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

A discharge lamp driving device comprising:

• a discharge lamp driving unit configured to supply a driving current to a discharge lamp including electrodes;
• and
• a controller configured to control the discharge lamp driving unit,
• wherein the controller controls the discharge lamp driving unit to provide
• a hybrid period in which a first period for supplying an AC current with a first frequency to the discharge lamp and a second period for supplying a DC current to the discharge lamp are alternately repeated,
• a fourth period in which an AC current with a second frequency lower than the first frequency is supplied to the discharge lamp, and
• a fifth period alternately including a third DC period in which a DC current is supplied to the discharge lamp, and a fourth DC period in which a DC current with a polarity opposite to a polarity of the DC current supplied to the discharge lamp in the third DC period is supplied to the discharge lamp,
• wherein a length of the third DC period is longer than a length of the fourth DC period,
• wherein the length of the fourth DC period is less than 0.5 ms, and
• wherein a total of lengths of the third DC periods in the fifth period is longer than a length of the second period, and is longer than a length of half a cycle of the AC current with the second frequency in the fourth period.

A discharge lamp driving method for supplying a driving current to a discharge lamp including electrodes and driving the discharge lamp, the method comprising:

• supplying the driving current including
• a hybrid period in which a first period for supplying an AC current with a first frequency to the discharge lamp and a second period for supplying a DC current to the discharge lamp are alternately repeated,
• a fourth period in which an AC current with a second frequency lower than the first frequency is supplied to the discharge lamp, and
• a fifth period in which a third DC period in which a DC current is supplied to the discharge lamp, and a fourth DC period in which a DC current with a polarity opposite to a polarity of the DC current supplied to the discharge lamp in the third DC period is supplied to the discharge lamp, are alternately included,
• wherein a length of the third DC period is longer than a length of the fourth DC period,
• wherein the length of the fourth DC period is less than 0.5 ms, and
• wherein a total of lengths of the third DC periods in the fifth period is longer than a length of the second period, and is longer than a length of half a cycle of the AC current with the second frequency in the fourth period.