| 摘要 |
PROBLEM TO BE SOLVED: To provide a discharge tube lighting device for multiple lights equipped with a safety circuit capable of coping with a plurality of kinds of discharge tube lengths and performing automatic negative feedback control to a suitable operation frequency in correspondence with a terminal condition of a discharge tube. SOLUTION: This discharge tube lighting device for multiple lights of LC resonance type wherein the discharge tubes FL1-n are connected to output of a high frequency lighting circuit 3 in parallel and inductors CH1-n and capacitors Cf1-n are connected to the respective discharge tubes FL1-n is provided with a life terminal stage tube detecting means K (DC component detecting circuit 4) for detecting DC component of the tube current of the life terminal stage tube in the one-side emitter-less state, and a operation frequency control means M for turning off only the tube of which operation frequency of the high frequency lighting circuit 3 is the one of the life terminal stage tube in accordance with the terminal stage condition of the life terminal stage tube after detection and performing automatic negative feedback control so that other normal tubes are varied to the frequency by which the lighting can be maintained, in other words, a negative feedback circuit 8 whereby the detected current is made to be a negative return electric current ic and is converted by an I-V converting circuit 5 and a V-F converting circuit 6 and thereby a control signal S for controlling the operation frequency of the high frequency lighting circuit 3 can be achieved. COPYRIGHT: (C)2004,JPO |
