| 摘要 |
PROBLEM TO BE SOLVED: To provide a lighting device for a discharge lamp for preventing a resonant circuit from operating in a phase-advanced area, and a lighting fixture as well as a projector using the same. SOLUTION: The device includes a step-down circuit 1 stepping down and outputting direct-current voltage from a direct-current power source DC, an inversion circuit 2 equipped with switching elements Q2 to Q5 for outputting high-frequency voltage, a resonant circuit 20 impressed with the high-frequency voltage of the inversion circuit 2 and lighting the discharge lamp La by resonation action, a step-down control circuit 4 controlling output voltage of the step-down circuit 1, and a driving circuit 3 for controlling high-frequency voltage by varying driving frequencies of driving signals. The driving circuit 3 includes a frequency-setting mode for setting driving frequencies in the vicinity of the resonant frequency in a phase-delayed area of the resonant circuit 20 and a startup mode for impressing a high-frequency voltage large enough to start up the discharge lamp La on the discharge lamp La, and the step-down control circuit 4 controls the step-down circuit 1 so as to step down output voltage of the step-down circuit 1 to an extent in which the discharge lamp La does not start up in the frequency setting mode. COPYRIGHT: (C)2010,JPO&INPIT |
