Research On Single Inductor Quadratic Buck Converter

The rapid development of new energy systems in modern society requires switching power converters to meet the requirements of a wider input voltage range.Although the traditional cascaded switching power converter can achieve the purpose of widening the input voltage range,the volume of the converter is significantly increased due to the increase of its power switch tube and inductance.In order to meet the market’s demand for small and high-power switching power converters,the research of component multiplexing switching power converters has attracted more and more attention from scholars and researchers.The inductor multiplexing converter uses the principle of time-division multiplexing the inductor to reduce the use of inductors in the switching power supply converter,thereby achieving the purpose of reducing the volume of the converter,and thus has attracted wide attention.In practical applications,setting the duty cycle of the Buck converter to be too high or too low will cause the converter drive pulse to be distorted,and the system is prone to problems such as oscillation.Therefore,the duty cycle of the converter can only be set at a moderate value.Position,which causes the Buck converter’s step-down ratio to be limited.Although the cascaded Buck converter and the single-switch quadratic Buck converter can achieve the purpose of widening the converter voltage ratio,because the converter is divided into two parts,the front stage and the back stage,two inductors are required,resulting in the converter increased volume cannot form an advantage in many practical applications.On the basis of in-depth research on the structure and working principle of traditional Buck converters,cascaded Buck converters and single-switch quadratic Buck converters,in view of the shortcomings of the above converters,this thesis is based on the principle of inductor multiplexing,a single-inductance quadratic Buck converter structure is developed.Starting from the basic principle of the single-inductor quadratic Buck DC-DC converter,the thesis analyzes and derives the sequence of the converter working in discontinuous mode,and discusses in detail the selection of inductance parameters,switch tube voltage,current stress,and the relationship between the input and output voltages,and finally the voltage-type PWM control method is used to simulate and analyze the converter working in discontinuous mode.This thesis optimizes the structure and control mode of the single-inductor quadratic Buck DC-DC converter,and proposes an improved single-inductor quadratic Buck converter that uses the output terminal to freewheel the previous stage.Research shows that the improved converter reduces the use of switching tubes and diodes,and has simplified the topology.Due to the reduction in the use of switching tubes,the working mode changes,and the converter has simplified control methods.When the two-stage PFC converter works,the front stage completes the power factor correction,and the latter stage adjusts the output voltage.The converter needs two inductors to meet the working requirements.This thesis also uses the working principle of the two-stage PFC converter,and realizes the purpose of sharing an inductor for the two-stage PFC converter by multiplexing the inductance of the front and rear Buck converters.The working sequence of the single-inductor quadratic Buck PFC converter is the same as that of the single-inductor quadratic Buck DC-DC converter.This thesis gives a detailed theoretical derivation of the converter working in critical continuous mode and uses voltage-based control methods.Simulate and analyze the single-inductance quadratic Buck PFC converter working in critical continuous mode.The final result shows that the single-inductor quadratic Buck PFC converter can achieve the function of power factor correction,and compared with the quadratic Buck PFC converter,it reduces the use of inductance,thereby reducing the converter’s cost volume.In order to verify the correctness of the theoretical derivation and simulation analysis,the thesis finally uses UC3842 as the closed-loop control chip and IR2110 as the driver chip to build an experimental prototype and experimentally verify the improved single-inductance quadratic Buck DC-DC converter.And the experiment shows that the results are consistent with the simulation results,which proves the correctness of the converter’s working principle.