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I
OPERATIONS
AND
TIMING!
D.
Primary/Transfer
Corona
Current
and
Grid Bias
Voltage Control
System
1.
Outline
The
circuit
shown
in
Figure
3-17
conntrols
the
primary/transfer coronal current
and
the
bias voltage
of
the
grid.
of
the
primary
corona.
Main
functions are
as
follows.
a.
Switching
primary/transfer
corona
current
ON/OFF
b.
Maintaining primary/transfer
corona
cur-
rent
constant
c.
Switching primary
corona
grid
bias
volt-
age
d.
Switching primary
corona
grid
bias
ON/OFF
In
order
to
eliminate the
effect of
changes
in
atmospheric
conditions
on
the
effective-
ness
of
the
corona
discharge, the current
to
the primary
corona
wire
is
maintained
constant.
The
primary
corona and
transfer
corona
current are switch
ed
ON
a
nd
OFF
by the
HVT
ON
command
(HVTON).
The
grid
bias voltage
is
switched by
the
GRID
ON
signal
(GRDON).
2.
Switching Primary/Transfer
Corona
Current
ON/OFF
When
HVTON
=
1
(-.Differential
amplifier
goes OFF.
I—
Variable pulse width
oscillator
goes OFF.
I
—
High-voltage
transformer
goes OFF.
When
HVTON
=
I,
Differential
amplifier
goes ON.
riabie
pulse width
oscillator
goes
Ol
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
feedback
signal
to
the
differential
amplifier
circuit
will
increase
and
the output
from 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
assembly
should
be
overloaded, the
current
will
be
limited to
a
certain
maximum.
DC
controller
PCB
High-voltage transformer
(HVT)
Primary
corona
assembly
I
Photosensitive
1
Transfer
corona
assembly
Figure 3-19
COPYRIGHT©
1992
CANON
DC.
CANON
NP-1550
REV.1
SEPT. 1992
PRINTED
IN
JAPAN
(IMPRIME
AU
JAPON)
3-21
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