Patent ID: 7999481

Claim:
A lighting method for a high-pressure discharge lamp that has a halogen material enclosed therein, and includes an arc tube having a pair of electrodes disposed therein, each of the electrodes having a protuberance formed on an end thereof, the lighting method being for lighting the high-pressure discharge lamp by a supply of an alternating current, performing constant current control after a startup, and thereafter changing to lighting at a constant power, the lighting method comprising: a switching step of switching a frequency of the alternating current, in accordance with a change in a voltage value between the pair of electrodes, from a first value that is a rated frequency to a second value that is different from the first value and that has a higher degree of audibility than the first value; and a maintenance step of prohibiting the switching step and maintaining the frequency of the alternating current at the first value during a period that is one of (i) a predetermined time period that starts at the startup of the high-pressure discharge lamp and ends before the change to lighting at the constant power, (ii) a time period from the startup to a time of the change to lighting at the constant power, and (iii) a time period that begins at the startup and ends when a predetermined time period after the change to lighting at the constant power has elapsed.