Laser Control Circuit - Canon LBP-2000 Service Manual

B. Laser Control Circuit
1. Outline
DC controller PCB
J104-20 /PRNT
ASIC
/BDO
J104-30
CPU
J104-31 /VDO
J104-32 VDO
The laser control circuit operates in response to the video signals (/VDO, VDO) from the video
controller to turn on/off the laser diode (LD) at a specific intensity.
The /VDO and VDO signals from the video controller are low-amplification differential signals
with suppressed radiating noise, and they are sent to the receiver in the laser unit as they are. The
receiver serves to demodulate the low-voltage differential signals and to forward them to the logic
circuit of the laser driver IC in the form of the video out signal (/VDOUT).
When the image formation enable signal (/ENBLO) from the ASIC is 'L', the laser unit turns on/off
the laser diode in keeping with the /VDOUT signal.
+5V
J102
J907
-1
-8
/LONO
-4 -5
/ENBLO
-3 -6
/BDIN
-10
-2
/DPICH -7
/VDOUT
-2
/VDO
-7
-3
-6 VDO
Receiver
-5/-8
-1/-4
J908
-2
Figure 2-3-2
Laser unit
LD
PD
(laser
(photodiode)
diode)
Laser driver IC
Logic
circuit
Drive
circuit
Power
adjust
Control
ment
amplification
circuit
circuit
BD PCB
CHAPTER 2
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