| 摘要 |
PURPOSE:To prevent lighting failure of a discharge lamp resulting from an erroneous lighting judgement. CONSTITUTION:The apparatus comprises a timer 4 for counting a preheating period. Immediately after completion of this timer 4 counting operation, a time constant circuit 5 gradually raises the control input of a control circuit 1. In relation thereto, the control circuit 1 gradually raises the level of the voltage applied to a discharge lamp La to start the lighting thereof. The apparatus further comprises a voltage detection circuit 2 and a comparator 3 for judging on the lighting of the discharge lamp La. The apparatus further comprises an AND gate G1 for taking an AND of the comparator 6 output and the comparator 3 output. By the AND gate G1 and the comparator 6, any erroneous signal is prevented from being inputted from the comparator 3 into the control circuit 1 during at least the preheating period for the discharge lamp La. |
