DIMMER, LIGHTING DEVICE, AND ILLUMINATING CONTROL SYSTEM

PROBLEM TO BE SOLVED: To supply power necessary for stable operation of a lighting device while transferring dimming signals through a power source line. SOLUTION: A bidirectional thyristor T54 (a switching element) lies in the way of the power source line 811 supplying alternating-current power to a lighting device 300. A zero-cross detection circuit 120 detects voltage zero-cross of the alternating-current power source AC. A switch control circuit 140 has a dimming-degree directing period consisting of a period of conducting the bidirectional thyristor 54 and a period of insulating the bidirectional thyristor 54 in one half-cycle period, and a power-feeding period for conducting the bidirectional thyristor 54 continuously during one half-cycle period. COPYRIGHT: (C)2010,JPO&INPIT