Research On A Interleaving LLC Resonant Converter With Hybird Control Method

LLC resonant converter has been widely studied owing to its good soft switching characteristics,since it is an effective way to improve the power density and the efficiency of the converter by reducing the switching loss caused by high switching frequency.To reduce the output current ripple and improve power level,the interleaving LLC resonant converter has been studied.The current unbalance problem exists because of the tolerance of the resonant parameters,which will decrease the reliability of the converter.In this paper,related research on interleaving converter is developed.The working principle of the interleaving LLC resonant converter is introduced,and the relationship between the interleaving and the single phase one is studied.Then,its mathematical model is built,and the voltage gain and soft switching characteristics is analyzed.Considering the tolerance of the resonant parameters,the current imbalance mechanism is studied,and the relationship between current error and the tolerance of the resonant parameters is built.For the current imbalance problem,a two-phase three-arm interleaving LLC resonant converter with hybrid control is proposed.Through the topology analysis,this converter is decoupled into two single-phase LLC resonant converters with phase-shift angles of 90 degrees,and mathematical modeling of the proposed two-phase three-leg interleaved parallel LLC resonant converter is presented.The PFM(pulse frequency modulation)plus PSM(phase shift modulation)hybrid control strategy for the proposed topology structure is introduced,the current sharing is achieved by control the phase shift angle of the common arm,and the superiority compared to the traditional method is analyzed.Furthermore,the main working characteristics are studied.The mathematical relation between the phase shift angle and the tolerance of the resonant parameters is calculated to validate the feasibility of the control strategy.On this basis,the soft switching characteristics of the three arms and secondary diodes in the converter are analyzed respectively considering the effect caused by the PSM control.The results shows good current sharing characteristic is achieved with simplified control strategy,and the soft switching characteristics is improved since the working frequency range to achieve ZVS for the primary switch and ZCS for the secondary diode at the same time is enlarged.Finally,the current sharing characteristics and soft switching characteristics of the proposed converter are verified by Saber numerical simulation and a 1kW experiment prototype.