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

A discharge lamp driving device comprising:

• a discharge lamp driving section configured to supply a driving current to a discharge lamp including a first electrode and a second electrode;
• a control section configured to control the discharge lamp driving section;
• and
• a voltage detecting section configured to detect an inter-electrode voltage of the discharge lamp,
• wherein the control section is configured to alternately provide
• a first period including a first direct current period in which a direct current having a first polarity is supplied to the discharge lamp and a first alternating current period in which an alternating current is supplied to the discharge lamp and
• a second period including a second direct current period in which a direct current having a second polarity is supplied to the discharge lamp and a second alternating current period in which the alternating current is supplied to the discharge lamp,
• wherein length of a direct current period including the first direct current period and the second direct current period is a first length when the inter-electrode voltage is equal to or higher than a first voltage,
• wherein the length of the direct current period is larger than the first length when the inter-electrode voltage is lower than the first voltage and equal to or higher than a second voltage lower than the first voltage, and
• wherein the length of the direct current period is smaller than the first length when the inter-electrode voltage is lower than the second voltage.

A discharge lamp driving device comprising:

• a discharge lamp driving section configured to supply a driving current to a discharge lamp including a first electrode and a second electrode;
• a control section configured to control the discharge lamp driving section;
• and
• a voltage detecting section configured to detect an inter-electrode voltage of the discharge lamp,
• wherein the control section is configured to provide a third alternating current period alternately including
• a fourth alternating current period in which a fourth alternating current is supplied to the discharge lamp and
• a fifth alternating current period in which a fifth alternating current having a frequency which is lower than a frequency of the fourth alternating current is supplied to the discharge lamp,
• wherein a ratio of the fifth alternating current period in the third alternating current period is a first ratio when the inter-electrode voltage is equal to or higher than a first voltage,
• wherein the ratio of the fifth alternating current period is larger than the first ratio when the inter-electrode voltage is lower than the first voltage and equal to or higher than a second voltage lower than the first voltage, and
• wherein the ratio of the fifth alternating current period is smaller than the first ratio when the inter-electrode voltage is lower than the second voltage.