Research On The Wide-output Hybrid Converter With Full-bridge PWM And LLC

With the rapid development of industrialization,the global energy crisis and environmental crisis are becoming more and more serious,which forces people to seek a clean,efficient,safe and sustainable modern energy system.Electric vehicles have the advantages of low environmental pollution and high energy efficiency,so they are widely concerned.The development of the charger technology will provide strong support for the practical use of electric vehicles.The charger system is usually composed of a pre-stage PFC and a post-stage high-frequency isolated DC/DC converter.Because the voltage range of electric vehicle power battery is wide,so the post-stage DC/DC converter needs to satisfy the wide range output characteristic.Based on the above problems,a hybrid DC/DC converter is proposed to meet the charging requirements of the battery in this paper.Firstly,based on the research status of traditional phase-shifted full bridges at home and abroad,a hybrid full-bridge converter is proposed that consists of a phase shift control active rectification full-bridge(PSCAR-FB)converter and full-bridge LLC(FB-LLC)converter,which is suitable for applications with high voltage,high power and wide output voltage range.Furthermore,according to the characteristics of the proposed converter,the time-sharing phase shift control strategy is proposed.The working principle and voltage gain of the converter under different control modes are analyzed in detail in this paper.Finally,the simulation analysis is carried out by the Pspice simulation software.Secondly,in order to restrain the voltage stress on the secondary side power device of the PSCAR-FB converter,an auxiliary network of a resonant inductor and two clamp diodes can be introduced on the primary side.However,the circulation loss of auxiliary network and the hard turn-off of clamp diodes are brought on the above scheme.In order to solve the above problem,an auxiliary winding may be added in series to the current loop of the clamp diode,which can reset the current flowing through the clamp diode.Finally,the simulation of the PSCAR-FB converter with/without the auxiliary winding is performed and verified by Pspice simulation software.Based on the above work,the hardware design and software design of the 3kW hybrid full-bridge converter is completed in this paper.Finally,in order to verify the working principle and superiority of the hybrid converter,the experimental verification of the 3kW experimental prototype was carried out,and the experimental results were given.In addition,the comparative experiments results of the different measures to suppress the voltage spike on PSCAR-FB converter are given,and the theoretical analysis and experimental verification are consistent.At the same time,the efficiency curves of different output voltages under different loads are given,and the peak efficiency achieves 97.4%.