| 摘要 |
PURPOSE:To prevent the resonance current from becoming a phase advanced current even through a discharge lamp concerned is in half wave lighted-up condition by setting longer the On period of one of the switching elements, and setting the On period of the other switching element shorter. CONSTITUTION:A load circuit includes an LC series resonance circuitry consisting of an inductor L1 and a capacitor C2, and a discharge lamp l is connected as a load at the ends of the capacitor C2. The switching frequency f of a switching element is set lower than the resonance frequency f0 at the time of no load on this LC resonance circuitry, wherein the On period of one of the switching elements is set longer than 1/2f0, while the On period of the other switching element set shorter than 1/2f0. Thereby the resonance current will not become phase advanced current even in the half wave discharge state wherein the condition of the LC resonance circuitry differs half cycle by half cycle, and sufficient current can be supplied to the discharge lamp l. |
