Research And Design Of BUCK Type DC-DC Converter Based On Adaptive On-time Contro

With the upgrading of 5G communications,artificial intelligence and the Internet industry,the variety of electronic devices and the demand for Power Management Integrated Circuits(PMIC)is increasing also increasing.Due to the high efficiency miniaturization of Switching power supply,which have been widely concerned and recognized by researchers and the market.While the new equipment has higher requirements on the switching power supply stability,such as reliability,response speed of,thus the study of switching power supply is particularly important.Due to the high bandwidth and light load efficiency,the DC-DC Buck converter with Constant on Time(COT)control scheme has been widely used.However,the COT control scheme exists problems of overload transient response and sub-harmonic oscillation instability.In order to solve this series of problems,a high efficiency synchronous step-down chip based on valley Current Mode Adaptive on Time(CM-AOT)is proposed in this thesis.the main innovation focus on time conduction module in the traditional COT model,since comparator threshold of the traditional time conduction module is the variable related to output voltage,the fluctuation of the output voltage will cause the positive feedback information,which results in the slow transient response and loss of the stability of the system.Therefore,the novel AOT architecture was designed,which introducethe duty cycle to equivalent to the comparator threshold,the load switch can do the duty ratio of the adaptive adjustment,thus the influence of output voltage fluctuation on time conduction module is avoided,and system can realize fast transient response and efficiency when load has dramatic change in load.Compared with the compensation network architecture to speed up the system response,this structure simplifies the complexity of circuit design and further reduces the power consumption of the system.When the system works normally,the working frequency of the chip is only related to the charging capacitance and sampling resistot on chip,so the working frequency is constant.The chip adopts Hynix 0.18μm BCD process and has been successfully taped out.The chip adopts SOT＿23＿6L package,and has a wide input voltage of 4.5V to 20 V during normal operation.The typical operating frequency of the system is 500 k Hz,and the maximum operating current is 2 A.and the response time is about 20 μs when the load current varid from2 A to 0.5 A,.Finally the maximum working efficiency can reach more than 90%.