高功率LED驱动器找到自己的利基

　　高功率LED驱动器找到自己的利基

　　以高容量驱动一系列高亮度LED需要精心设计，同时实现宽调光比，同时保持颜色谱。幸运的是，有一些集成的驱动程序包可以应对挑战。

　　背景

　　大功率LED的光输出已经达到了100流明/ W的关键里程碑，一些制造商在实验室中声称拥有120流明/瓦特。这意味着LED在能效方面已经超过了CFL（80流明/瓦特）。不过，据预测，到2012年底，LED将达到150流明/ W输出。此外，所有目前的重点是“绿色”，LED不包含任何危险材料，如CFL，其中有有毒汞蒸汽管内。

　　LED照明成本已经下降的很快。个别白光二极管的成本，其中一些进入LED灯泡，占成本的大部分，已经从几年前的大约5美元降到了过去十二个月不到1美元的价格。许多LED行业分析师预测，在未来12个月内，LED灯泡替代白炽灯的价格将达到消费者可以接受的水平。一些LED制造商已经声称他们已经设计了发光芯片，可以为LED灯泡供电，这种灯可以与美国家庭中常用的75瓦白炽灯泡媲美。这种类型的LED芯片通常需要12瓦的功率才能输出这种光。

　　One key performance feature that an LED driver IC must have today is the ability to adequately dim LEDs. Since LEDs are driven with a constant current， where the DC current level is proportional to LED brightness， to vary the LED brightness， there are two methods of dimming the light by controlling the LED current. The first method is analog dimming， where the LED DC current level is reduced proportionally by reducing the constant LED current level. Reducing the LED current can result in a change in LED color or inaccurate control of the LED current. The second method is digital or pulse-width-modulation （PWM） dimming. PWM dimming switches the LED on and off at a frequency at， or above 100 Hz， which is not perceivable to the human eye. The PWM dimming duty cycle is proportional to LED brightness while the on-time LED current remains at the same level （as set by an LED driver IC）， maintaining constant LED color during high dimming ratios. This method of PWM dimming can be used with ratios as high as 10，000:1 in certain applications.