CHAPTER 5 IMAGE FORMATION SYSTEMCOPYRIGHT © 2002 CANON INC. 2000 CANON iR1600/iR2000/iR1610/iR2010 SERIES REV.0 MAR. 2002 5 - 52.2 Turning On and Off the BiasThe primary charging roller bias is turned on and off as follows:2.2.1 DC BiasThe DC bias is generated when the primary DC bias drive signal (PRDCFOT*) goesON. The level of the DC bias is controlled by the primary/developing DC bias output levelsignal (DCPWM*).2.2.2 AC BiasThe AC bias is applied when the primary AC bias drive signal (PRACFOT*) goes ONand the primary AC bias ON/OFF signal (PRACON*) goes ‘0’.2.3 Bias Constant Voltage/Constant Current ControlThe output levels of the DC and AC biases applied to the primary charging roller arecontrolled as follows:2.3.1 DC Bias Constant Voltage ControlThe output voltage level f the DC bias is detected by the bias voltage detection circuit,and is fed back to the DC generation circuit by way of the comparison circuit. The ASICon the DC controller PCB varies the pulse width of the primary/developing DC bias out-put level signal as needed to ensure that the voltage of the DC bias remains at a specificlevel.2.3.2 AC Bias Constant Current ControlThe output current level of the AC bias is detected by the primary AC bias current cir-cuit, and is fed back to the AC generation circuit by way of a comparison circuit. The ACgeneration circuit varies the amplitude of the primary AC bias ON/OFF signal as neededto ensure that the current of the AC bias remains at a specific level.
