Unified Voltage Balancing Feedforward for Three-Level Boost PFC Converter in Discontinuous and Critical Conduction Modes

This brief presents a unified voltage balancing feedforward (UVBFF) for three-level boost (TLB) power-factor-correction (PFC) circuit in discontinuous and critical conduction modes. In general, the topology in both modes puts emphasis on low-cost system. Thus, electrolytic capacitors with wide-tolerance are commonly used at outputs and voltage unbalance is inevitable even under symmetric operations of two boost cells. In this brief, three-level switching capability of TLB PFC is introduced and asymmetric on-time feedforward for main switches is proposed. The proposed UVBFF can be realized by a single equation and harmonized with conventional feedback voltage-loop so that easy implementation is the key merit. The effectiveness of UVBFF is proven by analyses and experimental results.