What is the optimal placement of the magnetic ring and filter in the PAC (Power Controller Acoustic Control Unit)?

In a Power Acoustic Controller (PAC), the placement of magnetic rings and filters directly affects EMC performance. Magnetic rings should be installed near the entry point of interference sources or sensitive lines. For example, using a nickel-zinc magnetic ring (such as the PBZ series integrated magnetic beads) on the output line of a switching power supply can attenuate high-frequency noise by more than 10dB. Filters (such as common-mode inductors) should be placed in the interface area of the PCB, following the principle of "protection first, filtering later": at the power input, the order is surge protection device → X capacitor → common-mode inductor → Y capacitor.

For signal lines, filters (such as CMZ2012A-900T) should be placed close to the connector to ensure that noise is filtered out before entering the board. At the same time, avoid placing filters above the heat dissipation path of power devices to prevent performance degradation due to temperature rise. Optimizing the position through near-field probe scanning can reduce the radiated emissions of the PAC by 6dB in the 30MHz-1GHz range and pass the IEC61000-4-3 radiated immunity test.