A family of Full-Bridge Single-Stage PFCs topologies: Identification of technical problems

In order to provide AC-DC conversion and power factor correction (PFC), Full-Bridge Single-Stage (FBSS) topologies are the most popular for high performance converters with power levels above 500W. Their behaviour and features are in general well defined and analysed. However, these topologies may introduce several complex operating limits and control problems that are not yet described in literature. This is mainly due to the fact that these limitations devaluate and restrict the number of applications. The most concerning problems are identified as: transformer primary saturation and output voltage perturbations. Wide load range variation can also be considered a complex issue because it leads to uncontrollable circuit variables, namely, input current and DC bus voltage. With the objective of clarification, this paper analyses in detail the referred technical problems considering their impact in the FBSS topologies operation and presents design criteria and control solutions to minimize their effects. Experimental results are presented to verify the theoretical concepts.