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C. Controlling
the Scanning
Lamp
The circuit shown in Figure 3-15
serves to
control the scanning lamp and has the follow-
ing functions:
.
Controls ON/OFF of the scanning lamp
.
Maintains
constant
light
intensity
against
power fluctuations
a.
Controlling ON/OFF of the Scanning Lamp
When
LRD is 'I',
the output
of the lamp
regulator
switch
circuit is '0'; this condi-
tion deprives
the phase
control circuit of
power, and the triac circuit is OFF and, as
a result, the scanning lamp is also OFF.
When
the
LRD is '0'.
the output
of the
lamp regulator is 'I'; the phase control cir-
cuit is supplied
with power,
and the triac
circuit goes ON and, as a result, the scan-
ning lamp also goes ON
Should
the scanning
lamp remain ON for
15 set to 30 set in the event the triac cir-
cuit fails, the relay is forced
open to turn
,- -
the scanning lamp OFF.
b.
Controlling the Light Intensity of the Scan-
,
ning Lamp
The power
supply voltage
fluctuation
de-
tection
circuit converts
the power
supply
voltage
into a DC-level
voltage and sends
it to the phase control circuit. The phase
control circuit, in response to the DC-level
voltage, controls the triac circuit by decid-
ing at which
phase the circuit should go
ON,
thereby
preventing
changes
in the
light intensity
due to fluctuations
in the
power supply voltage.
:-
I
,
1
I
I
I
I
I
I
I
I
I
I
Lamp
regulator
fuse
FUI
I
scanning
lamp
(HL)
Figure 3- 15
3-14
COPVAMIT
01986
CANON INC.
CANON HP-IO10
AN.0
OEC. 1908 PRIHTEO
IN JAPAN (IMPRIME
AU JAPONI
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