An Accurate Variable On-time Control for 400Hz CRM Boost PFC Converters

The critical conduction mode (CRM) boost PFC converter is widely used in low-to-medium power applications due to its low switching loss and simple control. Since input voltage varies sharply near the zero-crossing, where the variable on-time (VOT) control provides a longer on-time to compensate the negative inductor current, it is unprecise to assume that input voltage is constant during the switching period. Aiming at the impact of this unprecise assumption on the input current total harmonic distortion (THD), this paper establishes an accurate VOT table to reduce the input current distortion. Moreover, an input filter capacitor (IFC) current compensation method is also proposed to minimize the phase leading input current (PLIC). The experimental results of the proposed methods are demonstrated on a 160W GaN-based CRM boost PFC prototype. With the proposed methods, the input current THD is only 1.85% at 115VAC and 400Hz input with full load.