Asymmetric modulation of bridgeless single-stage full-bridge AC-DC converter for active power factor correction and zero voltage switching

Singe-phase single-stage AC-DC converters exhibit the advantages of lower cost, higher efficiency, and lower power semiconductor device count compared with traditional two-stage topologies. However, most existing single-stage AC-DC topologies encounter some or all the following drawbacks: hard-switching operation, bulky bus or output capacitor, uncontrolled bus voltage, not actively shaped input current, a large amount of power semiconductor devices, etc. The bridgeless single-stage full-bridge AC-DC converter can be considered a promising solution for high power capacity and efficiency. However, this topology still suffers from most of the drawbacks. In this paper, a new asymmetric modulation method of bridgeless single-stage full-bridge AC-DC converter is proposed to achieve active power factor (PF) correction and zero-voltage switching. Topology description, the proposed modulation and control methods, theoretical analysis progress, and reference design procedure are presented in detail. Finally, a 2-kW laboratory prototype is implemented with experimental results presented to validate the principle and design.