Technical information

v. PQWEW SUPPLY
A. DC Power Supply
1. Mechanism
The DC power supply PCB is supplied with AC
powerwhenthedoorswitchandPOWERswitchare
turned ON.
On the DC power supply PCB, the AC power is
rectiiied and smoothed out. lts voltage then is
lowered by the transformer (T201); thereafter, it is
made available in 24V, 12V. and 5V by filters and
regulator.
For 24V power, the output voltage is checked; it
is fed back to the switching regulator (Q204) by way
of a photocoupler (Q205) for stabilization.
5V power is stabilized by the regulator (Q207).
2. Protection Mechanism for Power Supply
Circuit
The DC powersupply is equipped with protection
mechanisms to cut off the power should any of the
loads suffer a shorl because of an error.
The protection mechanism for 24V power is the
over-current detection mechanism in the switching
regulator (Q204); upon activation, the circuit also
cuts off 12V and 5V outputs. For 12V power, a
current fuse serves to protect against an over-cur-
rent.
The protection mechanism for 5V power makes
use of the over-current detection circuit of the regu-
lator(Q207);upon activation, theoutput ofonly5Vis
cut off.
For24V power, an over-voltage protection circuit
isadditionallyprovidedusing aZenerdiode(ZD201)
and thyristor (Q208).
The output, after activation of these protection
mechanisms, can be recovered by turning the door
switch OFF, correctingthe relevant load, and turning
the door switch ON once again.
If only 12V has been cut out, the door switch
should be turned OFF, the relevant load should be
corrected, fuse (FU202) should be replaced. and the
door switch should be turned ON once again.
TL?01 D204
3-52
Q2Oi
i
Over-voltage
protection circuit
24V
Q207
MIMD
Figure 3-52
COPYAIGHT Q 1992 CANON INC. CANON NPZl20/2MU RN.0 MAY 1930 PRINTEU IN JAPAN IIMPNIME AU JAPUNI d