基于高速IGBT的100kHz高壓-低壓DC/DC轉換器

3.2 開通損耗分析

　　如圖7所示，盡管大多數負載點可以實現軟關斷，但是在輕載時由于原邊電流較小，儲存在變壓器漏感的能量較小，不足以使滯后臂實現軟關斷。從整體效果來看，主工作區間良好實現了軟關斷，IGBT的極低的輸出電容特性使得整個系統在沒有外置諧振電感的情況下實現了主工作區間的軟關斷，系統損耗由此明顯降低，這也是由前文提到的IGBT芯片面積遠小于MOSFET所決定。

3.3 效率測試與分析

　　經過前文對開通和關斷狀態的分析，進一步測試了整個系統的效率，效率的測試方法采用測量輸入電壓、輸入電流、輸出電壓、輸出電流并計算輸入功率和輸出功率的方法得到。輸入電壓采用電壓表測量，輸入電流采用高精度分流計測量，輸出電壓電流功率數據從電子負載中得到。最終測試結果顯示，在很寬的電壓輸入范圍里，系統都能超過90% 的效率。圖8展示了輸入電壓220V到400V，輸出電流20A到110A的系統效率曲線，其中系統效率較高的區域是電壓輸入較低的區域。最核心的負載段，即30%到70%的負載段是系統工作最典型的使用工況，也是本設計最重要的設計目標段，該段效率也達到了90%以上。

4 結論

　　當代高速IGBT(如英飛凌HS3系列)，對比傳統的溝槽柵場終止IGBT，在不增加集電極到發射極飽和壓降的情況下，拖尾電流和關斷損耗得到顯著改善，顯著地改善了溝槽柵。通過電路設計和實際測試，在這種軟開關式移相全橋DC/DC轉換器的應用中實現了替代超級結MOSFET的可能性，同時在功率較高的工況超越了超級結MOSFET的性能，同時芯片面積比MOSFET大幅縮小，因此芯片成本也會降低。

　　本設計采用13:1的匝比，配合移相全橋和全波同步整流的拓撲結構，以及無諧振電感特性，實現了220V到400V功率范圍，93%的最優效率，以及非常平緩的效率下降平臺，為高壓-低壓DC/DC變換器的設計提供了一種新的功率器件設計選擇方向。

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