The ON Semiconductor NCP series of an integrated dual mosfet driver for interleaved PFC applications. Interleaving consists of paralleling two small stages in lieu of a bigger one, more difficult to design. This approach has several merits like the ease of implementation, the use of smaller components or a better distribution of the heating. Also, Interleaving extends the power range of critical conduction mode that is an efficient and cost-effective technique.

Frequency foldback at low power
Improve light load efficiency
Optimize efficiency over the load range