The MC33260 is an active power factor controller that functions as a boost pre–converter which, meeting international standard requirement in electronic ballast and off–line power supply application. MC33260 is designed to drive a free running frequency discontinuous mode, it can also be synchronized and in any case, it features very effective protections that ensure a safe and reliable operation. This circuit is also optimized to offer extremely compact and cost effective PFC solutions. It does not entail the need of auxiliary winding for zero current detection hence a simple coil can be used instead of a transformer if the MC33260 Vcc is drawn from the load (please refer to page 19 of the data sheet). While it requires a minimum number of external components, the MC33260 can control the follower boost operation that is an innovative mode allowing a drastic size reduction of both the inductor and the power switch. Ultimately, the solution system cost is significantly lowered. Also able to function in a traditional way (constant output voltage regulation level), any intermediary solutions can be easily implemented. This flexibility makes it ideal to optimally cope with a wide range of applications. This application note will discuss on the design of power factor correction circuit with MC33260 with traditional boost constant output voltage regulation level operation and follower boost variable output voltage regulation level operation. For derivation of the design equations related to the IC please refer to MC33260 data sheet.