Design Of Control Strategy And Circuit In Electric Vehicle On Board Charger

In recent years,due to the depletion of petroleum resources and the emphasis on new energy industry in various countries,the production and sales of the electric vehicle industry have made a huge leap.As a core component in electric vehicles,on-board charger meets convenient charging needs of electric vehicle power batteries.This article focuses on the circuit and control design of a wide-range vehicle charger,and develops a 3.3k W wide-range high-efficiency high power-density prototype.First,this article investigates the common technical solutions in on-board charger(OBC),and analyzes the advantages and disadvantages of several typical topologies of the pre-stage AC /DC part and the post-stage DC / DC part.According to the parameter requirements of the vehicle charger in this paper,a two-stage circuit topology with bridgeless Boost PFC as the prestage circuit and full-bridge LLC resonant converter as the post-stage circuit is selected as the hardware circuit topology.According to the circuit topology and output range,the hardware parameters of each circuit are designed,and the design results are verified by simulation.Then the key components such as the magnetic components of the prototype are designed and selected,and loss calculations are performed.The loss distribution and efficiency of the circuits at various levels are given,which provides a reference for the prototype design.Secondly,the control schemes of PFC and LLC are designed.Based on the small signal modeling and analysis of the PFC circuit and the compensation control of the rectifier stage circuit,an optimization method of sampling for the PFC variable sampling point is proposed according to the characteristics of the actual digital control circuit.By analyzing the charging strategy of electric vehicle power batteries,the LLC-level circuit uses a constantvoltage/constant-current dual-loop switching output mode,and a hybrid control mode of PFM + Burst Mode.The two-stage circuit of the whole machine adopts Infineon's Aurix series MCU,and performs logic control and software protection through a program state machine.At the same time,it designs complete peripheral controls such as CAN communication and host computer,which meets the engineering requirements of vehicle chargers.Finally,a 3.3k W prototype was developed based on the above design results,and the test results of the prototype were given.The prototype meets the demand indicators such as voltage and power range.The whole machine has communication,soft start,and complete protection functions and control logic.Under full load conditions,the PFC rectifier circuit can reach a PF value of 0.999,a current THD of 5.8%,and the maximum efficiency of the whole machine can reach 95.5%.The working waveform conforms to the theoretical analysis and simulation results,which illustrates the correctness and effectiveness of the circuit design and control scheme.