本論文主要在研製一種5千瓦，400伏特轉48伏特之高效率、高功率密度的伺服器電源供應器。為提高效率，採用串聯諧振架構來降低切換損失以及同步整流技術降低二次側導通損失。所提系統運用三相Wye-Delta架構降壓特性減少匝數比，因而減少一次側匝數及線損。三相架構同時又可以降低各相之電流應力與輸入電流和輸出電流的漣波大小。為提高功率密度，除了使用子板與插槽結構以提高空間使用效率外，並運用平板變壓器減少變壓器體積。本文同時針對Wye-Delta串聯諧振電路進行動作原理與特性分析，以助於電路設計。最後，達成長20cm、寬22cm、高4cm且滿載效率達96.07%之高功率密度轉換器。

This thesis aims to study and design a 5 kW, 400 V to 48 V high efficiency and high power-density server power supply. In order to enhance efficiency, the power supply contains an LLC converter to reduce switching loss, together with synchronous rectification to reduce secondary side conduction loss. Furthermore, three-phase Wye-Delta transformer topology is applied to reduce transformer turns ratio, therefore lower primary side turns and conduction loss. Meanwhile, the three-phase transformer is able to reduce current stress of each phase and lower the input current and output current ripple. In order to enhance the power density, daughter board and plugin structure is adopted to maximize the space utilization efficiency; besides, flat transformer is applied to reduce transformer volume. This thesis also performs the operation mode and circuit characteristics analyses on Wye-Delta-based series resonant converter for circuit design. Finally, a size LWH of 20224 cm, full-load efficiency 96.07% high power density server power supply is implemented.

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