LLC諧振轉換器低頻響應之分析與評估

Analysis and Evaluation of Low-Frequency Response of the LLC Resonant Converter

張文翰(Wen-Han Chang)

指導教授 ： 吳黎明

健行科技大學/電資學院/電機工程系碩士班/碩士(2015年)

https://doi.org/10.6824/UCH.2015.00061

摘要

本論文提出一種創新的第三次頻控制方法，進行LLC諧振式電力轉換器之輕載效率改善研究。該方法係於LLC諧振式電力轉換器處於輕載時，以第二諧振頻率之第三次頻為切換頻率，以其三倍頻諧波能量較低而適用於輕載。所提方法具有低頻操作及零電壓切換特性，故於輕載時可保高效率，此外，相較於傳統的突衝模式，本方法不需添加額外控制電路。為驗證所提方法，本論文設計並實作一組180W/380Vin/19Vo LLC諧振轉換器，分別利用類比控制晶片 TL494與L6599，以及數位信號處理器TMS320F28035進行低頻控制與適用性探討，在實驗條件下，證實所提方法可明顯提升輕載效率，轉換器於3.13% 輕載的效率可由高頻切換的28.5%提升至三次頻切換的85.4%，效率提升約3倍。

關鍵字

LLC諧振轉換器 ； 零電壓切換 ； 低頻調變 ； 轉換器效率

並列摘要

This thesis proposes a novel third order sub-harmonic frequency control method to deal with the light load efficiency improvemet in LLC resonant power converter. The working principle of the method is that, when LLC resonant converter is lightly loaded, the third sub-harmonic of the second resonant frequency is adopted as the switching frequency. Since the sub-harmonic contains less enegy in its high-order harmonics, the resonant converter delivers only energy that is enough for light load after filtering out unwanted harmonics, therefore the proposed method is suitable for light load applications. Advantages of the method include low frequency operation and zero voltage switching, both are factors important to high efficiency. In addition, compared to traditional Burst Mode control, the proposed method requires no additional circuits for implemention. To verify the method, a 180W/380Vin/19Vo LLC resonant converter was designed and constructed, in which control ICs TL494, L6599, and DSP TMS320F28035 were applied respectively to investigate their suitability for low frequency. As a result, experiments showed that the proposed method is able to bring significant improvement in light load efficiency. Under 3.13% load condition, the third sub-harmonic frequency control gives converter efficiency 85.4%, compared to 28.5% for high frequency control, an improvement of 3 times high.

並列關鍵字

LLC resonant converter ； Zero voltage switching ； Low frequency modulation ； Converter efficiency

參考文獻

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