How to attenuate the power supply circuit noise of HMI (Human Machine Delivery) systems?

The key to attenuating HMI power supply loop noise lies in constructing a low-impedance power distribution network and inserting effective filtering stages. First, a common-mode filter circuit should be installed at the power input, including a common-mode inductor (e.g., CMZ7060A-701T) and safety X/Y capacitors, to attenuate common-mode and differential-mode noise from the mains. At the input and output of the DC-DC switching power supply, a combined filtering strategy should be used. For example, a power bead such as PBZ3216E121Z0T can be connected in series at the input, and a large-capacity electrolytic capacitor can be connected in parallel to absorb low-frequency ripple. An LC filter should be used at the output, with a molded power inductor and a combination of low-ESR MLCCs and polymer capacitors.

For LDOs powering sensitive analog circuits, RC or LC filtering should also be added to their input front end. Optimizing the PCB layout is crucial; power traces should be as short and wide as possible to reduce loop area. Decoupling capacitors should be placed near each power pin of the digital chip to form a local low-impedance energy storage loop. Meanwhile, analog power supplies, digital power supplies, and interface power supplies are isolated using ferrite beads or 0Ω resistors to prevent crosstalk between noise sources. By employing PBZ series ferrite beads and CMZ series inductors from Etymotic for targeted frequency band attenuation, conducted noise in the power supply circuit can be significantly reduced, improving system stability.