Patent ID: 7564199

Claim:
A discharge lamp lighting circuit for supplying, to a discharge lamp, an AC power to turn ON the discharge lamp, comprising: 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 driving circuitry to drive the switching units and supply the AC power to the discharge lamp; starting circuitry to apply a high voltage pulse to the discharge lamp, thereby promoting lighting; lighting confirming circuitry to generate a lighting confirmation signal indicating that a lighting operation for the discharge lamp fails or is successful by the high voltage pulse; and control circuitry to control a driving frequency of the driving circuitry based on the lighting confirmation signal, wherein the lighting confirming circuitry is operable to generate the lighting confirmation signal based on a relationship of a magnitude between an interelectrode voltage of the discharge lamp or an equivalent voltage thereto and a first predetermined voltage at a time that a predetermined time passes after the high voltage pulse is applied to the discharge lamp and includes: a comparing circuit to compare the interelectrode voltage or the equivalent voltage thereto with the first predetermined voltage; a pulse detecting circuit to generate a pulse applying signal indicative of a timing for applying the high voltage pulse; a delay circuit to delay the pulse applying signal by the predetermined time; and a signal generating circuit to check a signal from the comparing circuit in a timeframe indicated by the pulse applying signal which is delayed, and to generate the lighting confirmation signal as a signal indicating that the lighting operation for the discharge lamp fails when the interelectrode voltage or the equivalent voltage thereto is higher than the first predetermined voltage.