Conduction Mode (CCM) Power Factor Correction (PFC) controller

IC designed to drive the bridgeless totem pole PFC topology. The

bridgeless totem pole PFC consists of two totem pole legs: a fast−

switching leg driven at the PWM switching frequency and a second

leg that operates at the AC line frequency. This topology eliminates

the diode bridge present at the input of a conventional PFC circuit,

allowing significant improvement in efficiency and power density.

The NCP1681 is available as a Fixed Frequency (NCP1681Ax) or

Multi−Mode (NCP1681Bx) device.

General Features

• Totem Pole PFC Topology Eliminates Input Diode Bridge Enabling

Very High Efficiency & Compact Design

• AC Line Monitoring Circuit & AC Phase Detection

• Brownout Detection

• Digital Loop Compensation

• Novel Current Sensing Scheme Providing Inductor Current Upslope

and Downslope Sensing

• PFCOK Indicator

• Skip/Standby Mode for Optimizing Light Load Performance

• Near−Unity Power Factor in All Operating Modes

Multi−Mode Operation

• Continuous Conduction Mode (CCM) in Heavy−Load Conditions

• Critical Conduction Mode (CrM) in Light & Medium Load

Conditions

• Optional Fixed Frequency CCM Across Load Range

• Simplified Valley Sensing

Safety Features

• Soft and Fast Overvoltage Protection

• 2−level Latch Input for OVP & OTP

• Bulk Undervoltage Protection

• Internal Thermal Shutdown

• Cycle−by−cycle Current Limit

Applications

• Cloud/Server Power Supplies

• High Performance Computing

• 5G/Telecom Power Supplies

• Industrial Power Supplies

• Ultra−High Density (UHD) Power Supplies

• Merchant Power