How to control common-mode conducted interference in a concentrator?

Common-mode conducted interference in the concentrator mainly originates from the parasitic capacitance coupling to ground at the high dV/dt node of the switching power supply, manifesting as high-frequency noise current from the power line to ground. The control system needs to provide a low-impedance return path and block coupling. At the power input, a high-performance common-mode inductor CMZ1211-501T (500μH) is used, with a high-frequency impedance greater than 1kΩ at 1MHz. A Y2 capacitor (2.2nF) connected to the chassis ground (PE) provides a discharge path for common-mode noise.

The chassis grounding must be good, with a grounding impedance less than 0.1Ω. In the PCB design, grounded copper traces are placed below noise sources such as switching transistors and transformers, and connected to the inner ground plane via multiple vias. Simultaneously, to reduce coupling, the switching transistor heatsink should be grounded. Test verification shows that this solution can reduce common-mode conducted interference in the 150kHz-30MHz frequency band by more than 25dBμV, successfully passing the IEC 61000-4-6 conducted immunity test (10V).