Analysis of the conduction boundary of a boost PFP fed by universal input

This paper analyzes the conduction boundary of boost power factor preregulators fed by universal input (84 to 264 V rms). Former publications do not discuss the possible and undesirable continuous-discontinuous conduction traverse (or vice versa) when the conduction-boundary curve is not correctly considered. Therefore, we extend the results of the critical conduction parameter of a boost power factor preregulator (PFP) with constant rms input voltage to encompass universal input operation. It is shown that the CCM operation is always guaranteed by designing for the greatest rms input voltage. But for a DCM boost PFP it is necessary to find which input voltage (maximum M or minimum M, M being the output voltage/input voltage ratio) gives the more restrictive condition to the design. On other hand, the converter can traverse the discontinuous-continuous boundary unexpectedly. Some design examples and simulations complete the analysis.