Fault Detection; Laser Scanner Motor Control; Outline; Speed Control - Canon LBP5000 Series Service Manual

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Table of Contents

Chapter 2

2.3.2.6 Fault Detection

LBP5000 / LBP5100

The machine possesses a mechanism used to check the laser diode for a fault.

In the course of initial APC, the laser IC converts the laser current of the laser diode into its corresponding level of voltage (PDOUT), and sends the result to the

DC control PCB. If the voltage of the PDOUT signal is lower than a specific value, the DC controller PCB will identify the fact as the presence of a fault in the

laser unit, stopping the printer engine and, at the same time, indicating 'E100' in the status window.

2.3.3 Laser Scanner Motor Control

2.3.3.1 Outline

LBP5000 / LBP5100

The machine controls the rotation of the scanner motor so that the laser beam will correctly scan the surface of the photosensitive drum.

The scanner motor is a 3-phase, 8-pole DC brushless motor with a built-in Hall element. The drive circuit is part of the scanner motor, and its control circuitry is

as shown in the following diagram:

DC controller PCB

IC7

CPU

The laser scanner motor control mechanism is initiated by the DC controller PCB. The DC controller PCB generates reference clock signals based on the oscillation

frequency of an oscillator (X1). The frequency comparator compares the BD input signal (/BDI12) against the reference clock signal to monitor the rotation of the

scanner motor. The DC controller PCB sends the scanner motor acceleration signal (/SCNACC12) and the scanner motor deceleration signal (/SCNDEC12) it has

generated to suit the rotation of the motor to the scanner motor driver to control the speed of rotation.

1. speed control: used to rotate the scanner motor at a specific speed.

2. phase control: used to adjust the difference in phase between the 2 scanner mirrors occurring while the scanner motor is rotated at a specific speed, thereby

eliminating the variation in rotation between lines and, ultimately, preventing displacement of color in sub scanning direction.

2.3.3.2 Speed Control

LBP5000 / LBP5100

The machine controls the scanner motor so that it rotates at a specific speed as follows:

1) When the scanner motor starts up, the DC controller generates /SCNACC12 to force the scanner motor to increase its speed.

2) The DC controller PCB forces the laser to go on, and compares the interval of /BDI12 against that of the reference clock signal by way of monitoring the rotation

of the scanner motor.

3) When the speed of the scanner motor reaches a specific value, the DC controller generates /SCNDEC12 to decrease the speed of the scanner motor. Thereafter,

the DC controller generates /SCNACC12 or /SCNDEC12 to control the speed of the scanner motor.

2.3.3.3 Phase Control

LBP5000 / LBP5100

The machine executes its phase control mechanism to correct the difference in phase between the 2 scanner mirrors while the scanner motor is rotating at a specific

speed, thereby eliminating the variation between lines and, ultimately, preventing displacement of color in sub scanning direction.

1) When the scanner motor rotates at a specific speed in response to the phase control mechanism, the DC controller generates a phase reference clock signal based

on the reference clock signal.

2) The DC controller compares the phase of /BDI12 against that of the reference clock signal using the frequency comparator to detect variation in rotation between

lines.

2-6

J112

-15

IC8

ASIC

+24VA

J105

-5

-6

Frequency

comparator