DISCHARGE LAMP LIGHTING DEVICE

PROBLEM TO BE SOLVED: To provide a discharge lamp lighting device which is designed into a small, inexpensive one while the higher harmonic components of input currents are low and the power factor is high. SOLUTION: A DC output obtained by rectifying and smoothing an ac power supply AC is stepped down by a step-down chopper circuit comprising a bridge circuit 2 for switching elements Q1 to Q4 , a first inductor L1 , and a load circuit 3, and is supplied to the discharge lamp La of the load circuit 3 to turn on the discharge lamp La using rectangular waves. Circuit nodes of the step-down chopper circuit where potential sways like high frequencies, i.e., the output end of the bridge circuit 2 and the ac power supply AC, are connected together via a second inductor L2 through connecting paths 51 , 52 which involve capacitors C51 , C52 . Input currents can be sampled via the connecting paths 51 , 52 over almost all the blocks of the source voltage of the ac power supply AC, so that a reduction in higher harmonic components and improvement in power factor can be achieved, and so that a smoothing capacitor C0 can be given stepping-up action by the second inductor L2 .