Patent ID: 7235931

Claim:
A discharge lamp lighting apparatus comprising: a DC power supply; a control circuit; a step-up transformer defining a primary side and a secondary side; and switching elements connected to the DC power supply and functioning to drive the primary side of the step-up transformer by a signal from the control circuit thereby lighting at least two discharge lamps provided at the secondary side of the step-up transformer, wherein: one terminal of the secondary side of the step-up transformer is connected to one terminal of each of the at least two discharge lamps, and the other terminal of the secondary side of the step-up transformer is grounded; at least two series resonant circuits are each formed by a leakage inductance of the step-up transformer, and capacitors provided between the secondary side of the step-up transformer and each discharge lamp; at least two lamp current detecting units are each connected, via each of at least two variable inductance elements, to the other terminal of each discharge lamp; a signal of each of the at least two lamp current detecting units is connected to each of at least two lamp current control circuits; and an output signal from each lamp current control circuit is connected to each of the variable inductance elements so as to vary the inductance of each variable inductance element, whereby a lamp current flowing through each discharge lamp is controlled.