Canon LBP253 SM Manual page 30

The Figure below shows the configuration of the fixing control circuit.
DC controller
• Fixing heater (H1): Heats the fixing film
• Thermistor (TH1): Detects fixing temperature (Contact type)
• Thermoswitch (TP1):Prevents an abnormal temperature rise of the fixing heater (Contact type)
These temperature controls in the fixing unit are performed by the fixing heater control circuit and the fixing heater safety circuit
according to the commands from the DC controller.
■ Fixing temperature control
The fixing temperature control maintains the temperature of the fixing heater at its targeted temperature.
Block diagram of this control is shown below.
H1
TP1
TH1
FIXNG HEATER CONTROL signal
Fixing heater
control circuit
Low-voltage power supply unit
Engine controller
23
Fixing film
Pressure roller
FIXING TEMPERA TURE signal
Fixing heater
safety circuit
Fixing control circuit
2. Technology