單級PFC LED驅(qū)動器簡化T8燈管更換

　　照明工程師可以簡化LED管8（T8）熒光燈替代設(shè)計的單級非隔離，功率因數(shù)校正（PFC）降壓LED驅(qū)動器，可以減少元件數(shù)量，節(jié)省空間，降低成本。這種設(shè)計可以取代更昂貴的兩級拓?fù)浣Y(jié)構(gòu)，通常需要大的無源元件，難以適應(yīng)有限的管空間。

　　許多設(shè)計師使用孤立的方法，主要是出于安全考慮。在這種情況下，選擇的拓?fù)涫且粋€帶有主側(cè)反饋或調(diào)節(jié)的反激式配置。但隨著越來越多的照明設(shè)計師問如何用LED是成本有效的T8燈管燈具的設(shè)計，有一個從隔離非隔離LED驅(qū)動器由于其較高的效率，使用更少的組件。

　　設(shè)計師通常可以用單級非隔離PFC降壓拓?fù)涞玫阶罡咝У脑O(shè)計，消除了光耦和大型鋁電解電容器的輸入體。這實現(xiàn)了三件事：它增加了生命周期，減少了組件數(shù)量，降低了成本。這也使得它更容易安裝在T8的印刷電路板（PCB）。

　　There are several topologies – buck， buck-boost， and tapped buck – that can be used in single-stage PFC， non-isolated LED drivers for T8 tube designs. They all have their own advantages and trade-offs. Generally， these approaches boast high efficiency， high power factor （PF）， good total harmonic distortion （THD）， and low component counts， which translate into a lower-cost solution.

　　In terms of putting numbers to these specifications， Energy Star requirements call for a PF of at least 0.9 in commercial applications， although many designers are looking for 0.95 or 0.99. THD （EN 61000-3-2 describes harmonic content allowable in industrial/commercial power factor for lighting systems） typically must be less than 30 percent， although in many cases designers are looking for less than 20 percent and even 15 percent.