High-Voltage Power Supply; Circuit - Canon LBP1760P Service Manual

CHAPTER 2
C. High-Voltage Power Supply Circuit
1. Outline
CPU
IC501
High-voltage
control IC
Primary charging
AC control
Primary charging
DC
(density volume
control)
Developing DC
control
(density volume
control)
/PRNT
Developing AC
control
Toner level
/TOP
detection
Transfer control
In response to the instructions from the microprocessor (CPU: IC1501) on the engine controller,
this circuit applies the superimposed voltage of DC voltage and AC voltage to the primary charg-
ing roller and developing cylinder, and a positive or negative DC voltage to the transfer charging
roller.
According to the image density information sent from the video controller, this circuit varies
the primary DC bias and developing DC bias to adjust the image density.
2. Operation
a. Primary charging roller voltage generation
When the /PRNT signal sent from the video controller becomes "L," initial rotation starts and the
CPU outputs the PRIMARY AC BIAS FREQUENCY OUTPUT signal. The circuit then applies the
primary AC bias to the primary charging roller. When the PRIMARY DC BIAS FREQUENCY
OUTPUT signal is output after the specified period of time, the voltage superimposing primary
DC bias onto primary AC bias is applied to the primary charging roller.
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Engine controller PCB
Current detection

circuit

Amplifier
Inverter
transformer
Voltage detection
output control
circuit
Drive
Drive
Voltage detection
output control
circuit
Amplifier
Inverter
transformer
Voltage
division
circuit
Current detection
circuit
Amplifier
Flyback
transformer
Drive
Drive
Inverter
transformer
Figure 2-2-7
Primary
Superimpose charging
TB62
Inverter
transformer
Inverter
transformer
Superimpose Development
TB61
Antenna TB63
TB64
Transfer
TB401
TB402
Primary charging roller
Photosensitive drum
Developing
cylinder
Toner sensor
Transfer
charging roller