How can power ripple in HMI (Human Machine Delivery System) be prevented from affecting EMC (Electronic Mechanism)?

To ensure that HMI power supply ripple does not affect EMC performance, it is necessary to distinguish between ripple and high-frequency switching noise and take targeted measures. Ripple mainly refers to low-frequency periodic fluctuations, with a frequency equal to or greater than the switching frequency. Excessive amplitude may affect the accuracy of analog circuits, but its high-frequency harmonics are the radiation sources of concern for EMC. Reducing ripple amplitude is a fundamental requirement of power supply design and can be achieved by optimizing the feedback loop, increasing the output capacitor (especially low-ESR polymer capacitors), and using synchronous rectification technology. More importantly, it is crucial to suppress the high-frequency harmonic components in the ripple, as these harmonics are easily conducted through power lines and radiated into space.

Using MLCC capacitors with good high-frequency characteristics in parallel with electrolytic capacitors at the power output can effectively bypass high-frequency noise. Connecting power beads in series on the output lines, such as the PBZ3216E121Z0T, can block high-frequency noise from propagating to the load. Good PCB layout is essential for controlling ripple noise radiation; the switching loop area should be minimized, and the power ground path should be short and wide. Shielding the entire power module or using shielding covers at high-frequency noise sources such as switching nodes can effectively suppress space radiation. By employing low ESL/ESR capacitors and high-frequency ferrite beads from Eternity Electronics, combined with rigorous layout and shielding, power ripple and its high-frequency components can be controlled to extremely low levels, ensuring that they do not affect the overall EMC performance of the HMI system.