Digital controller design for fourth-order soft-switching boost converter

Abstract

In this paper a digital voltage-mode controller is designed for a fourth-order soft-switching boost converter. The proposed converter exhibits voltage gain same as that of conventional boost converter but has lower source current ripple as compared to it. Additionally, it exhibits reduced switch transition losses on account of zero voltage transition behavior. In soft-switching operation it exhibits seven different modes of operations in one switching cycle and also results in zero-voltage transition to the switching devices. As there are several operating modes in one switching cycle the small-signal z-domain transfer functions are formulated using MATLAB based system identification toolbox, which are then used in the direct digital controller design. A sisotool of matlab is adopted to arrive at final digital voltage-mode controller. Closed-loop converter performance is determined for a 12 to 28 V, 50 W prototype in simulation and then compared with experimental measurements. Experimental measurements are in close agreement with simulations.