Research On New High-efficiency LCLCL DC/DC Converter Based On Multi-order Resonance

The power electronics industry is increasingly demanding high power density and high efficiency.LLC resonant converters are widely used in isolated switching power supplies because of their high step-down ratio and easy implementation of soft switching and other advantages.However,despite the many advantages of LLC converters,there are problems of large secondary side rectification loss,narrow input voltage adjustment range,and no excellent current suppression capability.Aiming at the above-mentioned defects of LLC resonant converter,this article innovatively adds a group of parallel resonant elements to form LCLCL resonant converter.Topological analysis,parameter design,magnetic component design,small signal model establishment and closed-loop control were designed and optimized.Design a 400 W DC / DC high-order high-performance resonant converter.First,this article uses the fundamental wave analysis method to analyze the voltage frequency gain of the LCLCL resonant converter.The gain frequency curve is drawn through MATLAB.It is found that the gain curve has two solid-state operating points and a zero gain point.By refining the inductance and quality factor Parameter design with equal parameters enables the LCLCL resonant converter to introduce third harmonics for energy transmission compared to the LLC converter and thereby reduce the secondary rectifier diode losses to improve efficiency.The impedance analysis of the resonant converter is carried out,and the boundary of the soft-switching impedance is derived and used as an important reference for parameter design.As the main component of the resonant converter,it is not only the main influence element of power density but also one of the main sources of loss.In this paper,according to the principle of magnetic integration,the leakage inductance is adjusted through the magnetic barrier layer,and the resonance inductance is integrated into the planar transformer.Then,according to the response surface method,the influence of copper width,copper thickness,magnetic core volume and other influencing elements on the impedance and volume of the single-layer planar winding is explored.According to this,combined with the modular layer model method,the influence element analysis of the multilayer winding is carried out,and the planar transformer winding method and parameter selection scheme of the multilayer winding are obtained.In order to further reduce the winding impedance and parasitic capacitance,the optimization of variable-width windings is proposed,and the correctness of the above theory is verified by finite element simulation analysis.For small-signal modeling of multi-order resonant systems,this paper chooses extended description function method to establish small-signal model.According to the transfer function,a 4P4 Z compensator is designed.Improve the dynamic response speed while ensuring system stability and reliability.According to the zero gain point of the LCLCL resonant cavity,the soft start scheme and overcurrent protection scheme unique to the LCLCL resonant converter are designed,which improves the reliability and performance of the LCLCL resonant converter in this paper.Finally,this paper builds a main resonant frequency of 1MHz and a third harmonic injection frequency of 3MHz.With a power of 400 W,a system prototype with a full-range soft switching efficiency of 95.6% can be realized.It proves the correctness of the theory of this subject.