November 2003 © TOSHIBA TEC 13 - 11 e-STUDIO350/450 FUSER UNIT / PAPER EXIT SECTION
13
(6) Temperature detection configuration
Thermistor is a device whose resistance decreases as it detects a higher temperature. Thus its
input voltage to CPU changes and then CPU judges whether this change is normal or abnormal. If
one of the fuser roller thermistors is broken, the control circuit judges that the fuser roller tempera-
ture is extremely low and keeps turning the IH coil ON. As a result, the fuser roller temperature
rises, and possibly activates the thermostat which is a safety protection device. To prevent this in
advance, CPU works to detect whether each thermistor is broken or not.
Also, the thermistors constantly check the temperature of IH coil to prevent it from excessive heat-
ing by IH circuit abnormality, LGC circuit abnormality or thermistor abnormality. The thermistors
automatically turn OFF the power when the temperature of IH coil exceeds the specified tempera-
ture.
139
137
PC4/AN4
PC6/AN6
CPU
+5
Edge
thermistor
Main
thermistor
+5
Fig. 13-406
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