To protect main elements against temperature inexpensively through a simple circuit by arranging a Schottky barrier diode breaking in short circuit mode when a set temperature is exceeded in the temperature protective circuit for the main element.

A resistor R7 and a Schottky barrier diode D1 are connected in series with each other and connected in parallel with a power supply 10. When the temperature of a main element is lower than 125°C, a bipolar transistor Q4 is turned on to cause turn on of a bipolar transistor Q3 and the Schottky barrier diode D1 supplies an input. When the temperature of the main element exceeds 125°C, the Schottky barrier diode D1 is short-circuited and the bipolar transistor Q4 is turned off to cause turn off of the bipolar transistor Q3 thus interrupting the input. According to the arrangement, the circuitry is simplified significantly and an inexpensive temperature protection can be realized using an inexpensive Schottky barrier diode.