Research On Half-bridge Converter For Charging And Discharging Of Lithium Battery

With the consumption of fossil energy and the deterioration of the environment,sustainable development has received more and more attention.Lithium batteries are widely used in various energy storage devices in various industries because of their high rate energy,small self-discharge,no memory,long cycling life,etc,such as portable electronic products,aerospace,and electric vehicles.With the vigorous development of the lithium battery industry,the demand for related talents in the direction of lithium batteries has also risen sharply.For the practical training courses for lithium battery and its related major students in higher vocational colleges,this thesis designed a low-power lithium battery charge and discharge equipment,it can not only charge Li ion battery at constant current and voltage,and lithium battery can also be constant current and limiting voltage discharging.This thesis first selects the half-bridge buck-boost converter as the main research object,analyzes its working principle and characteristics,simulates its design based on the parameters of the circuit in MATLAB/Simulink simulation software,and builds a power electronic platform,validates the feasibility of the design.However,when the half-bridge buck-boost converter operates in the high-step buck mode,the duty cycle is too small and the circuit cannot output stably.In order to solve these problems,this paper theoretically analyzes the working principle of a tapped inductor half-bridge buck converter,and transforms it to make its power flow in both directions.The coupling inductance is selected for the number of turns and the calculating of parameters.A software simulation of the circuit was performed to verify the correctness of the theory.Secondly,the control circuit of the half-bridge buck-boost converter is designed.Firstly,the method of charge and discharge of lithium battery is briefly introduced.The principle of the control circuit is analyzed based on constant current-constant voltage discharging.Then the lithium battery test chip,PWM controller chip and driver chip are selected,the circuit design and loop parameters are calculated for the lithium battery test chip,set the operating frequency,maximum duty cycle,soft start time and working mode for the PWM pulse circuit,the parameters of the peripheral circuit are calculated and designed for the driving circuit.Finally,according to the principle analysis,device selection and circuit design of the main circuit and control circuit of the half-bridge buck-boost converter,the corresponding circuit experiment platform is set up to test the main circuit of the converter and each module of the control circuit,enables the converter to achieve the goal of charging and discharging 1～4 string lithium batteries.