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 including a polarity switching portion that alternately switches a polarity of a voltage applied between the electrodes so that an alternating current is supplied to the discharge lamp, and
• the power supply control unit including:
• an anode duty ratio modulating portion that modulates an anode duty ratio of the alternating current applied to the discharge lamp, 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, by setting first and second periods with different anode duty ratios;
• and
• a high duty period extending portion that sets the first period, in which the anode duty ratio of the alternating current applied to the discharge lamp is higher than that in the second period, longer than the second period in one modulation period, which includes the first and second periods and for which the modulation is performed, 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 so that an alternating current is supplied to 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 including a polarity switching portion that alternately switches a polarity of a voltage applied between the electrodes, and
• the power supply control unit including:
• an anode duty ratio modulating portion that modulates an anode duty ratio of the alternating current applied to the discharge lamp, 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, by setting first and second periods with different anode duty ratios;
• and
• a high duty period extending portion that sets the first period, in which the anode duty ratio of the alternating current applied to the discharge lamp is higher than that in the second period, longer than the second period in one modulation period, which includes the first and second periods and for which the modulation is performed, when a predetermined condition is satisfied.

An image display device, comprising:

• a discharge lamp that is 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 so that an alternating current is supplied to 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 including a polarity switching portion that alternately switches a polarity of a voltage applied between the electrodes, and
• the power supply control unit including:
• an anode duty ratio modulating portion that modulates an anode duty ratio of the alternating current applied to the discharge lamp, 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, by setting first and second periods with different anode duty ratios;
• and
• a high duty period extending portion that sets the first period, in which the anode duty ratio of the alternating current applied to the discharge lamp is higher than that in the second period, longer than the second period in one modulation period, which includes the first and second periods and for which the modulation is performed, when a predetermined condition is satisfied.