本文提出一種應用於多管冷陰極螢光燈之循環式數位調光技術,主要是將傳統的調光控制電路及數位調光技術(digital dimming)相互結合,達到循環調光之效果。數位調光技術是將冷陰極螢光燈操作在額定電流振幅的情況下,控制低頻調光信號的責任週期來調變燈管的平均亮度,此種調光技術可有效降低漏電流效應,並大幅增加調光範圍;其次,傳統的調光控制器則是藉由循環式的邏輯信號來控制亮度。而本文將上述兩種技術結合,藉由開關的循環切換來調整低頻調光信號之責任週期,以實現冷陰極螢光燈循環式數位調光的功能。最後由實驗結果證明所提理論之正確性。
This thesis proposes a circulating digital dimming technique for multiple cold cathode fluorescent lamps. The proposed method integrated the conventional dimming control circuit and digital dimming technique to achieve circulating dimming control. Digital–dimming control is used to modulate the average brightness of the CCFLs by adjusting the low frequency dimming signal under rated lamp current. Therefore, this method can reduce leakage current and widen the dimming range. Moreover, the conventional dimming control circuit can adjust lamp brightness by a circulating logic signal. The proposed circuit integrated these two techniques to adjust the duty cycle of the low frequency dimming signal by switching circulating logic signal, and then to achieve the circulating digital dimming function. All the experimental results are used to verify the feasibility of the proposed system.