Driving method for discharge lamp, driving device for discharge lamp, light source device, and image display apparatus

An image display apparatus comprising:

• a discharge lamp as a light source configured to display an image;
• an alternating current supply section configured to supply two electrodes of the discharge lamp with an alternating current to light the discharge lamp, the alternating current comprising a plurality of modulation periods;
• and
• a frequency modulation section configured to modulate a frequency of the alternating current in accordance with a predefined modulation pattern, the predefined modulation pattern comprising a plurality of retentive periods within each of the modulation periods, each retentive period having a constant frequency that is different from a frequency of temporally adjacent retentive periods,
• wherein the frequency modulation section makes a length of at least one of the retentive periods in the modulation period shorter in response to at least two conditions being met:
• (a) a predetermined condition occurring, and (b) the frequency of the at least one of the retentive periods is equal to or less than a predetermined reference frequency, and
• the frequency modulation section is configured to modulate the frequency of the alternating current in accordance with the predefined modulation pattern when the at least two conditions are not met.

A driving method for a discharge lamp, comprising:

• supplying an alternating current between two electrodes of the discharge lamp, the alternating current comprising a plurality of modulation periods;
• modulating a frequency of the alternating current in accordance with a predefined modulation pattern, the predefined modulation pattern comprising a plurality of retentive periods within each of the modulation periods, each retentive period having a constant frequency that is different from a frequency of temporally adjacent retentive periods;
• and
• shortening a length of at least one of the retentive periods in the modulation period in response to at least two conditions being met:
• (a) a predetermined condition occurring, and (b) the frequency of the at least one of the retentive periods is being equal to or less than a predetermined reference frequency,
• wherein the modulating of the frequency of the alternating current is performed in accordance with the predefined modulation pattern when the at least two conditions are not met.