Laser Control Circuit - Canon LBP-860 Service Manual

Control Circuit
C. Laser
1. Outline
This circuil switches the laser diode (LD)
ON and OFF at a constant intensity in
response lo the /VDO signal from the video
controller. The /VDO signal. sent from the
video controller to the DC controller, goes
to the switching circuit in the laser driver
it is as the /VDATA
circuit as
The m i c r o p r o c e s s o r (CPU:IC201)
outputs the INTENSITY CONTKOL signals
to the analog adder circuit according to the
internal data. The AF'COR and APCOS
signals are added to this circuit at a ratio
of approximately 8 to 1, and then sent to
the laser current setting circuit located in
the laser driver as the AUTOMATIC POWER
CONTROL OUTPUT signal (AF'COUT).
2 - 1 0
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DC controller
T
Figure 2- 12
signal
Laser driver PC6
The CPU adjusts the value of the
APCOUT signal by changing the APCOR
signal for coarse adjustment, and the
APCOS signal for fine adjustment.
The output current of the laser current
setting circuit is sent to the switching
circuit and the laser diode is switched ON
and OFF in response to the /VDATA signal
when the VIDEO DATA ENABLE signal