發光二極體發光光譜特性之模型建立與維持穩定

Modeling and Stabilization on Emission Spectra of Light-Emitting Diodes

周虹宇(Hung-yu Chou)

指導教授 ： 楊宗勳

國立中央大學/理學院/光電科學研究所/博士(2011年)

摘要

近年來，由於固態光源技術不斷地演進，再加上封裝製程與螢光粉材料技術持續地發展並漸趨成熟，使得發光二極體(LED, Light emitting diode)的發光效率日漸提升，由2006年的50 lm/W提升至2009年約250 lm/W，已經具有取代甚至超越傳統光源的能力。另外，搭配發光二極體的配光曲線設計對應之二次光學元件，進而衍生出各式各樣的應用光源產品諸如車頭燈、醫療用手術燈、路燈以及腳踏車燈等等。然而，發光二極體的發光特性會隨著操作時間而改變，例如發光強度的衰減和發光顏色的飄移，原因來自於伴隨著電流驅動而在發光二極體晶片內產生的熱，因此如何評估發光二極體隨著不同電源驅動條件所伴隨的熱特性，並提出有效的熱管理解決方案，使其發光特性可以有效地被掌握，進而達到光電熱整合的目標，已經成為目前最為重要的研究課題之一。
在本論文中，同時探討發光二極體的輻射光譜、驅動電流和接面溫度三種物理特性，而建立出光電熱整合的輻射光譜模型。此輻射光譜模型可藉由驅動電流和接面溫度，明確地掌握發光二極體的發光特性，例如光通量、色度和色溫等等。另外，本論文提出一套回授控制方法，使發光二極體有效地被維持在期望的發光狀態，而不受到熱特性的影響。
首先，藉由積分球量測系統所量測的各色發光二極體之輻射光譜，我們建立一個適用各色發光二極體的輻射光譜模型。另一方面，我們利用順向偏壓法建立一套發光二極體接面溫度的量測系統，使接面溫度和驅動電流得以嵌入此輻射光譜模型，以建立適用各色發光二極體的光電熱整合輻射光譜模型，其可用以預測已知驅動電流和接面溫度的輻射光譜分布，進一步得知發光二極體的發光特性。
接著，除了建立適用各色發光二極體的光電熱整合輻射光譜模型，我們進一步研究如何穩定發光二極體的發光特性。利用主動式散熱模組和適當的驅動電流，我們提出一套穩定發光二極體之發光特性的回授控制方法。由實驗結果可知，這個回授控制方法能夠有效地調控並維持發光二極體的發光特性，包括光通量、色度。

關鍵字

發光二極體，輻射光譜

並列摘要

Because of the rapid development in solid-state light technology, the luminescence efficiency of LEDs has been grown up from 50 lm/W in 2009 to 250 lm/W in 2008. LEDs have an extreme potential for future lighting. Besides, combining with the second optics component designed by the light distribution of LEDs, there are all kinds of LEDs products, such as car headlamp, light module for medical treatment, streetlight, and bike lamp etc. However, light emission properties of LEDs, for example light power and chromaticity, would be changed as the operation time goes by. The major factor caused this phenomenon is heat arisen from LEDs under electric current driving. Thus, how to effectively evaluate and manage the thermal effect to achieve an expected luminescence efficiency, is one of most important topics in LED lighting technology.
In this dissertation, an accurate model for LEDs’ emission spectra dependent on electric driving current and junction temperature is developed. Based on this emission-spectra model, light-emission characteristics of LEDs could be clearly described under different electric driving conditions, such as light power, light chromaticity and color temperature. And, in this dissertation, an effective method for stabilization on emission spectra of LEDs is proposed. Under this controlled method, light-emission characteristics could be stabilized on a steady state, and are independent on the thermal effect.
First we propose a model for precisely describing the emission-spectra distributions of various colored LED through an aid of the experimental data measured by an integrating sphere system. In addition, we developed a system for measuring the junction temperature of LEDs and made this junction temperature to be an influenced factor in this emission-spectra model. Thus, this emission-spectra model could be utilized to predict LED’s emission spectra under different electric driving current and junction temperature, and fit in with the practical situations.
Furthermore, we develop a controlled method for stabilization LEDs’ emission spectra. This method is implemented by an active-controlled heat sink and a proper electric current. As results shown, this method could not only modulate, but also stabilize LEDs’ emission spectra. Thus, the light emission characteristics of LEDs could be modulated and stabilized under this method, including light power and light chromaticity of LEDs.

並列關鍵字

emission spectra ； LEDs

參考文獻

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