Controller design issues and solutions for buck converters with phase shedding and AVP functions

For buck converters with high output current, multi-phase interleaving is popular. To improve light load efficiency, some phases can be shut down at light load. This is called phase shedding. Adaptive voltage positioning (AVP) is normally another requirement for high output current buck. Previous papers provided AVP design guidelines for buck converters without phase shedding. With phase shedding, are these design guidelines still valid? How to design the controller so that the output transient response doesn´t get worse? This paper points out the controller design issues for buck converters with phase shedding and AVP. It is shown that the output will have worse transient response if the controller is designed in the same way as without phase shedding. New design guidelines are developed in this paper to solve the problem, which are verified by simulation and experimental results.