Canon imageRUNNER ADVANCE C255 Series, Service Manual, Page: 60 / 987

4. The DC Controller PCB controls the Scanner Motor control signals (acceleration signals and deceleration signals) based on
the input timing of the BD signal to control the Scanner Motor rotation speed.
Y Laser
M Laser
C Laser
Bk Laser
Acceleration signal
Deceleration signal
Scanner Motor rotation speed signal
Y/M/C/K
Laser Driver
PCB (UN05)
DC Controller
PCB(UN04)
Laser Scanner Unit
Scanner
Motor
BD
sensor
BD
signal
APC (Auto Power Control)
Purpose
Ensures constant laser beam light intensity for each line.
Execution timing
For each line (before writing the image)
Control description
1. The Main Controller PCB outputs the APC signal to the Laser Driver IC in the Y/M/C/Bk Laser Driver PCB.
2. The APC mode is set for the Laser Driver ICs of each Y/M/C/Bk Laser Driver PCB and the laser diode of each color is forcibly
activated. The photo diode (PD) monitors the laser diode (LD), and each Laser Driver IC adjusts the output of laser diode
until the laser light intensity reaches a specified level.
LD
PD
LD
Y Laser
LD
PD
LD
M Laser
LD
PD
LD
C Laser
Y/M/C/K
Laser Driver
PCB (UN05)
Laser Scanner Unit
LD
PD
LD
Bk Laser
APC Signal Main Controller
PCB (UN81)
2. Technology
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