PURPOSE: To prevent the cutoff of a breaker and protect semiconductor elements by setting the cutoff current to 7-9 times the rated current of the breaker which is larger than the in-rush current of an incandescent lamp load and the same or below as the maximum surge-resistant current of the semiconductor elements.

CONSTITUTION: A breaker 3 concurrently using a thermal cutoff system and an electromagnetic cutoff system, a noise preventing coil 4 and semiconductor elements 5, 5 are provided as a structure in a control panel between a power source 1 and an incandescent lamp load 2. The cutoff current of the breaker 3 by the electromagnetic cutoff system is set to 7-9 times the rated current of the breaker 3. It can be attained by adjusting the number of turns of a solenoid coil constituting the electromagnetic cutoff system. The cutoff current of the breaker 3 by the electromagnetic cutoff system is made larger than the in-rush current of the incandescent lamp load 2 and the same or below as the maximum surge-resistant current of the semiconductor elements 5. The cutoff of the breaker 3 by the in-rush current of the incandescent lamp load 2 is prevented, and the semiconductor elements 5 are protected from the short- circuit current on the incandescent lamp load 2 side.