2. Turning OFF and ON the Primary
Charging Roller
The primary charging roller is turned ON and
OFF by the primary charging roller ON/OFF sig-
nal (HVPDC) from the DC controller PCB.
The primary side of the main transformer
(T101) on the composite power supply PCB oper-
ates under the control of the CPU (Q605). When
the HVPDC signal is sent to the composite power
supply PCB, the CPU (Q605) generates the DC
control signal (PPWM) to turn ON the secondary
side of T101, thereby applying a DC bias to the
primary charging roller.
Then, the CPU generates the AC control sig-
nal (PAPWM) according to the data obtained from
serial communications with the DC controller
PCB. As a result, the transformer T300 is driven
to apply an AC bias to the primary charging roller.
3. Controlling the Primary Charging
Roller Bias
The output values of the DC bias and the AC
bias applied to the primary charging roller are
controlled by the DC control signal (PDPWM) and
the AC control signal (PAPWM) generated by the
CPU (Q605). (These two signals are pulse sig-
nals.)
In the case of the DC bias, the output voltage
value is returned to the CPU (Q605) to vary the
duty ratio of the DC control signal continuously
and, thereby controlling it to a specific voltage
(constant voltage control).
In the case of the AC bias, on the other hand,
the current value of the AC bias output is detect-
ed and sent to the AC drive circuit.
The AC drive circuit uses the reference signal
(AC control signal PAPWM) and the AC bias cur-
rent value it has received to generate signals to
drive the transformer T300, thereby controlling
the AC bias to a constant current.
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COPYRIGHT © 1996 CANON INC. CANON GP215/200 REV.0 JULY 1996 PRINTED IN JAPAN (IMPRIME AU JAPON)
3. OPERATIONS AND TIMING
