针对典型正激变换器应用于单级功率因数校正中存在能量传输死区，输入电流谐波大的问题，本文对副边附加电容实现磁复位的单级正激PFC变换器进行研究，对于正激变换器在单级功率因数校正中的推广应用具有重要指导意义。

首先通过分析副边附加电容磁复位正激变换器的电路组成和基本工作原理，得出了变换器在半个工频周期内五种工作状态下的能量传输过程及相应特性。其次，对半个工频周期内变换器不同工作状态的演变过程进行了深入研究，指出附加电容既可使变压器磁复位，还能解决典型正激变换器在工频周期内存在的能量传输死区问题，并推导了变换器在不同工作状态下的输入电流表达式，以及实现单位功率因数的占空比变化关系，指出在交流输入电压过零点附近时，变换器的占空比保持恒定即可实现单位功率因数；随着输入电压瞬时值的升高，变换器实现单位功率因数的占空比开始逐渐下降。然后，探讨了输入电压和负载电阻对变换器临界正激电感及正激电感电流过零临界相角的影响，指出正激电感的临界值随输入电压瞬时值的升高或负载电阻的减小而减小，其电流过零的临界相角随交流输入电压有效值或负载电阻的增大而增大，考虑到附加电容与变压器励磁能量转移过程的关系，综合得出了附加电容的取值范围。最后，在给定的输入电压和负载电阻变化范围内结合输入功率脉动对功率器件应力的影响后，提出了功率器件的选型方法。

根据样机设计指标及所提出的变换器设计方法，研制了一台基于平均电流控制策略的48V/4A实验样机。实验结果表明：所研制样机在给定的交流输入电压和负载电阻变化范围内最高可获得0.996的功率因数，且其它各项电气技术指标均满足预期，验证了理论分析的正确性和设计方法的可行性。

Aiming at the problems of energy transmission dead zone and large input current harmonics in typical forward converters applied to single-stage power factor correction, this paper investigates the single-stage forward PFC converter with magnetic reset by attaching capacitors on the secondary side, which is an important guideline for the application of forward converter in single-stage power factor correction.

Firstly, the circuit composition and basic working principle of the magnetic reset forward converter with additional capacitor on the secondary side are analyzed, and the energy transfer process and corresponding characteristics of the converter under five operating states in half an operating frequency cycle are derived. Secondly, the evolution of different operating states of the converter in half an operating frequency cycle is studied in depth, and it is pointed out that the additional capacitor can not only magnetically reset the transformer, but also solve the problem of energy transfer dead zone in the operating frequency cycle of a typical forward converter. It is pointed out that the duty cycle of the converter can realize the unit power factor when the AC input voltage passes the zero point; as the input voltage transient value increases, the duty cycle of the converter to realize the unit power factor starts to decrease gradually. Then, the effects of input voltage and load resistance on the critical forward inductance and the critical phase angle of the forward inductance current over zero of the converter are discussed. The range of values of the additional capacitance is synthesized. Finally, the selection method of power devices is proposed after combining the influence of input power pulsation on power device stress within the given range of input voltage and load resistance variation.

According to the prototype design index and the proposed converter design method, a 48V/4A experimental prototype based on the average current control strategy was developed. The experimental results show that the developed prototype can obtain a power factor of up to 0.996 within the range of AC input voltage and load resistance, and other electrical technical indicators meet expectations, which verifies the correctness of the theoretical analysis and the feasibility of the design method.

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