Patent ID: 7109667

Claim:
A discharge lamp driving apparatus, comprising: a DC power supply; a control circuit; at least one step-up transformer; switching elements which are connected to the DC power supply and drive a primary side of the step-up transformer in accordance with a signal from the control circuit thereby driving at least two discharge lamps provided at a secondary side of the step-up transformer; at least two variable inductance elements which each have its one end connected to one end of the secondary side of the step-up transformer whose other end is grounded, and which each have its other end connected to one end of each of the discharge lamps; at least two series resonant circuits which are each constituted by a capacitor provided between each variable inductance element and each discharge lamp, leakage inductance of the step-up transformer, and inductance of the each variable inductance element; at least two lamp current detecting blocks which are each provided at the other end of the each discharge lamp; and at least two lamp current controlling circuits which are each connected to an output of each lamp current detecting block, and which each have its output connected to the each variable inductance element, wherein the inductance of the each variable inductance element is varied thereby controlling a lamp current of the each discharge lamp, wherein a secondary side coil of the step-up transformer is divided into a plurality of sections, and the at least two series resonant circuits, the at least two lamp current detecting blocks, and the at least two lamp current controlling circuits are provided at respective sections of the secondary side coil of the step-up transformer.