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UX-A450DE/IT/H
NX-A550DE/IT/FO-A650IT
[4] Circuit description of power supply PWB
This power supply unit has the function to convert the AC 220 - 240 V
50/60 Hz to DC +24 V, and provide these outputs to the equipment. The
following explains the function of each block.
1. Block diagram
F1
T2.5A/250V
AC IN
F2
T2.5A/250V
2-1. Noise filter circuit
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 varistor(Z1).)
2-2. Rectifying/smoothing circuit
This circuit rectifies and smoothes the AC input, and provides the DC
voltage to the switching circuit block.
2-3. Switching circuit
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 voltage on the secondary side provided by the energy de-
pend on the ratio of the winding turns(primary : secondary) etc.
[5] 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.
Noise
Rectifying
Filter
Smoothing
Circuit
Circuit
Switching
TRANSFORMER
Circuit
Control
Circuit
Photo Coupler
Fig. 7
2-4. Control circuit
This circuit block controls the output voltage by transmitting the detected
+24 V 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 providing the energy to the transformer by letting the Power-
Zener(D104; connected between the +24 V output voltage and GND)
into the short mode and letting the over-current protection circuit work.
2-5. +24V circuit
This circuit block rectifies and smoothes the high-fequency pulse volt-
age provided by the transformer, and provides the DC +24 V output to
the equipment. The output voltage is adjusted by the variable
resistor(VR101).
2-6. VREG(+5V) circuit
This circuit block rectifies and smoothes the high-fequency pulse volt-
age provided by the transformer, and provides the DC +5 V output to the
equipment.
2. Waveforms
The following clock is supplied from SCE214V of the control board,
and VO is output.
øT
2µs
CISCLK
VO
5 – 13
+24V
Circuit
+5V
Circuit
5ms
Approx.3.3V
0V
0.8V~2.9V
(White original paper)
Fig. 8
+24V
VREG
(+5V)
GND
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