Circuit - Canon LBP-1000 Service Manual

CHAPTER 2
C. High-voltage Power Supply Circuit
1. Outline
PRDCON
DCCK
DCPWM
PRACCK
PRACON
CRGSNS
CPU
IC402
DVDCON
DVACCK
DVCHG
TRFAD
TRPCK
TRPWM
TRNCK
In response to the instructions from the CPU (IC402) on the engine controller, this circuit applies
the superimposed voltage of DC voltage and AC voltage to the primary charging roller and devel-
oping cylinder, a positive or negative DC voltage to the transfer charging roller, and a negative
DC voltage to the pressure roller.
This circuit changes the primary DC bias and developing DC bias according to the image den-
sity information sent from the video controller in order to adjust the image density.
2. Operation
a. Primary charging roller voltage generation
When a print instruction command is sent from the video controller, initial rotation starts and
the CPU outputs the PRIMARY AC DRIVE signals (PRACCK and PRACON). As a result, the pri-
mary AC bias is applied to the primary charging roller from the AC generation circuit in the pri-
mary high-voltage circuit. At the same time, the PRIMARY DC BIAS DRIVE signals (DCCK and
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Engine controller PCB
Primary high-voltage circuit
Comparator
Voltage detection

circuit

circuit
DC generation
circuit
AC generation
circuit
AC current
Comparator
circuit detection circuit
Developing bias circuit
Comparator
Voltage detection
circuit
circuit
DC generation
circuit
AC generation
circuit
Transfer bias circuit
Positive current
detection circuit
Positive voltage
generation circuit
Voltage
control circuit
Negative voltage
generation circuit
Figure 2-2-6
Fixing
J505
Fixing film unit
Primary
Super- Primary charging roller
impose
charging
J501
Super-
impose
Development
J502
Transfer
J503
Photosensitive drum
Developing
cylinder
Transfer
charging roller
Pressure roller