基于光谱法的发光二极管稳态热阻测量方法

Steady-state thermal resistance measurement of light-emitting diodes based on spectroscopic method

根据白光发光二极管(LED)发光光谱特点,通过分析蓝光光谱和由蓝光激发黄色荧光粉产生的黄光光谱的交点(即整个光谱的波谷点)特性,利用常规可见光光谱仪设计了一套基于光谱法的LED稳态热阻测量系统,采用正常的驱动电流通过一定的函数算法进行拟合,得到整体光谱波谷处归一化光谱强度与结温间敏感系数K和定标函数,再根据温升曲线可计算出任意工作状态下LED结温相对于基底的温升,并结合LED的热耗散功率从而得到LED的稳态热阻.本方法避免了类似正向压降法采用极小电流定标而需要高速数据采集模块和高速取样转换等模块导致的设备昂贵的缺点,从而降低了成本.最后采用本文设计的系统和美国Mentor Graphics公司的T3Ster仪器分别对多种LED进行测量并对结果进行了比较,发现稳态热阻最大偏离度仅为3.64%.表明本文设计的系统和方法在不需要昂贵设备的情况下便可以达到与Mentor Graphics公司的T3Ster仪器相仿的精度.本方法采用非传统式光谱法测量,具有可远程实时在线检测LED结温和低成本的特点,对LED封装结构没有任何限制,因此比Mentor Graphics公司T3Ster设备采用的电压法有更广的应用范围,具有一定的实用价值.

According to the luminous spectrum characteristics of white light emission diode(WLED)light emission spectrum,through the analysis of the intersection(the trough point of the whole spectrum)of blue light spectrum and yellow light spectrum generated by blue light excited yellow phosphor,in this paper we design an LED steady-state thermal resistance measurement system based on the spectroscopic method by using the conventional spectrometer,and we also use the normal driving current to fit the whole spectrum trough through a certain function algorithm.According to the temperature rise curve,we can calculate the temperature rise of the LED junction temperature relative to the substrate under any working condition,and combine the heat dissipation power of the LED to get the steady-state thermal resistance of the LED.This method avoids the limitation of a similar forward voltage drop method which uses the minimum current calibration and requires the modules of high-speed data acquisition and high-speed sampling conversion,thus making the equipment expensive.Therefore it is necessary to reduce its cost.Finally,the system designed in this paper and the T3Ster instrument of Mentor Graphics Corporation in the United States are both used to measure various LEDs and their results are compared with each other.The results show that the maximum deviation of steady-state thermal resistance is only 3.64%.It indicates that the system and method designed in this paper can achieve the same precision as T3Ster instrument of Mentor Graphics Corporation,demonstrating that the system and method designed in this paper can achieve the same precision as the T3Ster instrument of Mentor Graphics,under the condition without needing expensive equipment,Moreover,this method uses non-traditional spectral method to measure the junction temperature of LED,which has the characteristics of remote real-time online detection of LED junction temperature,low cost,and no restrictions on the LED packaging structure.Therefore,this method has a wider application range than the voltage method adopted by Mentor Graphics T3Ster equipment,and has a certain practical value.