Abstract: An output transformer for an inverter driven by a pulsating voltage obtained through the full wave rectification of a low frequency alternating current voltage is provided with an auxiliary winding, and a high frequency voltage obtained from the auxiliary winding is rectified to obtain a voltage for charging a capacitor. The voltage across the capacitor is used as an auxiliary voltage together with the pulsating voltage for driving the inverter. The circuit for charging the capacitor includes a current limiting inductor having first and second coil sections, through which the charging current flows alternately in opposite directions depending upon the polarity of the high frequency voltage.

Abstract: A low frequency AC voltage is rectified through a full-wave rectifier to obtain a pulsating voltage, which is superimposed with an auxiliary voltage of a predetermined level provided from an auxiliary power source, and the resultant composite pulsating voltage is inverted at an inverter to a high frequency voltage. The high frequency voltage thus obtained from the inverter is used to operate a discharge lamp. Minimum value V.sub.min of the resultant voltage is set to be 1/3 to 4/5 of the maximum value V.sub.max of the resultant voltage.