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Hitachi C1421R User Manual

Hitachi C1421R
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This
is
connected
via
a
resistor
to
+8V.
As
the
beam
current
increases,
the
voltage
on
line
BeamCurr
decreases.
BeamCurr
is
damped
by
a
integration
filter
before
it
is
fed
back
to
TDA8374
pin
22.
The
TDA8374
will
decrease
the
contrast
(and
eventually
the
brightness)
to
limit
the
average
beam
current.
Video
amplifiers
Three
TDA61
060
integrated
vídeo
amplifiers
drive
cathodes
of
the
picture
tube
directly.
They
are
protected
against
CRT
flashover
discharges
and
ESD
(electro
static
discharge).
The
three
vídeo
amplifiers,
h
ave
a
beam
current
output
in
black,
used
by
the
TDA837
4
black
current
loop
to
control
the
black
levei
on
the
cathodes.
The
outputs
can
be
connected
together
because
the
black
current
loop
sequentially
controls
the
black
levei
for
each
cathode.
The
amplification
of
the
TDA61
060
is
set
by
the
resistors
between
pin
3
and
9
and
between
pin
3
(negative-input)
and
the
TDA837
4
output.
There
is
no
alignment
any
more
on
the
CPT
panei,
because
of
the
automatic
black
current
stabilization
and
because
the
white
point
adjustment
can
be
done
in
the
TDA8374
via
12C
bus.
Power
Supply
STR-55707
(1)
VIN
terminal,
start-up
circuit
The
start-up
circuit
is
to
start
and
stop
the
operation
of
the
controiiC
by
detecting
the
voltage
appearing
at
the
VIN
ter
minai
(pin-9).
At
start
up
of
the
power
supply,
when
a
voltage
at
the
VIN
terminal
reaches
to
BV
(typical)
by
charging
up
C807
by
the
function
of
the
start-up
resistor,
R803,
the
control
circuit
starts
operating
by
the
function
of
the
start-up
circuit.
After
the
control
circuit
starts
its
operation,
power
source
is
obtained
by
smoothing
voltage
appearing
at
winding
of
pin6-7
of
T801.
(2)
Oscillator,
F/B
terminal
voltage
(Pin
7)
An
oscillator
generates
pulse
signals
which
turns
the
power
transistor
on
and
off
by
making
use
of
charge
and
discharge
of
C1
and
C2
incorporated
in
the
Hybrid
IC.
Constant
voltage
control
of
the
switched-mode
power
supply
is
performed
by
changing
both
ON-time
and
OFF-time
except
when
the
load
is
light
(e.g.
remete
control
stand-by
mode
of
TVs).
The
ON-time
is
controlled
by
changing
a
current
charged
by
C1,
which
is
as
the
result
of
that
the
detection
winding
of
pin5-7
of
T801,
which
detects
a
change
of
voltage
on
the
secondary
side,
connected
to
the
sensing
terminal
(Pin
7)
has
the
current
in
accordance
with
an
output
signal
from
an
output
voltage
detection
circuit
(an
error
amplifier)
built
in.
As
the
AC
input
voltage
to
the
power
supply
becomes
higher
and
the
load
current
reduces,
the
current
flowing
to
the
SENS
terminal
becomes
larger,
and
the
ON-time
becomes
shorter.
(3)
Function
of
INH
terminal
(Pin
6),
control
of
OFF-time
Signal
to
the
lN
H
terminal
is
used
as
inputs
to
COMP.1
and
COMP.2
inside
of
the
controiiC.
A
threshold
voltage
of
COMP.1,
VTH1
is
set
at
0.75V
(Ta=25°)
and
an
input
signal
to
a
drive
circuit
becomes
almost
OV
(the
power
transistor
is
in
OFF
mode)
when
a
voltage
at
the
INH
terminal
reaches
the
VTH1.
A
threshold
voltage
of
COMP.2,
VTH2,
is
set
at
1.5V
(Ta=25°).
When
the
INH
terminal
voltage
reaches
VTH2,
an
output
from
COMP.2
reverses
(the
power
transistor
is
in
on
mode).
*
Ouasi-resonant
operation
By
inputting
the
voltage
of
winding
of
pin6-7
of
T801
which
is
synchronized
with
the
energy
discharge
time
of a
secondary
winding,
pin14(or
15)-16
of
T801,
to
the
INH
terminal
through
0805
and
R809,
quasi-resonant
operation
can
be
achieved.
13-
UK

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Hitachi C1421R Specifications

General IconGeneral
BrandHitachi
ModelC1421R
CategoryTV
LanguageEnglish

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