Power Supply - Canon imageFORMULA P-208 Service Manual With Parts Catalog

V. POWER SUPPLY

1. Power Supply

USB bus power is used to supply power
to this machine. This is a method of sup-
plying power from the computer through a
USB cable.
The rated power of a cable is 5 VDC,
0.5 A.
When a power supply cable is con-
nected and the pickup tray is opened, the
tray switch is pressed and the power is
switched ON. When the pickup tray is closed,
the power is switched OFF.
Each voltage required inside is gener-
ated on the control PCB.
The main parts that consume electricity
in this machine are the elements of the ICs,
etc. on the control PCB, the upper and lower
CIS units and the feed motor. The required
current value for the feed motor changes
according to the load during feeding. To use
a special method of feed motor control and
power supply if the load increases, the fol-
lowing components are provided:
1) Feed motor with an encoder
2) Electric double layer capacitor (EDLC)
The encoder detects that the feed load
increases and the number of revolutions
decreases, the pulse supplied to the feed
motor changes. If the current is insufficient,
the capacitor is discharged. If the capacity of
the capacitor becomes insufficient, feeding
and reading stop and the capacitor is
charged. When it is charged again, the
feeding and reading begin. However, if the
prescribed rotational speed is not reached
even when an electric current is added from
COPYRIGHT © CANON ELECTRONICS INC. 2012
the capacitor, the rotational speed is re-
duced and the timing of reading is changed
accordingly.
The reading cannot be started until the
electric double layer capacitor is sufficiently
charged. If the power is switched ON when
the capacitor is fully discharged, charging
takes approx. 15 seconds. Since it is dis-
charged when the power is OFF, reading
cannot be performed for a period of time of
approx. several to 15 seconds after the
power is switched ON.
CANON P-208 FIRST EDITION
CHAPTER 2 FUNCTION & OPERATION
2-15