傳統全橋轉換器被廣泛的使用在高輸入電壓與高功率的應用下。而許多的控制機制被應用在全橋轉換器下，如對稱控制、非對稱控制以及另一種非對稱控制。其中另一種非對稱控制很少受討論，故於本文作探討。
全橋轉換器運用對稱控制已行之有年，然而對稱控制為硬切換操作，故會產生大的切換損失，連帶影響轉換效率並且限制功率密度。為了提升效率，非對稱全橋轉換器在這近十年內被成功的提出。因非對稱控制達成了零電壓切換，在開關上能夠明顯的降低切換損失。然而，因為非對稱控制在變壓器上傳遞的電壓不平均，故會產生直流磁偏的問題，使變壓器容易飽和，進而失去限制電流的能力。為了解決直流磁偏的問題，無直流磁偏之非對稱全橋轉換器被提出。
然而，電壓源形式的轉換器為斷續的輸入電流，導致大的di/dt雜訊，其中電磁干擾為主要的干擾來源，因此，大的濾波元件將去降低雜訊的臨界值。而為了解決斷續的輸入電流漣波，無直流磁偏之低輸入電流漣波之非對稱全橋轉換器被提出。延續AFB轉換器的優點，RR-AFB轉換器因內建降低電流漣波機制，使的輸入電流漣波可以明顯地降低。因此，可以使用更小的EMI濾波器級來提升功率密度。
為了證明所提出技術的可行性，從電路工作原理進行理論與實務上的分析，並訂定300~400V的輸入電壓範圍，12V/30A/360W的輸出規格與100 kHz的操作頻率來做以驗證。

A conventional full-bridge converter has been widely used for high input-voltage high-power applications. Several control schemes have been applied to full bridge converter, such as symmetrical control, phase shift control, and asymmetrical control.
Employing symmetrical control, full-bridge (FB) has been used for a long time. It suffers from large switching losses due to its hard-switching operation. It will impact the conversion efficiency and limit power density.
To improve the efficiency, asymmetrical full-bridge (AFB) converter was successfully proposed instead in the last decades. Because it can achieve ZVS operation, the switching turn-on losses are significantly reduced. However, a DC bias occurs resulting in adding a gap on the transformer.
To achieve ZVS, an alternative AFB converter without DC bias is proposed in this thesis. It will be investigated and discussed in Chapter 2.
However, the proposed converter has pulsating input currents resulting in the generation of high di/dt noise, which is one of the noise sources of the electromagnetic interference (EMI) problem. Consequently, large filter components are required to attenuate the noise level within the threshold value. To reduce the pulsating input-current ripple, a low-input current-ripple reduction (RR-AFB) converter without DC bias is also proposed in Chapter 3.
To demonstrate the feasibility of the operational principle, circuit analysis and the experiments of the presented converters with 300~400 V input voltage range, 12 V/30 A/ 360 W output, 100 kHz switching frequency, are built to verify theoretical analysis.
Index Terms: full-bridge converter, asymmetrical control scheme, current ripple reduction, zero voltage switching (ZVS)

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