Research On Multiphase Interleaved Parallel Buck Converter And Current Sharing Control

With the continuous development and widespread popularization of electronic equipment,scenarios such as power supply of large computer servers and charging of power battery packs have higher and higher requirements for power supply equipment.The power supply equipment not only needs to provide a large output current under low voltage output conditions,but also the requirement for less ripple should also be met.As an interleaved parallel Buck converter with low ripple,low voltage and high current characteristics,it can better meet the needs of these specific equipment.However,due to the inconsistency of the parasitic parameters between the phases of the interleaved parallel Buck converters,it is easy to cause problems such as phase-to-phase current imbalance,reducing the system reliability and even reducing the service life of the converters.Therefore,the research on the current sharing control of the interleaved parallel Buck converters has important practical value.In view of this,the main research work of this paper is as follows:Firstly,the modes of three-phase interleaved parallel Buck converters under three different duty ratios are analyzed;the inductance state equations under different modes are listed;The single-phase Buck converters are compared,and the output voltage and current ripple curves of the three-phase interleaved parallel Buck converters are drawn.In principle,the low ripple output capability of the interleaved parallel Buck converters is explained.Secondly,the phase-to-phase current imbalance in the interleaved parallel converter is analyzed in detail,and the root cause of the current imbalance is found to be the phase-tophase parasitic impedance mismatch through the equivalent circuit model.On this basis,two current sharing control methods are proposed.Both of these two methods use the basic idea of duty cycle compensation for current sharing.In this paper,combining the advantages and disadvantages of the two methods,a combined mode current sharing control strategy is proposed.Compared with the traditional current sharing control strategy,the proposed current sharing control strategy is only In the case of using a voltage loop,there is no need to use a current sensor for phase-to-phase or I/O bus current detection,and a good current sharing effect can also be achieved.Then,by establishing a small signal model for the three-phase interleaved parallel Buck converter,the main topology transfer function of the converter from control to output is derived,and a reasonable compensation network is designed to correct the converter system using the voltage control mode.Combined with the current sharing the control method and voltage loop are simulated and verified in the MATLAB/Simulink platform.Finally,select the device according to the design requirements,and build an experimental prototype of a three-phase interleaved parallel Buck converter.Based on the code generation technology,the converter software system is designed through RTW realtime tools.In order to facilitate program debugging and control,MATLAB/Simulink is used to build a host computer platform.The platform uses serial communication to realize the data between the host computer and the digital controller DSP.transfer.At the same time,experiments are carried out on two-phase interleaved parallel and three-phase interleaved parallel Buck converters respectively.The experimental results show that the output voltage of the two-phase and three-phase interleaved parallel Buck converters is stable,and the output ripple is smaller than that of the traditional single-phase Buck converter.ripple,the current sharing effect is good and the current sharing error is less than 5%.At the same time,under the same load condition,the operating efficiency of the three-phase interleaved parallel Buck converter is 1-2% higher on average than that of the two-phase interleaved parallel Buck converter.