How should AC/DC filters be coordinated with concentrators?

The concentrator has both AC power input and DC power output (e.g., for powering external sensors). Its filtering design requires AC and DC coordination to prevent crosstalk. The AC input filtering, as described above, uses a common-mode and differential-mode combination. For the DC output, to prevent internal switching noise from radiating through the DC line, a π-type filter needs to be added at the output port, consisting of a power inductor (e.g., PBZ3216E120Z0T) and a capacitor (100μF + 0.1μF).

If the DC output powers the sensor, its return ground may introduce common-mode interference; a Y capacitor (e.g., 1nF/Y1) can be connected to the positive and negative DC output lines to the chassis ground. The ground planes of the AC and DC filtering circuits should be separate on the PCB, but connected at a single point, usually to the grounding point of the AC input filter capacitor. During layout, the AC and DC filtering areas should be physically isolated to avoid magnetic field coupling. Through coordinated design, it can be ensured that the AC side conducted emissions meet standards, while the DC output ripple is less than 50mVpp and no additional radiation is generated externally.