First dedicated CrM totem pole PFC controller

June 23, 2021 // By Nick Flaherty
First dedicated CrM totem pole PFC controller
The NCP1680 totem pole PFC controller is the industry’s first dedicated critical conduction mode (CrM) device.

On Semiconductor has launched the industry’s first dedicated controller for critical conduction mode (CrM) totem pole power factor correction (PFC).

The NCP1680 CrM totem pole PFC controller employs novel current limit architecture and line phase detection while incorporating proven control algorithms to boost the efficiency of totem pole designs with a range of different power devices for high power systems.

In conventional PFC circuits, the rectifier bridge diodes account for around 4 W of losses in a 240 W power supply, representing around 20% of total losses. In contrast, PFC stages are typically 97 percent efficient and the LLC circuit achieves similar performance. However, replacing the lossy diodes with switches in a ‘totem pole’ configuration and pulling in the boost PFC function can cut down the bridge losses and significantly improve overall efficiency.

The NCP1680 can accommodate any switch type whether it is super junction silicon MOSFET or Wide Bandgap switches such as Silicon Carbide (SiC) or Gallium Nitride (GaN) devices.

At the heart of the controller is an internally compensated digital loop control. This uses a constant on-time CrM architecture with valley switching. Modern efficiency standards, including those that require high efficiency at light load, can also be met due to inbuilt discontinuous conduction mode (DCM) with valley synchronized turn-on during frequency fold back operation.

Next: CrM totem pole evaluation board 

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