How to rectify the substandard conducted emission of the concentrator?

Concentrator conducted emissions (CE) test failures typically manifest as exceeding limits at certain frequency points between 150kHz and 30MHz. Rectification requires systematic analysis: First, identify the nature of the exceeding frequency point: If the exceedance is in the low-frequency band (<1MHz), it is usually related to differential-mode interference and grounding impedance; increasing the capacitance of the X capacitor or the inductance of the differential-mode inductor (PBZ3216E120Z0T) can help. If the exceedance is in the high-frequency band (>1MHz), it is often related to common-mode interference; strengthening common-mode filtering is necessary, such as increasing the inductance of the common-mode inductor CMZ1211-501T or optimizing the grounding of the Y capacitor. Second, check the filter circuit layout: whether the filter's input and output lines are separated, whether they are close to the power supply input, and whether the grounding is good. Then, check the internal noise sources: whether the switching frequency of the switching power supply and its harmonics fall into the exceeding frequency band; fine-tuning the switching frequency can help avoid this. Additionally, check if the PCB ground plane is intact. Finally, consider adding a ferrite core to the power supply line. Through rectification, the value of the exceeding frequency point can usually be reduced by 10-20dB.