Laser Control Circuit - Canon LBP1760P Service Manual

B. Laser Control Circuit
1. Outline
Engine controller PCB
IC501
/LON
/ENBL
J51-10 /PRNT
6
P67
CPU
P52
/BDI
J51-11
/VDO
This circuit switches the laser diode ON and OFF at a constant intensity in response to the
/VDO signal sent from the video controller.
The /VDO signal sent from the video controller to the engine controller is sent as is to the
logic circuit in the laser driver IC.
When the VIDEO DATA ENABLE signal (/ENBL) sent from the microprocessor (CPU: IC501)
is "L," the laser driver circuit turns the laser diode ON and OFF according to the /VDO signal.
As the beam intensity set value differs between 1200DPI and 600DPI, the LASER BEAM
INTENSITY SWITCHING signal (HALF) is set to "H" for 1200DPI and to "L" for 600DPI. The power
adjustment circuit in the laser driver IC switches the beam intensity.
+5V
J53-8
J53-10 /LON
93
J53-11 /ENBL J501-3
91
J53-12 /VDO
J53-9
HALF
43
J53-13
J53-6
/BDI
96
Figure 2-3-2
Laser driver PCB
(Photo Diode)
Laser driver IC
J501-6
VCC
J501-4
Logic
circuit
J501-2
Power
J501-5
adjustment
circuit
J501-1
GND
J551-2
CHAPTER 2
PD LD
(Laser Diode)
Drive
circuit
Control
amplification
circuit
BD PCB
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