A hybrid digital control method for synchronous buck converters using multisampled linear PID and V2constant on-time controllers

摘要

This paper presents a hybrid digital control method for a point-of-load (POL) synchronous buck converter. Two different controllers are used, seeking out to join good characteristics while eliminating drawbacks under different load conditions. For light loads, a constant on-time (COT) pulse frequency modulation (PFM) controller is used, in order to reduce power losses. For high loads, a linear pulse width modulation (PWM) PID controller is applied due to its better stability, with improved transitory response achieved by multisampling. The study was carried out for a step-down power converter from 3.3V to 1.2V with a maximum load current of 5A and the controller implemented in a Digital Signal Processor, DSP device. The feasibility of the proposed control method is shown with simulation and experimental results.