b. When the Primary Corona Current Output Is ONHVTPC is less than about 11 V.HVRMT is ‘1’.Variable width pulse generator circuit goes ON.Comparator circuit goes ON.Drive circuit turns on.Primary high-voltage transformer goes ON.Figure 4-111The above condition causes the high-voltage transformer to send high voltage suitedto the output of the primary charging level control signal (HVTPC) to the primary charg-ing assembly.If an excess corona current flows because of changes in the environment, the returncurrent to the comparator circuit increases, and the output decreases; this condition willdecrease the corona current from the primary charging assembly, controlling it to a spe-cific level at all times.In photo mode, the target value is lowered by about 80 V than the dark area potential(VD) used in normal copying mode. As such, potential control is executed while makingthe first copy in photo mode after power-on to control the primary corona current.+--+--DC controller PCBQ156Micro-processor D/Aconverter SwitchcircuitVariablewidth pulseoscillatorcircuitT502DrivecircuitPrimaryhigh-voltagetransformerTransferhigh-voltageHVTPCHVTCTHVRMTComparator circuitHVTT501T502 PrimarychargingassemblyPhoto-sensitivedrumTransferchargingassemblyJ779-6J779-5J779-1J114-A5J114-A6J114-A10Variablewidth pulseoscillatorcircuitT501DrivecircuitCHAPTER 4 IMAGE FORMATION SYSTEM4-12 COPYRIGHT © 1997 CANON INC. CANON NP6560/NP6360/NP6260 REV. 0 NOV. 1997 PRINTED IN JAPAN (IMPRIME AU JAPON)
