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First dedicated CrM totem pole PFC controller

Technology News |
By Nick Flaherty

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 


The highly integrated device can enable power supply designs for telecom 5G, industrial and high performance computing, that operate with universal mains (90 – 265 Vac) at recommended power levels up to 350 W. With 230 Vac 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.

In a 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.

Depending on the switch technology selected for the fast leg of the totem pole, NCP1680 can be used with either NCP51820 half bridge GaN HEMT gate driver or NCP51561 isolated SiC MOSFET gate driver.

The NCP51561 is an isolated dual-channel gate driver with 4.5 A source and 9 A sink peak current capability. The new device is suitable for fast switching of silicon power MOSFETs and SiC-based MOSFET devices, offering short and matched propagation delays.

Two independent and 5 kVRMS (UL1577 rated) galvanically isolated gate driver channels can be used as two low-side, two high-side switches or a half-bridge driver with programmable dead time. An enable pin will shut down both outputs simultaneously and the NCP51561 offers other important protection functions such as independent under-voltage lockout (UVLO) for both gate drivers and the enable function.

www.onsemi.com

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