现有正激变换器所采用的磁复位电路结构复杂、功能单一，导致励磁能量利用率低。本文提出了一种副边附加电容实现磁复位的正激变换器，简化了磁复位结构，同时可提高综合电气性能，对正激变换器的推广和应用具有重要意义。

本文对副边附加电容实现磁复位正激变换器的工作原理和能量传输过程进行了深入分析，依据励磁电感、正激电感以及续流二极管工作特性将变换器划分为6种组合工作模式。通过对不同工作模式能量传输过程和工作特性进行对比分析，得出了变换器最佳工作模式，即正激电感CCM/励磁电感DCM，而续流二极管在轻载时零电流关断，重载时承受反偏电压关断，该模式有利于提高能量传输效率，降低开关损耗和传输大功率。研究了附加电容C_b对开关管和续流二极管电压应力的影响，指出开关管电压应力随着附加电容C_b增大而降低，续流二极管电压应力随着附加电容C_b减小而降低，并且通过限制附加电容C_b的最小取值范围，可减小能量损耗和降低开关管电压应力。详细分析了变换器的输入输出关系、电感峰值电流、功率器件应力和临界正激电感等的解析表达式。对开关管低电压导通性能以及影响因素进行了分析，并指出低电压导通性能随着附加电容C_b及正激电感L取值的减小而提升。为了保证变换器能够传输大功率，并且能实现开关管的低电压导通，提出了一种参数设计方法。根据参数设计方法，选择了变压器磁芯、骨架型号，并计算了原、副边导线线径及股数；确定了附加电容C_b和正激电感L的取值范围；在输入电压和负载电阻变化范围内，考虑一定裕量后，给出了功率器件选型方法，为设计出高性能正激变换器提供了理论指导。

根据变换器工作特性以及参数设计方法，制定样机指标并选取了样机参数，利用PSIM软件对变换器进行仿真分析，同时研制了一台48V/10A的实验样机，仿真和实验结果均验证了理论分析正确性和参数设计可行性。

The magnetic reset circuit used in the existing forward converter has a complex structure and a single function, resulting in a low utilization rate of excitation energy. In this paper, a forward converter with secondary capacitors to achieve magnetic reset is proposed, which simplifies the magnetic reset structure and improves the overall electrical performance, which is of great significance to the promotion and application of forward converters.

In this paper, the working principle and energy transfer process of the magnetic reset forward converter realized by the additional capacitor on the secondary side are deeply analyzed.

By comparing and analyzing the energy transfer process and working characteristics of different working modes, the optimal working mode of the converter is obtained, that is, the forward inductor CCM/excitation inductor DCM, and freewheeling diode is turned off at zero current at light load, withstand reverse bias voltage turn-off at heavy load, this mode is beneficial to improve energy transfer efficiency, reduce switching losses and transmit high power. The influence of the additional capacitor C_b on the voltage stress of the switching tube and the freewheeling diode is studied, and it is pointed out that the voltage stress of the switching tube decreases with the increase of the additional capacitance C_b, and the voltage stress of the freewheeling diode decreases with the decrease of the additional capacitance C_b within a certain range, and by limiting the minimum value range of the additional capacitance C_b, the reactive power loss and the voltage stress of the switch tube can be reduced. Analytical expressions of the converter's input-output relationship, inductor peak current, power device stress and critical forward inductance are analyzed in detail. The low-voltage conduction performance of the switch tube and its influencing factors are analyzed, and it is pointed out that the low-voltage conduction performance is improved with the decrease of the value of the additional capacitor C_b and the forward inductance L. In order to ensure that the converter can transmit high power and realize the low-voltage conduction of the switch tube, a parameter design method is proposed. According to the parameter design method, the transformer core and skeleton model are selected, and the wire diameter and the number of strands of the primary and secondary wires are calculated; the value range of the additional capacitance C_b and the forward inductance L is determined; In this paper, after considering a certain margin, the power device selection method is given, which provides theoretical guidance for the design of high-performance forward converters.

According to the working characteristics of the converter and the parameter design method, the prototype indicators are formulated and the prototype parameters are selected. The PSIM software is used to simulate and analyze the converter. At the same time, a 48V/10A experimental prototype is developed. The simulation and experimental results both verify the correctness of theoretical analysis and the feasibility of parameter design.

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