A first sense resistor is connected between a fourth terminal of a power source potential of a high-potential region and a first terminal of a ground potential. A second sense resistor is connected between a third terminal of a reference potential of the high-potential region and the first terminal. A comparator is disposed in a low-potential region and uses the ground potential as a reference potential for operation. The comparator compares a voltage between an intermediate potential point of the first sense resistor and an intermediate potential point of the second sense resistor with a predetermined reference voltage. The output of the comparator is input through a control circuit and a level shift circuit to a high-side drive circuit driving an upper-arm IGBT. The output of the comparator is input to a driver circuit driving a lower-arm IGBT.