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4.CIRCUITRY
4-1
POWER CIRCUIT
This
machine
has
two different
power
sources,
the one
is
a
power
circuit
and
the other
is a BATTERY.
The
power
circuit
generates
five different
DC voltage
sources,
+5V
for the
logic,
+17¥
for the printer
driving,
+4V and -24V
for the display
and +11.2V
for
the power
fail
detection
circuit.
The
BATTERY
applies
+3.6V
to the back-up
circuit.
A. VPP(+17V)
The
VPP
voltage
is used
for the source
voltage
of the printer
drive
circuit.
The AC 18V is rectified
by the
BRIDGE
DIODE RECTIFIER
BD1 and
it is regulared
by the capacitor
50V 2200uF.
The switching
circuit
composes
circuit
of 2 Transistors
KSC945
and
KSD288,a
zener
diode
18V,
to maintain
the output
voltage
at DC 17V.
B. VPF(+11.2V)
The
VPF
voltage
is used
for
the input
voltage
of the power
fail
detection
and reset
circuit.
The
AC9.5V
is
rectified
by the
BRIDGE
DIODE
RECTIFIER
BD2
and
regulated
by the capacitor
35V
10uF.
Then
the output
is +11.2V.
C. VCC(+5V)
The
VCC
is used
for
the power
source
of the system
logic.
The
most
part of
this
voltage,
rectified
by the
BD2
and passed
through
the diode
1N4003
, is
regulated
by
the capacitor
35V 2200uF,
and it input
the 3 - terminal
regulating
IC MC7805.
Then
output
voltage
is applied
to directly
to the logic and other
+5V terminal.
1N4003
VF
a
VF
TE:
<\PF
Rees
"<V GE
Ss
tri
BV 100UE
ae
es,
"a
pane
Los rr
1K-1W
Since
a
Mav
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ae
2200UF
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