| 摘要 |
PROBLEM TO BE SOLVED: To prevent the voltage of a smoothing capacitor from excessively rising. SOLUTION: This discharge lamp lighting device has a structure wherein a D.C. voltage provided by rectifying an A.C. power source AC with a rectifier DB1 is supplied, through an inductor L1 and a diode D3, to the connection point of a first and second switching elements Q1, Q2 to which parasite diodes D1, D2 are reversely and parallel connected, respectively, so as not to block a reverse current, a smoothing capacitor C2 is connected in parallel with the first switching element Q1, a discharge lamp FL is connected through a capacitor C3, a coil L2, and a capacitor C4 from the connection point of the first and second switching elements Q1, Q2, and a control circuit 1 for alternately turning on and off the first and second switching elements Q1, Q2 is provided. The control circuit 1 alternately turns on and off the first and second switching elements Q1, Q2 with a pulse output, controls the on-duty of the second switching element Q2 so as to keep it small and to restrict its maximum on-duty by sensing its voltage or current. |
