Canon CANOSCAN FB330 series Service Manual page 70

CHAPTER 2
V. POWER SUPPLY
A. CanoScan FB330P/FB630P
AC adapter is adopted for the CanoScan FB330P/FB630P power source. The AC adapter
converts the AC power into +10.5 VDC. The output DC power is converted into +5 VDC in the
main PCB. +5 VDC is used for the IC in the main PCB, the scanning unit drive motor and the
contact image sensor.
The scanner has an overvoltage detection function to check if an AC adapter for other
scanner is connected and overvoltage is input.
The CPU performs A/D conversion of an AC adapter divided voltage input to P17 port, and
starts to check when the hardware setting in the power ON sequence has completed, then
keeps on checking during standby.
When the CPU judges an overvoltage beyond preset level is input, it stops all processing
except for the communication with the host computer and sends an overvoltage detection error
to the host computer.
AC adapter
AC power
AC/DC
conversion
circuit
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COPYRIGHT © 1999 CANON INC. CANOSCAN FB330/FB630 SERIES REV.0 OCT. 1999 PRINTED IN JAPAN (IMPRIME AU JAPON)
+10.5 VDC
Figure 2-35
Main PCB
+5 VDC
conversion
circuit
Contact
image sensor
Scanning unit
drive motor