Circuit Description Of Power Supply Pwb; Circuit Description Of Cis Unit - Sharp UX-B700 Service Manual

[5] Circuit description of power supply PWB

1. Block diagram
(1)
FILTER
INPUT
CIRCUIT
BLOCK
This power supply unit has the function to convert the A110-120V(50/60Hz) to DC5V, and provide these outputs to the equipment.
The following explains the function of each block.
2-1. Filter circuit block
This circuit reduces the outgoing noise through the input lines which is
generated in the power supply unit, and prevents the invasion of the
noise from the lines. (the excessive surge such as the thunder is pre-
vented by the varitstor(Z1).)
2-2. Rectification and smoothing circuit block
This circuit rectifies and smoothes the AC input, and provides the DC
voltage to the switching circuit block.
2-3. Switching circuit block
This circuit converts the DC voltage(provided from the Rectification and
smoothing circuit block) to the high-frequency pulse voltage by FET(Q1)'s
switching (on/off repeat), and provides the energy to the transformer(T1).
It discharges the energy(charged during the FET ON time) to the sec-
ondary side during the FET OFF time through the secondary windings.
The output voltages on the secondary side provided by the energy de-
pend on the ratio of the winding turns (primary : secondary) etc.

[6] Circuit description of CIS unit

1. CIS
Cis is an image sensor which puts the original paper in close contact
with the full-size sensor for scanning, being a monochromatic type
with the pixel number of 1,728 dots and the main scanning density of
8 dots/mm.
It is composed of sensor, rod lens, LED light source, light-conductive
plate, control circuit and so on, and the reading line and focus are
previously adjusted as the unit.
Due to the full-size sensor, the focus distance is so short that the set
is changed from the light weight type to the compact type.
(2)
(3)
RECTIFICATION
SWITCHING
AND SMOOTHING
CIRCUIT
CIRCUIT BLOCK
BLOCK
(4)
CONTROL
CIRCUIT BLOCK
TRANSFORMER
(5)
30V CIRCUIT
PHOTO-COUPLER
Fig. 10
2-4. Control circuit block
This circuit block controls the output voltage by transmitting the detected
5V voltage to the primary control circuit through the photo-coupler(PC1).
In case of the over-current, this circuit reduces providing the energy to
the transformer. In case of the over-voltage, this circuit reduces provid-
ing the energy to the transformer by letting the Power-Zener(D104; con-
nected between the 30V output voltage and GND) into the short mode
and letting the over-current protection circuit work.
2-5. 30V output circuit block
This circuit block rectifies and smoothes the high-frequency pulse volt-
age provided by the transformer, and provides the DC 30V output to the
equipment.
2-6. 5V output circuit block
This circuit block rectifies and smoothes the high-frequency pulse volt-
age provided by the transformer, and provides the DC 5V output to the
equipment. The output voltage is adjusted by the variable
resistor(VR101).
2. Waveforms
The following clock is supplied from SCE214 of the control board,
and VO is output.
5ms
øT
2 s
CISCLK
VO
5 – 18
UX-B700U
FO-B1600U
BLOCK
(6)
5V CIRCUIT
BLOCK
Approx.3.3V
0V
0.6V~2.6V
(White original paper)
Fig. 11
30V
5V
GND