New duty ratio control of switching converters following a reference model based scheme

A robust scheme for duty ratio control of dc-dc switching converters is presented. The proposed method adds a high gain robust loop with two controllers to the conventional single loop, achieving an analog adaptive scheme in which the voltage loop gain is not very sensitive to the changing power stage parameters: input voltage, load and component tolerances. The proposed loop improves drastically the disturbance rejection of the control system, i.e. closed loop output impedance and audiosusceptibility, while preserving stability and loop gain crossover frequency to a significant extent. Experimental results carried out on a Buck prototype 5V-5A, 50kHz demonstrate the superiority of the proposed scheme with respect to the conventional single loop.