| 摘要 |
<p>PURPOSE:To simplify circuits for the fault detection, preheating, dimming and the like of a plurality of fluorescent lamps by providing a fluorescent-lamp disconnection detecting circuit device that detects the current of only one winding of a multiple-winding choke coil using a current detection means. CONSTITUTION:A multiple-winding choke coil L2a is used as a lighting-current limiting device for a plurality of fluorescent lamps FL1-3 and a current transformer CT 1 for the disconnection detecting circuit 4 of each fluorescent lamp filament is connected only to the circuit of the fluorescent lamp FL3. If the fluorescent lamp FL1 or FL2 is disconnected, the inductance of the coil L2a as seen from the circuit of the fluorescent lamp FL 3 becomes two-thirds as great and the limiting value of lighting current becomes three-seconds as great and can be detected by the transformer CT 1. In the case of disconnection of the fluorescent lamp FL 3, the current of the circuit of the lamp FL 3 becomes zero and can be detected by the transformer CT 1. This indicates that even when the fluorescent lamps are turned off, i.e., when equipment is in a standby state, fault detection is possible.</p> |
