Modeling System Of Peak-Current-Mode-Controlled Buck Converter And Design Of The Controller

High efficiency electrical portable products are widely used to promote the rapid development of power supply chips. The switching power converters are increasingly replacing traditional linear power supply due to its small space, light weight, low power dissipation, high efficiency, adoption and broad applicability, etc. Currently domestic switching power converters are under the transition from voltage control mode to current control mode. Because of the complexity of the double-loop control theory, the research of current control mode is rare. Considering these factors, a highly efficient current-mode buck converter has been designed from the starting point of system-level.This thesis firstly studies the basic principle of the switching power converters. The peak current mode (PCM) control of the Buck converter has been thoroughly analyzed. Then the PCM controlled Buck converter is modeled base on power stage and control closed-loop, then a small signal model of the system and closed-loop transfer functions of the system are obtained. Through thorough analysis and research on current loop and voltage loop of the converter, a system-level design of the converter is completed. Performance of the system-level design is validated with Matlab. Finally, the converter on circuit-level is designed. Especially some critical blocks, such as error amplifier block and PWM comparator block design are designed.The design is implemented base on the 0.6μm BCD technologies, with the fully system-level simulations. The results indicate that the controller has a fast transient response and a good soft start performance, small output ripple and high conversion efficiency up to 90% in typical application.