| 摘要 |
PURPOSE:To simplify the structure of a circuit, and to reduce the cost. CONSTITUTION:Relation between the starting frequency f1 at the time of starting discharge of a frequency changeable inverter 17, the lighting frequency f2 at the time of lighting and the resonance frequency f0 of a series resonance circuit is set at f0<f2<f1. In the case where a discharge lamp 11 is not lighted, the detection level frequency f3 of a frequency changeable inverter 17 required for setting the voltage of both ends of the discharge lamp 11 at a set voltage is set at f2<f3<f1. Since misjudgment of the lifetime of the discharge lamp before starting the discharge lamp and the protection on the basis of the misjudgment are eliminated, a timing means for stopping the operation of a judging circuit to eliminate the operation error is unnecessary. |
