Temperature control system for electric heating appliance

摘要

A system comprising a heat generating load such as a heater, a power control element for directly or indirectly supplying current to the heat generating load, a temperature detecting circuit for producing an ON signal when the temperature of the heat generating load is lower than a set temperature and an OFF signal when the temperature is higher than the setting, and a control circuit for feeding an ON or OFF signal to the power control element in response to the ON or OFF signal from the temperature detecting circuit. The control circuit includes a failure detecting circuit for logically comparing the signal from the temperature detecting circuit with the terminal voltage across the power control element to produce output when the power control element is in conduction although the signal from the temperature detecting circuit is an OFF signal. Upon the failure of the power control element, for example, due to self-triggering, the failure is detected directly by the failure detecting circuit and, in response to the resulting output therefrom, the power supply to the heat generating load is stopped to assure safety.