Research On Phase-shifted Full-bridge DC/DC Variable Gain Control Method

In recent years,the iterative update speed of digital control technology has become faster and faster.For the field of switching power supplies,The digitization level gradually increases and the volume gradually decreases,and the phase shift is one of the most widely used converters because the power supply efficiency is ideally high and the output voltage ripple level is extremely low.We introduce a phase shift full bridge DC/DC converter and design a set of phase shift full bridge power supply control systems in combination with the latest digital control technology.The main component parameters are calculated,a mathematical model is established for the converter,and a specific control method is proposed.The specific content is as follows.(1)Develop a reasonable design scheme based on the phase-shifted full-bridge power supply system.The topological structure of the DC/DC converter and its widely used control strategy are described in detail.The phase-shifted full-bridge soft-switching converter is determined as the main power supply topology.The composition of the converter is introduced and analyzed in detail for each operating mode.According to the formula,the method to realize ZVS is obtained.Analyzing the phenomenon of loss of duty cycle on the secondary side and its cause,and it is concluded that it is related to resonance.The relationship between inductance,load,and input voltage.(2)According to the specific requirements of the system design,further obtain the specific parameters of different components.Through combing the data of domestic and foreign scholars and the design experience of other researchers,detailed calculations of the high-frequency transformer,resonance inductance,output filter inductance,output filter capacitor and other parameters in the main power circuit;the main elements of the phase-shifted full-bridge conversion main circuit Device parameter design and device selection,including high-frequency transformer,main power MOS tube,and secondary side rectifier diode.Matlab/Simulink software was also used to build the main circuit simulation model and perform simulation,which verified the correctness of the main circuit parameter design.(3)Study the control strategy of the phase-shifted full-bridge converter based on the selected main controller,model and analyze small signals,and design the PID control parameters for the phase-shifted full-bridge converter.Input voltage and load are variable parameters of the systemthe LPV model of convex polyhedron structure formed by the combination of extreme values of the two parameters is established,and the amount of calculation is small.By comparing and analyzing the simulation results of the traditional PID controller under different voltage setting conditions,in addition,the hardware and software of the phase-shifted full-bridge converter are designed and the power supply experiment is built,and the variable gain control strategy based on the LPV model is obtained.It has a better response speed under different voltages and the conclusion that no overshoot can be achieved.Compared with the traditional PID control,the LPV variable gain control output is stable at 10 ms,while the conventional PID control has overshoot and is stable at 25 ms.The control accuracy is within 0.1V ripple,which is less than 10% of the traditional PID control accuracy of 1.0V..The output voltage ripple peak-to-peak value is only 79 m V,and the ripple content is about 0.329%.It has a very low output voltage ripple content and meets the design requirements.The paper has 43 figures,3 tables,and 61 references.