Industrial Electronics

Ultra-high density offline power solutions

07 July 2021

Industry’s first dedicated critical conduction mode (CrM) totem pole power factor correction (PFC) controller is a new addition to the ON Semiconductor solution set for ultra-high density offline power supplies.

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% 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 Source: ON SemiconductorSource: ON Semiconductorimprove overall efficiency. Further, NCP1680 can accommodate any switch type whether it is super junction silicon metal-oxide semiconductor field-effect transistor or wide bandgap switches such as silicon carbide (SiC) or gallium nitride (GaN) devices.

The new NCP1680 CrM totem pole PFC controller employs novel current limit architecture and line phase detection while incorporating proven control algorithms to deliver a cost-effective totem pole PFC solution without compromising on performance. At the heart of this IC is an internally compensated digital loop control. The innovative device employs 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.

This highly integrated device can enable power supply designs that operate with universal mains (90 V AC to 265 V AC) at recommended power levels up to 350 W. With 230 V AC mains input, PFC circuits based upon the NCP1680 are capable of achieving close to 99% efficiency at 300 W. Just a few simple components are required externally to realize a fully featured totem pole PFC, thereby saving space and component cost. Further reducing component count, the cycle-by-cycle current limit is realized without the need for a Hall Effect sensor.

Housed in a tiny SOIC-16 package, the NCP1680 is also available as part of an evaluation platform that allows rapid development and debugging of advanced totem pole PFC designs.

To contact the author of this article, email engineering360editors@globalspec.com


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