准确测量大功率LED热阻的新方法

Thermal Resistance Evaluation of High Power LED

准确测量大功率LED的热阻,关键是准确地确定LED的结温增量。首先利用正向电压法获得LED的结温;通过测量LED的降温曲线,计算获得LED稳定工作时底座的温度,从而得到LED的结温相对底座温度的增量。然后,再与注入电功率相除,即可得到准确的热阻。与常规方法相比,避免了直接测量LED底座温度中界面热阻的影响,使得测量LED的热阻更加准确、方便。该方法还可以用于测量贴片封装LED等常规方法难以测量的LED以及用于分析大功率LED二次封装时引入的热阻,为评价大功率LED的封装质量提供了一种有效的评测手段。

A novel method for thermal resistance evaluation of high power LED is proposed. The junction temperature of LED chip is obtained by forward voltage method. The temperature of solder point of LED lamp is obtained through curve fitting of the dropping temperature after shutting. The difference of the two represents the thermal resistance of the I.ED. The proposed method avoids measuring the temperature of the solder point of the LED lamp, which is inevitable in common ways. The error introduced by contact thermal resistance is eliminated. The proposed method is more convenient, accurate and consistent. The proposed method is capable to evaluate the thermal resistance of surface mount LEDs （SMT-LEDs） which are difficult to test for common methods. Moreover, the method is capable to test the thermal resistance introduced by second time packaging.