9-2. Fusing Temperature Control

(1)Fusing Temperature Control Circuit

•The resistance of the Thermistor (TH) mounted to the Fusing Roller varies with tempera- ture. The higher the temperature, the smaller the resistance value. The output from the Thermistor (TH) is applied to the analog port of the CPU.

•When the temperature increases and the resistance of the Thermistor (TH) decreases, the input voltage to the analog port becomes smaller.

•The CPU monitors the output from the Thermistor and turns ON or OFF the Heater Lamp as necessary to control the temperature of the Fusing Roller.

•To energize the Fusing Roller Heater Lamp (H1), the CPU turns ON (LOW) the Heater Remote output signal. This turns ON the triac in the Power Unit, which allows an AC volt- age to be applied to the Fusing Roller Heater Lamp (H1) to heat it.

•When the temperature of the Fusing Roller runs inordinately high, the Abnormal Heater Temperature Detecting Circuit is activated to shut down power to the Fusing Roller Heater Lamp (H1).

PWB-A (Main Board)

CPU

A/D

Main Switch

AC

 

Abnormal Heater

Input

H1

Temperature

 

Detecting Circuit

 

 

 

H2

 

Heater Remote

Power Unit On/Off

4131M060AA

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