Research And Realization Of Electric Vehicle On-board Charger Based On DSP

Electric vehicles are driven by electricity,which is more environmental,and has a great advantage in saving energy.Recentlt,researchers pay much effort on the electric vehicle and related technology.As the energy source of electric vehicles,the battery is not only the core of electric vehicles,but also the key combination of electric power industry and the automotive industry.The function of the on board charger is to convert the electric energy from the grid into the electric vehicle battery.The purpose of this paper is to design a compact,lightweight on board charger based on the battery charging curve,whose rated power is 1.2kW,to charge for the electric vehicle battery safe and fully.The paper describes the design process of the on board charger,including the main circuit topology selection,power components selection,control circuit hardware design,charging strategy software realization.The on board charger adopts half-bridge DC-DC converter as the main circuit topology.DSP chip TMS320F28020 is adopted as the main control chip.The charging strategy and protection function of the OBC are realized through sampling and feeding back the output voltage and current.A flyback auxiliary power supply circuit based on chip IW1961 is designed to supply power to the control circuit.In order to realize the safe isolation between the main circuit and the control circuit and ensure the safe and efficient operation of the MOSFET,a pulse transformer isolation driving circuit is designed.On the basis of the three-stage charging strategy,a pulse current precharging process is increased.The voltage and current double closed-loop control system is adopted to ensure the output current smooth from the constant current stage to the constant voltage stage.The software design of charging strategy and the corresponding program flow charts are introduced.The test results show that the design of the OBC system topology is feasible and the hardware circuit is reasonable.Besides,the charging strategy and software program meet the design requirements and have practical value.