| 摘要 |
PURPOSE:To provide a discharge lamp lighting device which can surely detect failures even with variations in discharge lamps. CONSTITUTION:The switching contact SW11c of an analog switch SW11 is switched to a terminal SW11a to read the voltage Va of a capacitor 16, and the switching contact SW11 is switched to a terminal SW11b to read the voltage value Vb of a capacitor C17. The difference between the absolute values of the voltage value Va of the capacitor C16 and the voltage value Vb of the capacitor C17 is calculated to determine whether or not the difference between the absolute values is greater than a predetermined value VF2. When the difference between the absolute values is greater than the predetermined value VF2, the output of an inverter circuit 13 is lowered. When a fluorescent lamp FL comes to the end of its life, the emitters of filaments FLI, FL2 are extinguished and the fluorescent lamp FL causes a half-wave discharge, so the difference between the lamp current of the fluorescent lamp FL in one direction and that in the other direction increases; therefore, when the difference between the absolute values is greater than the predetermined value VF2, the fluorescent lamp FL is determined as being at the end of its life. |
