Patent ID: 8044613

Claim:
A discharge lamp lighting device comprising: a power control circuit outputting DC current; an AC conversion circuit generating and outputting discharge lamp driving AC current by inverting the polarity of the DC current at a predetermined timing; a control circuit performing an AC conversion control process of controlling a polarity inversion timing of the discharge lamp driving AC current on the AC conversion circuit and performing an interval current control process of controlling a current value of the DC current every polarity inversion timing interval on the power control circuit; a detection unit detecting a discharge lamp driving voltage at the time of normal lighting; a history information storage periodically storing history information of the detected discharge lamp driving voltage; a statistics processing unit statistically processing the stored history information every predetermined period; and a statistical information storage storing information having been subjected to the statistical process as statistical information, wherein the control circuit sets and controls at least one of a frequency, a duty ratio, and a waveform of the discharge lamp driving AC current on the basis of a time-dependent tendency of the statistical information.