~正激变换器具有结构简单、不存在开关直通问题且输入输出电气隔离等优点，因而在中小功率电源中占据主导地位。但由于其单向磁化会导致变压器磁芯饱和，必须采取磁复位措施，而现有磁复位技术功能单一，励磁能量利用率低且电路结构复杂。因此，对可实现磁复位电路功能复用的高性能副边LCD并联型正激变换器进行研究具有理论意义和工程应用价值。
本文在分析正激变换器磁复位机理的基础上，提出了一种既可传输正激能量，又可传输励磁能量且可避免输出能量倒灌的高性能副边LCD并联型正激变换器。通过分析正激电感和附加电感工作模式之间的相互制约关系，指出正激电感和附加电感不可同时工作于CCM，据此得出变换器存在六种不同的组合工作模式；通过对各种组合工作模式的电气性能特点进行分析，得出了可降低开关损耗，提升变换器能量传输效率，确保大功率传输的最佳组合工作模式：励磁电感Lm-DCM/正激电感L1-CCM/附加电感L2-DCM。通过分析其能量传输过程对开关特性的影响，发现励磁电感工作于DCM时可同时实现低电压关断和导通，且推导得出了关断及导通瞬间开关管漏源电压的解析关系式，并指出低电压关断和导通性能随着储能电容C2及附加电感L2取值的减小而提升。通过对影响开关管电压应力的因素进行分析，指出开关管电压应力随着储能电容C2取值的增大而减小。同时，为保证变压器可靠磁复位，且可实现低电压导通和关断，提出了一种电容、电感元件参数的优化设计方法。
根据所提出的参数设计方法，研制一台48V/10A的副边LCD并联型正激变换器样机并进行仿真分析和实验研究，结果表明：样机的各项功能和性能指标均满足预期要求，验证了理论分析的正确性及所提出变换器与参数设计方法的可行性。
 

~Because of the simple structure, electrical isolation and no direct conduction problem of the switch tube, the forward converter has been widely used in supplies with low to medium power fields. However, due to its unidirectional magnetization will lead to saturation of the transformer core, magnetic reset measures must be taken, and the existing magnetic reset technology has a single function, low excitation energy utilization, and complex circuit structure. Therefore, it is of theoretical research significance and engineering application value to study the high-performance secondary-side LCD parallel forward converter that can realize the function multiplexing of the magnetic reset circuit.
The paper on the basis of analysis of the advantages and disadvantages of the existing magnetic reset technology, a high-performance secondary-side LCD parallel forward converter that can transmit both forward energy and excitation energy and avoid output energy backflow is proposed. By analyzing the relationship between the forward inductance and the additional inductance working mode, it is pointed out that the forward inductance and the additional inductance cannot work in the CCM at the same time, according to this, it is concluded that there are six different combined working modes of the converter. The electrical performance characteristics of the working mode are analyzed, and the optimal combined working mode that can reduce the switching loss, improve the energy transmission efficiency of the converter, and ensure high-power transmission is obtained: inductance Lm-DCM/L1-CCM/L2-DCM. By analyzing the influence of its energy transfer process on the switching characteristics, it is found that the excitation inductor can realize low-voltage turn-off and turn-on at the same time when working in DCM, and the analytical relationship between the drain-source voltage of the switch tube at the moment of turn-off and turn-on is deduced formula, and it is pointed out that the low-voltage turn-off and turn-on performance improves with the decrease of the value of the energy storage capacitor C2 and the additional inductance L2. By analyzing the factors affecting the voltage stress of the switch, it is pointed out that the voltage stress of the switch is relatively low when the excitation inductance works in CCM, and decreases with the increase of the value of the energy storage capacitor C2. In order to ensure the reliable magnetic reset of the transformer and realize the low-voltage turn-on and turn-off at the same time under the condition of low voltage stress of the switch tube, an optimal design method for the parameters of the capacitor and the inductor is proposed.
According to the parameter design method, a 48V/10A prototype is developed for simulation and experimental verification. The results show that the performance indicators of the prototype meet the expected requirements, and the improvement of multiple electrical performance indicators has been achieved, which verified the feasibility of the parameter design method and the correctness of theoretical analysis.
 

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