D. Controlling the Separation/Pre-Transfer Corona Current1. OutlineFigure 4-113 shows the circuit used to control the separation corona current and thepre-transfer corona current, and the circuit has the following functions:q Turning on and off the separation/pre-transfer corona current.w Switching the separation corona current level.e Controlling the separation corona current to a specific level.r Switching the pre-transfer corona current level.t Controlling the re-transfer corona current to a specific level.The DC component of the separation charging assembly and the pre-transfer charg-ing assembly is controlled to a specific current by obtaining a sampling signal from thesecondary side of the high-voltage transformer (HVT) with the aim of eliminating theeffects of changes in the environment on corona charging. (The AC transformer is con-trolled to a specific voltage.)The separation corona current is varied to eliminate the effects of changes in theenvironment by measuring the surface potential of the drum and in relation to the outputof the environment sensor.Figure 4-113+--+--DC controller PCBACONDCPCQ156D/A converterROEDJ114-A7HVRMTJ779-4J114-A1J779-10J114-A10J779-1J114-A8J779-3J114-A9J779-2HVSCTHVTOFF SwitchingcircuitAC controlcircuitConstantcurrentcontrol circuitDrivecircuitDrivecircuit(HVT)OvercurrentdetectioncircuitSwitchingcircuitConstantcurrent controlcircuitDrivecircuitDC transformerT302DC transformerT402(positive power supply)DC transformerT301(negative power supply)AC transformerT201Photosensitive drumMicroprocessor (master)SwitchingcircuitSwitchingcircuitCHAPTER 4 IMAGE FORMATION SYSTEM4-15COPYRIGHT © 1997 CANON INC. CANON NP6560/NP6360/NP6260 REV. 0 NOV. 1997 PRINTED IN JAPAN (IMPRIME AU JAPON)
