How to filter and prevent interference in the encoder power supply?

Encoder power supply lines (typically 5V or 24V) are susceptible to conducted interference, affecting the stability of the encoder's internal circuitry and leading to signal abnormalities. The Eintraelectronics filtering protection solution employs a two-stage filtering approach at the encoder power output within the servo driver.

The first stage is an LC filter: using a PWR4020R4R7M0T power inductor (4.7μH) in series, with electrolytic capacitors (e.g., 220μF/35V) and ceramic capacitors (10μF + 100nF) in parallel.

The second stage adds a common-mode choke (e.g., CML3225A-101T, 100μH) and a TVS (e.g., SMBJ5.0CA for 5V power supply) near the output connector.

Simultaneously, the power supply lines should be kept away from noise sources on the PCB, using wide traces to reduce impedance. For long-distance power supply, it is recommended to increase the supply voltage (e.g., 24V) and add a local LDO regulator at the encoder end. Tests show that this filtering scheme can reduce the noise ripple on the encoder power supply to <50mVpp, ensuring reliable encoder operation even in environments with strong interference.