冷陰極燈管CCFL驅動電路設計與分析

Abstract

本論文採用1955年由Royer發明的推挽式共振架構作為設計的基礎。負載冷陰極燈管CCFLs由於具有高發光效率與低功率消耗特點，因此廣泛被使用在照明設備上，然而CCFL燈管具有非線性負載特性，因此驅動電路的設計便是系統效率與穩定的關鍵。CCFL燈管的驅動可以使用直流電源，但是為了確保燈管的效率以及使用壽命，交流電源是被建議採用的，然而交流電源的產生有很多種方法，我們採用的是推挽式(push-pull)架構，使用推挽式的理由一來可以透過兩顆電晶體輪流的切換分攤切換時電晶體產生的熱量；二來使用自然諧振的方法與切換式換流器比較起來可以降低EMI電磁干擾效應。我們在本論文中提出兩個驅動電路的架構，分別為Type I及Type II，根據實驗結果，其中Type II架構不論在長度120mm燈管或170mm燈管上的效率都達到九成。

In the thesis, the Royer push-pull resonant scheme developed by Royer in 1955 was employed and modified. Since the load, CCFLs, have high optical efficiency and low power demanded, CCFLs are widely used in illumination. Nevertheless the CCFL lamps have non-linear I-V character. Thus, to design a driving circuit which can operate the whole system in high efficiency and stability is the primary objective. CCFL lamps can be driven with DC power source, but to obtain high light efficiency and long lifetime, AC power source is recommended instead of DC source. To generate an AC output; a switched push-pull output stage is proposed. This circuit style has two advantages: (1) Two transistors are switching in turn. Therefore the transistors will have lower temperature rising. (2) Using oscillation function, the electro-magnetic interference (EMI) can be greatly reduced. We have proposed two driving circuit schemes in the thesis, Type I and Type II respectively. The results of experiment have shown that the efficiency on Type II can achieve 90% while 120mm and 170mm length lamps were used as loads.