全球因空氣污染與能源問題，各國積極推動能源轉型策略，發展低碳、無汙染的潔淨能源。隨著車輛環保法規對於能源使用效率標準日益嚴苛，為符合高燃油效率與低二氧化碳排放的法規要求，新能源車成為國際發展趨勢。本論文旨在研製一2.5 kW雙向直流-直流轉換器模組，應用於48 V雙電池系統之輕油電混合式動力車(Mild Hybrid Electric Vehicle, MHEV)。採用氮化鎵(Gallium Nitride, GaN)功率元件，提高轉換效率及功率密度。電路架構選用四相交錯式同步升/降壓型轉換器，此架構簡單、可靠度高，具備電流漣波抵消及可實現雙向能量傳遞等優勢，且因多相式的架構，能有效降低導通損耗，適合大電流需求之應用。閉迴路控制以微控制器(Microcontroller, MCU)實現數位化之電壓、電流雙迴路控制及均流控制，可對電池實施定電流(Constant Current, CC)、定電壓(Constant Voltage, CV)之充放電策略。控制器設計與系統穩定度分析亦於文中進行探討。週邊功能結合CAN與UART通信界面，可透過個人電腦或是電子控制器(Electronic Control Unit, ECU)對系統進行監控。本論文使用PSIM模擬軟體驗證數位控制法及電路參數，並實作出一台基於氮化鎵之2.5 kW雙向直流-直流轉換器模組，峰值效率可達到97.5%。

Due to air pollution and energy issues around the world, countries are actively promoting energy transition strategies and developing low-carbon, pollution-free clean energy. With the increasingly stringent standards for energy efficiency in vehicle environmental protection regula-tions, in order to meet the regulatory requirements for high fuel efficiency and low carbon dioxide emissions, alternative fuel vehicles have become a global development trend. This thesis aims to study and implement a bidi-rectional DC-DC converter module for 48 V dual-battery system Mild Hybrid Electric Vehicle (MHEV), using GaN devices to improve the con-version efficiency and power density. A four-phase interleaved synchro-nous buck-boost converter topology is adopted. The benefits of this to-pology are simple structure, high reliability, ripple cancellation and can re-alize bidirectional energy transfer. Owing to the multi-phase structure, the conduction loss can be effectively reduced, which is suitable for applica-tions with high current requirements. The closed-loop control is imple-mented by using microcontroller (MCU). To realize digital voltage and current dual-loop control and current balancing control, and can imple-ment constant current (CC) and constant voltage (CV) charging and dis-charging strategies for the battery. Controller design and stability analysis are discussed in this thesis. The system can be monitored by using person-al computer (PC) or electronic control unit (ECU) through CAN or UART communication interfaces. In this thesis, PSIM simulation software is used to verify the digital control method and circuit parameters. A GaN based 2.5 kW bidirectional DC-DC converter module is implemented and can achieve 97.5% peak efficiency.

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