| 摘要 |
PURPOSE:To light a discharge lamp reliably and instantly in stationary frequency without cutting off electric power supply once when the discharge lamp is replaced by protecting a circuit part without breaking down it when the discharge lamp is put in an emissionless condition. CONSTITUTION:The fact that the direct current level of output of secondary coils 18a and 18b derived converter-like from inductance elements 12a and 12b being the constituent of a serial resonance circuit of an inverter 17 is heightened due to an emissionless condition, is detected by an emissionlessness sensing circuit 19. Oscillation frequency of the inverter 17 is switched to frequency separated from stationary frequency by a frequency switching circuit 6, and synthetic impedance of the resonance circuit is lightened, and a discharge lamp electric current is reduced, and the breakdown of a circuit element is prevented. The fact that this discharge lamp is removed, is detected by lamp connection and disconnection detecting circuits 33a and 33b, and the oscillation frequency of the inverter is restored compulsorily to the stationary frequency by the frequency switching circuit, and oscillation operation is continued, and a new discharge lamp is lighted reliably and instantly when it is installed. |
