B. Laser Control Circuit - Canon LBP-1000 Service Manual

B. Laser Control Circuit

1. Outline
Engine controller PCB
IC402
CPU
+5V
J401-5/6
CNTRL1 J1001-19
J401-9
64
CONT1
CNTRL0 J1001-18
J401-10
1
CONT0
J401-7/8
/BDI
J401-11
2
/BDI
J1707-1 VDO
Video
controller
PCB J1707-2 /VDO
This circuit turns ON/OFF the laser diode (LD) at a constant intensity in response to the /VDO
and VDO signals sent from the video controller.
The /VDO and VDO signals sent from the video controller enter the logic circuit in the laser
driver IC via the intermediate PCB.
The LASER CONTROL signals (CNTRL0, CNTRL1) sent from the CPU (IC402) perform forced
emission of laser diode, masking in the non-image area, and laser diode automatic power con-
trol (APC).
When the CNTRL0 and CNTRL1 signals are "H" and "L" respectively, the laser driver circuit
turns ON/OFF the laser diode according to the /VDO and VDO signals.
Intermediate PCB
+5V
J1001-23/22 J1009-5
J1009-10
J1009-11
J1009-7
J1009-8
J1001-21/20 J1009-6/9 J801-6/3
J1001-17 J1009-13
J1006-10
J1006-9
J1706-2
Figure 2-3-2
Laser driver PCB
PD
(Photo diode)
Laser driver IC
J801-7
VCC
J801-2
J801-1
Logic
circuit
J801-5
J801-4
Current
/voltage Differential
amplifier
converting
circuit
BD PCB
CHAPTER 2
LD
(Laser diode)
Drive
circuit
C804
Sample
hold
circuit
2 - 19