| 摘要 |
PROBLEM TO BE SOLVED: To provide a discharge lamp lighting device for simply and surely detecting the end of a life time of a discharge lamp 43. SOLUTION: The device has a DC source 10 and a switching circuit including a pair of sequentially serially connected switching elements 21, 22. The DC source 10 and the switching circuit are connected in parallel. The device has flywheel diodes 23, 24 connected in back-to-back connection with each of the switching elements 21, 22 and a driving circuit 30 for driving so as to turning on/off in turn each of the switching elements 21, 22. The device has a lighting circuit 40 serially including a discharge lamp 43, an inductor for ballast 41, a resonance capacitor 42 and a capacitor 44. The device has a positive and a negative voltage detecting circuits 31, 32 for detecting a positive and a negative voltages of a lamp voltage wave of the discharge lamp 43, respectively; and a pair of differential amplifying circuits 33, 34 for detecting a voltage difference between the detected positive and negative voltages. The device has a life time determining circuit 35 for outputting an operation stoppage command signal to the driving circuit 30, when the output voltages from the amplifying circuits 33, 34 exceed a prescribed threshold. COPYRIGHT: (C)2004,JPO |
