Scanner System - Canon LBP-2000 Service Manual

CHAPTER 2
C. Scanner System
1 . Controlling the scanner motor
The following is a diagram of the scanner motor control circuit:
J106-20
The scanner motor is a 3-phase, 8-pole DC brushless motor with a built-in Hall element, and it is
built as one with the driver circuit of the scanner motor.
When the ASIC receives the /PRINT signal form the video controller, it causes the scanner motor
acceleration signal (/ACCO) to go 'L' in 0.15 sec. When the /ACCO signal goes 'L', the scanner
driver IC rotates the scanner motor, and increases the speed of its rotation while the /ACCO signal
remains 'L'.
While the scanner motor is rotating, the ASIC forces the laser ON, causing the BD PCB to send the
/BDIN signal.
The ASIC compares the cycle of the /BDIN signal and the target cycle inside, and continues to
control the rotation of the scanner by controlling the /ACCO signal until the rotation reaches a
specific speed.
To stop the scanner, the scanner motor deceleration signal (/DECO) is caused to go 'L', thereby
slowing down the rotation of the scanner until it comes to a stop.
2 - 34
DC controller PCB
/BDIN J102-10
/PRNT +24V
J106-4
ASIC
-5
-6
-7
CPU
Figure 2-3-4
BD PCB
J1001-2
+24V
J911-4
Scanner
driver IC
/ACCO -3
Drive
circuit
/DECO -2
-1
M102
Scanner motor