How to optimize the EMC (Electrical Performance Measurement) of PMS (Power Management System) and mechanical switches?

Mechanical switches (such as buttons, selector switches, and relays) used in PMS generate contact bounce arcs and jitter during operation, producing broadband electromagnetic noise. Optimizing their EMC requires addressing contact treatment, arc suppression circuits, and shielding. First, select switches with built-in internal RC buffers or metal shielding shells. For exposed contacts, connect an RC buffer circuit in parallel across both ends, with a resistor of 10-100Ω and a capacitor of 0.01-0.1μF; the specific values should be determined experimentally for optimal oscillation damping. For inductive loads (such as relay coils), a freewheeling diode or TVS diode (such as SMBJ24CA) must be connected in reverse parallel across the coil. Second, place the switch and its drive circuit in a separate area on the PCB and surround it with grounded copper foil. If the switch mounting panel is metal, ensure good conductive contact between the switch's metal casing and the panel to form an electrically continuous shield. Use shielded wire or twisted multi-strand leads. On the software side, implement debouncing delay (10-50ms). After optimization, conducted interference generated by mechanical switches can be reduced by 20dBμV in the 30-100MHz frequency band, radiated interference can be reduced by 10dB, while switch life is extended and malfunction rate is reduced.