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ViewSonic E95 - Page 49

ViewSonic E95
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44
SYNC.
PROCESSOR
The
horizontal
sync.
is
connected
from
signal
cable
to
IC301(MCU)
pin8
input
and
from
IC301
pin7
output
positive
polarity
sync
to
IC401
pin15.
Vertical
sync.
is
connector
from
signal
cable
to
IC301(MCU)
pin9
input
comes
out
at
pin6
a
positive
polarity
sync
to
IC401
pin14.
The
1C301
and
the
IC401
(TDA4856)
sync
input
can
handle
either
composite
or
separate
sync
input.
45
DEFLECTION
CIRCUIT
45.1
Horizontal
Synchronization
Processing
The
horizontal
synchronization
processor
is
integrated
inside
the
chip
of
IC401.
It
uses
a
dual
phase-
lock-loop
(PLL1/PLL2)
design.
This
operation
ensures
a
smooth
tuning
and
avoids
fast
changes
of
H-
frequency
during
catching.
The
processor
can
synchronize
with
the
input
sync.
up
to
triple
of
free-run
frequency
which
is
determined
by
R408,
R409
and
C407.
The
PLL1
phase
detector
circuit
is
used
to
control
the
oscillator
frequency
and
maintains
it
in
proper
frequency
and
phase
with
the
incoming
sync
signal.
One
input
is
coupled
from
output
of
VCO
that
is
built
inside
the
IC.
A
loop
filter
with
a
properly
selected
time
constant
(C406,
R407)
is
connected
at
pin26.
The
PLL2
circuit
is
used
to
compare
the
line
flyback
pulse
at
pin
HFLB
with
the
oscillator
sawtooth
voltage,
to
compensate
the
delay
in
H-deflection
by
adjusting
the
PHASE
of
HDRV.
One
input
is
from
the
output
of
VCO
(which
is
inside
the
IC)
and
a
second
input
(pin!
of
IC
401)
is
from
Q415
collector
pulse
via
C483,
C484.
The
control
voltage
formed
through
loop
filter
is
to
control
horizontal
output
pulse
output
at
proper
duty
cycle
and
maintains
the
phase
between
raster
and
picture.
4.5.2
Horizontal
Driver
Stage
The
horizontal
drive
pulse
from
pin8
of
IC401
is
applied
to
the
base
of
driver
MOSFET
Q4125.
B*
is
provided
by
the
regulated
15V-voltage
source
via
R446,
R446
and
C424.
The
output
of
driver
transformer
T401
is
coupled
to
the
base
of
Horizontal
output
Transistor
Q415.
R441
C442
compose
of
damping
network,
which
is
to
eliminate
the
leakage
flux
of
T401
during
Q412turn
off.
46
astcetectd
teeny
ViewSonic
Corporation
at

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