本論文目標為建構出一全橋相移轉換器的設計流程，以達到高效
率的表現。為達到此目的，本論文先從初級側橋臂開關損耗模型開始
分析，探討使用新的損耗模型與傳統之間的差異，並從中找出全橋相
移轉換器在輕載硬開關切換時導通與截止所造成的切換損失以及改
善的方法。為了降低次級側開關的電壓應力以及使轉換器能更輕易地
達到零電壓切換，本文接著介紹使用箝位二極體的全橋相移轉換器動
作行為，分析轉換器的等效電路以及推導出箝位二極體的損耗，並比
較兩種連接方式找出適合應用的場合以及加入箝位二極體前後對整
體轉換器損耗的影響，方便設計者在前期規劃時能選擇合適的設計參
數。此外，由於擁有較高的di/dt 關斷電流造成同步整流元件較高的
電壓應力，因此使用無損箝位型主動緩振電路來達到降低損失的目的，
並透過動作分析推導出緩振電路的設計方式，來獲得高功率密度、低
損耗的目的。最後整合出上述的模型並使用一設計流程分別針對各部
分的損耗進行分析，進而達到設計出一高效率的全橋相移轉換器。

The purpose is to build a design procedure of phase shifted full bridge
converter for high efficient performance. Firstly, this dissertation analyzes
the loss model of primary-side MOSFET whitch is used to be compare the
difference with the conventional loss model. And find out how to reduce
the turn on and turn off loss of hard switching condition during light load
condition.
Secondly, in order to reduce voltage stress of synchronous rectifier
and achieve the zero voltage switching for primary-side MOSFET more
easily, the paper then introduces the operating principle of phase shifted
full bridge converter with clamping diode, analyzes the equvalent circuit
of the converter and derives the loss of the clamping diode. Moreover, two
types of clamping diode methods are compared to find the appropriate
application and the effect for the entire loss of converter, whitch is more
convenient for designer to choose the suitable parameters in the advance
planning.
Thirdly, the high voltage stress on the synchronous rectifier due to
high di/dt turn off current, which has larger power loss of snubber circuit.
This dissertation purposed a method to design buck-type lossless snubber.
By using the different input capacitance of snubber circuit, a high density,
low cost and low loss lossless snubber is achieved.
Finally, integrate all the loss model and build a design flow chart to
achieve high efficiency phase shifted full bridge converter.

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