HEATING MEDIUM HEATING APPARATUS, AND VEHICLE AIR CONDITIONER PROVIDED WITH SAME

摘要

Provided are: a heating medium heating apparatus that enables the temperature of semiconductor switching elements such as insulated gate bipolar transistors (IGBT) to be directly detected, and enables overheat protection control to be performed in a highly reliable manner, while minimizing the number of installed temperature sensors; and a vehicle air conditioner provided with the heating medium heating apparatus. The heating medium heating apparatus is provided with at least two positive temperature coefficient (PTC) heaters. The electrification of each PTC heater is controlled by switching a plurality of circuits, which is provided with semiconductor switching elements (34), on and off, enabling the amount of heating to be adjusted. Temperature sensors (58, 59) for overheat protection are each installed between two semiconductor switching elements (34) of the plurality of semiconductor switching elements (34), and overheat protection control is performed by the semiconductor switching elements (34) on the basis of the temperature detected by the temperature sensors (58, 59), and a first threshold value (TH1) when one of the circuits is on and a second threshold value (TH2) when both of the circuits are on.