The primary charging bias circuit generates the negative DC voltage and AC voltage. They are superimposed and applied to the primary charging roller. The circuit

also applies the negative DC voltage to the fixing film unit through the pressure roller. In addition, this circuit detects the presence of cartridge.

The developing bias circuit generates negative DC voltage and AC voltage. They are superimposed and applied to the developing cylinder.

The transfer charging bias circuit generates positive or negative DC voltage and applies the positive or negative DC voltage to the transfer charging roller.

These circuits are controlled by the commands from the CPU (IC201) on the engine controller.

The following section describes each generation circuit.

IC201

CPU

PRDCC

PRACC

CRGSNS

DVACC

TRPFOT

TRPWM

TRNFOT

TRCRNT

2.4.2.2 Primary charging bias generation

LBP3370 / LBP3310

The primary charging bias (PR) is generated according to two signals output from the CPU: the PRIMARY CHARGING DC BIAS DRIVE signal (PRDCC) and

the PRIMARY CHARGING AC BIAS DRIVE signal (PRACC).

The PRDCC signal is a clock signal to generate the DC bias and the primary charging DC bias is generated according to this signal. The PRACC signal is a clock

signal to generate the AC bias and the primary charging AC bias is generated according to this signal. The superimposed voltage of primary charging AC and the

primary charging DC biases is applied to the primary charging roller.

The primary DC bias changes with the developing DC bias in response to the image density information sent from the video controller.