Epson GT-1200, Руководство по обслуживанию

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GT-12000 Operating Principles
Rev. A
2-5
2.3.2 Power Supply Circuit Operation
Since the power supply circuit board B054PSH for this scanner meets the
universal specification, it can use the rated voltage in the range from 100V
to 240V.
The electrical circuit for the AC input part is designed on the basis of
200V line. In case the input voltage is 200V line level, the ordinary full
wave rectifying system is used. With this system, the voltage is rectified by
the diode bridge DB1 and then smoothed by the serial smoothing
capacitors C11 and C32 to produce approximately 250 VDC.
On the other hand, if the input voltage is 100V line level, the doubled
voltage rectifying system is used instead. With this system, the input AC
current is separated into the following 2 flows; the positive half cycles of
the current flow through the control IC (IC2) (from Pin 2 to Pin 3) via the
diode bridge (DB1) and the smoothing capacitor C11, and the negative
half cycles of the current, however, flow through the smoothing capacitor
(C32) and DB1 via IC2 (from Pin 3 to Pin 2). Through these flows, the
positive and negative AC current are separately charged in the smoothing
capacitors C11 and C32, respectively, and the doubled VDC
(approximately 250 VDC) equivalent to the input voltage of the 200V line
is produced. At power-on, the control circuit (IC2) is activated by the full
wave rectifying system. Then, if the input voltage is 100 VDC line level,
the system is automatically switched to the doubled voltage rectifying
system after certain period set by the circuit constant.
Except for the full wave rectifier circuit/voltage doubler rectifier circuit at
the AC input part, the normal RCC (Ringing Choke Converter) regulator
circuit is used for the rest part of the power supply circuit, and the different
levels of VDC are distributed to corresponding mechanisms, as shown in
Table 2-1:
Table 2-1. DC Output Power
Output VDC Application
+5 V Logic power lines
+24 V
q
Motor drive power source
q
Power source for the lamp (inverter)
+15 V +12 V production
(Power used to drive the cooling fan for the shield
compartment which stores B054 MAIN and B054PSH.)
+
+
Positive
Component
AC input
DB1
C11
C32
IC2
Negative
Component
Doubled Voltage
Output
[AC Input]
100 V = On
200 V = Off
Figure 2-4. Voltage Doubler Rectifier Circuit Operation