Canon 1000 Service Manual page 168

3. OPERATION AND TIMING
3. Controlling the Internal Static Eliminating Current
Figure 3-556 shows the circuit that controls the internal static eliminating current, and the circuit has the
following functions:
• Turns on and off the internal static eliminating current.
• Executes constant voltage control.
OC
The internal static eliminating current is turned on and off by the internal static eliminating current drive
signal (HVER) as follows:
Input is made in the range of HVER=0V to 12V
Q1 turns ON to supply a drive voltage suited to the voltage of the HVER to the transformer.
The output of the internal static current is monitored by its voltage value, and the data is sent to the
transistor Q1 in the form of feedback. The feedback signal is used to control the transformer drive voltage,
thereby maintaining the internal static eliminating current to a specific level.
If an abnormally high voltage occurs and, as a result, an overcurrent is detected, the OC signal turns Q1
off to stop the supply of transformer drive voltage for 20 msec; the supply will return automatically thereafter.
Further, with the help of the environmental sensor, the current value is corrected each time the Start key
is pressed.
3-124
COPYRIGHT © 2001 CANON INC.
DC controller PCB
24V
Q1
Q2
Pulse oscillator
circuit
Voltage detection
circuit
Internal static eliminating roller
External static eliminating roller
The transformer is driven, and a DC bias suited to the voltage of HVER is
generated.
HVT1
Transformer
Overcurrent
detection circuit
Figure 3-556
CANON CLC1000/1000S/3100 REV.2 MAY 2001 PRINTED IN JAPAN (IMPRIME AU JAPON)