Patent ID: 7215087

Claim:
A discharge lamp lighting apparatus comprising: a first 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, via each of at least two variable inductance elements, to one terminal of each of the 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, an inductance of each of the at least two variable inductance elements, and capacitors provided between each variable inductance element and each discharge lamp; at least two lamp current detecting units are each provided at the other terminal of each discharge lamp, and 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; a phase adjusting circuit is connected to at least two switches each of which is connected to a connecting node between each lamp current detecting unit and each lamp current control circuit; each of the at least two switches is turned on and off according to an output signal from the phase adjusting circuit; and an output signal sent from each lamp current control circuit and having a phase shifted from others is connected to each of the at least two 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.