Design And Implementation Of High Efficiency, Low Power Off-line Switching Power Controller

In recent years,rapid development of portable electronic products provides a large number of new demands for power management;it also brings new opportunities and challenges.Thanks for smaller size,lighter weight and higher efficiency,switching power supplies have been widely used in almost all the electronic equipment,such as computer and communication equipment.Lower power and higher efficiency have been constantly the objectives of IC designers.The topic of this thesis is to design a high efficiency,low power off-line power supply controller for general use.An off-line power supply controller based on peak current mode with pulse width modulation(PWM) and pulse skipping modulation(PSM) is presented.The chip operates at PWM mode when feedback voltage is between 3.35～4.75V,in which power MOS transistor is on and off according to clock falling edge and peak current,ensuring high efficiency and small ripple voltage.When feedback voltage is between 4.75～5.5V,the chip enters PSM mode,in which power MOS transistor is remain off until feedback voltage is below 4.75V,so switching power is reduced and high efficiency is attained.For reducing the Electro Magnetic Interference (EMI),the switching frequency is designed to be randomized to flatten power spectral density (PSD) of rapid changing voltage and current of power MOS transistor.Pins of the chip are multiplex used,which resultes in only three pins,simple structure and easy application. Additional features such as short-circuit protection,over-voltage protection,under-voltage lockout,internal slope compensation,leading-edge blanking on current sense are included.The chip was implemented by using TSMC 0.6μm 40V high voltage BCD process.Simulation results indicate that the chip can operate at PWM mode and PSM mode and there is smooth conversion between them.When it is used for Li-ion battery charger,it can realize constant voltage charging and constant current charging and perform seamless switching between them. When it is used for power adapter,it has good line regulation and load regulation.The highest conversion efficiency is up to 98%. Chapter 1 firstly introduces background,current research,development and significance of the topic,then describes major work of the thesis,and last summarizes the innovation.Chapter 2 discusses research content of the thesis in detail,especially topology,control mode,power consumption,electro-magnetic interference,also it summarizes and compares technologies on the art.Chapter 3 introduces topology of the chip,describes principle of system off chip, analyzes stability,and gives working modes of the chip and design the slope compensation. Chapter 4 gives the schematic and implemation of each module.Chapter 5 presents system simulation and layout.Chapter 6 summarizes the thesis and discusses future development.