选择脱机LED驱动拓扑的挑战

　　选择脱机LED驱动拓扑的挑战

　　LED阵列的驱动要求与总体设计标准相差很大。您选择的驱动拓扑也是如此。

　　当考虑将交流输入电压恒定调节电流源的LED负载LED驱动器的拓扑结构，有助于观三总功率级LED应用：低功耗应用需要小于20瓦的输入，例如，光条，r-lamps，和白炽灯；中功率下的光和l-light应用50瓦的输入；大功率标志或路灯照明要求高于50瓦的输入。设计者在这三种功率范围内面临不同的挑战，从成本、空间到LED驱动程序、效率、设计复杂度、功率因数、平均故障时间和可靠性，但其中只有一些挑战。建议在这三个基本功率范围内的基本拓扑以满足设计挑战。

　　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.