Research On Current Sharing Control Strategy In High Step-down Ratio Multiphase Step-down Converter

With the rapid development of 5G,cloud computing and artificial intelligence industries,data centers have become an important infrastructure in modern society.These applications usually require power supply devices and power electronic converters to have the characteristics of low output voltage,high output current,and fast load transient response.The multiphase series-capacitor Buck converter has the characteristics of single-stage power structure,high step-down ratio and low device stress,which perfectly meets these requirements.This thesis mainly explores the current sharing and control strategy of this type of converter,so as to ensure that the converter has good current sharing characteristics and fast load transient response speed.In response to the problem that the series capacitor Buck converter can only achieve high step down ratio and automatic current sharing characteristics when operating in specific operating zones,resulting in limited operating range and low maximum output voltage of the converter,this thesis first analyzes the reasons why the converter cannot achieve automatic current sharing in these operating zones,and proposes a current sharing strategy based on the principle of series capacitor’s charge balance,This enables the converter to achieve automatic phase current balancing and linear high step down ratio in all operating zones.In addition,the proposed current sharing strategy has the advantages of not requiring additional current sensors,insensitive current sharing accuracy to parameter inconsistency,and easy implementation.This thesis investigates the application of charge balance control based on dynamic current sharing technology in two-phase series capacitor Buck converters,which have many state variables and working modes,making dynamic process analysis difficult.The charge balance control based on dynamic current sharing technology has a fixed switching frequency and zero steady-state error in steady-state,and the charge balance control has the optimal voltage drop,overshoot,and recovery time when load transients occur.During the transient process,the dynamic current sharing of the phase current is maintained,and the dynamic process of the system is a second-order system,greatly reducing the difficulty of analysis.Afterwards,this thesis extends the charge balance control based on dynamic current sharing technology to the three-phase series capacitor Buck converter,improving the load dynamic response speed of the converter,and summarizes the dynamic current sharing technology of the series capacitor Buck converter.In this thesis,the experimental platform corresponding to the multiphase seriescapacitor Buck converter is built,and DSP TMS320F28379 D is used to realize the corresponding control.The correctness of the theoretical analysis is verified by the simulation and experimental results.