An Improved Digital Algorithm for Boost PFC Converter Operating in Mixed Conduction Mode

This article proposes an improved digital algorithm based on predictive control for the operation of a boost power factor correction (PFC) converter in the mixed conduction mode (MCM). The proposed MCM algorithm comprises of a proposed digital conduction mode detection method, a proposed predictive discontinuous conduction mode (DCM) average current controller, a proposed digital compensation technique in DCM to account for the initial nonzero inductor current during switch turn-on and also a predictive continuous conduction mode (CCM) average current controller. The proposed algorithm flow is computationally efficient with no additional sensor/circuit requirements and ensures low harmonic content in the input current. The proposed MCM algorithm is verified experimentally on a 300-W boost PFC converter hardware prototype for converter operation in MCM, pure DCM, and pure CCM within a half line cycle. The proposed MCM algorithm is evaluated experimentally in terms of current tracking, current harmonics, and computation times.