本論文主旨為高功率密度條件下使用對稱諧振槽之雙向轉換器的研製與探討。對比於傳統諧振式轉換器，本文提出一對稱式諧振槽架構，搭配變壓器一次側與二次側全橋同步開關之動作，同時藉由外加電感之電流使變壓器二次側開關達成零電壓切換，以降低二次側開關之切換損耗並提升效率。本文一開始對新型對稱諧振槽之雙向轉換器的架構動作及原理進行分析，並考量應用於直流變壓器之設計條件下，對轉換器與傳統諧振式轉換器的零電壓切換條件、諧振槽設計及開關訊號控制做比較。另外，針對高功率、高切換頻率條件下設計及選用可靠之功率電晶體、開關驅動電路與諧振槽元件及電路佈局。最後實作完成一台尺寸長寬高為160x100x100mm，功率密度為11.25W/cm^3，操作頻率為300kHz，輸出功率為18kW之轉換器。其效率於高壓輸入條件下，半載可達98.3% ，滿載效率為98.2%，並測試在功率潮流變化下，轉換器可達成功率潮流自然換向之功能，並將實測結果與模擬相互驗證。

The thesis focuses on design and implementation of a bidirectional converter with symmetrical resonant tank in high power-density condition. To compare with traditional resonant converter, the new structure with symmetrical resonant tank and using synchronous controlled on primary-side and secondary-side switches, and by the current of additional inductor helps the secondary-side switches achieve the zero-voltage switching (ZVS) operation, also reduces the switching loss and improve the efficiency. Firstly, the analysis of circuit theories and operation principles are discussed. Considering application for dc transformer, the requirement of ZVS operation, design of resonant tank, and controlled signal of switches of purpose converter and traditional resonant converter are compared. Besides, the design and selection of power MOSFET, gate driver, resonant tank, and circuit layout are purposed. Finally, an 18kW prototype circuit was implemented, the size of converter is 160 x 100 x100 mm, power density is 11.25W/cm^3, and the operation frequency is 300kHz.Under the high input voltage condition, the efficiency 98.3% at 50% load, and 98.2% at full load. Under the condition that direction of power flow changed, the current flow of converter is also changed naturally, and the simulate results are verified with the experimental results.

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