How to locate system-level interference sources in a PAC (Power Controller Acoustics) system?

In a PAC (Power Control Controller) system, locating system-level interference sources is fundamental to EMC (Electronic Control Computation) design. Major interference sources include internal noise from multi-core processors, high-frequency switching noise from power supplies, differential-mode radiation from high-speed buses, and common-mode interference introduced by ground loops.

The location method involves three steps: First, a near-field probe combined with a spectrum analyzer is used to scan the PAC casing, power ports, and key chips in the frequency bands. For example, a spectrum analyzer can be used to locate switching power supply noise in the 150kHz-30MHz range and bus radiation in the 30MHz-1GHz range. Second, current clamping and... Differential probes are used to measure conducted interference on critical paths on the PCB, identifying common-mode and differential-mode components. Finally, temporary filtering verification is performed using a CMZ3225A-510T series common-mode inductor (51μH) and a PBZ2012E600Z0T ferrite bead (600Ω@100MHz). An increase in insertion loss of more than 15dB confirms the interference path.

Testing and verification are conducted according to the IEC61000-4-6 conducted immunity standard and the EN55032 radiated emission standard to ensure accurate interference location and provide a basis for subsequent suppression design.