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Ultra High-Density Offline Power Solutions from ON Semiconductor

The Totem pole PFC controller is the first of its kind and provides high performance at a cost-effective price point.

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

The rectifier bridge diodes make up around 20% of the total losses in PFC circuits. The PFC stages are usually 97 percent efficient, and the LLC circuit has similar performance. Replacing the lossy diodes with switches in a ‘totem pole’ configuration and pulling in the boost PFC function can cut down the bridge losses. NCP1680 can accommodate any switch type, whether it is a Wide Bandgap switch or a super junction Silicon MOSFET switch.

The NCP1680 CrM Totem Pole PFC controller uses novel current limit architecture and line phase detection to deliver a cost-effective Totem Pole PFC solution. The internal compensated digital loop control is at the center of this IC. The device has a constant on-time architecture with valley switches. Modern efficiency standards, including those requiring high efficiency at light load, can be met because there is a valley synchronized turn-on during frequency fold back.

At recommended power levels up to 350 W, this device can be used to enable power supply designs with universal mains. PFC circuits based upon the NCP1680 can achieve close to 99% efficiency at 300 W with 230Vac mains input. Saving space and component cost are achieved by just a few simple components needed to realize a totem-pole PFC. The cycle-by-cycle limit is realized without the need for a Hall Effect sensor.

The NCP1680 is housed in a tiny SOIC-16 package and can be used as part of an evaluation platform that allows the rapid development of advanced totem pole PFC designs. Depending on the switch technology chosen 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 gate driver. The new device can be used to switch SiC-based and Silicon power MOSFETs quickly. Two 5 kV RMS galvanically isolated gate driver channels can be used as two low-side, two high-side switches, or a half-bridge driver. The NCP51561 has an enable pin that will shut down both outputs at the same time.

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