Laser Driver Circuit; Controlling The Laser - Canon iR5000 Service Manual

CHAPTER 3 LASER EXPOSURE SYSTEM

3. Laser Driver Circuit

3.1 Controlling the Laser

The laser driver circuit serves to drive the semiconductor laser in response to the laser
drive signal (LD) from the DC controller PCB.
The following are control items associated with the laser driver circuit:
1. Turning on/off laser light.
2. Controlling the intensity of laser light (ACP control).
3. Controlling the intensity of laser light to suit the surface potential of the drum.
The following signals are used:
[1] Laser drive signal.
[2] Sample laser activation signal. Used to turn on laser light for an intensity sample (for
each scan).
[3] Laser enable signal. Goes '0' when the laser becomes ready after the Start key has been
pressed.
[4] Laser write start signal. Used to start a laser write when paper reaches the laser write
start sensor (PS28), mounted in front of the registration roller.
[5] The intensity of laser light is monitored while it is turned on to collect a sample; an ap-
propriate value is fed back to the laser drive circuit.
[6] The output is controlled so that the reference value from the DC controller (EEPROM)
and the value returned as feedback will be identical.
[7] Laser intensity reference signal. Used as the laser activation reference value, and is de-
termined by potential control (EEPROM).
3-6 P
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