Canon LBP1760P, Service Manual

Page: 52 / 394

C. High-Voltage Power Supply Circuit
1. Outline
Figure 2-2-7
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.
2 - 14
CHAPTER 2
/PRNT
/TOP
CPU
IC501
Primary charging
AC control
Primary charging
DC
(density volume
control)
Developing AC
control
Transfer control
Voltage detection
output control
circuit
Amplifier
High-voltage
control IC
Voltage detection
output control
circuit
Amplifier
Current detection
circuit
Superimpose
Drive
Drive
Inverter
transformer
Voltage
division
circuit
Drive
Drive
Flyback
transformer
Amplifier
Current detection
circuit
Developing
cylinder
Photosensitive drum
Primary charging roller
Transfer
charging roller
Toner sensor
TB63
TB62
TB61
TB401
Primary
charging
Development
TB64
TB402
Developing DC
control
(density volume
control
)
Engine controller PCB
Toner level
detection
Inverter
transformer
Inverter
transformer
Inverter
transformer
Inverter
transformer
Superimpose
Antenna
Transfer