Discharge lamp lighting device

A discharge lamp lighting device which comprises a DC power source for generating a voltage necessary for a discharge lamp from a DC power source, a control circuit for calculating a power required by the discharge lamp to perform feedback control over the DC power source, a polarity switching circuit for switching polarities of an output of the DC power source to apply the output to the discharge lamp, an ignitor for superposing a high pulse voltage to the discharge lamp at the time of starting the discharge lamp, and a capacitor which forms a closed circuit together with the ignitor, wherein, in order to suppress excessive charging and discharging currents flowing through the capacitor when the polarities of the polarity switching circuit are switched, the control circuit controls the polarity switching circuit to be operated at a low frequency and simultaneously be chopper-operated at a high frequency. Thereby the excessive current flowing through switching elements at the time of switching the polarities can be suppressed and stresses imposed on the switching elements can be sufficiently prevented.