Current and Voltage Balancing Slim-type 3-level Boost PFC Converter

Compared to a conventional boost power factor correction (PFC) converter, the flying-capacitor clamp three-level boost (FCTLB) PFC converter operates its inductor at twice the switching frequency. The voltage of the flying capacitor reduces the slope of the inductor current, allowing the maximum inductor current ripple to be reduced by a factor of four. This outcome enables the use of a smaller inductor. Additionally, all switching devices in the FCTLB PFC converter experience only half of the output voltage as voltage stress, making it advantageous for achieving high efficiency and high power density. To realize these benefits, the flying capacitor voltage must be maintained at half the output voltage. However, conventional control methods struggle to maintain this voltage. Specifically, achieving an optimal controller design while considering the dynamic characteristics of the flying capacitor voltage is difficult, and in practical cases with parasitic elements or deviations in gate driver circuits, steady-state errors in the flying voltage control can occur. This paper proposes an independent control method that overcome the limitations of conventional approaches. The proposed method not only facilitates optimal controller design but also eliminates steady-state errors. It can also be implemented by simply adding a general voltage controller for the flying capacitor to a conventional PFC controller, allowing for analog implementation using low-cost general-purpose ICs and OP-AMPs. The effectiveness of the proposed control method was validated through experimental results using a 400 W prototype of the FCTLB PFC converter