Design Guidelines for Y Capacitance Based on CM Noise Caused by Line Frequency Switch of Totem-Pole PFC

Totem-pole power factor correction (PFC) converter as front-end becomes a popular solution for two-stage AC-DC. This paper presents an analysis of the common mode (CM) noise performance of the totem-pole PFC as a front-end for AC-DC converter, by establishing an equivalent model that takes into account the Y capacitance of the DC-DC converter. Based on the proposed CM noise model and operational waveforms, it is shown that the CM current is caused by the line frequency switch, and the relationship between the value of Y capacitance and the maximum CM current is described. Experimental results indicate that a large value of Y capacitance causes a large CM current, which can lead to CM choke saturation. Therefore, the selection of the Y capacitance value plays a significant role in the CM model of totem-pole PFC.