Solving Technical Problems on the Full-Bridge Single-Stage PFCs

AC-DC conversion with power factor correction using full-bridge single-stage (FBSS) converters may introduce various complex operating limits and control problems that are not usually described in literature. This is mainly due to the fact that they devaluate and restrict the number of applications of those topologies. These problems are identified as primary transformer saturation and output voltage perturbations. The operation at light loads and with wide load variation is also a complex issue that leads to uncontrollable input current and dc bus voltage. This paper clarifies such technical problems referring their impact in the FBSS topologies operation, and presents design criteria and control solutions to minimize their effects. A low cost free wheeling circuit (FWC) that allows null input current to solve the light load operation problem is also presented.