Epson PhotoPC600, Service Manual, Page: 41 / 116

PhotoPC600
Chapter 2 Operating Principles
Rev. A 2-4
ST1 BOARD
ST1 board can be divided into 2 blocks; power supply circuit part and strobe control circuit part.
Following explains each part.
Table 2-4. ST1 Board (Electric Block)
No. Location Function
1 IC311 This has a PWM-type switching regulator circuit with 6 channels.
Output voltage is;
1) Power supply voltage for LCD
5 V(L), 12 V(L), 15.5V(L)
2) Digital power supply voltage 5 V(D), 3.4 V(D)
3) Analog power supply voltage 5 V(A), 12 V(A), -6.5 V(A)
There are two safety circuits on this regulator;
1) Short-circuit protection circuit
2) Mis-operation prevention circuit for cases of low input voltage
2 T3101 Pressure rise/fall transformer for Analog output voltage
3 T3103 Pressure rise transformer for LCD drive voltage output
There are two parts of circuits in the strobe control circuit part; charge circuit parts and light
emission circuit. They are described below.
Table 2-5. ST1 Board (Strobe Control Block)
No. Circuit Name Function
1 Charge circuit When the flash is emitted during the Forced or Auto flash, CHG
signal is output high from the SY1 board and charges the main
electrolytic capacitor into high voltage direct current.
Charge 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
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 2.7 V DC.
2 Light emission
circuit Strobe emits light when SDY and TRIG signals are input to from
ASIC. Emission circuit consists of mainly the following 3 circuits;
1) Emission control circuit part
When the RDY signal is
input to this circuit, Q5409
which is the main source of
the emission current, is
turned on.
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.