Patent ID: 7855512

Claim:
A high-pressure discharge lamp lighting device comprising: a lighting circuit supplying an alternating current to a high-pressure discharge lamp to cause lighting, the high-pressure discharge lamp having an arc tube in which a halogen material is enclosed and a pair of electrodes is disposed, and each electrode having a protuberance at a tip thereof; and a frequency controlling unit varying a frequency of the alternating current without dependency on operating data that varies with an elapsed lighting time of the high-pressure discharge lamp, wherein the frequency controlling unit performs any one of the following controls (i)-(iv) during a predetermined period without dependency on the operating data; (i) to vary the frequency in a regular manner, and to repeat the predetermined period consecutively; (ii) to vary the frequency in a regular manner, and to repeat the predetermined period intermittently; (iii) to vary the frequency in an irregular manner, and to repeat the predetermined period consecutively; and (iv) to vary the frequency in an irregular manner, to repeat the predetermined period intermittently.