Design Of On-board Charger Based On Phase-shifted Full-Bridge Converter

With the vigorous development of the domestic new energy automobile industry,switching power supplies have gradually replaced linear power supplies with their advantages such as high efficiency,small size and light weight,which have a wide range of application values and development prospects in the on-board charger market.This thesis selects the phase-shifted full-bridge DC-DC converter as the main topology of the on-board charger,briefly analyzes the key issues of the traditional phase-shifted full-bridge DC-DC converter,such as the working principle and control strategy,and builds on this small signal model of phase-shifted full-bridge DC-DC converter.The dual-loop digital control system of the on-board charger in the average current control mode is built,and the digital PI parameters of the current inner loop and the voltage outer loop are set and simulated based on MATLAB / Simulink.On this basis,the traditional analog control method is improved,and the digital control system of the car power charger is designed.Analyze the shortcomings of the traditional phase-shifted full-bridge DC-DC converter,the lagging bridge arm is difficult to achieve ZVS,and the auxiliary power network cannot achieve reactive current control.Multi-variable control technology with switching tube duty cycle and phase shift angle as control variables and PWM control strategy based on multi-variable control technology are proposed.The disadvantages of the lagging bridge arm of the traditional phase-shifted full-bridge DC-DC converter are difficult to achieve ZVS,and the auxiliary power network cannot achieve reactive current control.The multivariable control technology with the duty cycle and phase shift angle of the switch as the control variables and the PWM control strategy based on the multivariable control technology are proposed.According to the functions and actual operation requirements of the on-board charger,the hardware control system of the on-board charger is designed.The hardware control system consists of two parts: the main circuit and the control circuit.The main circuit design mainly includes power input,APFC circuit and power circuit;the control circuit mainly includes auxiliary power circuit,main control chip,PWM drive circuit,sampling circuit,LED and relay control circuit,primary current protection circuit and communication circuit.According to the actual operation requirements of on-board charger,a software control system of on-board charger based on DSP is designed.The software control system is divided into two parts: configuration function and function function according to the difference of functions.The adjusted dual-loop PI control function realizes the stable adjustment of the on-board charger.The prototype of the on-board charger was tested on the built experimental platform.The oscilloscope was used to observe the driving signal waveform,the primary current waveform in steady state,the primary current waveform in output short circuit state,and the output voltage response waveform.The soft-start function,overcurrent protection function,low-frequency oscillation of output voltage and current,input inrush current,and efficiency,power factor and harmonic distortion of the charger are tested.The simulation results are verified through tests,and the rationality of the hardware control system and software control system is verified.