Patent ID: 8120282

Claim:
A discharge lamp lighting device comprising: a power control circuit that outputs a DC current; an AC converter circuit that takes the DC current as its input, inverts a polarity of the DC current in predetermined timing, and thereby generates and outputs an AC current for discharge lamp driving; and a control unit configured to control the AC converter circuit to perform an AC conversion control for controlling the timings at which a polarity of the AC current for discharge lamp driving is inverted and configured to control the power control circuit to perform a current control for controlling a current value of the DC current wherein the control unit changes, in a cyclical pattern, an cumulative energy supplied to each electrode of a discharge lamp during one cycle of the AC current for discharge lamp driving; the cyclical pattern includes plural sectional periods in which the cumulative energy is maintained at a same value over plural cycles of the AC current for discharge lamp driving, and a level of the cumulative energy differs between at least two of the sectional periods; and the control unit performs the current control by receiving a power control signal from outside, and setting an average value of the DC current in a section corresponding to the one cycle of the AC current for discharge lamp driving to a current value corresponding to the power control signal, and controlling a length of the sectional period included in the cyclical pattern in relation to the average value of the DC current.