Exposure Control Circuit; Brief Description - Toshiba 1550 Service Manual

7.5 Exposure Control Circuit

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Brief description

The exposure control circuit is composed of the following four blocks.
1 Lamp regulator
2 Automatic exposure sensor circuit
3 Arithmetic and control unit
*Note: The ON/OFF state of the exposure lamp is controlled by a special signal (EXPON), which is
different from the EXP-PWM signal.
Original
UP/DOWN key
Switching power supply
PS-ACC
Zero-cross signal
Mar. 1998 © TOSHIBA
Exposure lamp
Automatic exposure
sensor circuit
PWA-AES-140
AES signal
K-RTN
Impresses a voltage corresponding to the duty ratio of
the EXP-PWM signal upon the exposure lamp.
Generates an AES signal indicating the density of the
original by sensing the light reflected by the surface of
the document.
Determines the lamp voltage by computation on the
basis of AES and K-RTN signals, etc., and outputs the
EXP-PWM signal to the lamp regulator.
Arithmetic and control unit
PWA-LGC
CPU
IC10: TMP96C141AFZ
7 - 19
EXP-PWM
signal
Lamp
regulator
GA
IC12
EEPROM included
IC9:10C68-P45V
1550/1560 OPTICAL