The NCP1655 is an innovative multimode power factor controller. The circuit naturally transitions from Continuous Conduction Mode (CCM) to Critical Conduction Mode (CrM) and vice versa depending on the switching period duration, so that the efficiency is optimized over the line/load range. In every-light-load conditions, the circuit can enter the soft-SKIP mode for minimized losses. Housed in a SO-9 package, the circuit further incorporates the features necessary for robust and compact PFC stages, with few external components.