本論文提出一個新型四相交錯式耦合電感，採用對稱的磁路架構，使每一相電感自感量均相等，利用整合鐵心達到中心柱完全直流磁通抵消以降低鐵心磁通密度以及鐵心損耗，與傳統鐵心結構相比中心柱截面積縮減四倍，同時具有調整氣隙控制磁阻比例關係來調整耦合係數之特點，解決傳統耦合電感無法同時兼具鐵心縮減與調整耦合係數的問題。調整耦合係數能改變等效感量與磁通抵消量值，進而評估不同耦合係數對應的電流有效值與磁通密度，透過調整耦合係數的特點，得到最佳鐵心損耗、銅線損耗與開關損耗的平衡點，在降壓或升壓轉換器的任意輸入輸出條件與磁性元件規格下，使轉換器達到最佳效率。文中解釋耦合係數對於等效感量的影響，以及耦合係數對於電流有效值與漣波量值的關係。在開關損耗方面，採用了比傳統矽元件具有更高切換速度的寬能隙元件氮化鎵來降低開關的損耗。針對鐵心分析的部份，提出利用磁阻模型說明鐵心磁通與耦合係數的對應關係，並探討耦合係數對鐵心直流磁通抵消的量值。而磁性元件採用了參數化的設計方式，在有限的佔地面積下，考量鐵心損耗與銅線損耗設計鐵心。接著在鐵心優化的部份，同時考量氣隙擺放位置對於邊緣磁通的影響，利用ANSYS Maxwell模擬驗證邊緣磁通對繞組的影響，最後模擬比較本論文之鐵心結構與傳統兩相耦合電感在相同電路規格條件下的電感損耗與佔地面積表現。最終實現切換頻率在100 kHz、輸入電壓為400 V - 450 V、輸出電壓為370 V、輸出功率為2000 W的條件下，滿載效率達99.5%的降壓式轉換器。

In this thesis, a novel type of four-phase interleaved coupled inductor is proposed. The symmetrical magnetic path of the structure is able to make the inductance of the coupled inductor even in every phase. This novel inductor structure has flux cancellation to reduce the volume of the magnetic core. Meanwhile, this structure is able to adjust the coupling coefficient via the proportion of the gap reluctance, which overcomes the disadvantage of the conventional coupled inductor. The optimal point of losses can be selected in any input and output specification of buck or boost converter by using coupling coefficient control. The influence of the equivalent inductance based on coupling coefficient and the relationship between the coupling coefficient, RMS value and current ripple are discussed. Moreover, a wide bandgap device, namely gallium nitride, replaces the conventional silicon device to reduce switching loss in the power device. The relationship between the flux and coupling coefficient are discussed by using the reluctance model. Also, the influence of flux cancellation according to the coupling coefficient is analyzed in this structure. Within a limited footprint for the magnetics, optimal points of the core loss and copper loss are calculated. ANSYS Maxwell is used to optimize the copper loss based on the fringing flux in different gap positions, then present the comparison of the losses and footprint for the novel structure and the conventional coupled inductor. Finally, a buck converter is achieved with a switching frequency operating at 100 kHz, an input voltage of 400 V - 450 V, an output voltage of 370 V, an output power of 2000 W and maximum efficiency of 99.5%.

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