Analysis and Suppression of Common-Mode EMI Noise in 1 MHz 380 V-12 V DCX Converter With Low NFoM Devices

For the thriving information technology industrial applications, the series resonant converter (SRC) dc transformer (DCX) using integrated printed circuit board (PCB) windings is a preferred candidate because of its high efficiency and high power density characteristics by pushing the frequency to megahertz. However, the planar PCB transformer possesses large interwinding capacitance, which leads to severe common-mode (CM) noise and a large electromagnetic interference filter. Hence, the total volume of the conversion system is still high. In this article, a series inputs and parallel outputs (ISOP) structure for DCX is analyzed and discussed to demonstrate the CM noise reduction with the static point construction method, in which several dv/dt static points are constructed. Unlike most of the present suppressing methods, it can maintain high efficiency as well. Additionally, the ISOP structure provides more opportunities for optimizing control strategies to achieve the cancelation effect and further reducing the CM noise by the interleaving within a cell and the interleaving among cells. The excellence of the aforementioned methods is verified by experiments on 1-MHz 380 V-12 V 1.8-kW SRC DCX prototypes with a peak efficiency of 98.3%. The proposed methods ultimately reduce the CM noise by 50 dB.