| 摘要 |
PURPOSE:To surely detect the abnormal discharge state even when a minus side filament is abnormal by detecting the superimposition quantity of the DC power in a lighting device feeding the high-frequency power and the DC power in superimposition over it. CONSTITUTION:An AC power source AC is converted into the high-frequency power and DC power and applied to a discharge lamp l. The DC power is obtained via a diode D11 and applied to the discharge lamp 1 via an inductor L2. Current detecting resistors R1 and R'1 are inserted in series with the inductor L2 serving as a Dc power feed path, and a DC current is detected as a potential at the middle point (d) between both resistors R1 and R'l. When the minus side filament of the discharge lamp 1 is made the emissionless state, the DC current is made larger than that when both filaments Af and B are normal. The detected DC current value is compared with the reference value by a comparator IC2, and the power feed is stopped and non-lighting is detected by its output. |
