Patent ID: 7417381

Claim:
A discharge lamp lighting circuit comprising: a DC/AC converter for performing AC conversion upon the reception of an input DC voltage; a starting circuit for supplying a start signal to a discharge lamp; and a control unit for controlling power output by the DC/AC converter, wherein the DC/AC converter includes a plurality of switching devices to be driven by the control unit, and a series resonant circuit that includes either an inductance device or a transformer and a capacitor, wherein, the DC/AC converter is configured such that, if a resonance frequency for the series resonant circuit when the discharge lamp is turned off is denoted by “f 1 ”, and if a resonance frequency of the series resonant circuit when the discharge lamp is turned on is denoted by “f 2 ”, before the discharge lamp is turned on, the switching devices are controlled so that a drive frequency for the switching devices gradually approaches f 1 , and so that the start signal is supplied to the discharge lamp by the starting circuit, wherein, the discharge lamp is configured so that, after lighting of the discharge lamp has been initiated, if the drive frequency for the switching device immediately before the discharge lamp is turned on is employed as a reference, the drive frequency is defined at a level higher by a predetermined frequency displacement value than the reference so that the drive frequency of the switching devices is shifted to a frequency area higher than f 2 .