Light Emission Circuit - Epson PhotoPC 850Z Service Manual

EPSON PhotoPC 850Z
POWER SWITCH
When the CHG signal switches to High, Q5406 turns ON and the charging
circuit starts operating.
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.
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 generates a
drive pulse with a frequency of approximately 50-100 kHz. Since self-excited
light omission is used, the oscillation frequency changes according to the drive
conditions.
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.
Operating Principles

2.2.4.2 Light Emission Circuit

When RDY and TRIG signals are input from the ASIC expansion port, the
stroboscope emits light.
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.
When a STOP signal is input, the stroboscope stops emitting light.
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 applied to the light emitting part.
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 Circuit Boards
There is a danger of getting electric shock from the PW1
board because of C5412. When handling this board, make
sure to hold the edges of the board and never touch the
board surface. For your safety, discharge the charged
energy of C5412 before handling the board. (See Chapter 4
"Disassembly and Assembly" for more details.)
Revision A
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