本文提出一種三相交錯式直流對直流降壓轉換器之電路架構，係由三個相同之降壓式轉換器並聯運轉。與一般降壓轉換器不同處在於各個轉換器間各以一諧振電感相互連接，並且利用準諧振之原理，讓額外加上之諧振電感與開關寄生電容諧振，達到主動開關零電壓導通之條件；且完成飛輪二極體的零電流截止，可以減輕二極體的反向恢復損失。其次，並聯架構可以均分在各個轉換器上的電流，提供較大的輸出功率。而主動開關以交錯式脈波寬度調變控制，可以降低輸入及輸出的電流漣波，減輕濾波電容的需求，進而提升功率密度。最後，本文設計一150 W的具零電壓切換之三相交錯式降壓轉換器，輔以傳統降壓式轉換器之原理及軟體模擬結果，分析轉換器的電路特性方程式及操作模式，實際量測平均效率達97%。

This thesis proposed an interleaved three-phase DC-DC buck converter which is composed of three identical paralleled buck converters. Compared to the conventional paralleled buck converter, the proposed solution has three resonant inductors connected between each other of the three converters. By making use of the principle of quasi-resonant converter, the imposed inductors and the MOSFET parasitic capacitances will resonate to achieve zero-voltage-switching. Besides, the current through the free-wheeling diodes can be zero-current turned off to minimize their reverse-recovery losses. Paralleled topology can help sharing the load currents on each converter and is able to provide higher output power. MOSFETs are controlled by interleaved PWM (Pulse-Width-Modulation) signals to reduce the ripples of input and output currents. Therefore, the filtering capacitances on the input and output sides can be reduced and the power density can be improved. Circuit operation analyses, characteristic equations and simulations are given to understand the circuit. Finally, a 150W three-phase interleaved buck converter is designed, implemented and tested. According to the experimental results, high conversion efficiency over 97 % can be achieved.

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