CHAPTER 5 IMAGE FORMATION SYSTEMCOPYRIGHT © 2002 CANON INC. 2000 CANON iR1600/iR2000/iR1610/iR2010 SERIES REV.0 MAR. 2002 5 - 73.2 Turning On/Off the BiasThe developing bias is turned on/off as follows:3.2.1 DC BiasWhen the developing DC bias drive single (DVDCFOT*) goes ON, the DC bias is gen-erated. The output level of the DC bias is controlled by the primary/developing DC biasoutput level signal (DCPWM*).3.2.2 AC BiasWhen the primary AC bias drive signal (DVACFOT*) goes ON and the developing ACbias ON/OFF signal (DVACON*) goes ‘0’, the AC bias is generated.To prevent stray toner inside the machine, the AC bias is also turned on for image areasand off for non-image areas.3.3 Controlling the Bias to a Constant Voltage LevelThe output level of the DC bias applied to the developing cylinder is controlled as fol-lows:3.3.1 Controlling the Developing DC Bias to a Constant LevelThe output voltage level of the DC bias is detected by the developing DC bias voltagedetection circuit, and is fed back to the DC generation circuit by way of the comparisoncircuit. The ASIC on the DC controller PCB varies the pulse width of the primary/devel-oping bias output level signal as needed to keep the DC bias to a specific voltage level.3.3.2 Controlling the Developing AC Bias to a Constant Voltage LevelThe output voltage level of the AC bias is detected by the developing AC bias voltagedetection circuit, and is fed back to the DC generation circuit by way of the comparisoncircuit. The ASIC on the DC controller PCB varies the amplitude of the developing ACbias ON/OFF signal as needed to ensure that the AC bias is kept to a specific level.3.4 Controlling the Voltage Level of the Developing DC BiasThe voltage level of the developing DC bias is controlled by varying the pulse width ofthe primary/developing DC bias output level signal (DCPWM*) to suit such factors as theprint density setting.
