Controlling The Primary/Transfer Corona Current; Outline; Controlling The Primary Corona Current - Canon NP6251 Service Manual

C. Controlling the Primary/Transfer Corona Current

1. Outline

Figure 4-111 shows the circuit used to control the primary/transfer corona current,
and the circuit has the following functions:
Turning on and off the primary corona current.
Controlling the primary corona current to a specific level.
Turning on and off the transfer corona.
Controlling the transfer corona current to a fixed level.

2. Controlling the Primary Corona Current

The DC controller compares the drum surface potential VD obtained by the potential
detection circuit against the target value; and, if there is a discrepancy, the signal from
the 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/A
converter circuit, and is sent to the high-voltage transformer, thereby controlling the
primary corona current.
The primary corona current output is turned on and off by DCON, and is controlled
by the HVTPC control.
When HVTPC is 3 to 11 V, the primary corona current turns on; it turns off when the
signal is about 12 V or more.
a. When the Primary Corona Current Output Is Off
HVTPC is about 12 V
DCON 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 SYSTEM
4-11