Research On High Efficiency Dual-bridge Series Resonant Converter

Global warming has become one of the most serious problems in the 21 st century,in order to reduce greenhouse gas emissions,many countries have introduced policies to shift from traditional gasoline vehicles to electric vehicles.Electric vehicles have been greatly developed in recent years for their advantages of high efficiency,energy saving and environmental protection.The On-Board Converter is an important part of the electric vehicle,which manages the energy flow inside the electric vehicle and controls the charging and discharging of the power battery,which is related to the service life of the power battery.With the gradual increase of the voltage level of the power battery in the car,the voltage range also increases,which places higher requirements for the high efficiency operation of the converter in a wide output range.Also,it brings new challenges and opportunities to power electronics technology.In this paper,the working principle of the dual bride series resonant converter is analyzed at first.Then,the power transmission characteristics,soft switching characteristics and root mean square values of the resonant tank current are respectively analyzed by time domain and frequency domain,followed by the comparison between the two analytical methods.In order to get more accurate results,in this paper,the influence of the commutation process on the soft-switching characteristics of the circuit is derived in terms of charge based on time domain analysis,and put forward a variable frequency mixed with phase shift modulation control strategy for dual bride series resonant converter.This method is verified by experiment and it can make the circuit work achieve soft switching under a wide range of output voltage.Meanwhile,this paper produces a fitted formula to minimize the conduction loss of the converter at different working point.Then the switching character is further analyzed,and the result proves that the zero voltage switching and minimum root mean square of resonant tank current can be guaranteed at the same time,the efficiency of the circuit is improved.Finally,a 3.3kw dual bride series resonant converter prototype is designed in this paper.Experimental results show that the proposed control strategy can achieve high working efficiency in a wide output voltage range,and all the Mosfets can realize soft switching.