Novel control design for the buck converter

A novel control design approach for average current-mode controlled buck converters is presented. The buck converter large-signal averaged model is shown to be easily large-signal linearisable. The linear model is then examined as a multivariable system with no inner and outer loops, using both the state-space and frequency domain descriptions. Transfer functions of the system are derived as a function of the desired closed-loop poles, simplifying the design procedure and bringing forward all the important characteristics of the closed-loop system. Several advantages can be gained by the use of capacitor current instead of inductor current feedback. Theoretical analysis is applied and confirmed with simulation and experimental results on a 250 W prototype. The proposed approach can be used with all small-signal linear models of DC–DC converters, offering simplicity and a better insight on system characteristics.