Research On Phase Shifted Full Bridge Electronic Load

Traditional load is gradually replaced by electronic load because of its big loss and high cost when it is used to do factory performance test for all kinds of power supply.The use of electronic load can greatly increase the utilization rate of electric energy,improve the safety performance,reduce the cost of use,so the research on electronic load is of great significance.Firstly,the research status and control methods of AC/DC electronic load at home and abroad are described.Then the working principle of electronic load is analyzed,and the topology of load analog circuit and energy recovery circuit is selected.Because the phase-shifting full bridge circuit can be applied in high-power occasions and soft switching characteristics,the energy consumption of the whole system is smaller and the efficiency is higher,so the load analog circuit and energy recovery circuit adopt the phase-shifting full bridge circuit.The small signal analysis of phase-shifting full bridge circuit is carried out,and the transfer function of input current about duty cycle is established.When the system parameters are fixed,the duty cycle can control the input current,and then the load simulation is completed.On this basis,firstly,the PI controller of load analog circuit is designed.The amplitude frequency and phase frequency characteristics of Bode diagram show that the phase margin of the PI controller designed in this paper is in the best range.Secondly,an exponential function is added to the traditional constant velocity reaching law to form an optimized constant velocity reaching law,which solves the problems of slow tracking speed and serious jitter of the traditional constant velocity reaching law.The optimal constant velocity reaching law is applied to the energy recovery circuit,and the sliding mode controller of the energy recovery circuit is established.Then,taking the energy recovery circuit as an example,the hardware circuit is designed,the high frequency transformer is calculated and analyzed,and the DSP system resource configuration and program flow of digital control are given.Finally,the simulation model of electronic load is built in matlab/simulink to verify the control method of load simulation circuit and energy recovery circuit designed in this paper.The simulation results show that the optimized constant velocity reaching law makes the energy recovery circuit have faster response speed and smoother output waveform when the load changes suddenly.The experimental prototype is made and the sliding mode controller of the energy recovery circuit is tested.The experimental results verify the feasibility of the optimized sliding mode controller with constant velocity reaching law.Figure[75]table[4]reference[91]...