LICHTSTROMKREIS FUER FAHRZEUG-ENTLADUNGSLAMPE

A lighting circuit for a vehicular discharge lamp comprises a DC-to-AC converter, a lamp voltage detector, a lamp current detector, a voltage-current controller, and a power change reducing means. The DC-to-AC converter converts a DC voltage into an AC voltage and supplies it to the discharge lamp. The lamp voltage detector acquires a detection signal concerning a lamp voltage of the discharge lamp. The lamp current detector acquires a detection signal concerning a lamp current of the discharge lamp. The voltage-current controller produces a lamp current controller instruction signal generated with respect to the lamp voltage upon reception of the detection signal from the lamp voltage detector, and supplies a control signal to the DC-to-AC converter so as to minimize differences between the instruction signal and the detection signal from the lamp current detector, thereby controlling the output voltage of the DC-to-AC converter. This controller has at least a lighting acceleration area for producing the lamp-current control instruction signal to permit supply of greater power than rated power of the discharge lamp and a steady power control area for performing steady power control of the discharge lamp with the rated power, as a control area based on lamp voltage-lamp current characteristic. The power change reducing means suppresses a change in power supply to the discharge lamp with respect to the lamp voltage at a time of transition to the steady power control area from the lighting acceleration area, thereby shortening the time required for flux of light from the discharge lamp to become stable.