Research On The Modeling Methods Of AC-AC Switched-Capacitor Converters

As human society enters the information era,electronic devices,most of which are powered by switching converters,have occupied an increasingly more important position these days.With the miniaturization trends of switching converters,the SC converter,which only consists of switches and capacitors,takes advantage of the small volume,light weight,high efficiency,high power density,low EMI.As capacitors can be more easily integrated than the inductors,SC converter has found its place in emerging areas such as wearable devices,automotive systems and renewable energy.It also has great application prospects with its scalability for power.As the switched-capacitor converter presents nonlinear characteristic,the modeling of the converter has its specialty and complexity.Early modeling methods like the state-space averaging method ideally transformed the converter to a linear one and made use of classical control theory for the design of control.The switching frequency,which is an important parameter,was left out in the idealized model and that leads to an inaccurate model and certain limitations in use.In recent years,researchers at home and abroad have put forward couples of modeling techniques to analyze the switched-capacitor converter.However,most of them have own shortages.A transient analysis modeling method is proposed in this thesis inspired by previous studies.SC converters with conversion ratio of 2 and 3 being the main studying object,the conversion ratios of the converters are derived based on the transient operational states to analyze how circuit parameters affect the performance.Based on the mathematical model,the equivalent circuit is established to analyze the steady-state characteristics and the efficiency.Theoretical analysis is performed to illustrate transient behaviors under different operation modes as well as component stress.The effectiveness of the proposed method is verified by simulation results and experimental results that it is more precise than the previous methods and can reflect the properties of the switched-capacitor converter comprehensively.