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EPSON Stylus PHOTO 810/820/830 Revision B
Operating Principles Electrical Circuit Operating Principles 45
2.2.1.2 C482 PSH board
1. Regardless of the state of the power switch (On or OFF), the voltage is always
applied to the primary side of the power supply board from the moment or at the
state that AC-plug is plugged in. At this time, F1 plays a role of preventing
AC250V from coming into the F1.
L1 also prevents high harmonic wave noise generated in the RC circuit filter
which consists of C1 from going out, and eliminates the noise from outside here.
2. The AC is full-wave rectified by the diode bridge DB1, and converted to x
AC in voltage by the smoothing electrolytic capacitor C11.
3. The pressured up direct current turns Q1 on through the starting resistor R18, R28,
R17 & R19 and starts the primary side of the circuit.
4. When the primary side is On, the energy (current) led by the electromagnetic
induction through the trans (T1) does not flow to the secondary side since the
diode (D51) on the secondary side is installed in the opposite direction.
5. When the energy which is charged in the trans is reaching the saturated state, the
voltage which makes Q1 on becomes weak gradually. At the point that this voltage
drops at the certain voltage, C13 absorbs the current in the opposite direction and
Q1 is quickly shut off by the resulting sharp drop.
6. When the primary side is turned off, the energy charged in the T1 is opened
according to the diode (D51) direction which is installed on the secondary side.
Basically, 42 V DC is output by these circuit operations and the number of T1
spiral coil.
* Unlike the Stylus Photo 810/820, IC51 which generates +5VDC is not on the C482
PSH board for the Stylus Photo 820/830. +5VDC is generated on the C483/C484
Main-B board.
The C482 PSH board has the various control circuits to stop voltage output if a
malfunction occurs on the power supply board or the main board or while the printer
mechanism is on duty. Following explains each control and protection circuit.
+42V line constant voltage control circuit :
The output voltage level of the +42V line is monitored by R91, R92, R93, Q91 and
ZD51. When +42V line reaches about +42.8V, PC1 starts the operation via Q91.
Consequently, FET Q1 switching operation is controlled by this circuit to stabilize
the +42V line.
+5VDC Line
Over Voltage
Limitation
+42VDC Line
Over Voltage
Limitation
+42VDC Line
Drop Limitation
+42VDC Line
Constant
Control
Smoothing
Circuit
Photo Coupler
TRANS(T1)
PSC Signal from
Main board
ZD53
+5VDC Signal from
Main baord
+42VDC
R91,R92,R93,Q91,ZD51
ZD52,87
ZD90
C51
Q1C11
D51
Q2,Q3,Q31
Abnormally Feed
back circuit
Main Switching
Circuit
Smoothing
Circuit
Over Current
Protection
Filter Circuit
Full Wave
Rectifier circuit
DB1
R1,L1,C1
F1,TH1
AC Input
PC1
2