Canon LBP-2000 Service Manual download pdf (Page 59)

CHAPTER 2

2 - 20

2 . Operation

a. Primary charging

TB401/TB402Pr

/PRACON

/PRACFOT

/DCPWM

/PRDCFOT

To developing bias circuit

To primary

charging roller

DC controller PCB

Primary bias circuit

ASIC

CPU

Primary DC bias

voltage detection

circuit

generation circuit

Comparison

circuit

Primary AC bias

current detection

circuit

Comparison

circuit

Combination

Figure 2-2-10

The ASIC generates the primary AC bias drive signal (/PRACFOT), the primary AC bias ON/OFF

signal (/PRACON), the primary DC bias drive signal (/PRDCFOT), and the primary/developing DC

bias output level signal (/DCPWM); it also applies a voltage which is a combination of a primary AC

bias and a primary DC bias to the primary charging roller.

The primary AC bias is detected by the primary AC bias current detection circuit, and is fed

back to the AC generation circuit by way of the comparison circuit, thereby controlling the current

of the primary charging bias.

The primary DC bias is detected by the primary DC bias voltage detection circuit, and is fed

back to the DC generation circuit by way of the comparison circuit, thereby controlling the voltage

of the primary DC bias. The voltage of the primary DC bias is varied in conjunction with the

voltage of the developing DC bias according to the image data from the video controller PCB.

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Canon LBP-2000 Service Manual Page 59