| 摘要 |
PROBLEM TO BE SOLVED: To prevent transmission of the varied voltage to voltage being applied to a lamp even if input voltage is varied by correcting luminance control voltage inputting in an inverter circuit whose input side is connected to a DC voltage source and output side is connected to the lamp, according to the varying amount of DC voltage on input side with a luminance control circuit. SOLUTION: Input voltage V1 varying in a normal lighting state of a lamp P is applied to a transformer 18 and a control IC14 within an inverter circuit 12, inputted in a differential circuit 32, the differential output (the voltage varying amount of the input voltage V1) is converted into DC with a rectifying circuit 36 through a reversing amplifying circuit 34. This DC output is adjusted in the specified level with a variable attenuation circuit 38, the voltage varying amount Vs is added to adjusting voltage 21 from a pulse DC voltage conversion circuit 26 in a suitable ratio with an adding circuit 40. If the input voltage V1 and the adjusting voltage V21 are the same polarity, subtraction is conducted. The time of a switching element 16 is corrected with corrected luminance adjusting voltage 22, and the variation of the input voltage V1 is offset. |
