Design Of Fuzzy PI Controller For Digital Controlled Buck DC-DC Converters

With the arrival of Artificial intelligence Era,switching power supply has been greatly developed.DC-DC converters also gradually attract widespread attention for acting as a commonly switching power supply.Comparing with the traditional analog control,the digital control switching power supply has several advantages,such as simple structure.flexible control algorithm and strong reliability.At the same time,with the gradual reduction of the size of electronic devices,the applications of digital control power supply becomes more and more extensive with higher integration、smaller volume and consumption.In this thesis,A fuzzy PI(equivalent single input-fuzzy PI(ESIF-PI))controller with superior dynamic performance is designed for the buck DC-DC converter,which is verified by simulation and FPGA test.Firstly,the basic principle of the converter system is introduced,and the transfer function of the main topology is established by the state space averaging method.Furthermore,the stable boundary of PI parameters is tuned by Julie criterion so that the PI algorithm is designed.Then introducing fuzzy algorithm and PI algorithm with analyzing the output voltage waveform and the expression of PI algorithm,the corresponding two-dimensional fuzzy rule table is established with the double-input fuzzy PI(DIF-PI)controller is obtained.Subsequently,using two Toeplitz type fuzzy rule tables substituting the function of the fuzzy rule table equally for the purpose of utilizing the signed-distance method to reduce the dimension of Toeplitz type fuzzy rule tables to obtain the SIF-PI controller.Meanwhile,the parameter is optimized using genetic algorithm to guarantee the equivalence of ESIF-PI and DIF-PI controllers in terms of control performance.Finally,the ESIF-PI controller which is really working in a single cycle is determined by a selector according to the relationship between E and EC.Since a unique SIF-PI controller is working in each sampling period so that it can be seen as an ESIF-PI controller during the whole working time domain.The FPGA based verification platform of DC-DC Buck converter is tested under different conditions.The results of dynamic test condition are followed as that the setting time of ESIF-PI and DIF-PI based on converter is 496ps and 508μ s respectively which are all less than 1.4ms of the PI algorithm.When the load current steps between 1A and 0.5A the maximum recovery time of the converter system based on the ESIF-PI algorithm is 218μs and the maximum overshoot is 212mV,which has similar dynamic performance with DIF-PI algorithm,while both are superior to that of PI algorithm.The output voltage is steady at 1.8V and it’s variation is within 1%and ripple voltage is 18mV when the input voltage changes from 1.9V to 5.0V or the load current changes from 0A to 1.1 A for the ESIF-PI which meets the design specifications.