What is the relationship between screen flickering on HMI (Human Machine Delivery) displays and EMC (Electronic Manufacturing Compatibility)?

HMI display screen flickering is closely related to EMC issues, usually caused by external electromagnetic interference coupling into the display signal chain. Flickering manifests as garbled characters, stripes, snow, or localized flickering on the screen. Interference can couple through the following pathways: In the conducted path, noise contamination of the display driver chip's power supply can lead to logic errors or unstable output levels; this can be verified by testing ripple and noise on the power supply. In the radiated path, spatial electromagnetic fields can couple directly into the LVDS/RGB cable or the LCD panel, interfering with analog pixel voltages or digital signals; this is easily reproduced in radiated immunity tests. Ground loop noise causes common-mode voltage fluctuations in the display interface, exceeding the common-mode input range of the receiver chip.

Clock signal interference can cause timing irregularities. During troubleshooting, first check the shielding and grounding of the display interface cable, using a high-quality shielded cable and ensuring good grounding at both ends. Add common-mode chokes, such as the CMZ2012A-900T, to the differential lines of the display signal to enhance common-mode immunity. Strengthen the power supply filtering of the driver chip by using ferrite beads and low-ESL capacitors. Ensure the metal frame of the display panel fits snugly against the device casing. Observe the waveforms of key signals using an oscilloscope, combine this with EMC testing to pinpoint the type of interference, and then implement filtering and shielding measures from Audiotech Electronics for rectification. This usually eliminates the screen flickering phenomenon.