功率效应对功率LED热阻的影响

分析比较了在不同输入功率条件下1 W GaN基LED样品的热学特性,得出了有效热阻随加载功率的变化规律。基于瞬态热测试方法,讨论了结-环境热阻与输入功率之间的关系。加载电流为100~500 mA的区域随着电功率增加,有效热阻明显降低;当电流增至500 mA以上时,有效热阻减小幅度越来越小;而当加载电流为900~1 650 mA时,结-环境的热阻随着电功率的增加而缓慢升高。随着注入电功率的增加,在不同电流区域同一个样品的热阻变化趋势却是相反的,这个现象归因于串联电阻热耦合随输入功率的变化。该结果对分析功率型LED热特性具有一定参考价值。

Influence of Power Effect on The Thermal Resistance of Power LED

We analyze the thermal characteristics of 1 W GaN-LED as function of input power. Based on the transient thermal measurement, the relationship of junction-ambient thermal resistance and input power is discussed. The thermal resistance and the thermal capacitance in the heat flow path can be captured by the diffe-rential structure function and cumulative structure function, offering reliable evidence for thermal management. The devices exhibit a decrease of effective thermal resistance from 14.3 K/W to 12.5 K/W when the input current increases from 100 mA to 500 mA at the heatsink temperature of 25 ℃. However the effective thermal resistance gradually decrease from 12.5 K/W to 12.3 K/W with the input current from 500 mA to 800 mA. On the other hand, when the input current increases from 900 mA to 1 650 mA, the change trend is completely opposite, while the device exhibits an increase of effective thermal resistance from 14.7 K/W to 15.4 K/W. With the same devices, the different trends of thermal resistance go with different current regions. All packaged LEDs can be simplified to the model composed of an ideal diode and a series resistance.