Epson PhotoPC 800 Service Manual page 50
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- User manual (224 pages) ,
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EPSON PhotoPC 800
2.2.4.3 PW1 Strobe Circuit Description
Figure below shows the block diagram of Strobe circuit.
Figure 2-16. Strobe Circuit Block Diagram
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Charging Circuit
When UNREG power supplied to the charge circuit and the CHG signal
becomes High (3.3V), the charging circuit starts operating and the main
electrolytic capacitor is charged with high-voltage direct current. However,
when the CHG signal is Low (0V), the charging circuit does not operate.
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Power switch:
When the CHG signal switches to Hi, Q5406 turns ON and the
charging circuit starts operating.
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Power supply filter
L5401 and C5401 constitute the power supply filter. They smooth out
ripples in the current which accompany the switching of the oscillation
transformer.
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Oscillation circuit
This circuit generates an AC voltage (pulse) in order to increase the
UNREG power supply voltage when drops in current occur. This circuit
Operating Principle
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Light Emission Circuit
When RDY and TRIG signals are input from the ASIC expansion port, the
stroboscope emits light.
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Emission control circuit
When the RDY signal is input to the emission control circuit, Q5409
switches on and preparation is made to let current flow to the light emitting
element. Moreover, when a STOP signal is input, the stroboscope stops
emitting light.
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Trigger circuit
when a TRIG signal is input to the trigger circuit, D5405 switches on, a
high-voltage pulse of several kilovolts is generated inside the trigger circuit,
and this pulse is then applied to the light emitting part.
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Light emitting element
When the high-voltage pulse from the trigger circuit is applied to the light
emitting part, current flows to the light emitting element and light is emitted.
Operating principles of the Circuit Boards
generates a drive pulse with a frequency of approximately 50-100 kHz.
Because self-excited light omission is used, the oscillation frequency
changes according to the drive conditions.
Oscillation transformer
The low-voltage alternating current which is generated by the
oscillation control circuit is converted to a high-voltage alternating
current by the oscillation transformer.
Rectifier circuit
The high-voltage alternating current which is generated at the
secondary side of T5401 is rectified to produce a high-voltage direct
current and is accumulated at electrolytic capacitor C5412 on the main
circuit board.
Voltage monitoring circuit
This circuit is used to maintain the voltage accumulated at C5412 at a
constance level. After the charging voltage is divided and converted to
a lower voltage by R5417 and R5419, it is output to the SY1 circuit
board as the monitoring voltage VMONIT. When this VMONIT voltage
reaches a specified level at the SY1 circuit board, the CHG signal is
switched to Low and charging is interrupted.
Revision A
50
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