Canon iR2000 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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3.2 Turning On/Off the Bias
The developing bias is turned on/off as follows:
3.2.1 DC Bias
When 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 bias
output level signal (DCPWM*).
3.2.2 AC Bias
When the primary AC bias drive signal (DVACFOT*) goes ON and the developing AC
bias 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 areas
and off for non-image areas.
3.3 Controlling the Bias to a Constant Voltage Level
The 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 Level
The output voltage level of the DC bias is detected by the developing DC 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/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 Level
The output voltage level of the AC bias is detected by the developing AC 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 amplitude of the developing AC
bias 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 Bias
The voltage level of the developing DC bias is controlled by varying the pulse width of
the primary/developing DC bias output level signal (DCPWM*) to suit such factors as the
print density setting.