選擇脫機LED驅動拓撲的挑戰

　　LED陣列的驅動要求與總體設計標準相差很大。您選擇的驅動拓撲也是如此。

　　當考慮將交流輸入電壓恒定調節電流源的LED負載LED驅動器的拓撲結構，有助于觀三總功率級LED應用：低功耗應用需要小于20瓦的輸入，例如，光條，r-lamps，和白熾燈；中功率下的光和l-light應用50瓦的輸入；大功率標志或路燈照明要求高于50瓦的輸入。設計者在這三種功率范圍內面臨不同的挑戰，從成本、空間到LED驅動程序、效率、設計復雜度、功率因數、平均故障時間和可靠性，但其中只有一些挑戰。建議在這三個基本功率范圍內的基本拓撲以滿足設計挑戰。

　　The low-power solutions targeting small lamp sizes require small design volumes to fit the LED driver， consistent light radiation by controlling the current through the LED， efficiency， and low cost. In order to be compliant with Energy Star Program Requirements for Luminaires， the light fixture must have a power factor ≥0.7 for residential applications and ≥0.9 for commercial applications for input power greater than five watts.1 If isolation from the LED driver is not required， a buck regulator topology is the lowest BOM and therefore a low cost solution to consider. Figure 1 is a non-isolated buck topology example which also includes power factor correction and dimming capability. There is only one magnetic component， which is a simple inductor and a single MOSFET/diode pair for buck power conversion. This topology choice is best selected when the input voltage is larger than the output voltage required from the LED load.