The present invention comprises: a TRIAC (110) operated by TRIAC driving current input to a gate terminal (g); a bridge diode (120) for full-wave rectifying current which is output from the gate terminal (g) of the TRIAC (110) or input to the gate terminal (g) of the TRIAC (110); a TRIAC triggering unit (130) which operates the TRIAC (110) by receiving current (I) output from the bridge diode (120) as an input and outputting a TRIAC driving current (I1) for turning on the TRIAC (110) to the gate terminal (g) of the TRIAC (110); and a latch circuit unit (140) for outputting latch current which is in a latch-on state and has a smaller value than critical current (Ith) of the TRIAC (110) to the gate terminal (g) of the TRIAC (110).