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Panasonic C1381 - Page 14

Panasonic C1381
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ELECTRONIC
CIRCUIT
DESCRIPTION
e
Over
Voltage
Protection
Circuit
+13V +13V
Figure
25
a.
According
to
the
change
of
secondary
output
voltage,
the
output
voltage
of
D805
changes.
b.
When
the
secondary
output
voltage
increases
abnormally,
the
equivalent
voltage
to
the
change
is
detected
from
D805,
and
D807
conducts.
As
a
result
the
pin
10
voltage
of
1C801
increases.
c,
When
the
pin
10
voltage
of
IC801
increases
and
exceeds
the
reference
voltage,
the
comparator
turns
on
and
the
Q809
base
voltage
decreases.
@
Horizontal
Osc.
Disable
Circuit
1C5002
Figure
26
a.
A
pulse
from
the
FBT
is
rectified
and
smoothed
by
D553
and
C560.
R567
and
R566
share
the
voltage
drop.
—14—
D553
.
By
the
decrease
of
Q809
base
voltage,
the
emitter
current
increases
causing
the
pin
9
voltage
of
IC801
to
decrease.
.
By
decreasing
the
pin
9
voltage
of
|1C801,
the
pulse
width
of
pin
14
becomes
too
narrow.
By
this
operation,
the
secondary
output
voltage
decreases.
R534
FBT
b.
If
the
high
voltage
rises,
the
shared
voltage
rises
and
turns
D555
on.
_
os
Parnes
By
this,
horizontal
osc.
disable
circuit
in
1C5002
turs
on.
.
Result
of
this,
the
frequency
of
the
horizontal
osc.
rises
and
it
works
to
decrease
the
high
voltage.

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