Common mode carried out emissions tend to be brought on by parasitic capacitances like Individuals with the heatsink and transformer along with the board structure, and switching voltage waveform through the switch. Conduction Coupling occurs when EMI emissions are handed along conductors (wires, cables, enclosures, and copper traces on PCBs) https://shanefrcir.blogthisbiz.com/37659424/not-known-facts-about-emi-filter-vs-emc-filter