How to control EMI in HMI display modules?

Controlling EMI in HMI display modules requires separate measures for the display driver circuit, backlight circuit, and signal interface. Display driver chips typically operate at high frequencies and are the primary source of radiation. Decoupling capacitors, such as 0.1μF and 10μF capacitors in parallel, should be placed near the chip's power pins, and ferrite beads, such as PBZ2012E121Z0T, should be used on the power input path to filter high-frequency noise. For high-speed display interfaces such as LVDS or RGB, differential traces should be used with strict impedance matching. Common-mode chokes, such as CMZ2012A-900T, can be connected in series on the differential pairs to suppress common-mode noise radiation.

Backlight driver circuits, especially the switching noise of LED drivers, are significant interference sources. A π-type filter can be used at the driver output, and low-ESR electrolytic capacitors should be selected. The metal frame of the display panel should be connected to the system chassis with low impedance via conductive foam or metal springs to ensure shielding continuity. If display signals are connected via long cables, TVS diodes, such as SMBJ5.0CA, should be used at the interface for transient protection. Furthermore, optimizing the PCB layout by keeping the display module circuitry away from sensitive circuits and system clock areas can reduce crosstalk. These comprehensive EMC design features effectively control the conducted and radiated emissions of the display module.