Research On Interleaved And Magnetic Integrated LLC Resonant Converter

The good soft switching characteristics of LLC resonant converter make it very obvious in the power transformation of future DC power distribution network.Firstly,the operating principle and characteristics of the LLC resonant converter are analyzed.The equivalent steady state model of LLC resonant converter is established by using the First Harmonic Approximation,and the expression of input impedance and voltage gain are obtained.The influence of parameters on converter losses and resonant circuit transmission efficiency are analyzed.It provides a theoretical basis for determining the specific operating range of the converter and selecting the parameters of the resonant component.Then,in view of the capacity of the traditional LLC resonant converter at high power output,the interleaving parallel technology is introduced into the converter,and the main operating process of the converter in the ideal operating frequency region is analyzed in detail,and the influence of resonant parameters variation on the load sharing characteristic of the converter is analyzed.Aiming at the problem of uneven current easily occurs when there are deviations in circuit components of interleaved LLC resonant converter,the magnetic integration technology is introduced into the converter,and the load sharing scheme with a magnetic integration structure of two resonant inductors is proposed.The equivalent circuit model of the interleaved magnetic integrated LLC resonant converter is established,and the voltage gain characteristics including coupling coefficient and current ratio are analyzed respectively.The selection method of the coupling coefficient and the design process of the coupling inductor are given.Next,a simple and accurate new resonant circuit parameter design method is presented to design the resonant parameters.The converter designed by this method can realize the gain requirement of the converter,the zero voltage switching of the primary side switch tube and the zero current switching of the second side rectifier diode,so that the efficiency of the converter can be greatly improved.According to the optional parameters,the devices of the main circuit of the interleaved magnetic integrated LLC resonant converter are selected.Finally,the experimental system is built,the hardware circuit is completed,and the DSP software flow is given.The correctness of the parameter design method and the effectiveness of the load sharing scheme are verified by saber simulation and experiment,and the designed converter achieves high efficiency in full load range.