Discharge lamp lighting device, discharge lamp lighting method, and projector

A discharge lamp lighting device comprising:

• a resonance circuit unit connected to a discharge lamp;
• a power converting unit configured to convert direct-current power into alternating-current power and supply the alternating-current power to the discharge lamp via the resonance circuit unit;
• and
• a control unit configured to supply the alternating-current power alternately having a first frequency and a second frequency different from the first frequency, to the discharge lamp in a lighting start period from a start of lighting of the discharge lamp to the time the discharge lamp is lit, wherein
• the control unit changes stepwise the first frequency to decrease from a frequency higher than a frequency for causing resonance of the resonance circuit unit toward the frequency for causing the resonance, and
• the second frequency is higher than the frequency for causing the resonance and equal to or higher than 100 kHz.