Rare gas discharge lamp lighting device

PROBLEM TO BE SOLVED : To relatively stabilize the light variation of a rare gas discharge lamp after operation. SOLUTION : This device comprises a rare gas discharge lamp DL having external electrodes 5, 6 arranged on the outer periphery of an envelope, a high frequency voltage generation circuit HC containing a first driving circuit PD1 for granting driving signals having constant duty ratio and frequency to an output transformer TR having primary and secondary coils, a first switching element S1 connected in series to the primary coil, a current detecting circuit R1 and a first switching element, a DC conversion circuit PH for detecting a voltage to be converted into a DC voltage corresponding to a peak current in the current detecting circuit R1, and a DC/DC converter CV. The DC/DC converter CV and the rare gas discharge lamp DL are connected to the input side of the high frequency voltage generation circuit HC and to the output side thereof, respectively, for control of power on the input side of the high frequency voltage generation circuit HC to be almost constant by using the power stabilizing function of the DC/DC converter CV through PWM control, based on output signals from the DC conversion circuit PH.