Patent ID: 7960923

Claim:
A high pressure discharge lamp lighting apparatus for lighting a discharge lamp, comprising: a discharge container made of quartz glass that encloses 0.20 mg/mm 3 or more of mercury and halogen in a range of 10 −6 μmol/mm 3 -10 −2 μmol/mm 3 ; a pair of electrodes arranged in the discharge container, with a projection is formed at a tip of each of the electrodes, wherein the projections face each other at an interval of 2.0 mm or less; and a power supply apparatus which performs constant electric power control over the discharge lamp; the power supply apparatus supplies a first alternating current of stationary frequency selected from a range of 60-1000 Hz to the discharge lamp; wherein the power supply apparatus inserts a second alternating current of lower frequency, which is lower than the stationary frequency, periodically into the first alternating current; wherein, when a lighting current value of the discharge lamp is smaller than a predetermined lower limit, the lower frequency is set as a predetermined minimum frequency; when the lighting current value is larger than a predetermined maximum value, the lower frequency is set as a predetermined maximum frequency; and when the lighting current value is between the lower limit and the maximum value, the lower frequency is set as a first selected frequency corresponding to the lighting current value; wherein the first selected frequency increases based on an increase of change value as the lighting current value increases.