Dynamic Modeling and Analysis of Constant On Time Variable Frequency One-Cycle Control for Switched-Capacitor Converters

A constant on time variable frequency one-cycle control technique (CVFOCC) for switched-capacitor (SC) converters is presented in this paper. It is designed to accomplish the continuous variable conversion ratio and fast dynamical response to reject the external disturbance. A proper regulation can be obtained by controlling the related "off time" of a transistor with the constant "on time" which is less than the time constant tau of the charge loop. A unique large-signal dynamic capacitor ampere-second balance (CASB) model for SC converters is applied in this research study. It is implemented to instantaneously estimate transient values of the equivalent circuits. The proposed modeling method and analysis have been verified by comparing the modeling expressions with simulation and experiment results for different input voltages, load currents and switching frequencies. The simulation and experiment results show that the external disturbance of a single-stage SC converter could be immediately rejected by the proposed control method. The good line and load regulation are demonstrated. The proposed control method is stable and global. It can work in a wide operation range with a simple control circuit for general SC converters.