集成Buck-Boost LLC级联变换器最小续流电流的闭环相移控制策略OA

Aiming at the problem of single-stage LLC resonant converter losing soft-switching capability and efficiency degradation due to over-regulation in wide-voltage input applications,this paper proposed a closed-loop phase-shift control strategy without look-up table for a novel integrated cascade topology,which was designed to ensure the soft-switching performance over a wide input voltage range and to reduce the freewheeling loss to improve the efficiency.Taking the two-stage integrated structure composed of four-switch Buck-Boost and LLC as the object of study,first,the integration mechanism and voltage regulation principle of the topology were elaborated in details.Second,by dissecting and calculating the zero-voltage switching(ZVS)process of the switches,as well as studying the impact of freewheeling current on losses,a closed-loop phase-shift control strategy was proposed to ensure soft-switching and minimize freewheeling current over a wide input voltage range.Finally,the effectiveness of the proposed control strategy was verified by MATLAB/Simulink simulation.The simulation results demonstrate that the strategy can promptly adjust the phase shift across the entire input voltage range and under load transients,ensuring ZVS for all switches,maintaining minimal circulating current,and exhibiting favorable dynamic performance.