当前的LED技术提供了与MR16相容、高度可靠、具有高性价比的卤素灯替代品.例如,LedEnginTM公司的新一代5W(单片,4mm×4mm封装)和10W(四片,7mm×7mm封装)大功率LED,在电流为1000mA、结温(TJ)+120℃时,具有45lm/W的典型光效.实际工作条件下,5W封装相当於155lm的典型光输出通量(电流为1000mA,结温TJ=+120℃时),而10W封装提供345lm的典型光输出通量(电流为700mA,结温TJ=+120℃时).当LED产生与卤素灯相同的亮度时,功耗大约降低50%.此外,LedEngin即将推出具有高达90%发光效率(100khr,结温TJ=+120℃时)的LED,在整个产品的有效使用期内无需更换灯泡.
MR16 LED的参考设计
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图1. 采用MAX16820 LED驱动器构建的5W MR16 LED灯驱动电路.图中LED为LedEngin的5W WLED.
在图1所示MR16 LED参考设计中,Maxim选择LedEngin的5W白光LED(WLED),用於演示MAX16820的1000mA电流驱动能力.表1和表2列出了详细的MR16参考设计的元件和电气参数,该参考设计采用大多数MR16应用中的12VAC±10%典型输入电压.
MAX16820是针对LED驱动应用,特别是基於LED的MR16而设计,是MR16LED灯电路的理想选择.MAX16820采用超小型、6引脚TDFN封装,工作在4.5V至28V输入电压,能够驱动外部高性价比MOSFET,以提供宽范围的LED电流驱动能力.MAX16820工作在汽车级温度范围(-40℃至+125℃),可安全工作於MR16灯具的高温环境中.此外,MAX16820还可提供高达25W或更高的功率,其2MHz(典型值)的开关频率允许使用小尺寸外部电感和电容,使驱动电路可以放置到MR16灯具内.
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