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

A driving device for a discharge lamp, comprising:

• a discharge lamp lighting unit that makes the discharge lamp light by supplying the power between two electrodes of the discharge lamp;
• and
• a power supply control unit that controls a power supply state of the discharge lamp lighting unit,
• the discharge lamp lighting unit includes a polarity switching portion that alternately switches a polarity of a voltage applied between the electrodes, and
• the power supply control unit includes:
• an anode duty ratio modulating portion that modulates an anode duty ratio, which is a ratio of an anode time for which one of the electrodes operates as an anode in one period of the polarity switching, within a predetermined range;
• and
• a modulation range changing portion that changes the predetermined range to make a maximum value of the modulated anode duty ratio higher than a maximum value of an initial anode duty ratio of the discharge lamp when a predetermined condition is satisfied.

A light source device, comprising:

• a discharge lamp;
• a discharge lamp lighting unit that makes the discharge lamp light by supplying the power between two electrodes of the discharge lamp;
• and
• a power supply control unit that controls a power supply state of the discharge lamp lighting unit,
• the discharge lamp lighting unit includes a polarity switching portion that alternately switches a polarity of a voltage applied between the electrodes, and
• the power supply control unit includes:
• an anode duty ratio modulating portion that modulates an anode duty ratio, which is a ratio of an anode time for which one of the electrodes operates as an anode in one period of the polarity switching, within a predetermined range;
• and
• a modulation range changing portion that changes the predetermined range to make a maximum value of the modulated anode duty ratio higher than a maximum value of an initial anode duty ratio of the discharge lamp when a predetermined condition is satisfied.

An image display device, comprising:

• a discharge lamp as a light source for image display;
• a discharge lamp lighting unit that makes the discharge lamp light by supplying the power between two electrodes of the discharge lamp;
• and
• a power supply control unit that controls a power supply state of the discharge lamp lighting unit,
• the discharge lamp lighting unit includes a polarity switching portion that alternately switches a polarity of a voltage applied between the electrodes, and
• the power supply control unit includes:
• an anode duty ratio modulating portion that modulates an anode duty ratio, which is a ratio of an anode time for which one of the electrodes operates as an anode in one period of the polarity switching, within a predetermined range;
• and
• a modulation range changing portion that changes the predetermined range to make a maximum value of the modulated anode duty ratio higher than a maximum value of an initial anode duty ratio of the discharge lamp when a predetermined condition is satisfied.