| 摘要 |
PURPOSE:To prevent erronous operation of an abnormality discrimination circuit in a variable period of a light adjustment condition. CONSTITUTION:A dc power fed from a dc power source E is inverted into high frequency power by an inverter circuit 1, and a discharge lamp La is lighted at high frequency. The high frequency power fed from the inverter circuit 1 to the discharge lamp La is changed by a light adjustment control circuit 4, and the light of the discharge lamp La is adjusted and the lamp is lighted. The abnormality of the discharge lamp La is discriminated by an abnormality discriminating circuit 3 based on the lamp voltage of the discharge lamp La, and the oscillation operation of the inverter circuit 1 is stopped. It is inhibited by an AND gate G1 that the output of the abnormality discriminating circuit 3 is input into the inverter 1, in a period when the light adjustment condition is varied, and erronous operation by which the oscillation operation of the inverter circuit 1 is stopped, is thus prevented. |
