液晶本身並不會發光,所以需要一背光模組來做為其光源。本篇論文所做的研究就是設計一個高頻的反流器,將背光源點亮,並讓它能維持固定亮度及高效率,且探討多根冷陰極螢光燈管應用於直下式之背光模組的均流電路的設計與製作。 本文採用全橋式反流器,使得開關具備零電壓切換之性能,以達到降低功率開關之切換應力、切換損失及改善電磁干擾現象。搭配諧振電路使得變壓器匝比減少,進而提高整體效率。在傳統的均流電路中,每根燈管皆需接一迴授電路,成本較高。本文所採用的均流方法為屬於開迴路式的均流方式,不需大量迴授電路即能夠達到均流效果。調光方式採用數位調光來實現,增加調光範圍。控制IC選用LX1692,功率開關選用NIKO-SEM公司所生產的P2804ND5G、變壓器鐵芯部分選TDK公司所生產的PC40EI40-Z型式之鐵芯。 最後,對本研究的點燈系統操作特性與整體效率進行說明與量測,並且比較不同均流變壓器的均流效果,並且利用公式推導証明變壓器匝比對均流效果的影響,經實驗結果驗證其正確性與可行性。
The liquid crystal screen will not shine voluntarily, it needs a backlight module to laminate. This thesis focus on a high frequency inverter to drive CCFL to reach flexible brightness as well as the high efficiency, and discusses the balance method for multiple CCFLs driving. For this study, a full bridge inverter has been employed for less switching losses, component stresses, and electromagnetic interferences. For current-balance, Jin balancing method is adopted to avoid feedback circuit for each lamp. Finally, the test and measurement of this system is carried out to show its performance under different operating characteristics. And the experimental results confirm that it can fulfill the design purposes.