| 摘要 |
PROBLEM TO BE SOLVED: To provide a discharge lamp lighting device capable of detecting the last stage of the service life of discharge lamps by the whole light dimming levels. SOLUTION: When half wave discharge is generated after either of discharge lamps La1, La2 becomes the last stage of the service life, a balance between the two lamps is lost, and since voltage is generated in a balancer BR, a balancer voltage detecting circuit 9 detects the last stage of the service life since voltage generated in the balancer BR becomes larger than prescribed reference voltage. While, either of the discharge lamps La1, La2 becomes the last stage of the service life, and when the discharge lamps La1, La2 are extinguished since lighting cannot be maintained, an electric current flowing to a resonance circuit becomes an advance phase to a switching frequency, and since the electric current increases, a phase advance electric current detecting circuit 8 detects the last stage of the service life since end-to-end voltage of a resistance R10 becomes larger than the prescribed reference voltage. The abnormality detecting part 10 detects the last stage of the service life of the discharge lamps La1, La2 by combining detecting signals of both detecting circuits 8, 9. |
