APEC 2021: Critical conduction mode totem pole PFC controller

Bridge-less in this case is a misnomer. It indicates no front-end diode bridge (saving the diode drops), which is instead replaced with a bridge of four transistors- two in a totem-pole operating at the mains frequency, and two in a high speed totem-pole.

Called NCP1680, at its heart is an internally compensated digital loop control implementing a constant on-time CCM architecture with valley switching.

“Modern efficiency standards, including those that require high efficiency at light load, can also be met due to in-built discontinuous conduction mode with valley synchronised turn-on during frequency fold back operation,” according to the company.

Cycle-by-cycle current limit is realised without a Hall effect sensor.

Operation across 90 – 265Vac is possible, with use recommended at up to 350W. With 230Vac mains input, close to 99% efficiency is possible at 300W, according to the company.

It comes in a SOIC-16 package, and there is an evaluation kit.

Silicon, GaN or SiC

Depending on the switch technology selected for the high-speed leg of the totem pole, for GaN the IC can be used with the NCP51820 half bridge HEMT gate driver, or for SiC mosfets the NCP51561 dual-channel isolated gate driver (4.5A source and 9A sink peak) can be used.

On Semiconductor offers a range of SiC mosfets that provide increased efficiency when compared to silicon mosfets,” according to the company. “The low on resistance and compact chip size ensure low capacitance and gate charge.” It has 650V SiC devices in TO-247-4L and D2PAK-7L packages, plus 650V silicon ‘SuperFet III mosfets.

APEC 2021: Critical conduction mode totem pole PFC controllerIn the associated evaluation kit (left), the slow silicon totem-pole is driven from a NCP51530.

The company will show a SiC industrial PSU at APEC 2021.

Applications are foreseen in universal mains power supplies for telecom 5G, industrial and high performance computing.

The NCP1680 product page is here. No data sheet was posted at the time of writing.

Author: Yoyokuo