The Design Of AOT Control Buck DC/DC Converter With Chip Ripple Compensation

In recent years,with the continuous development of electronic power technology,portable electronic products such as mobile phones and tablet computers have gradually penetrated into people’s daily life and become an integral part of daily life and office.As the core device of electronic products,the power management chip plays a vital role in the battery life and service life of electronic products.Therefore,power management chips have become an important research topic in modern science.Switching power supplies have the characteristics of high efficiency and small size,and are one of the most widely used power types.DC/DC converters,as an important member of the switching power supplies,have the functions of boosting,bucking,and polarity conversion of DC voltage.However,at present,the domestic market is still dominated by low-end products,and high-end fields are firmly occupied by joint ventures or foreign-funded enterprises.In the face of this situation,we need to make more efforts.This thesis first introduces several circuit topological structures of DC/DC converters,which focuses on buck converters,then explains the working principle,modulation mode,and control mode of DC/DC converters,and compares their advantages and disadvantages.Synchronous rectification technology is also briefly explained in this thesis.Then,this thesis introduces the system design of the buck converter,which mainly includes design goals,working principle,application circuit and efficiency analysis.After a brief description of the functions of the converter sub-modules,the detailed theoretical analysis of the adaptive ontime generation circuit,ripple compensation circuit,voltage reference circuit,feedback comparator,under-voltage lockout circuit,and over-temperature protection circuit is carried out,and the circuit function is simulated and verified.Finally,the overall simulation of the system is performed,including system soft-start simulation,steady-state working simulation,load transient response simulation,linear regulation simulation and system efficiency simulation,and this thesis verifies key performance indicators,and briefly introduces layout design.The buck DC/DC converter in this thesis uses an adaptive on-time control mode.On the basis of the constant on-time control mode,the on-time is not related to the input and output voltage,so that the system frequency can keep constant,which improves the conversion efficiency of the converter.Because the converter selects ceramic capacitor as the output capacitor,an on-chip ripple compensation circuit needs to be designed to prevent the subharmonic oscillation that may be caused by the small ESR of the output capacitor.At the same time,depending on the load,the converter can choose between two different working modes: continuous conduction mode and discontinuous conduction mode.The continuous conduction mode is selected at heavy load,and the discontinuous conduction mode is selected at light load.The converter integrates a series of protection circuits such as undervoltage lockout,over-temperature protection,and over-current protection to ensure the safe operation of the converter.The buck DC/DC converter using adaptive on-time control mode designed in this thesis has a simple structure,fast transient response speed,high conversion efficiency,and has broad application prospects.The DC/DC converter designed in this thesis is based on a 0.25?m Bi CMOS process.Cadence circuit design software is used to design the system structure and submodule schematic diagrams,and the Spectre simulation software is used for simulation and verification.It can be seen from the simulation results that the overall system function and the sub-module functions meet the design requirement.