一般而言，為了改善電力品質，必須具有高功因校正電路，然而一般高功因校正電路之電力轉換效率不高。因此，吾人遂應用柔切技術於高功因校正電力轉換器，以設計出新型零電壓轉移(ZVT)單級高功因順向式電力轉換器。
論文中應用元件移位法及接枝法，將降-升壓式(buck-boost)與順向式(forward)電力轉換器進行合併，並以諧振方法作為變壓器磁通之重置，設計出新型單級高功因順向式電力轉換器。當前級的降-升壓式電力轉換器操作於DCM時，天生就具有功因校正能力，故無須設計內迴路電流控制器。而後級為順向式電力轉換器，在磁通重置的過程中，激磁電流會回到零，故磁化電感電流係操作於DCM。此外，輸出電感電流亦操作於DCM，因此，儲能電容電壓不易受到負載變動的影響而產生高電壓應力。
接著，吾人將ZVT柔切技術應用於上述單級高功因電力轉換器中，使轉換器之主開關由off切換為on之前，使開關兩端電壓先共振至零，再進行切換，以降低切換損失，提升電力轉換效率。
論文中，針對提出的新型ZVT單級HPFC順向式電力轉換器，進行動作原理分析，再以平均化法，推導半線電壓週期 下之平均化狀態方程式。再依據吾人設定之電氣規格與轉換器之操作條件，設計轉換器之直流工作點以求得元件值( 及 )。最後，針對設計之直流工作點作線性化，以推導轉換器之小信號數學模式。
在推導小信號數學模式過程中，因狀態方程式為非線性微分方程式，其中包含非常複雜的積分項，無法直接求出各項在直流工作點的偏導數。因此，吾人應用指導教授Lin提出之圖解法，即可簡易地求出每一個偏導數。最後，應用IsSpice模擬軟體與電路實作之結果，驗證理論推導之正確性。
由實作結果顯示：當輸出功率為100 W時，新型單級高功因電力轉換器之功率因數為0.99、電力轉換效率為73 %，而新型ZVT單級HPFC順向式電力轉換器之功率因數為0.98、電力轉換效率為80 %。因此，本論文所提出之新型ZVT單級HPFC順向式轉換器不僅具有高功率因數，並可驗證柔切技術確實能提升電力轉換效率。
最後，利用古典控制理論設計PI控制器，由實作結果可知：加入控制器能使轉換器之輸出電壓不受輸入線電壓與負載變動之影響，達到輸出穩壓之性能。

Generally, in order to improve the power quality, a high power factor correction circuit is necessarily needed. However, the power efficiency of high power factor correction converters is not high. Thus the soft-switching technique is applicable to high power factor correction power converters. Accordingly, a novel zero-voltage-transition (ZVT) single-stage high power factor correction forward converter is proposed in this thesis.
By means of components placement and synchronous switching technology, the buck-boost and forward cells are combined. Additionally, the flux resetting of the transformer is maintained by a resonant method. Thus a novel single-stage high power factor correction forward converter is proposed. When the buck-boost cell, the first stage, operates in DCM, the proposed single-stage power converter exhibits an inherent gift of high power factor. Hence, the inner loop current controller is not necessary. Moreover, the transformer of the forward cell, the second stage, is achieved flux resetting, and the magnetizing inductor current starts and ends at zero. It means that the magnetizing inductor current also operates in DCM. In addition, since the output inductor current operates in DCM, the voltage across the bulk capacitor is not high and independent of the load variations.
To proceed, the ZVT soft-switching technique is applied to the proposed single-stage power converter. The voltage across the main switch is decreased due to the resonance, before the switch changes state form off to on. It means that the main switch turns on under ZVS operation. Thus, the switching losses are reduced, and the power efficiency is increased.
In this thesis, the operating principle of the proposed novel ZVT single-stage HPFC forward converter is presented herein. Moreover, the averaged state equations over one half line period are derived by the averaging method. Then, based on the design specifications and operation conditions, the operating point can be determined, and thus the component values, and , are designed. Finally, the small-signal model linearized around the operating points is then derived.
In the process of deriving the small-signal model, the state equations are nonlinear differential equations, which contain complicated integrals, so that the partial derivatives around the operating points are quite difficult to be obtained. Therefore, the graphical method proposed by Professor Lin is adopted to easily derive partial derivatives. Finally, the theoretical analysis is validated by IsSpice simulations and experimental results.
Notably, it reveals from experimental results that the novel single-stage HPFC forward converter without ZVT soft-switching technique exhibits the power factor of and power efficiency of for output power of . However, the proposed novel ZVT single-stage HPFC forward converter with output power of exhibits power factor of and power efficiency of . Consequently, the ZVT soft-switching technique can be used to effectively improve the efficiency of the novel single-stage forward power converter.
Finally, based on the classical control theory, a PI controller is designed and the experimental results show that output voltage regulation can be achieved despite of the line voltage and load variations.

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