Canon D1300 Series Service Manual

Canon D1300 Series Service Manual Manual pdf 45 page image

22 2-212-21Technical Overview > Fixing System > Fixing Control Circuit > Protective FunctionTechnical Overview > Fixing System > Fixing Control Circuit > Protective Function■ Fixing Temperature ControlThe Fixing temperature control maintains the temperature of the Fixing Heater at its targetedtemperature.Block diagram of this control is shown below.FREQSNSTH1 TP1 H1: Fixing heaterTP1: ThermoswitchTH1: ThermistorFSRDRLYDFSRTH+24VRL101Pressure rollerFixing film unitFixing heatercontrol circuitFixing heatersafety circuitDC controllerLow-voltage power supplyEngine controllerFixing control circuitFixing unitRelaycontrolcircuitFrequencydetection circuitF-2-25The DC Controller monitors the FIXING TEMPERATURE (FSRTH) signal and sends theFIXING HEATER CONTROL (FSRD) signal according to the detected temperature. TheFixing Heater control circuit controls the Fixing Heater depending on the signal so that theheater remains at the targeted temperature.■ Protective FunctionThe protective function detects an abnormal temperature rise in the Fixing Assembly andinterrupts power supply to the Fixing Heater.The following three protective components prevent an abnormal temperature rise of theFixing Heater:• DC Controller• Fixing Heater safety circuit• Thermoswitch1) DC ControllerThe DC Controller monitors the detected temperature of the thermistor. The DCControllermakes the FIXING HEATER CONTROL signal inactive and releases the relay to interruptpower supply to the Fixing Heater under the following condition:2) Fixing Heater safety circuitThe Fixing Heater safety circuit monitors the detected temperature of the thermistor.The Fixing Heater safety circuit releases the relay control circuit to interrupt powersupplyto the Fixing Heater under the following condition:3) ThermoswitchThe contact of the thermoswitch is broken to interrupt power supply to the Fixing Heaterunder the following condition: