Research And Design Of High Efficiency Buck Converter With Multi-mode Modulation

In the era of rapid development of Internet technology,any information service is inseparable from the hardware support of electronic equipment.Power chips are indispensable as the heart of electronic devices,switching power chips are widely used in real life due to their high integration and high efficiency.To meet the real needs of continuous updates,as the most important type of switching power supply chip,buck converters are developing towards a wide input range,low EMI,high power density,and low quiescent current,in which high power density means high power.The conversion efficiency of traditional synchronous buck converters is very low at light load.How to continuously improve the light load conversion efficiency of synchronous buck converters has also become a research focus in recent years.In this thesis,a monolithic integrated switching power supply BUCK converter based on peak current mode control is designed.It adopts 0.25μm BCD process,has a wide input range of 3V-65 V,the maximum stable load current can reach 3.5A,and the operating frequency is 200KHz-3MHz,the operating frequency can be set by an external resistor or the external clock can be synchronized,and the spread spectrum mode and the power tube block driving technology are used to achieve low EMI characteristics.The focus of this thesis is to achieve high light-load efficiency of the system through different operating modes,so that the BUCK converter can automatically work with pulse-skipping modulation when the system load is reduced.In this mode,the light-load efficiency of the system can be further improved,and the static power consumption is smaller.To achieve the above design goals,this thesis first introduces the basic theory of the buck converter,analyzes and calculates the possible power loss during its operation,and determines the basic structure of peak current mode control and PWM modulation.On this basis,pulse skipping mode and burst mode are introduced,and the design principles of the two modes are expounded.Then,the circuit design of some sub-modules of the system is introduced,including the burst mode control module,the multi-mode control module including the spread spectrum mode and frequency foldback function,and the zero-crossing and overcurrent detection module of the inductor current.Each subcircuit of the module is analyzed in detail.Finally,the overall simulation of the BUCK converter designed in this thesis is carried out,including the simulation of steady-state characteristics and transient response.According to the simulation results,it is calculated that the load regulation rate and linear regulation rate of the system are both lower than 0.2%.This thesis also include the simulation of the system in pulse skip mode and burst mode under different loads and calculates the efficiency.The results show that when the load current is 10 m A-200 m A,the system can maintain the conversion efficiency of about 83% in burst mode.When the load current is 200 m A-500 m A,the conversion efficiency in the pulse skipping mode reaches about 80%.In short,the system has high efficiency at light load,which meets the circuit design requirements.