Pulse Bursting Phenomenon in Constant On-time Controlled Boost Converter

Abstract

Constant on-time (COT) is a pulse frequency modulation based control method, which is widely used for the controller of switching mode power supplies due to the advantages of simple implementation, low cost and good performances. In fact, like hysteretic control, COT is also a ripple-based control, and its loop stability is very dependent on the output voltage ripple characteristic. COT controlled buck converter is mainly concerned in nowadays. For boost converter, the output voltage ripple characteristic is quite different with that of buck converter. Thus, the stability of COT controlled boost converter is necessary to be investigated. In this paper, with particular theoretical analysis, the unique pulse bursting phenomenon in COT controlled boost converter appears when the time constant of the output capacitor is relatively small, which results in large inductor current and output voltage swing. The quantitative relationship between the time constant and the other circuit parameters such as input voltage, output current and inductance is deduced, which is very different with that of COT controlled buck converter. Simulation and ex-perimental results are provided to verify the theoretical analysis results. The investigation presented in this paper gives an im-portant guideline for the circuit parameter design of COT con-trolled boost converter.