Design Of A DC/DC Conversion System For Electric Vehicles And Its Electromagnetic Compatibility

It has been realized that the use of traditional-fuel vehicles all over the world is one of the important factors which caused environmental pollution and atmospheric haze.The advent of electric vehicles is of great significance to ease air pollution.Compared to traditional-fuel vehicle,a DC/DC conversion system and a DC/AC drive inverter system are introduced in electric vehicle,which is no need to consume a lot of oil energy.Thus,it has of great significance of running electric vehicle for energy conservation and pollution emissions reduction around the world.However,some problems,such as working efficiency,energy consumption and electromagnetic interference of the two power conversion systems of electric vehicle,is still the major issues to be solved in academia and industry,because these problems are related to the efficient,stable and reliable operation of the present electric vehicle.As we all know,the soft-switching technology is an effective means to improve the efficiency of high-frequency switching power supply,reduce switching loss and reduce electromagnetic interference.In this paper,the principle of phase-shifted full-bridge converter is analyzed in detail,and a soft-switching technology is applied to the proposed topology to improve the power transmission and utilization efficiency of the DC/DC conversion system of the electric vehicle.In addition,the electromagnetic interference of the system is expected to reduce.In this paper,the phase-shifted full-bridge ZVS converter is used as the main circuit topology,and the detailed analysis has been made from the improvement of the main circuit topology to the parameter calculation and setting.The principle of phase shifting and regulation of the control circuit are analyzed in detail,and the parameter setting methods of the external control circuit were also described in detail.Then through the circuit modeling,the theory was verified by the Saber software simulation.Finally,the noise generation mechanism was described in theory and the suppression program was put forward.The main work of the paper is as follows:(1)The structural characteristics of several kinds of full-bridge DC/DC converters based on soft-switching technology,are analyzed,and determined the circuit topology structure used in this design by comparing,that is,phase-shifted full-bridge ZVS transform circuit.This paper also analyzed the working principle of this circuit and the existence of the problem-the secondary side of the duty cycle loss,the transformer primary side of the existence of DC components,secondary rectifier circuit selection.And these problems were presented the resolutions.(2)For the phase-shifted full-bridge ZVS conversion circuit,the paper starts design from the main circuit,the control circuit,the driving circuit and the voltage feedback adjusting circuit.The circuit design,component selection and parameter calculation were carried out for each circuit module.Such as the design of the main transformer,the design of the resonant capacitor inductance,the selection of the DC blocking capacitor,the parameter calculation of the output of the filter capacitor and inductance,the design of the control chip peripheral circuit and the accurate calculation of the relevant control circuit parameters.(3)In Saber software,the circuit module was designed and it was built to the phase-shifted full-bridge ZVS converter simulation circuit.And the theoretical analysis has been proved to be correct by simulation.The simulation results showed that the phase-shifted full-bridge converter system could realize soft-switching and phase-shifting functions.And the output is controllable.(4)It was analyzed to the generation mechanism of the peak pulse in the voltage and current waveform of the power switch and rectifier.The conduction path and the harm of the electromagnetic interference were discussed in the circuit.And the suppression method was put forward.