How to improve conducted disturbance rejection (CS) of HMI (Human Machine Delivery) systems?

Improving HMI conducted immunity hinges on preventing interference currents from coupling into the internal circuitry via cables. Conducted immunity testing involves directly injecting interference signals into power or signal lines. For power ports, the primary method for enhancing immunity is using high-performance EMI filters. These filters not only suppress emissions but also attenuate externally injected interference. Common-mode inductors in the filters, such as the CMZ7060A-701T, along with Y capacitors, form a low-pass network to prevent high-frequency interference from entering. Filters should be installed close to the power input, and their grounding terminal must be connected to the chassis with low impedance. For signal ports, such as communication lines, a combination of common-mode chokes and TVS/ESD protection devices can be used at the interface.

Common-mode chokes suppress common-mode interference currents, while TVS diodes clamp any potential overvoltages. For unshielded cables, consider using filtered connectors or adding filtering circuitry at the PCB interface. Internally, PCB design should avoid directly mixing I/O circuit grounds with sensitive digital circuit grounds; isolation is typically achieved using ferrite beads or 0Ω resistors. On the software side, add verification and retransmission mechanisms to data transmitted through interfered ports. By selecting high-performance filters and protection devices from Eternity Electronics and optimizing their installation and grounding, the HMI's resistance to conducted interference can be significantly improved.