99% Efficient 2.5-kW Four-Level Flying Capacitor Multilevel GaN Totem-Pole PFC

In this article, a high-efficiency and high-density 2.5 kW four-level flying capacitor multilevel (FCML) totem-pole bridgeless power-factor-correction (PFC) rectifier with 200 V GaN devices is analyzed, designed, and tested. This 2.5 kW four-level continuous conduction mode (CCM) GaN totem pole PFC operates with 360 kHz current ripple frequency which significantly reduces the inductor size while keeping a very low switching loss. This article compares the device loss of the four-level and two-level CCM GaN totem-pole PFC with the same ripple frequency (360 kHz) and shows that the four-level CCM GaN PFC has much less device loss. In addition, this article introduces the detailed design of a compact and low-profile matrix inductor based on the commercial composite inductors. This article also introduces the design of a high-density and low-loss flying capacitor. A 2.5 kW four-level FCML GaN totem-pole PFC prototype with 120 kHz switching frequency (360 kHz current ripple frequency) is developed and tested in this article. The tested peak efficiency is 99.25%. The PFC system power density is 104 W/in3, without a heatsink and with forced air cooling.