| 摘要 |
PURPOSE:To control the illuminance with a simple circuit structure by providing a lead terminal on a choke coil inserted between an AC power supply and a fluorescent lamp and transferring the connection between the lead terminal and the AC power supply with an electronic switch. CONSTITUTION:A driver DR, a photo-TRIAC coupler 5, and an electronic switch 4 are turned on by the high-level output voltage of an initial state setting circuit 8, and a fluorescent lamp 2 is lit. When the voltage of a time limit capacitor CT rises, the output of the circuit 8 is made a low level, the switch 4 is turned off, choke coils L1, L2 are connected in series between the fluorescent lamp 2 and an AC power supply, the tube current is decreased, and the illuminance is lowered. If a lead terminal is provided at the optional position on the coils and the connection or disconnection of the coils is performed with the electronic switch, the illuminance can be controlled in stages. The illuminance can be thereby controlled with a simple circuit structure. |
