In this slide, three of the most common topologies of PFC implementation are presented. These topologies are: buck, boost, and buck-boost converters. Starting with the Buck converter, the output voltage provided to the load is always less than the input terminals (also known as a step down converter). For the purpose of power factor correction, the buck converter will function in discontinuous conduction mode. The Boost converter has the output voltage greater than the input (also known as a step up converter). When using this topology for power factor correction, the current is continuous. As shown in the current diagram, Continuous Conduction Mode allows a continuous current through the inductor. The Buck-Boost converter, as the name suggests, is a combination of a buck converter and a boost converter so that the characteristics of both are achievable.