Protection Mechanism - Canon Image Reader-A1 iR5000i Service Manual

CHAPTER 7 EXTERNALS AND CONTROLS

3.3 Protection Mechanism

The machine is designed to automatically turn off the output of DC power as soon as the
over-current protection circuit of the DC power supply PCB turns on.
When the over-current detection circuits a high level of current, the machine will stop out-
puts [1], [2], and [3]; in other words, the over-current detection circuit 1 is arranged at an
upper level of detective circuitry, and its activation will turn off all outputs located under it.
When the over-current detection circuit 2 detects over-current, the machine will stop out-
puts [2] and [3]. Likewise, when the over-current circuit 3 detects a high level of current, the
machine will stop output [3].
The machine is also equipped with a fuse to cut off outputs in the event any of the ele-
ments in circuits fails.
Over-
current
detection
circuit 1
Over-
current
detection
circuit 2
Over-
current
detection
circuit 3
7-10 P
DC power supply PCB
Converter
circuit 1
3VB
Converter
circuit 2
3VA1/3VA2/
3VA3/5V/
12VU
Converter
circuit 3
24VU1/24VU2/
24VU3/24VU4/
24VA
Sequence
control
circuit
F07-303-01
COPYRIGHT © 2001 CANON INC.
Output
Over-
current
3VB
protection
circuit 1
Output
3VA1
Over-
3VA2
current
protection
3VA3
circuit 2
5V
12VU
Output
24VU1
24VU2
Over-
current 24VU3
protection
24VU4
circuit 3
24VA
Fuse
(F4001)
2000 2000 2000 2000 CANON iR5000i/iR6000i REV.0 JUNE 2001
PCBs
[1]
[2]
[3]