Canon iR1600 Series, Service Manual

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CHAPTER 5 IMAGE FORMATION SYSTEM
COPYRIGHT© 2002 CANON INC. 2000 CANON iR1600/iR2000/iR1610/iR2010 SERIES REV.0 MAR. 2002
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2.2 Turning On and Off the Bias
The primary charging roller bias is turned on and off as follows:
2.2.1 DC Bias
The DC bias is generated when the primary DC bias drive signal (PRDCFOT*) goes
ON. The level of the DC bias is controlled by the primary/developing DC bias output level
signal (DCPWM*).
2.2.2 AC Bias
The AC bias is applied when the primary AC bias drive signal (PRACFOT*) goes ON
and the primary AC bias ON/OFF signal (PRACON*) goes ‘0’.
2.3 Bias Constant Voltage/Constant Current Control
The output levels of the DC and AC biases applied to the primary charging roller are
controlled as follows:
2.3.1 DC Bias Constant Voltage Control
The 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 ASIC
on 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 specific
level.
2.3.2 AC Bias Constant Current Control
The 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 AC
generation circuit varies the amplitude of the primary AC bias ON/OFF signal as needed
to ensure that the current of the AC bias remains at a specific level.