Patent ID: 6891336

Claim:
A high-pressure discharge lamp lighting apparatus, comprising: a DC power source; an inverter for converting a DC supplied from the DC power source to an AC; an AC path for transmitting the AC output from the inverter to a high-pressure discharge lamp; a resonator having a predetermined resonance frequency, and interposed in the AC path; an inverter controller for controlling the inverter according to its variable frequency oscillation function by selectively impressing a first frequency in a stable operation window free from causing acoustic resonance in the high-pressure discharge lamp, and a second frequency higher than the first frequency to the inverter; a lamp wattage detector for detecting a lamp wattage of the high-pressure discharge lamp from a voltage across the high-pressure discharge lamp and a current flowing through the high-pressure discharge lamp; and a time ratio controller for controlling a time ratio of an operation time at the first frequency and an operation time at the second frequency of the inverter controller so that the inverter outputs are alternately impressed to the high-pressure discharge lamp at an adequate time at the first frequency and the second frequency, said time ratio being based on a lamp voltage of the discharge lamp detected in the steady lighting state using the lamp wattage detector.