| 摘要 |
PROBLEM TO BE SOLVED: To reduce the withstand voltage of parts for smoothing capacitor and a high frequency converting circuit by generating a filament current by use of the current carried to a second resonance circuit as input in the preheating of a filament, and supplying no high frequency voltage to a first resonance circuit until a discharge lamp is lighted. SOLUTION: In preheating, an inverter circuit 5 is operated at a frequency rather higher than the resonance frequency of a second resonance circuit 14 to carry a current to preheating windings 20a, 20b which are the secondary windings of a second coil 15. A rather high voltage is not generated in a second capacitor 16, and a discharge lamp 18 does not start. By connecting the preheating windings 20a, 20b which are the secondary windings of the second coil 15 to a filament in this way, the rising operation of smoothing voltage by a first resonance circuit 9 can be stopped in the preheating. In starting and lighting, the inverter circuit 5 is operated at about the resonance frequency of the second resonance circuit 14 to generate a high voltage in the second capacitor 16, and the discharge lamp 18 starts to discharge. |
