同步整流降壓式轉換器之新型控制策略

本文提出一提高同步整流降壓式轉換器輕載效率的控制策略。同步整流的控制技術適用於直流低壓的輸出上，因為以MOSFET取代輸出整流器的二極體，且MOSFET具有較低導通損失，可以大幅提升整體電路效率。但在輕載條件時的效率，電感電流會產生負電流造成損失增加。因此本文提出具有限頻功能的波谷切換技術，提高同步整流降壓式轉換器的輕載效率。利用電容充放電所產生的電壓漣波模擬電感電流漣波，因此不需任何電流感測器，即可判斷電感電流的零點位置。而且為了避免波谷切換的頻率過高，採用555計時器來完成頻率的限制。本研究具有簡單的控制方式、低成本和體積小等優點。一組輸出電壓5V來判斷電感電流的零點，且輸出功率25W並具有同步整流技術的降壓式轉換器架構被發展出來，透過實驗結果確認了本文所提技術的可能性，驗證所提控制策略之可行性。

關鍵字

輕載效率；同步整流；降壓式；波谷切換

並列摘要

The control strategies for improving the efficiency of synchronous rectifier buck converter light load control strategies. Synchronous rectification control technique is suitable for DC low voltage at the output, as replaced by the MOSFET output rectifier diodes, and lower MOSFET conduction loss can significantly enhance the efficiency of the whole circuit. But the efficiency during light load conditions, the negative current of the inductor causes increase losses. Therefore this article has proposed limiting the troughs of frequency-limited valley switching technique, improved light load efficiency of synchronous rectifier buck converter. Use the voltage of the capacitor charge and discharge simulation inductor current ripple to ripple and therefore do not require any current sensors, and judge the current zero point. And in order to avoid the trough switching frequency is too high,555 timer is used to complete the limitation of frequency. This study has advantages simple control, the determines the zero position of the inductor current. Low cost, and small size. A set of output voltage of 5V inductor current is zero output power. A 25W with synchronous rectifier buck converter structures has been developed,According to the experimental results and whit the possibilities of this technology is recognized, and also the feasibility of the proposed strategy is verified.

並列關鍵字

light-load efficiency ； synchronous rectifier ； buck ； valley switching

參考文獻

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[25]. 江成忠，“具同步整流輸出之返馳式轉換器”，中原大學電機工程學系碩士班，民國九十五年。

[3]. A. I. Pressman, “Switching Power Supply Design,” Sencond Edition, McGraw-Hill,1998.

[4]. 吳健銘，“降壓同步倍流整流半橋轉換器之研究”，國立成功大學大學電機工程系碩士班，民國九十三年。

[6]. Nobuhiko Yamashita,Naoki Murakami,and Toshiaki Yachi, “Conduction Power Loss in MOSFET Synchronous Rectifier with Parallel-Connected Schottky Barrier Diode, ?IEEE Transactions on Power Electronics, Vol. 13, NO. 4,pp.667-673, July 1998.

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同步整流降壓式轉換器之新型控制策略

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