Description
This design uses a Critical Conduction Mode (CrCM/DCM) PFC (AC-400 VDC), followed by an LLC DC-DC (400-19 VDC). For both stages, the switching frequency was increased to the maximum allowed by the off-the-shelf control ICs available. The board is designed to be a ‘demonstration’ board, and is not yet optimized as a production design. With this design, a power density of 2.18 W/cc or 35.75 W/in3 is achieved, which is around 2x typical and 40% more than the best-on-class Si-based design today. Customer designs are expected to achieve even higher power density. The PFC section is a standard ON Semi NCP1615 CrCM/DCM powering 2x NV6115 (parallel) GaNFast Power ICs directly. Critical mode PFC (also known as boundary mode) is a soft-switching topology which allows higher frequency operation. The DC-DC section uses the NCP13992 current-mode resonant controller (LLC) driving NV6115s. The NV6115s have monolithically-integrated gate drivers, so the NCP13992’s drivers are not used and loss is minimized.