Discharge lamp lighting device

A discharge lamp lighting device comprising:

• a feeding unit adapted to supply an AC electric current to a discharge lamp having a pair of electrodes placed to oppose each other within a discharge container which encloses a predetermined gas;
• and
• a control unit adapted to control a frequency of the AC electric current supplied to the discharge lamp by the feeding unit, in different manners within a first term and a second term which are alternately repeated;
• wherein the control unit is adapted to control the frequency of the AC electric current in such a way as to alternately repeat a basic term and a lower-frequency term, the basic term being provided for controlling the frequency of the AC electric current in different manners within the first term and the second term which are alternately repeated, and the lower-frequency term being provided for controlling the frequency of the AC electric current such that the frequency of the AC electric current becomes a frequency lower than a lowest frequency within the previous basic term, and
• wherein the control unit is adapted to control the frequency of the AC electric current, independent of a current value of the discharge lamp, such that, within at least one the first term, the frequency of the AC electric current becomes at least two fixed frequency out of plural set fixed frequencies, and the control unit is adapted to control the frequency of the AC electric current to a varied frequency varied based on the at least one fixed frequency and an electric current value within the previous first term, such that, within the second term directly after the first term, the frequency of the AC electric current becomes the varied frequency lower than the at least one fixed frequency.

A discharge lamp lighting device comprising:

• a feeding unit adapted to supply an AC electric current to a discharge lamp having a pair of electrodes placed to oppose each other within a discharge container which encloses a predetermined gas;
• and
• a control unit adapted to control a frequency of the AC electric current supplied to the discharge lamp;
• wherein
• the control unit is adapted to control the frequency of the AC electric current in such a way as to alternately repeat a basic term and a lower-frequency term, the basic term being provided for controlling the frequency of the AC electric current in different manners within the first term and the second term which are alternately repeated, and the lower-frequency term being provided for controlling the frequency of the AC electric current such that the frequency of the AC electric current becomes a frequency lower than a lowest frequency within the previous basic term,
• the control unit is adapted to control the frequency of the AC electric current, independent of a current value of the discharge lamp, such that, within the first term, the frequency of the AC electric current becomes at least one fixed frequency out of plural set fixed frequencies,
• the control unit is adapted to control the frequency of the AC electric current to a varied frequency varied based on the at least one fixed frequency and an electric current value within the previous first term, such that, within the second term directly after the first term, the frequency of the AC electric current becomes the varied frequency lower than the at least one fixed frequency, and
• the control unit is adapted to control the frequency of the AC electric current, within at least one the basic term, the frequency of the AC electric current becomes at least two fixed frequencies and at least two varied frequencies.