Patent ID: 6437515
Filing Date: 2002-08-20
Classification: H05B,Y02B

Abstract:
A discharge lamp lighting device comprising:a D.C. power source circuit having a pair of output terminals for supplying a D.C. power; a polarity inverting circuit including a series circuit of at least first and second switching elements connected in parallel with the output terminals of the D.C. power source circuit for converting the D.C. power received from the D.C. power source circuit into an A.C. power; a load resonance circuit including a first inductor, a first capacitor and a discharge lamp as a load for receiving the A.C. power from the polarity inverting circuit; and control means for alternately turning ON and OFF the first and second switching elements of the polarity inverting circuit to control a voltage to be applied to the discharge lamp of the load resonance circuit; wherein the control means alternately turns ON and OFF the first and second switching elements at a high ON/OFF frequency so as to alternately provide a first period during which an ON duration of the second switching element is longer than that of the first switching element and a second period during which the ON duration of the second switching element is shorter than that of the first switching element to thereby apply a low frequency voltage of a rectangular waveform to the discharge lamp, superimposes a D.C. component upon resonance pulse signal received from the load resonance circuit in an ignition mode of the discharge lamp, and continuously changes a switching frequency of the switching elements to apply a high voltage to the discharge lamp.