在切換式電源供應器中，升壓型轉換器現今已廣泛應用於各種高壓電源設備。此外，近年來由於能源危機導致各國致力於推廣太陽能、風力與燃料電池等潔淨式再生能源，而其中太陽能及燃料電池等低電壓輸出能源也需要高升壓比轉換器將其電壓提高以供後級應用。本論文即針對此點提出一新型高升壓比轉換器。
本論文的主要貢獻有三點。首先，本文提出一新型半共振式高升壓比直流轉換器，該新型轉換器具有高升壓比、元件數較少及不需添加額外磁性元件只使用一變壓器即可達到儲能、電流共振與柔性切換等特點。此外，其與傳統半共振式轉換器不同之處在於，所提新型轉換器是利用隔離變壓器一次側之漏電感與二次側等效串聯電容進行半共振，可達到所有主動開關均具有零電壓切換(Zero Voltage Switching)與所有二極體皆有零電流切換(Zero Current Switching)之柔性切換效果。第二點貢獻則是針對新型轉換器直流電路特性進行分析，且進一步推導出小訊號數學模型以方便補償器設計。第三點貢獻則依據理論分析的結果，實際製作一輸入電壓30V、輸出電壓400V以及輸出功率150W之雛型系統以驗證新型轉換器的可行性。經由電路模擬與實測結果顯示本論文所研製之新型轉換器，其能夠有柔性切換之特性，其電源轉換效率於30W至150W的負載情況下均為91%以上，負載在60W時效率最高可達到95%，以此驗證該新型轉換器之可行性與優越性。

High voltage DC converters have now been widely used in various high-voltage applications. In addition, in recent years due to energy crisis and environmental impact a lot of efforts have been made to promote various clean energy such as photovoltaic(PV), wind energy, and fuel cells(FC). For the PV and FC low output voltage energy sources, they reguire a high step-up ratio converter to raise their voltage for proper applications. Hence, the objective of the thesis is forcused on developing a novel high step-up DC/DC converter.
The main contributions of this thesis may be summarized as follows. First, a new qusai-resonant high step-up DC/DC converter topology is proposed. The new converter has characteristics like high step-up ratio, fewer components, with leakage inductor energy recycled, current resonance and soft switching. In addition, compared the new converter with a traditional qusi-resonant converter it is seen that the new converter uses the isolation transformer leakage inductance of the primary side and the secondary side equivalent series capacitor as the resonant tank such that all the active switches can achieve zero voltage switching and all diodes can achieve zero current switching. The second contribution includes the derivation of DC and AC models of the proposed converter and analysis of fundamental characteristics of the new converter. The third contribution is the construction of a 150W prototype with an input voltage of 30V and the output voltage of 400V for verifying the feasibility of the new converter. It is found that this converter can indeed achieve soft switching characteristics and the power conversion efficiency from 30W to 150W is more than 91%. Also, the corresponding measured maximum efficiency is 95% when the load is 60W. Both simulation and experimental results agree with each other very closely.

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