Research On CCM Switching Converter With Improved Pulse Train Control

To meet the demand of miniaturization and lightweight development of portable electronic devices,switching power supply with high power density and high conversion efficiency has ushered in tremendous development space and market potential.However,due to the strong nonlinear of switching power supply,PWM control based on linear control theory is fail to obtain better transient performance and robustness.Although the nonlinear PT control can effectively remedy the shortcomings of traditional PWM control,its application is still limited to the DCM switching converter,and its power level is small.In order to expand the power application of PT control,this paper focuses on the current development of PT control technology in CCM switching converters,and two improved PT control methods are proposed.The main research contents of this paper are depicted as follows:1.Background and significance of this paper are analyzed,the working principles,application occasion,merits and faults of linear stabilized Power supply with switching Power supply are introduced respectively.Besides,the control methods of switching converter are summarized systematically,and several control methods with distinguishing features are selected for a brief analysis.2.The research status of PT controlled CCM switching converter is summarized and the causes of low frequency oscillation are briefly described.Simultaneously,the control methods of suppressing low frequency oscillation in the existing literature are summarized,and several representative control methods are selected for detailed analysis and research.The working principle,control characteristics,merits and drawbacks of these control methods are elaborated in detail,which is of great significance and value for further understanding and researching the phenomenon of low frequency oscillation.3.In order to solve the problem of low frequency oscillation in CCM Buck converter controlled by traditional PT,a dual edge modulation pulse train(DEM-PT)control is proposed in this paper,and its control principle and implementation aredescribed in detail.The rule of control pulse combination and dynamic behavior of DCM Buck converter controlled by DEM-PT are studied in depth;For CCM Buck converter,the mechanism of DEM-PT suppressing low frequency oscillation is studied,and its synchronous switching mapping model is established.The influence of circuit parameters on the stability of DEM-PT controlled switching converter is analyzed and compared with traditional PT.Finally,the validity of the research on pulse combination rule of DCM Buck converter controlled by DEM-PT and the feasibility of CCM Buck converter controlled by DEM-PT to suppress low frequency oscillation are verified through simulation and hardware experiment successively.4.By analyzing the sufficient condition of traditional PT controlled CCM Buck converter without low frequency oscillation,two capacitor current boundaries are derived when low frequency oscillation just disappears,thus,a discrete hysteresis capacitor current pulse train(DHCC-PT)control is proposed.According to the mechanism of DHCC-PT control to suppress low frequency oscillation,a simple and reliable controller circuit is designed.Simultaneously,the working principle and six working modes of DHCC-PT are analyzed in detail.The working characteristics of DHCC-PT are studied by simulation.The research shows that DHCC-PT control not only inherits the excellent transient and robust performance of traditional PT control,but also has better starting characteristics and steady state performance than traditional PT control.Finally,the validity of the theoretical research is further verified by experiments,and the expected control objectives are achieved.