C. Controlling the Primary/Transfer Corona Current1. OutlineFigure 4-111 shows the circuit used to control the primary/transfer corona current,and the circuit has the following functions:q Turning on and off the primary corona current.w Controlling the primary corona current to a specific level.e Turning on and off the transfer corona.r Controlling the transfer corona current to a fixed level.2. Controlling the Primary Corona CurrentThe DC controller compares the drum surface potential VD obtained by the potentialdetection circuit against the target value; and, if there is a discrepancy, the signal fromthe DC controller used to control the primary corona current is corrected.The corrected signal is converted into an analog value (HVTPC signal) by the D/Aconverter circuit, and is sent to the high-voltage transformer, thereby controlling theprimary corona current.The primary corona current output is turned on and off by DCON, and is controlledby the HVTPC control.When HVTPC is 3 to 11 V, the primary corona current turns on; it turns off when thesignal is about 12 V or more.a. When the Primary Corona Current Output Is OffHVTPC is about 12 VDCON is ‘0’Variable width pulse oscillator circuit goes OFF.Comparator circuit goes OFF.Drive circuit goes OFF.Primary high-voltage transformer goes OFF.COPYRIGHT © 1997 CANON INC. CANON NP6350/NP6251 REV. 0 JULY 1997 PRINTED IN JAPAN (IMPRIME AU JAPON)CHAPTER 4 IMAGE FORMATION SYSTEM4-11Download service manual and resetter printer at http://printer1.blogspot.com
