ON Semiconductor's power factory corrections (PFC) are utilized to shape the input current of off-line power supplies to maximize the real power available from the mains. Ideally, the input current would be a perfect in-phase replica of the input voltage, reducing the current draw from the mains and thus minimizing losses and costs associated with the distribution and generation of the power. This, along with minimized interference thanks to freedom from harmonics, enables the design of highly efficient power supplies that comply with today's every-expanding regulatory requirements.

ON Semiconductor offers PFC controllers implementing innovative CCFF, VSFF, and FCCrM methods that provide significant light-load efficiency improvements. In addition, these methods enable the use of a smaller transformer when compared to the traditional Critical Conduction Mode (CrM) approach. For example, in a 100 W application with similar performance, a CrM implementation requires a ~450 µH transformer whereas applications using ON Semiconductor solutions would require only ~300 µH. The smaller size and improved light load efficiency make them a good fit for products required to meet new industry efficiency standards.

Current Controlled Frequency Fold-back (CCFF)
CCFF reduces frequency when the instantaneous line current is below a present level; where switching losses are dominant. Frequency decay rate is controlled for optimized efficiency.

Valley Synchonized Frequency Fold-back (VSFF)
With VSFF, the frequency is reduced when the control signal is below a present level by adding a constant dead-time over the sinusoid.

Frequency Clamped Critical Conduction Mode (FCCrM)
FCCrM firmly limits the frequency at a present level.