The exposure control circuit has the following two functions:
A Manual exposure mode .................. Impresses a constant lamp voltage corresponding to the
B Automatic exposure mode ............. The quantity of light reflected by the surface of the original,
(2) Function of lamp regulator
A typical characteristic curve is shown below. By means of a phase-angle control system, it is
controlled so that a lamp voltage corresponding to EXP-PWM pulse duty ratio input is generated
even when some fluctuation occurs in the AC input voltage.
Lamp voltage
184, 92 V approx.
92, 46 V approx.
100 V series
200 V series
1550/1560 OPTICAL
setting by the UP/DOWN keys on the exposure lamp.
which varies according to its lightness and darkness, is
detected by the automatic exposure sensor circuit, and the
voltage impressed on the exposure lamp is varied accord-
ingly; a high lamp voltage being impressed when the origi-
nal is dark and a low lamp voltage when it is light.
Range of actual use
40 V%
[Characteristics of the curve of the lamp regulator]
7 - 20
Limiter voltage (90V)
90 V%
PWM pulse duty ratio
Mar. 1998 © TOSHIBA