具同步電流倍增整流主動箝位零電壓切換順向轉換器之研製

Abstract

本論文研製一個具有同步電流倍增整流功能的主動箝位零電壓切換順向轉換器，利用諧振開關技術來取代傳統洩磁繞組及被動箝位電路，將變壓器的激磁電感及漏電感的儲能予以重複利用，以提高轉換器的效率，另一方面也可藉由主動箝位零電壓切換降低主功率元件的導通損失。去除了工作週期不得高於50 %的限制，同時利用二次側的同步電流倍增整流電路改善低壓大電流輸出時的效率。本論文詳細介紹並推導轉換器於各個階段的操作原理及等效電路，針對電路設計提出了系統化的分析及設計方法，並以IsSpice4(ICAP/4)進行模擬分析，最後以設計實例完成一個輸入電壓為48 V(變動範圍36~72 V)、輸出為3.3 V/30 A、最高效率為90.4 %的直流-直流電源轉換器，以驗證電腦模擬與理論分析的估測。

This thesis presents the design and implementation of an active-clamped ZVS forward converter with synchronous current-doubler rectifier. The active-clamped forward converter can eliminate the reset winding and passive clamp circuit used in conventional forward converter. The energy stored in the magnetizing and leakage inductance of the forward transformer can be retrieved by the active-clamped circuit. The developed control scheme can also guarantee a ZVS for the turn-on of the main switch to reduce the switching stressed and improve the converter efficiency. This active-clamped circuit can also break the 50 % barrier of the conventional forward converter. We employ a synchronous current-doubler-rectifier in the secondary winding of the forward converter to improve efficiency of the converter when operating in low-voltage heavy-load conditions. The operation principle and equivalent circuits of the active-clamped ZVS forward converter in every operating stage have be described and analyzed in detail. We also develop a systematic design procedure for the converter. Computer simulation using IsSpice4(ICAP/4) has been extensively applied in design and analyzing this active-clamped ZVS forward converter. Experimental verification has been carried out in the design of a DC/DC converter with an input of 48 V (ranged from 36~72 V), an output of 3.3 V/30 A, and a maximum efficiency of 90.4 %.