Research And Design Of A High-efficiency BUCK Synchronous Rectification DC-DC Converter

Compared with linear regulator,switching power converter has small size,low electromagnetic interference and high conversion efficiency.Therefore,the proposal of smart city and the popularity of portable mobile devices advance the development of switching power converters.Portable mobile devices are in low current when standby and high current when operate in high load.In the context of slow development of battery technology and miniaturization of portable mobile devices,how to improve the conversion efficiency of switching power converters in the full load range has became the focus of current research.In the thesis,a BUCK DC-DC converter with dual control operation modes is designed.The thesis analyzes the principle and advantages of dual-control mode converter and the stability of the system loop,and calculates the loss caused by the parasitic effect of the converter.The converter chooses different control modes in different output load current to improve the power conversion efficiency in a wide load range.The converter works in Pulse Skip Modulation mode(PSM)under low load current and in Pulse Width Modulation(PWM)mode under high load current.To solve the problem of loop stability of converter under PWM control mode of peak current detection,the thesis analyzes the loop transfer function of converter system through small signal modeling.After that,circuit compensation network parameters and slope compensation values will be obtained.Virtuoso integrated circuit design platform can be used to build and simulate the stability of process angle of the small signal model.The simulation results show that each process angle loop meets the requirements of stability.The bandwidth of typical process angle system is 50.42 KHz and the phase margin is 62.43°.By using 0.35 μm 2P3 M BCD technology,key circuits such as current feedback circuit,PSM control mode,PWM/PSM selection circuit and non-crossover control signal module are analyzed and designed.In this paper,the front-end simulation analysis of the converter modules is performed,the layout design of the converter is performed using Virtuoso platform,the layout parasitic parameters are extracted by Calibre tool,and the back-end simulation analysis of the converter is performed.The back-end simulation results show that the converter can maintain a stable 3 V output at each process angle.In the back-end simulation,the output ripple voltage will less than 30 m V under high current load.On the other hand,the output ripple voltage of the converter which works in PSM control mode does not exceed 50 m V under low current load.When the load switches between light and heavy load,the load adjustment rate is about 6%.The peak conversion efficiency of the converter reaches 96.8% in the load range of 10 m A to500 m A,which meets the design requirements.