Discharge lamp driving device, light source device, projector, and discharge lamp driving method

A discharge lamp driving device comprising:

• a discharge lamp driving unit that supplies a driving current for driving a discharge lamp to the discharge lamp;
• and
• a control unit that controls the discharge lamp driving unit,
• wherein the control unit controls the discharge lamp driving unit such that the driving current having driving periods is supplied to the discharge lamp, the driving period including:
• a mixing period which alternately has an AC period in which an alternating current is supplied to the discharge lamp and a first DC period in which a direct current is supplied to the discharge lamp,
• a second DC period which is provided immediately after the mixing period and in which a direct current having a polarity which is the same as that of the direct current in the first DC period is supplied to the discharge lamp, and
• a third DC period which is provided immediately after the second DC period and in which a direct current having a polarity opposite to that of the direct current in the second DC period is supplied to the discharge lamp,
• the length of the second DC period is longer than the length of the first DC period, and
• the length of the third DC period is longer than or equal to the length of the first DC period and shorter than the length of the second DC period.