CHAPTER 5 IMAGE FORMATION SYSTEM
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2002 CANON INC. 2000 CANON iR1600/iR2000 REV.1 JAN. 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 de-
tection circuit, and is fed back to the DC generation circuit by way of the comparison cir-
cuit. The ASIC on the DC controller PCB varies the pulse width of the primary/developing
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 de-
tection circuit, and is fed back to the DC generation circuit by way of the comparison cir-
cuit. 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.
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