The filtering technique is used to suppress conducted interference along the wire, and is mainly used for power supply interference and signal line interference suppression. A filter is a frequency-selective network of inductors, capacitors, resistors, or ferrite devices that can be inserted into a transmission line to suppress unwanted frequencies from propagating. First, the power filter The power supply filter is bidirectional. It not only prevents noise in the power grid from entering the device, but also suppresses noise generated by the device from polluting the power grid. 1. Structure of power line filter