Ballast for high-pressure discharge lamp and method of operating the same

A high-frequency start type ballast for a discharge lamp comprising:

• a direct current power source;
• a DC-DC converter for DC-DC converting a current from the direct current power source;
• a commutator for converting a direct current output from the DC-DC converter into an alternating current;
• a discharge lamp supplied with the alternating current from the commutator;
• and
• an operating device control section for controlling an output current of the DC-DC converter, and controlling a commutation frequency of the commutator,
• wherein the operating device control section operates the discharge lamp, at start of operating the discharge lamp, with a predetermined voltage value lower than a rated voltage of the discharge lamp and a first target current value higher than a rated current of the discharge lamp, then, at an end of a predetermined high frequency start period elapsed from the start of operating the discharge lamp, controls the commutator to switch from a commutation frequency higher than that during a steady lamp operation to a commutation frequency during the steady lamp operation, and then, after a voltage applied to the discharge lamp increases and reaches a voltage not lower than a predetermined threshold voltage lower than the rated voltage of the discharge lamp, controls the DC-DC converter so that the first target current value is switched to a second target current value not higher than the rated current of the discharge lamp.