基于高速IGBT的100kHz高壓-低壓DC/DC轉(zhuǎn)換器

3.2 開通損耗分析

　　如圖7所示，盡管大多數(shù)負載點可以實現(xiàn)軟關(guān)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(xiàn)軟關(guān)斷。從整體效果來看，主工作區(qū)間良好實現(xiàn)了軟關(guān)斷，IGBT的極低的輸出電容特性使得整個系統(tǒng)在沒有外置諧振電感的情況下實現(xiàn)了主工作區(qū)間的軟關(guān)斷，系統(tǒng)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(jīng)過前文對開通和關(guān)斷狀態(tài)的分析，進一步測試了整個系統(tǒng)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(shù)據(jù)從電子負載中得到。最終測試結(jié)果顯示，在很寬的電壓輸入范圍里，系統(tǒng)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(tǒng)效率曲線，其中系統(tǒng)效率較高的區(qū)域是電壓輸入較低的區(qū)域。最核心的負載段，即30%到70%的負載段是系統(tǒng)工作最典型的使用工況，也是本設(shè)計最重要的設(shè)計目標(biāo)段，該段效率也達到了90%以上。

4 結(jié)論

　　當(dāng)代高速IGBT(如英飛凌HS3系列)，對比傳統(tǒng)的溝槽柵場終止IGBT，在不增加集電極到發(fā)射極飽和壓降的情況下，拖尾電流和關(guān)斷損耗得到顯著改善，顯著地改善了溝槽柵。通過電路設(shè)計和實際測試，在這種軟開關(guān)式移相全橋DC/DC轉(zhuǎn)換器的應(yīng)用中實現(xiàn)了替代超級結(jié)MOSFET的可能性，同時在功率較高的工況超越了超級結(jié)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(shè)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(jié)構(gòu)，以及無諧振電感特性，實現(xiàn)了220V到400V功率范圍，93%的最優(yōu)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(shè)計提供了一種新的功率器件設(shè)計選擇方向。

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