| 摘要 |
PURPOSE:To provide stable lighting even when a filament of a discharge lamp is broken by changing a resonance frequency between the case where the filament is broken and the case where it is not broken, though a resonance circuit is formed. CONSTITUTION:For lighting a discharge lamp 10, a voltage generating means 4 generates such a voltage that a voltage control oscillator 2 outputs a frequency around a resonance point of a curved line A. When a filament of the discharge lamp 10 is not broken, a necessary voltage for lighting is generated at both ends of the discharge lamp 10, so it can be lighted. However, in the case where the filament is broken, a timer means 5 transmits passage of a preliminarily determined time after resetting to the voltage generating means 4. The means 4 receives this, and detects breakage of the filament based on an output of an impedance detection means 6, and the voltage control oscillator 2 changes it into such a voltage that the frequency of the curved line B around the resonance point. The discharge lamp 10 can thus be lighted. |
