Optimal Zero-Voltage-Switching Method and Variable on-Time Control for Predictive Boundary Conduction Mode Boost PFC Converter

This article presents a fully zero-voltage-switching (ZVS) method and an optimal variable on-time (VOT) control for the predictive boundary conduction mode (BCM) boost power factor correction (PFC) converter. The operation analysis of the BCM boost PFC converter, which considers the parasitic capacitances, is performed. Based on the analysis, a novel Taylor approximation method to derive the equations of switching off-time for achieving fully ZVS is proposed. Then, an inductor current approximation method is applied to derive the VOT equation in order to reduce the input current total harmonic distortion (THD). A calculation method for selecting the accurate parasitic capacitance is proposed. Most importantly, the derived equations for achieving ZVS and VOT control are simple and take short calculation time in a DSP controller, and, thus, they can be applied to the predictive control. Experimental results demonstrate that the fully ZVS operation can be achieved by the proposed ZVS method. The input current THD is indeed improved by the optimal VOT control.