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EPSON PhotoPC-750Z
Table 2-5. ST1 Board (Strobe Control Block)
No.
Circuit Name
When the flash is emitted during the Forced or Auto flash,
CHQ signal is output high from the SY1 board and
charges the main electrolytic condenser into high voltage
direct current. Charging circuit consists of mainly
following 5 circuits.
1) Power supply filter: It smooth out ripples in the current
which accompany the switching of the oscillation
transformer and LC circuit composition.
2) Oscillation control: Outputs a drive pulse with a
1
Charging Circuit
frequency of 15 K Hz to increase DC voltage.
3) Oscillation Transformer: Converts the low voltage
alternating current to a high-voltage alternating current by
this transformer.
4) Rectifier: Converts the high-voltage alternating current
to a high voltage direct current.
5) Voltage monitoring: Monitors the voltage level of
C5412. Detects full charge by 2.7VDC.
Strobe emits light when RDY and TRIG signals are input
from ASIC. Emission circuit consists of mainly the
following 3 circuits.
1) Emission control circuit: When the RDY signal is input
to this circuit, Q5409 which is the main source of the
Discharging
emission current, is turned on. STOP signal turns off
2
(Light Emission)
Q5409.
Circuit
2) Trigger Circuit: D5405 is turned on with input of TRIG
signal.
3) Light emitting element: Light is emitted when the high-
voltage pulse is applied to the light emitting part.
Operating principles
Function
Board Component
2.1.1.4 SY1 Board
4-bit microprocessor is mounted on the SY1 board, and following
operations are handled.
Table 2-6. Various Circuits of the SY1 Board
No.
Function
This board outputs the /CHG On signal to the ST1
board. Also, it monitors the value of partial pressure of
C5412 and controls to stop charging.
1
Charging
Also, it judges if the power supply is AC adapter or
battery and changes the ending time of the battery
charge subtly. This prevents the AC adapter from
being heat up.
Controls On/Off of LCD back light. However,
2
LCD light ON
characters for explanation on the LCD are transferred
by internal ASIC.
When RS-232C cable is installed, this circuit makes all
3
Cable Detection
button functions on the camera invalid.
Performs serial communication with internal main
4
CPU communication
CPU(SPARC).
Outputs 2 Wake-up signals in order to generate power
5
Power supply control
supply for digital and analog individually.
6
Battery life monitor
Monitors the AA-size battery life at the voltage level.
7
Video terminal monitor Monitors if the cable for video output is installed or not.
When the power is ON, this circuit reads empty raster
and calculates how many pictures can be taken after
Card installation
8
detecting the existence of the compact flash card.
monitor
Also, after the card is detected, internal memory (4M)
becomes invalid.
9
Buzzer control
On/Off control of buzzer drive.
Controls the present various settings and indication of
10
LCD panel control
available photos to take by the key matrix.
11
LED control
Controls all 3 LED drives.
Revision A
Details
27
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