CHAPTER 4 IMAGE FORMATION SYSTEMCOPYRIGHT © 1999 CANON INC. CANON NP6512/6612/7120/7130/7130F REV.0 AUG. 1999 PRINTED IN JAPAN (IMPRIME AU JAPON) 4-9D. Controlling the Transfer Roller Bias1. OutlineThe circuit shown in Figure 4-105 is used to control the voltage applied to the transfer chargingroller, and has the following functions:• Turning on and off the transfer bias.• Controlling the transfer bias to a constant voltage.• Correcting the transfer bias voltage level (ATVC)• Switching the transfer bias polarity (cleaning bias)Figure 4-105Maintransformer Transfer positive DCbias generation circuitTransfer positive DC bias ON signalT_REV_ON*T101Transfer current detection signalT_FW_SPhoto-sensitivedrumTransferchargingrollerTransfer DC biascontrol signalT_FW_DRVTransfer bias voltagedetection signalT_FEEDBACKTransfer DC bias ON signalT_FW_ONHigh-voltage transformercontrol signalCLK32KTransfer overcurrent detection signalHV_LIMIT+24V T302Transferhigh-voltagetransformerSerialcommuni-cation(Q101) (Q900)MicroprocessorMicroprocessorDC controller PCB Composite power supply PCBTransfer biasdetection circuitTransfer biascontrol circuit
