本研究提出一套適用於電動車系統，扮演輔助電源的直流/直流轉換器，其取代傳統汽車原有的電動機通過皮帶帶動發電機的供電，分開推進系統與輔助供電系統，提升系統效率。在轉換器中，前級降壓型轉換器提供輸入端降壓，而後半橋轉換器，藉由諧振電路使開關達到軟切換特性，降低開關損失；電氣隔離，採用兩組變壓器，一次側串聯，二次側並聯，增加降壓倍率；變壓器二次側採用橋式全波整流，使交流電轉換成直流電。此外，根據輸出電壓大小，調整前級降壓型轉換器的參考電壓，使得輸出維持27±2 V。
本論文主要貢獻包括：(1)根據轉換器規格、高壓側與低壓側電壓及諧振頻率
，提出設計流程，再經由微調修正，計算出各諧振槽元件參數。(2)採用兩級架構，前級為降壓型轉換器，後級為半橋諧振轉換器。(3)本研究研製一輸入電壓300~750 V，輸出電壓27±2 V，切換頻率500 kHz，最大額定功率2 kW的直流/直流轉換器。

This research develops a dc/dc converter which is suitable for electric vehicle systems and acts as an auxiliary power source. It replaces a conventional motor in a traditional car to supply power for electric appliance, it separates the propulsion system and the auxiliary power supply system, and improves the system efficiency. In the converter, the front-stage step-downs the input voltage, and then the half-bridge converter uses resonant circuit to achieve soft-switching characteristics for the switches and reduce switching loss. Two sets of transformers are used to achieve galvanic isolation in which the primary side is connected in series and the secondary side is connected in parallel, increasing the step-down ratio. In the secondary side of the transformer, the full-wave bridge rectifier is used to convert alternating current into direct current. In addition, according to the output voltage, the dc-link voltage of the previous step-down converter is adjusted so that the output is maintained at 27±2 V.
The main contributions of this thesis include: (1) according to the converter specifications, high-voltage side and low-voltage side voltages, resonance frequency, proposed design process, and then through adjustment, the parameters of resonant tank component have been determined, (2) adopting a two-stage architecture, in which the front stage is a step-down converter, and the rear stage is a resonant half-bridge converter. (3) Developing a dc/dc converter with input voltage of 300~750 V, output voltage of 27±2 V, switching frequency of 500 kHz, and maximum power rating of 2 kW.

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