led熱管理研究進展

　　LED在市場營銷材料中通常被描述為“酷”的照明，實際上LED是很酷的觸摸，因為他們一般不產生熱的形式，紅外線（IR）輻射。另一方面，LED在二極管半導體結構中產生熱量（除了光子），這種熱量必須通過傳導和對流離開系統。因此，燈具設計者必須意識到潛在的散熱挑戰，以及這些挑戰如何影響LED性能、壽命，甚至燈具的安全性。

　　高結溫已被證明導致LED產生較少的光（流明輸出）和更少的正向電壓。隨著時間的推移，更高的結溫也可能顯著加速芯片的退化，可能在正常使用時從100°C增加到135°C，增加75%。

　　工程師和材料科學家已經并且正在開發新的LED相關的熱管理解決方案，包括改進的驅動程序、膜片驅動的強制對流方法、更好的散熱裝置，甚至引入石墨泡沫作為冷卻介質。本文將首先描述三個結溫的考慮——基本熱阻、功耗和結溫測量——然后簡要地看一下上述改進LED熱管理的每一種方法的進展。

　　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.