Digital Control for Improved Efficiency and Reduced Harmonic Distortion over Wide Load Range in Boost PFC Rectifiers

This paper addresses control techniques aimed at improving light-load efficiency and reducing harmonic distortion in digitally controlled single-phase boost power factor correction (PFC) rectifiers. Based on a discontinuous conduction mode (DCM) detection circuit, it is shown how an extension to the predictive current control law leads to improved current regulation over wide load range in both continuous conduction mode (CCM) and in DCM. Furthermore, adaptive switching and adaptive switching frequency techniques are introduced to reduce switching losses and improve efficiency at light loads. Experimental results are shown for a 300W boost PFC rectifier.