Patent ID: 7656102

Claim:
A discharge lamp lighting circuit for supplying, to a discharge lamp, an AC power to turn ON the discharge lamp, the lighting circuit comprising: a power supplying circuitry having a series resonant circuit including a plurality of switching units, at least one of an inductor or a transformer, and a capacitor, and a driving portion to drive the switching units and to convert a DC power and to supply the AC power to the discharge lamp; a control circuitry to generate a control signal to control a driving frequency of the driving portion; and a starting circuitry to apply a high voltage pulse to the discharge lamp to promote lighting, the control circuitry having: a first circuit portion to generate a constant control signal; a second circuit portion to generate a control signal so that a phase difference between a voltage and a current in the series resonant circuit is approximately zero; and a third circuit portion to generate a control signal so that a magnitude of the AC power approximates a steady value in accordance with a predetermined time function, wherein the lighting circuit is operable so that: the control signal from the first circuit portion is selected after a first time that the high voltage pulse is applied, the control signal from the third circuit portion is selected after a third time when a driving frequency based on the control signal from the third circuit portion exceeds a driving frequency based on the control signal from the second circuit portion, and the control signal from the second circuit portion is selected during a period from a second time, which is between the first time and the third time, to the third time.