Nonlinear Modeling Of Multiphase Peak-current-mode-controlled Buck Converter

With the development and gradually mature of microprocessor's performance,currently the microprocessor needs higher computing performance,faster computing speed and faster transient response.The power supply of microprocessor needs to meet the requirement of smaller output voltage,miniaturization,lower EMI,the increas-ing output current capacity,higher power density,faster load transient response and other characteristics.So the traditional single-phase DC/DC converter has its limitation.In order to meet above characteristics,it opens a new way for power supply of microprocessor,which is the multi-phase DC/DC converter with its unique performance.This thesis introduces a nonlinear model for two-phase Buck converter with peak current mode(PCM)con-trol,which works on continuous conduction mode(CCM).And the model is used for analysis and verification of the actual converter.Firstly,using the traditional state-space averaging method,the synchronous rectifier module model of CCM PCM Buck converter is built.And combing the power module model,control circuit module mod-el,current sampling module model and error amplifier module model,a small-signal nonlinear average model of PCM Buck converter is built.Secondly,according to the work method of the multiphase PCM Buck converter and each module model of single-phase PCM Buck converter,the nonlinear model of two-phase PCM Buck converter is built,which uses the state-space averaging method.Finally,the proposed nonlinear model of two-phase PCM Buck converter is applied to the actual two-phase PCM Buck converter,compared with circuit simulation model,and predicts behaviors of the effective frequency well.Simulation experiments show that for the two-phase PCM Buck converter with switching frequency of2MHz,when the bandwidth is 600 kHz,the frequency is up to 2MHz comparing the curves of gain-frequency characteristic between the nonlinear model and the circuit simulation model.And the frequency is up to 1MHz,1/2 f_s,comparing the curves of phase-frequency characteristic between the nonlinear model and the circuit simula-tion model.Therefore,the nonlinear model of two-phase PCM Buck converter can predict behaviors well of the effective frequency(<1/2 f_s)and provide a theoretical guidance for the accurate design of the power converter.