Patent ID: 7211970

Claim:
A discharge lamp lighting device comprising: an inverter circuit carrying out on/off control with respect to switch elements to convert a direct current power supply voltage into a high-frequency voltage; a resonance load circuit supplied with the high-frequency voltage from the inverter circuit, and including an inductor, a capacitor and a discharge lamp lighted at a predetermined lighting frequency fs, and further, configured so that declination with respect to the lighting frequency fs is set to a range from −20° to 40° in impedance when the discharge lamp is operating at rating; and a control circuit carrying out the following control of continuously generating a pulse voltage for driving on and off the switch elements at a cycle (period) shorter than a lighting cycle of the discharge lamp, and making pulse-width modulation with respect to an on-state width of the pulse voltage in accordance with a waveform change of a sinusoidal voltage corresponding to the lighting cycle, and further, supplying an approximately sinusoidal current to the discharge lamp from the inverter circuit.