本論文針對具寬範圍輸入電壓穩壓之隔離型直流/直流轉換器進行優化，並選擇串聯諧振轉換器作為本論文架構。在大瓦數的應用下，操作於LLC SRC模式之串聯諧振轉換器因解耦區間的緣故，其二次側開關的導通損耗會大於操作於SRC模式之串聯諧振轉換器。因此本論文選擇具有一次側開關零電壓切換特性之串聯諧振轉換器SRC模式做為電路架構，並搭配二次側開關訊號的相移控制，在特定動作區間下，輸入電源直接對諧振槽儲能，以此來解決SRC模式電壓增益低於1的問題。電路的設計採用寬能隙元件氮化鎵取代矽元件降低功率開關的截止損耗。本論文提出新型五柱式變壓器結構與三柱式電感結構，並利用ANSYS Maxwell模擬驗證鐵心模型在損耗計算上的差異，接著針對平板式繞線其鄰近效應與集膚效應進行分析與比較。根據鐵心磁通分布來優化鐵心結構，並分析不同繞組排列結構以此降低磁動勢進而降低交流阻抗損耗。並且將磁性元件以鐵心參數化的形式設計，在不同的鐵心尺寸下得到最佳的損耗設計點；對於五柱式變壓結構更是提出新式的繞線方法，在維持預期圈數比的前提下，有效降低繞線長度，且大幅度降低銅損。最後結合ANSYS Maxwell和參數化形式優化邊緣磁通對於鐵心繞線損耗影響。最終實現輸入電壓為36 V - 60 V、輸出電壓為380 V，輸出功率為3 kW、最高效率為96.7%寬增益型諧振式直流/直流轉換器。

This dissertation proposes an optimization method for an isolated DC-to-DC converter with a wide voltage range and the series resonant converter topology. Moreover, in high power applications, the conduction loss of the secondary side switch of the LLC series resonant converter will be greater than that of the SRC. Therefore, the prototype for this dissertation uses the series resonant converter to achieve zero-voltage switching of the power devices on the primary side and reduce the conduction loss of the power devices on the secondary side. In order to solve the problem that the voltage gain of the SRC is lower than 1, this dissertation applies the phase shift control on the secondary-side power devices to let the input voltage source directly store energy in the resonant tank at the specific operation intervals. The design of the circuit adopts wide bandgap devices instead of silicon devices to reduce the turn-off loss of the power devices. This dissertation proposes a novel five-leg transformer structure and a three-leg inductor structure, and uses ANSYS Maxwell simulation to verify the difference in the loss calculation of the core model, and then analyzes and compares the proximity effect and the skin effect of the planar winding. According to the core magnetic flux distribution, the core structure is optimized, and different winding arrangements are analyzed to reduce the magnetomotive force and the AC resistance loss. Moreover, the magnetic element is designed by core parameterization, and the lowest loss design point is obtained under different core sizes. This dissertation also proposes an optimized winding structure with lower length and copper loss without influencing the turns ratio of the five-leg transformer. Last, ANSYS Maxwell and parameterized form results are combined to optimize the influence of the fringing flux on the core winding loss. The final prototype’s input voltage is 36 V - 60 V, the output voltage is 380 V, the output power is 3 kW, and the highest efficiency is 96.7% for the wide-gain resonant DC-to-DC converter.

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