How to isolate noise from the switching power supply of a smart controller (PAC)?

The switching power supply noise of the intelligent controller PAC interferes with the system through both conduction and radiation, making isolation crucial. Firstly, a common-mode filter is constructed on the power input side using a CMZ7060A-701T common-mode inductor (700μH) and a Y capacitor to confine the noise within the power module. On the secondary side, an isolated DC/DC converter is used, with a PWRA6045 power inductor (6.8μH) and a PBZ1608A-102Z0T ferrite bead deployed at its output for differential-mode filtering. For noise-sensitive circuits, a separate LDO regulator can be used for secondary voltage regulation. Physically, the switching power supply module is placed in an independent shielded compartment within the PAC chassis. The compartment is continuously connected to the main housing via EMI springs, with a connection impedance of less than 10mΩ. Shielded twisted-pair cables are used for the power cables, with the shielding layer terminated 360 degrees to the connector housing. This isolation scheme, tested according to IEC61000-4-17, reduces conducted noise by 30dB and radiated noise by 20dB, ensuring stable system operation.