The NCP1608 is an active power factor correction (PFC) controller specifically designed for use as a pre-converter in ac-dc adapters, electronic ballasts, and other medium power off-line converters (typically up to 350 W). It uses Critical Conduction Mode (CrM) to ensure near unity power factor across a wide range of input voltages and output power. The NCP1608 minimizes the number of external components by integrating safety features, making it an excellent choice for designing robust PFC stages.