led热管理研究进展

　　led热管理研究进展

　　LED在市场营销材料中通常被描述为“酷”的照明，实际上LED是很酷的触摸，因为他们一般不产生热的形式，红外线（IR）辐射。另一方面，LED在二极管半导体结构中产生热量（除了光子），这种热量必须通过传导和对流离开系统。因此，灯具设计者必须意识到潜在的散热挑战，以及这些挑战如何影响LED性能、寿命，甚至灯具的安全性。

　　高结温已被证明导致LED产生较少的光（流明输出）和更少的正向电压。随着时间的推移，更高的结温也可能显著加速芯片的退化，可能在正常使用时从100°C增加到135°C，增加75%。

　　工程师和材料科学家已经并且正在开发新的LED相关的热管理解决方案，包括改进的驱动程序、膜片驱动的强制对流方法、更好的散热装置，甚至引入石墨泡沫作为冷却介质。本文将首先描述三个结温的考虑——基本热阻、功耗和结温测量——然后简要地看一下上述改进LED热管理的每一种方法的进展。

　　Junction temperature considerations

　　When considering LED thermal management， there are generally three factors that tend to act on junction temperature. These are the ambient air temperature， the thermal path between the LED junction and the surrounding environment （the thermal path， of course， should be optimized to encourage natural heat convection） and the LED‘s efficiency.

　　Ambient temperatures will vary by application， so that luminaire designers will want to pay attention to how designs will be used in real world environments. For example， a few years ago the Rensselaer Polytechnic Institute’s Lighting Research Center and the Alliance for Solid-State Illumination Systems and Technologies experimented with LEDs in various open air， semi-ventilated， and enclosed environments. Board temperatures for a 12-watt LED reached 60°C in the enclosed environment， a 26-watt LED‘s board temperature rose to 119°C.

　　As for efficiency， LED efficiency will vary based on several factors with some devices converting as much as 80 percent — or perhaps even more — of the input electrical power to heat. Efficiency becomes more of an issue as LEDs increase in power. For example， when LEDs were primarily used as indicator lights， current levels were only a few milliamps whereas hundreds of milliamps or even amps are becoming commonplace in present day applications.