Canon i-SENSYS MF229dw Service Manual

Canon i-SENSYS MF229dw Service Manual Manual pdf 36 page image

22 2-122-12Technical Overview > Laser Exposure System > Controlling the Laser Activation Timing > Horizontal Sync ControlTechnical Overview > Laser Exposure System > Controlling the Laser Activation Timing > Horizontal Sync ControlControlling the Laser Activation Timing■ Laser ON/OFF ControlIn this control, the laser driver turns on/off the 2 laser diodes (LD1, LD2) according to thelaser control signal sent from the engine controller.The following is the circuit diagram of the laser control.Logic circuitPDLD1Enginecontroller PCB Laser driver PCBLaser driver ICIC102ASICGNDVCCBD PCB/BDIJ116-2 J31-2LD2LD1switchingcircuitVDO1/VDO1VDO2/VDO2CNT0CNT1CNT2Standard voltageComparatorSamplehold circuitC18C16PDOUTJ11-1J102-13-2-4-8-10-12-10-6-4-11 -3-5-6-7-9-8-7-3/9/12 -2/5/11IC101CPUComparatorSamplehold circuit+5VLD2switchingcircuitF-2-14The engine controller sends the laser control signals (CNT0, CNT1, CNT2) for changingthe operation mode of the laser to the logic circuit in the laser driver IC, as well as the videosignals (VDO1, /VDO1, VDO2, /VDO2) for image formation.The laser driver IC executes laser control according to the combination of the CNT0, CNT1,CNT2 signals.The following is the combination of the laser control signal (CNT0, CNT1, CNT2).Operation mode CNT0 CNT1 CNT2 DetailsStandby L L L Laser control OFFPrint H H H Can emit the laser according to the video signalLD1 forced ON L H L LD1 forcibly turned ONLD2 forced ON H L L LD2 forcibly turned ONLD forced OFF H H L LD1, LD2 forcibly turned OFF■ Horizontal Sync ControlThis is the control to adjust the writing position in the image horizontal direction.The following is the details of control procedure.1) The engine controller controls the laser control signal during unblanking (*) to emit the laserdiode (LD) forcibly.2) The BD PCB exists on the scanning route of the laser beam, which is sent to the BD PCB.3) The BD PCB detects this laser beam, creates BD input signal (/BDI) and sends it to theengine controller.4) The engine controller creates horizontal sync signals (/BD) based on /BDI signal and sendsthe /BD signal to the main controller.5) When /BD signal is input, the main controller outputs the video signal (VD0, /VD0) to theengine controller to adjust the writing position in image horizontal direction.*: Unblanking periodThe period during which the laser diode is emitted in non-image area.T-2-3