單級AC/DC LLC諧振式轉換器分析與設計

Analysis and Design of Single-Stage AC/DC LLC Resonant Converter

李竹容(Zhu-Rong Li)

指導教授 ： 陳秋麟

國立臺灣大學/電機資訊學院/電子工程學研究所/碩士(2009年)

https://doi.org/10.6342/NTU.2009.00682

摘要

一般市售的電源轉換器，通常在轉換器前端加入一級功率因數校正(PFC)電路，以通過諧波測試標準的規範。如此不僅降低了能量轉換的效率，也提高了電路製作的複雜度與成本。
LLC諧振轉換器架構簡單，具有高效率、低雜訊的特性，逐漸應用在各種系統之中。它有別於傳統PWM轉換器，上下橋MOSFETs切換的責任週期皆為50%，藉由改變切換頻率的方式調節能量。設計上通常讓LLC工作於增益頻譜圖的ZVS區，該區間的LC共振腔呈現電感性，在工作頻率較低時增益較大，可傳送較多能量。
本論文提出整合PFC與DC-DC的單級LLC諧振轉換器。前半級為傳統boost架構，後半級為LLC電路的變形，LLC電路的下橋MOSFET同時作為前半級PFC的開關。上下橋MOSFETs的控制方式依然為LLC電路所使用的頻率調變，在負載較大時，開關切換頻率降低，LLC電路的增益較大；PFC電路則因電感充電時間較長，傳送較多能量。由於責任週期固定為50%，PFC電路工作於不連續模式(DCM)。如此架構省去了PFC電路開關及其控制迴路，在能量散失和成本上皆有所改善。為達到前半級與後半級能量轉換的平衡，LLC工作區間有別於傳統，本論文提出一種LC共振腔的元件值的計算方法，解決電路中儲能電容電壓漂移的問題。
最後，實作電路與理論相互驗證。

關鍵字

單級 ； 諧振轉換器 ； 功率因數 ； 總諧波失真

並列摘要

A conventional power supply was designed with two stages, the former stage function as a power factor corrector (PFC), and the latter stage is a DC/DC converter which regulates the output voltage of the system. However, the cost and energy conversion efficiency of the two-stage system is higher than a single-stage one.
LLC resonant converters not only have characteristics of high efficiency and low noise but also are easy to control. This circuit topology is becoming more and more widely used in application of power conversion. The duty cycle of both MOSFETs of a LLC converter is 50% that is different from a traditional PWM converter. The output regulation is control by modulation of frequency, in the ZVS region, the energy from primary side to load increases as the switching frequency decreases.
In this thesis, a single-stage LLC resonant converter which combines a boost-type PFC cell and an LLC resonant DC/DC cell is proposed. The control method of it is the same as a conventional LLC resonant converter that regulate output voltage by modulating switching frequency. When the load increases, the switching frequency decreases so that the LLC gain increases and more energy can be transferred by input inductor due to longer charging time. The proposed circuit could not only reduce components and circuit size but also increase the power conversion efficiency.
It has no control of the voltage of the DC-bus capacitor because there is no separate converter that can control it as there is in a two-stage converter. The capacitor voltage is dependent on the energy equilibrium established between the energy flowing into the capacitor from the input inductor and the energy flowing out of the capacitor and transferred to the output. Therefore, the characteristics of LLC tank are investigated and a new LLC design consideration is proposed, which insures the DC-bus capacitor voltage can be kept in a tolerable region.
Finally, an experimental circuit is implemented to verify the analysis.

並列關鍵字

single-stage ； LLC resonant converter ； power factor ； total harmonic distortion

參考文獻

[1] G. Moschopoulos and P. Jain, "Single-phase single-stage power-factor-corrected converter topologies," IEEE Trans. Industrial Electronics, vol. 52, no. 1, pp. 23-35, Feb. 2005.

[3] R. Redl, L. Balogh, and N. O. Sokal, "A new family of single-stage isolated power-factor correctors with fast regulation of the output voltage," in Proc. Power Electronics Specialists Conference, pp. 1137-1144, Jun. 1994.

[4] Q. Mei, G. Moschopoulos, H. Pinheiro, and P. Jain, "Analysis and design of a single stage power factor corrected full-bridge converter," in Proc. Applied Power Electronics Conference and Exposition, pp. 119-125, Mar. 1999.

[8] Y. Bo, C. Rengang, and F. C. Lee, "Integrated magnetic for LLC resonant converter," in Proc. Applied Power Electronics Conference and Exposition, pp. 346-351, Mar. 2002.

[9] H. Choi, "Analysis and design of LLC resonant converter with integrated transformer," in Proc. Applied Power Electronics Conference, pp. 1630-1635, Feb. 2007.