全橋相移式轉換器具有零電壓切換的特性，可有效降低切換損失和高頻雜訊所造成的干擾，提升轉換器效率，但其缺點在次級側的同步整流開關上會有電壓突波現象。本論文主旨為研究消除次級側電壓突波，在次級側加上一組主動式緩振電路，並和傳統RC、RCD緩振電路做優缺點比較。主動式緩振電路將次級側電壓突波能量存到緩振電容上，再利用第三繞組將緩振電容的能量傳回變壓器初級側。由於緩振器能量的回收，改善了運用消耗式被動緩振電路的能量效率；並且也能有效抑制次級側電壓突波現象，使得同步整流開關突波電壓降低。因此，同步整流開關的耐壓與導通電阻也得以降低，使得導通損也能降低，進一步提高整體效率。

Full-bridge phase-shift converter has the merit of zero-voltage switching (ZVS) which can reduce the switching loss and the high frequency noise interference. However, there will be voltage spike induced on the secondary side synchronous rectification MOSEFTs. This thesis presents the study upon an active snubber circuit which is designed to reduce the spike. This active snubber is compared with the well-known RC and RCD passive snubbers. The stray energy on the secondary-side is restored to the snubber capacitors, then the snubber transfers the stored energy back to the primary-side. Due to the energy retrieval, the active snubber circuit surpasses the passive counterpart on energy efficiency. Besides, the voltage stress on the synchronous rectification MOSFETs is lowered benefited from the spike reduction; the MOSFET conduction resistance i.e. the conduction loss can also be reduced. That is, the power efficiency is further improved by the application of the active snubber.

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