本論文提出一返馳式轉換器二次側控制方法，將控制晶片器置於返馳式轉換器之輸出端，以迅速精準的因應負載變化。當系統操作在重載時，電路特性為類臨界導通模式；當系統操作在輕載時，電路特性為具零電壓切換之準諧振模式。透過考量功率開關元件中輸出電容本身所儲存的能量、估算返馳式轉換器磁化電感與開關輸出電容的諧振週期及輸入電壓，使一次側功率開關可在沒有額外循環電流及責任週期損失下以最少反向變壓器磁化電流能量達到零電壓切換。最後，使用數位訊號處理器TMS320F28335作為控制器，實作一系統規格之輸入電壓範圍為130 ~ 370 V，輸出電壓/電流為20 V/5A之實驗雛型電路，以驗證所提出方法之實務可行性。實驗結果顯示其一次側主要開關皆可達到零電壓切換特性，且系統最高轉換效率可達94.4 %。

In this thesis, a novel secondary-side controlled flyback converter is proposed. Putting the controller at secondary side allows the system to respond output condition rapidly. When the system is operated in heavy load, the circuit behavior is like boundary conduction mode. When the system is operated in light load, the circuit behavior is like quasi-resonant mode with zero voltage switching (ZVS). By considering the energy in output capacitance, Coss of power switch, estimating the resonant period of the magnetizing inductance, Lm and Coss, and input voltage, ZVS is achieved in all operational conditions with less reverse energy stored in Lm and without circulating current and duty loss. Finally, an experimental prototype with digital controller TMS320F28335 is implemented to verify the theoretical feasibility with input voltage of 130 V~370 V and output voltage/current of 20 V / 5 A. The experimental results show that the main switch at primary side can achieve ZVS and the highest system efficiency is 94.4 %.

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