目前量測LED接面溫度的量測方法有顯微拉曼光譜法、光致發光法、電致發光法、非接觸法、順向偏壓法。目前最常被使用的為順向偏壓法，因為順向偏壓法較容易使用並具有較高的準確度。順向偏壓法容易使用於量測定電流操作的DC LED，但通過AC LED的電壓隨時間快速的改變，因此較難使用順向偏壓法量測AC LED。由於AC LED的發熱情形與DC LED在穩定的直流電操作有所差異，而目前對於AC LED之接面溫度量測方法的相關研究甚少。 為了量測AC LED之接面溫度，本論文開發出一套量測AC LED接面溫度的方法，從Shockley方程式推導出電流與溫度的線性關係。並透過實驗找出起始電壓所對應電流與溫度的關係來驗證推導的結果。利用起始電壓所對應電流的初始值與達準穩態時的電流值配合實驗量測所得的線性關係計算出AC LED之平均接面溫度與最大接面溫度。並定義了AC LED接面至基板熱阻的計算方法，以及計算AC LED有效電功率的方法。使用熱阻推算法來驗證本文AC LED平均接面溫度量測的準確度。最後利用最大接面溫度與輸入有效功率之關係推算AC LED 接面溫度隨時間的變化。 There are several methods employed to measure junction temperature using Micro-Raman spectroscopy, electroluminescence, photoluminescence, noncontact method, and forward voltage method. The forward voltage method is most popularly used today because it is easy to operate and has the better accuracy. Forward voltage method can be easily used in DC LED device due to the constant current input, but it is very difficult to be extended for measuring the junction temperature of AC LED because the AC LED device is driven by a time varying voltage. The condition of heat generation in AC LED for AC operation is different from that in DC LED for constant DC input. But little investigation on the measurement of junction temperature for AC LED was proposed. In this study, the method for measuring the junction temperature of AC LED is proposed. The linear relationship between the temperature and the input current is derived from the Shockley equation. The variation of threshold current with temperature under the threshold voltage is performed experimentally to confirm this linear relation. The average and maximum junction temperature of AC LED at the quasi-steady state can be determined by using the linear temperature dependence of the threshold current and measuring the threshold currents at both initial and quasi-steady states. The thermal resistance of AC LED and the effective input power are defined in this study. The accurate of the average junction temperature measurement can be verified by the thermal resistance of AC LED. Finally, the relation between maximum junction temperature and the effective input power can be used to calculate the junction temperature vary with time.
