Fan Motor Drive Circuit - Toshiba DP120F Service Manual

3.12 Fan Motor Drive Circuit

The fan motor drive circuit consists of the I/OP2-GA (IC48), PTC GA (IC45), A/D converter
(IC54) and other peripheral devices. It drives the DC motor connected to CN9 on the Mother
PBA to operate the fan for cooling this machine.
The fan motor is driven by the FANL signal and FANH signal which are output from the I/OP-2
GA. When the FANL signal goes HIGH, Q255 and Q251 turn on and the voltage of the FANPS
signal becomes +18V, thus allowing the fan motor to operate at low speed. When the FANH
signal goes HIGH, Q254 and Q10 turn on and the voltage of the FANPS becomes +24V, thus
allowing the fan motor to operate at high speed. When both FANL and FANH signals go LOW,
the fan motor will be stopped.
A speed of the fan motor is selected according to the fuser's temperature sensed by the ther-
mistor. The motor stops when the temperature is less than 106°C and operates when 122°C or
more. The speed is also controlled from low to high speed when starting the polygon motor in
the LSU, and from high to low speed when ending the printing.
The connection status of the fan motor is detected by converting the voltage of the FANDET
signal to a digital value by the A/D converter and comparing it with the reference value by the
PTC GA. The digital value distinguishes between connection and non-connection of the fan
motor.
Signal Name Type
FANL O
FANH O
FANPS O
FANDET I
March 2000 © TOSHIBA TEC
Fig. 7-3-12
Active
H Fan Motor Low Speed Signal
H Fan Motor High Speed Signal
- Fan Motor Drive Signal
- Fan Motor Connection Detect Signal
Description
7-45
Destination
Q255
Q254
Fan motor
A/D converter
DP120F/DP125F Circuit Description
07-03-12