The NCP1631 is a controller for use in 2-phase interleaved power factor correction pre-converters. Interleaving consists of paralleling two small stages in lieu of a single big stage. This approach has several merits like ease of implementation, ability to use smaller components, and better distribution of heating. These attributes make the interleaved PFC topology attractive to slim form factor applications such as flat panel TVs and ultra-slim notebook adapters.

180° out of phase operation
Frequency foldback at low power
Integrated Over current protection, overvoltage protection, UVLO, and brown-out protection
Frequency clamped critical conduction mode (FcCrM) operation
Low EMI and reduces RMS current in the bulk capacitor
Improved light load efficiency
Increased robustness with few external components
Optimized efficiency over the load range