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UX-22oocMu/cMC
I0215oCMUCMc
[4] Circuit description
of power supply PWB
1. Block diagram
TRANSFORMER
SWITCHING
1
1
Fl
4.OA 125V
ACIN
0
w
RECTITYING
+5v
12ov
0
50/6OHZ
GND
+24V
_
CIRCUIT
-
+24V
A
The power unit intakes input of AC 12OV, 50/60 Hz and supplies output
of +24V, +7.4V and +5V as shown in the block diagram. (See Fig. 8.)
2-1. Filter, rectifying and smoothening circuit
In the filter section, the noise generated
from the power unit is elimi-
nated from being discharged
to the external, and external
noise is pre-
vented from entering. Thunder or other excessive surge is prevented by
the varistor 21.
In
the rectifying and smoothening
section, AC input is rectified by the
diodes Dl 0, 11, 12 and 13, and is smoothened
by the capacitor C5.
Thus, DC voltage is supplied
to the switching section.
Moreover,
the
thermistor NTCl prevents
surge current when the power is turned on.
2-2. Switching section
The circuit uses the tinging choke converter
of a self-excited
type.
Since MOS.
FETQl
is repeatedly
turned on and off in this system, the DC voltage
supplied from the rectifying
and smoothening
section is converted
into
the high frequency pulses. While Ql is on, energy is accumulated
in the
primary winding of the transformer
Tl , and while Ql
is off, energy is
discharged to the secondary
side. Thus, the power is supplied.
Moreover, the frequency
is varied depending
on the load of the output.
As the load becomes the heavier, the frequency becomes the smaller to
extend the ON period.
The constant voltage is controlled by applying the feedback
to the con-
[5]
Circuit description
of CIS PWB
The CIS board picks up optical information
from the document,
con-
verts it into an electrical
(analog) signal and transfers
it to the control
board.
(1) Block diagram
SH
CISCLK
VLED
GLED
CIS
+5v
GND
AiN
Fig. 9
Fig. 8
COUPLER u
trol circuit through
the photo coupler
PC1 from +24V output.
The
overcurrent-protective
circuit detects that the ON period becomes the
wider as the output load becomes the heavier. For the control, the OFF
period is extended by the control circuit to squeeze the energy which is
accumulated
in the primary winding of the transformer
Tl.
For protection against overvoltage,
the rise of the output voltage of +24V
on the secondary side is brought into the overcurrent
state through the
continuity
of the power zener diode D104 between
+24V output and
GND. Thus, the overcurrent-protective
circuit of the control circuit is ac-
tivated for the protection.
2-3. +24V circuit
Output is supplied by rectifying and smoothening
the output of the trans-
former Tl with the diode Dl 01 and capacitor Cl01 .
2-4. +5V circuit
+5
V output is generated by rectifying and smoothening
the output of the
transformer
Tl with the diode
D102 and capacitor Cl02 and stabilizing
it with the 3-terminal regulator IC103.
2-5. +7.4V circuit
This circuit rectificats and smoothings the high-frequency
pulse voltage,
and output the DC +7.4V to the equipment.
(2) Description of blocks
1. CIS
The DLlOO-05AUJS
is a highly sensitive charged coupled image
sensor
that consists of 2160 picture elements.
Receiving four drive signal (SI,CLK) from the control board, the tranfened
photoelectric analog signal SIG is impedance converted, and the signal
AiN, is supplied to the control board.
2. Waveforms
1.
CLK, SI, SIG signals within the control board.
CLK
JJ-/JJ_.______JJ-L
s,
n_______ n
SIG U
.------
A
Fig. 10
5-14
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