Aspects of the invention include a constant current source that generates a constant current, apart from a constant current circuit, and a temperature detection zener diode (a temperature detection element). The input side of the constant current source can be connected to a power source. The output side of the constant current source can be connected to the anode of the temperature detection diode. The anode of the temperature detection zener diode can also be connected to one end of a resistor provided in the constant current circuit. Further, the cathode of the temperature detection zener diode can be connected to a GND. Further, the temperature detection zener diode can be incorporated in the same semiconductor substrate as a semiconductor substrate into which an IGBT is built.