Circuit Description Of Power Supply Pwb; Circuit Description Of Ccd Pwb - Sharp FO-1470 Service Manual

UX-510UA
FO-1470U

[4] Circuit description of power supply PWB

1. Block diagram
2.5A/125V
AC IN
2-1. Noise filter circuit
The input noise filter section is composed of L1 and C1, C15, which
reduces normal mode noise from the AC line and common mode noise
to the AC line.
2-2. Rectifying/smoothing circuit
The AC input voltage is rectified by diode stack DS1 and smoothed by
capacitor C2 to supply DC voltage to the switching circuit section.
2-3. Switching circuit
This circuit includes MOS FET Q1 and the gate drive circuit, and com-
ponents around Q1.
In this circuit, the DC voltage supplied from the rectifying/smoothing
section is converted into high frequency pulses by ON/OFF repetition of
Q1.

[5] Circuit description of CCD PWB

The CCD 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
T
1
2
R
+5V
GND
OUTPUT CIRCUIT
VO
(emitter follower)
Noise
Rectifying
Filter
Smoothing
Circuit
CCD
TCD1208AP
OS
Fig. 9
Switching
Circuit
Circuit
(RCC system)
Control
Circuit
Photo Coupler
Fig. 8
2-4. Control circuit
This circuit controls output voltage of +24V by adjusting ON period of
Q1, looking at signal from photo coupler PC1.
In this operation IC1 takes charge of important part.
The over current protection is performed by bringing Q1 to OFF state
through detection of voltage of T1 subwiding.
The over voltage protection is performed by operating the over current
protection circuit through detection of zener diode ZD4 and short-circuiting
of load.
2-5. +5V circuit
DC voltage supplied by rectifying the output of transformer T1 with diode
D8 is stabilized by 3-terminal regulator IC1.
(2) Description of blocks
1. CCD
The TCD1208AP is a highly sensitive charged coupled image sensor
that consists of 2160 picture elements.
Receiving four drive signal (øT, ø2, ø1, øR) from the control board, the
transferred photoelectric analog signal OS is impedance converted, and
the signal VO, is supplied to the control board.
2. Waveforms
1. ø1, ø2 (=ø1) signals within the control board.
øT
ø1 (=ø2)
2. OS ø
1.74 SEC
øR
OS
5 – 11
Regulator
+5V
Circuit
+24V
FUSE
4A/72V
Approx. 5V
0V
Approx. 5V
0V
Approx. 5V
0V
Approx. 100mV
Fig. 10