Sanyo VPC-PD1EXBK, Service Manual

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1-4. 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. Charge switch
When the CHG signal switches to Hi, IC541 starts charging
operation.
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 in-
crease the UNREG power supply voltage when drops in cur-
rent occur. This circuit generates a drive pulse with a frequency
of approximately 200-300 kHz, and drive the oscillation trans-
former.
1-4. Oscillation transformer
The low-voltage alternating current which is generated by the
oscillation control circuit is converted to a high-voltage alter-
nating 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 ca-
pacitor C5412.
1-6. Charge monitoring circuit
The functions programmed in the IC541 monitor oscillations
and estimate the charging voltage. If the voltage exceeds the
rated value, charging automatically stops. Then, the
ZCHG_DONE signal is changed to Lo output and a "charging
stopped" signal is sent to the microcomputer.
2. Light Emission Circuit
When FLCTL signal is input from the ASIC, the stroboscope
emits light.
2-1. Emission control circuit
When the FLCTL signal is input to the emission control cir-
cuit, Q5402 switches on and preparation is made to the light
emitting. Moreover, when a FLCTL signal becomes Lo, the
stroboscope stops emitting light.
2-2. Trigger circuit
The Q5402 is turned ON by the FLCTL signal and light emis-
sion preparation is preformed. Simultaneously, high voltage
pulses of several kV are emitted from the trigger coil and ap-
plied 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 emit-
ting element and light is emitted.
Beware of electric shocks.