led熱管理研究進(jìn)展

　　LED在市場營銷材料中通常被描述為“酷”的照明，實(shí)際上LED是很酷的觸摸，因?yàn)樗麄円话悴划a(chǎn)生熱的形式，紅外線（IR）輻射。另一方面，LED在二極管半導(dǎo)體結(jié)構(gòu)中產(chǎn)生熱量（除了光子），這種熱量必須通過傳導(dǎo)和對流離開系統(tǒng)。因此，燈具設(shè)計(jì)者必須意識到潛在的散熱挑戰(zhàn)，以及這些挑戰(zhàn)如何影響LED性能、壽命，甚至燈具的安全性。

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

　　工程師和材料科學(xué)家已經(jīng)并且正在開發(fā)新的LED相關(guān)的熱管理解決方案，包括改進(jìn)的驅(qū)動程序、膜片驅(qū)動的強(qiáng)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(zhì)。本文將首先描述三個(gè)結(jié)溫的考慮——基本熱阻、功耗和結(jié)溫測量——然后簡要地看一下上述改進(jìn)LED熱管理的每一種方法的進(jìn)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.