降壓調節器使驅動高亮度LED容易

　　“垃圾輸入，垃圾輸出”不只是適用于計算機編程。LED產生的光的質量直接關系到驅動器的電壓和電流的質量，這使得驅動電路和發射器一樣重要。對于低亮度LED，線性調節器通常可以完成這項工作。高亮度應用提出更嚴格的性能規格，促使工程師選擇更先進的解決方案，如開關穩壓器，開關電容轉換器或反激式轉換器。在這個組中，降壓開關降壓開關通常是首選，因為它們簡單、高效且易于穩定。當適當地指定和設計成一個系統時，降壓調節器可以提供令人印象深刻的成本/效益性能。

　　LED是直接帶隙半導體，其輸出隨電壓的變化而非線性變化（圖1）。閾值電壓，或正向電壓（VF），從設備到設備的任何類型的LED略有不同。即使是單個設備，VF也會隨溫度和年齡的變化而漂移。相反，作為驅動電流函數的輸出對于任何設備都是線性的，所以用恒流源驅動led提供最佳性能。

　　Figure 1： LED current varies nonlinearly with respect to voltage. （Courtesy： RECOM）

　　Drive circuitry is often an afterthought， especially for lighting designers. Focusing on the illumination aspects of the design and leaving the power aspects for the end may compromise performance and manufacturability.

　　“［Designers］ want to make their fixture look a certain way and generate a certain amount of light，” says Alex Craig， application systems engineer for lighting， Fairchild Semiconductor. “As a result， they might put six LEDs in parallel， but six LEDs in parallel are likely not as efficient as six LEDs in series.” Smart engineers take a holistic design approach by developing an efficient lighting configuration that lends itself to common power topologies.