二次侧并联LCD正激变换器的能量传输过程分析及辅助电容设计

Analysis of Energy Transmission Process and Design of Auxiliary Capacitor for Secondary Side Parallel LCD Forward Converter

针对现有正激变换器磁复位电路存在励磁能量利用率低、电路组成复杂或控制难度大的问题,提出一种二次侧并联LCD的正激变换器拓扑。对所提出正激变换器的工作原理及能量传输机理进行深入分析,指出附加LCD的正激变换器可同时传输正激能量和励磁能量,且反激期间的励磁电感既可工作于连续导电模式(CCM),也可工作于不连续导电模式(DCM),即所提出正激变换器不再需要传统意义上的磁复位,且励磁电感工作于CCM时的开关管电压应力更低;通过分析辅助电容对励磁电感工作模式的影响,提出一种确保所提出正激变换器的励磁电感工作于CCM的辅助电容设计方法,实例及实验结果验证了所提正激变换器的可行性及理论分析和设计方法的正确性。

Aiming at the problems of low excitation energy utilization rate,complicated circuit composition or large control difficulty of the existing forward converter magnetic reset circuit,a forward converter topology with a secondary side parallel LCD is proposed.The working principle and energy transmission mechanism of the proposed forward converter are analyzed in depth,and it is pointed out that the forward converter with LCD can transmit forward energy and excitation energy at the same time,and the excitation inductance during the flyback can work in continuous conduction mode(CCM),It can also work in discontinuous conduction mode(DCM),that is,the proposed forward converter no longer needs the traditional magnetic reset,and the voltage stress of the switching tube when the magnetizing inductor works in CCM is lower;by analyzing the effect of the auxiliary capacitor on the working mode of the magnetizing inductor,An auxiliary capacitance design method to ensure that the magnetizing inductance of the forward converter is working in CCM is proposed.The examples and experimental results verify the feasibility of the proposed forward converter and the correctness of the theoretical analysis and design method.