CONTROLLER FOR HEATING TEMPERATURE

摘要

PURPOSE:To prevent surely overheat due to the short circuit of a transistor TR for sensor, by turning off a heater when a set temperature detecting signal reaches a preliminarily determined level even if the set temperature detecting signal is larger than a heater temperature detecting signal. CONSTITUTION:A voltage Vs of a common contact D at the time when a TR2 is turned off and TRs 4 and 5 are turned on is inputted to a microcomputer 20, and an A/D-converted digital value VDS is stored in an RAM. A set value VDP of a preliminarily determined level is stored in the RAM of the microcomputer 20. When the digital value VDS reaches the set value VDP, a heater 32 is turned off even if a set temperature detecting signal V2 is larger than a sensor temperature detecting signal V1, thus preventing the overheat. Thus, the overheat due to the short circuit of the TR2 for sensor is prevented surely.