How to design feedback loop isolation for motion controller MC

The isolation design of the MC feedback loop in a motion controller aims to block power-side noise from entering the control side. For analog feedback, an isolation amplifier or isolated ADC is used, transmitting analog or digital signals via magnetic or capacitive coupling. For digital feedback, such as encoders, digital isolators or fiber optic transmission are used. The isolation device must meet the bandwidth and accuracy requirements of the feedback signal. Isolated power supply is critical, providing independent isolated power to the sensor or encoder on the isolated side; isolated DC-DC modules are typically used.

In PCB layout, the isolation device is connected across an isolation strip, with the circuitry on both sides strictly separated, including the ground plane. The isolation withstand voltage rating is selected based on the application voltage and safety requirements. After design, withstand voltage and functional tests are required to verify the accuracy and interference immunity of the feedback signal under isolation. While isolation increases cost, it significantly improves the reliability and safety of the system in noisy environments.