驱动发光二极管：Cap还是Cap

　　驱动发光二极管：Cap还是Cap

　　高亮度发光二极管今天可以使用，其正向电流比它们的前辈大100倍以上。这些新设备不仅高亮度，而且高功率。单芯片与耗散5 W和多芯片模块与超过25瓦的功率现已。高效率和低功耗的要求决定了新一代高亮度（HB）、高功率（HP）发光二极管的开关电源，因为电压调节器和限流电阻不再合适。高亮度，高功率LED需要一个恒流源，以充分利用其不断增长的发光效率和充满活力，纯颜色。这种新型开关恒流源的拓扑结构是基本降压变换器。使用降压转换器的最有说服力的论点是将这种简单的DC/DC转换器转换成恒流源。这篇文章将解释如何选择，或可能排除的输出电容器时，设计一个降压稳压器恒流驱动的HB发光二极管。

　　Controlled current

　　The buck regulator is uniquely suited to be a constant current driver because the output inductor is in series with the load. Regardless of whether a buck regulator is used as a voltage source or a current source， selection of the inductor forms the cornerstone of the system design. With an inductor in series with the output， the average inductor current is always equal to the average output current， and the buck converter naturally maintains control of the AC-current ripple. By definition， the LED driver is a constant load system; hence a large amount of output capacitance is not necessary to maintain VO during load transients.