HvT)
__-_-_-_--y
GRDON
Figure 3-17
3-
16
COPYGIGHT
0
1908 CANON MC.
CANON HP-iOl5/1215S
REV.0 OCT. 1988 PGINTEG
IN JAW
[IMPGlMf
AU JAPONI
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