Research On Hybrid Control Phase Shift Full Bridge Converter Based On Burst Mode

Under the dual pressure of the increasing shortage of fossil energy and the increasingly severe environmental problems,the development of the new energy industry has been paid more and more attention.Among them,the development of wind power,photovoltaic and electric vehicles is the top priority.Electric vehicles have entered our lives and have begun to gradually replace traditional fuel vehicles.However,compared with traditional fuel vehicles,current electric vehicles still have some obvious shortcomings.At present,charging speed and battery life are the main factors hindering the development of new energy vehicles.Phase-shifted full-bridge converters have been widely used in low-voltage,high-current,and high-power applications due to their simple control and small voltage stress.In addition,the phase-shifted full-bridge converter has the advantages of low switching loss,high efficiency,and low electromagnetic interference because it can realize soft switching.However,since soft switching under light load conditions is difficult to achieve,its light load efficiency is relatively low compared to other soft switching converters such as LLC converters.Compared with other applications,DC-DC converters,which are used as electric vehicle chargers,in-vehicle electrical equipment and motor-driven power supply devices,will work for a long time under light load conditions.Aiming at the problem of low light-load efficiency of phase-shifted full-bridge converters,most of the current research is to change the topology or add auxiliary circuits to achieve soft-switching under light-load conditions.However,the additional auxiliary circuit will cause a reduction in efficiency.Therefore,it is very necessary to study how to increase the soft-switching range and improve the light-load efficiency by improving the original common control methods or combining multiple control methods.First of all,this paper takes the phase-shift full-bridge converter applied to electric vehicle charging pile and power supply device as the research object,and studies its working principle and working mode.By analyzing the operating mode and soft-switching principle of the traditional phase-shifted full-bridge converter,the factors that limit its soft-switching range are obtained.Characteristics and influence on the voltage and current in the topology operation process,a hybrid control method combining voltage-type control and Burst mode is used in the phase-shift full-bridge topology to increase the light-load soft switching range.Then the theoretical analysis,simulation analysis and experimental verification are carried out on the voltage-type hybrid control.Aiming at the shortcomings of the voltage-based hybrid control method,the principle and characteristics of the peak current control and the burst mode control are analyzed in detail,and a peak current-based hybrid control method is proposed.Peak current control is used when the load is large,and hybrid control is used when the load is light.The primary-side resonant inductor current is controlled to be greater than the critical value for soft switching by the phase-shifted duty ratio,the output voltage is adjusted by the burst duty ratio,and the soft switching under light load conditions is achieved by hybrid control.The efficiency curve of the converter is further obtained through theoretical analysis and experimental testing.Under the same input voltage,through the hybrid control method,the operating state of the higher efficiency point is tracked under light load,so that the efficiency under full load conditions can be improved.Finally,based on theoretical analysis and simulation results,a 240 W experimental prototype is made.The parameters design,software design and hardware design process of the experimental prototype are described in detail,and the efficiency analysis is carried out.Finally,the experimental results under the same input voltage,different load currents and control modes are presented.Theoretical analysis,simulation results and experimental results have good consistency.