0 Introduction Dedicated servo drive power supplies for DC motors are no longer just traditional switching power supplies; they directly participate in the control of DC motors. Their unique microcomputer interface control and power-on timing control functions are particularly suitable for DC motor drive systems, offering significant technical advantages over traditional general-purpose high-power power supplies. Their multi-functional technical features align with the development direction of motor drive power supply systems. However, with the proliferation and widespread use of electronic design, computers, and home appliances, power grid noise interference has become increasingly serious and a public nuisance. Transient noise interference, in particular, is characterized by its rapid rise time, short duration, high voltage amplitude (hundreds to thousands of volts), and strong randomness, easily causing severe interference to microcomputers and servo drive systems, often proving difficult to prevent. Electromagnetic interference filters (EMT filters) are a new type of combined device that has been widely promoted and applied in recent years. They can effectively suppress power grid noise, improve the anti-interference capability and system reliability of servo systems and electronic equipment, and can be widely used in electronic measuring instruments, computer room equipment, switching power supplies, and measurement and control systems. This article introduces the design of an EMI filter for a DC motor servo drive switching power supply. 1. Filter Design Based on the characteristics of the DC motor servo drive switching power supply system, the EMI filter in this design adopts a two-stage LC network design. The position of the two-stage LC network inserted into the switching power supply circuit is shown in Figure 1. (See full text: EMI Filter Design of DC Motor Servo Drive Switching Power Supply.pdf)