Investigation of Zero-crossing Common-Mode Noise and Current Spike in GaN Based Totem-Pole PFC

Totem-pole PFC has the potential to achieve high efficiency and power density by using GaN HEMTs as the high-frequency switching device. With the advent of 600-650V rated commercial GaN HEMTs, the totem-pole PFC is expected to emerge as the dominant topology for the front-end of telecom and data center power supplies. Like most bridgeless topologies, totem-pole PFC generates a large amount of common-mode (CM) noise. Especially around the zero-crossings of input line voltage, the noise is very prominent and a huge current spike is also observed in the input current. A few existing works have theorized about the origin of the CM noise and the spike current but they lack the proper explanation to relate these two mutual issues and estimate the influence of different circuit parameters. The objective of this work is to establish the relationship between these two issues, primarily through the investigation of practical waveforms and a modified CM noise model. To facilitate the design of the totem-pole PFC with reduced EMI, a set of mathematical equations are also developed from a proposed equivalent circuit. Finally, the contribution of different circuit parameters on CM noise and spike current generation at zero-crossing is identified and outlined from the analysis of the equivalent circuit.