LED结温测试方法研究

致谢

在即将完成两年半的硕士学业之际，在此首先要感谢导师牟同升老师对我的悉心指导。在硕士论文期间的每一次进步，都凝聚着牟老师的心血帮助指导。无论从学习、到工作，始终都得到导师的悉心指导和亲切关怀，使我受益颇多。牟老师严谨的治学态度、高尚的师德、活跃的学术思想，牟老师一丝不苟的科研作风以及勇于创新的精神，都将成为我毕生学习的楷模。在此，谨对导师两半年来的辛勤培养和无私的关怀表示由衷的敬意和深深的感谢。

在我硕士课程学习期间，我还得到了浙江大学信息工程学院光电系白剑、沈永行、何建军、李海峰、杨甬英、王晓萍、王秀萍等老师以及李莉、奚海燕、管信等同学还有浙大三色有限公司虞建栋、李俊凯等多位同事的无私帮助。他们热情的指导、有益的启发，对我硕士期间学习有很大促进和帮助。

感谢两年半以来一直关心和帮助过我的学院各位领导、老师，还有其他的师兄师姐。

摘要

发光二极管(LED)由于其节能效率高、寿命长、可靠性高等特点，十分符合当前低碳经济的要求，在许多领域特别是半导体照明领域中得到广泛应用。然而LED器件的热特性检测和散热是一个突出的问题，如何保持LED的结温在允许范围内，使LED始终获得稳定的光输出和维持正常的器件寿命，一直是一个当前急待解决的课题。

本文在充分调研大功率LED的结温测量方法基础上，重点研究了LED结温K系数测量方法降低测量噪声的措施以及产生的效果；同时还重点研究了脉冲电流法，该方法通过给被测LED器件注入方波电流脉冲，脉冲的电流幅度与实际额定工作电流相等，分别测量该LED器件在不同温度下的正向电压，获得正向电压与温度的敏感度系数S。因此，在实际应用中，只要直接测量LED在额定工作电流下的正向结电压，利用温度敏感系数就可得到此时LED的结温。文章重点研究了方波电流的脉宽对结温测量精度的影响，通过对12μs、24μs、50μs、100μs、150μs几种脉冲的研究，得出要使脉冲电流对结温的测量影响小于1℃，脉冲宽度控制在几个到十几个μs数量级上。文章还对脉冲电流法用于LED器件热容的测量进行了初步探索。

本文在实验论证基础上，提出了脉冲电流式LED的结温测量仪器的雏形结构，希望能为LED的结温测量有所贡献。

关键词：LED结温、噪声、脉冲电流法，热容

Abstract

LED meets the requirements of low-carbon economy because of their high energy saving efficiency,long life-time and high reliability,and it is widely used in many fields especially the fields of semiconductor lighting.However,the test of thermal performance and heat dissipation is still a prominent problem.In order to obtain stable light output and maintain normal lifetime of the devices,how to keep the junction temperature within the allowable range?This is still a burning question at present.

On the basis of making enough investigation on the measuring methods of LED junction temperature,this text mainly studies the K coefficient measuring method which can reduce the measurement noise and the effect.Meanwhile,it also studies a new method-the pulse current method which can measure the junction temperature and thermal capacity of LED device at the same time.By injecting constant narrow pulse of square-wave current to the LED devices,it will obtain the sensitivity coefficient dVF/dT of forward voltage and the temperature under a certain current. Then,by measuring the forward junction voltage under the rated current,users can use the sensitivity coefficient to obtain the junction temperature.Through the study of 12μs,24μs and50μs and other pulses whit different pulse width,it is concluded that in order to achieve the effect of pulse current on junction temperature measuring accuracy lower than1℃,the pulse width should be controlled from a few to a dozen μs.This text also makes primary exploration of the pulse current method on the thermal capacity measurement of LED devices.

Based on the experimental demonstration,this text offers a prototype structure of LED junction temperature measuring instruments with pulse current method.Hope it will contribute to the measurement of LED junction temperature.

K ey words:LED junction temperature,noise,pulse measurement,thermal capacity