St1 Strobe Circuit Description - Olympus Camedia C-7070 Repair Manual

C-7070 Wide Zoom

[4] ST1 STROBE CIRCUIT DESCRIPTION

1. Charging Circuit
When UNREG power is supplied to the charge circuit and
the CHG signal from microprocessor becomes High (3.3
V), the charging circuit starts operating and the main
electorolytic capacitor is charged with high-voltage direct
current.
However, when the CHG signal is Low (0 V), the charging
circuit does not operate.
1-1. Charging switch
The CHG signal becomes High, Q5407 becomes ON and
the charging circuit starts operating.
1-2. Power supply filter
C5401 constitutes the power supply filter. They smooth
out ripples in the current which accompany the switching
of the oscillation transformer.
1-3. 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. Because self-ex-
cited light omission is used, the oscillation frequency
changes according to the drive conditions.
1-4. 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.
1-5. 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.
1-6. 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 as the
monitoring voltage VMONIT. When VMONIT voltage
reaches a specified level, the CHG signal is switched to
Low and charging is interrupted.
Ver. 1
H. DESCRIPTION OF MECHANISM
2. Light Emission Circuit
When FLCLT signals are input from the ASIC expansion
port, the stroboscope emits light.
2-1. Emission control circuit
When the FLCLT signal is input to Hi at the emission
control circuit, Q5409 switches on and preparation is made
to the light emitting. Moreover, when a FLCLT signal be-
comes Lo, the stroboscope stops emitting light.
2-2. Trigger circuit
The Q5409 is turned ON by the FLCLT signal and light
emission preparation is preformed. Simultaneously, high
voltage pulses of several kV are emitted from the trigger
coil and applied to the light emitter.
2-3. Light emitting element
When the high-voltage pulse form the trigger circuit is ap-
plied to the light emitting part, currnet flows to the light
emitting element and light is emitted.
Beware of electric shocks.
H-7