Research On A New Full-Bridge Soft-Switching Converter In Electric Vehicle

Facing with the ever severe environmental pollution and energy crisis problem,the use of energy-saving and enviroment-friendly electric vehicle(EV)instead of traditional fuel vehicles has become the key development strategy for many coutries.The assisted DC/DC converter of EV is an important part of power transformation.It is used to transform the energy stored in high-voltage power battery into low voltage to supply power for the whole EV equipment,and to charge the low voltage battery at the same time.Therefore,it must have high reliability,high efficiency and high power density in the assisted DC/DC converters,so as to facilitate the promotion and use of EVs.Aiming at the characteristics of wide range of input voltage and low voltage and high current of output in the assisted DC/DC converters,it compares several main application topology and analyzes the advantages and disadvantages of each topology.Finally,the diodes with balance capacitance symmetrical clamped ZVS full-bridge converter is proposed in the paper.Then,the control strategy of PWM is summarized,and several asymmetrical control modes are compared with the phase-shifted full-bridge control mode.Finally,the central-symmetric asymmetric control mode is chosen for the proposed converter.Based on the asymmetric control mode,the working mode and characteristics of the proposed converter are studied in detail.The state-space averaging method is generally as the modeling method of full-bridge converter.The paper introduces the PWM switch three-port equivalent modeling method.Based the state-space averaging method,through the PWM switch three-port equivalent transformation,the equivalent small signal and large signal model is extracted.It takes into account the effects of parasitic parameters and loss in the three-port equivalent model,so the model is more accurate.Based on the peak current control method,the closed loop system and the compensation network of the proposed converter is designed.Then,the main circuit parameters of the proposed converter are designed,including the design of transformer,resonant inductor,filter inductor and filter capacitor,as well as the selection of main switch,rectifier tube,clamping tube and balance capacitance.In addition,the design of the auxiliary power supply and MCU are given briefly.Based on the theoretical analysis,a 320 V input,13.8V/130 A output prototype is fabricated.The effect of the balanced capacitor and the clamping diode is verified by the simulation analysis.The experimental results show that it can realize the ZVS of the switch,depress the peak of the rectifier,and has good steady-state and dynamic performance in the proposed converter,which are consistent with the theoretical analysis.In the end,the efficiency and loss of each part of the proposed converter is briefly analyzed,and the direction of efficiency optimization is further given.