How to face the EMC problem of the adapter

　　What should I do if there is an EMC problem with the adapter? Many inexperienced engineers do not know how to deal with the EMC problem of the adapter. They have a hammer in the east and a hammer in the west. They are lucky enough to solve the problem and feel relieved, but this is not a long-term solution. I encountered it this time, and maybe not next time. So lucky. The EMC problem is a system problem. It is necessary to have a comprehensive understanding of the system architecture, control strategy, circuit principle, and electromagnetic field principle of the entire product. In addition, there is no effective method, and it is difficult to quickly find the problem with the correct idea. A solution that can be used in two or two ways.

　　Never change from its ancestry, and see the moonlight when the clouds are removed. If you want to solve the problem, you need to grasp the main points. The main points of the EMC problem are the three elements of the old saying: interference source, transmission path, and sensitive equipment. When encountering EMC problems, we must firmly grasp the three elements. When you encounter a problem, start with the three elements, and the problem is often solved. Starting from the three elements in the design stage, we can often design better EMC products without worries.

　　Reduce the interference of the adapter interference source

　　1. Optimize the electrical structure of the equipment: For inductive loads such as motors, current noise can be reduced through internal filter circuits and mechanical structures; printed circuit boards of various electronic control units should be optimized for wiring to reduce electromagnetic emission levels. For example, if LDO can meet the demand, don't use Buck and Boost circuits with large electromagnetic interference.

　　2. Choose appropriate electronic components: The various control units on the car should not be over-designed, and the frequency and drive current should be sufficient. The use of lower frequency chips will help reduce radiation interference.

　　3. Reduce the power of the device: In the case of meeting the functional requirements, reducing the power of the device can reduce the interference voltage and current, thereby reducing the intensity of electromagnetic interference.

　　Reduce adapter coupling path

　　1. Shielding interference source equipment and related wiring harness: The main electronic control unit in the car should be encapsulated with a shielding shell as much as possible. The PCB board should try to satisfy a complete ground layer. With a complete stratum, many problems will not be a problem.

　　2. Increase wire harness filtering: For longer wire harnesses, in order to reduce conduction and radiation interference, more optimizations should be made on the wire harness. For example, CAN communication uses twisted-pair wires, and shielded wires are used for signals with large interference. For new energy vehicles, the role of shielding cables is often limited. At this time, it is necessary to consider the architecture. For example, the motor driver should be as close as possible to the motor to reduce the transmission distance of interference signals. For traditional cars, try to use external drive ignition coils and so on.

　　3. Reasonably plan the wiring harness: The wiring harness layout makes the low-power sensitive circuit close to the signal source and the high-power interference circuit close to the load. Separate low-power signals and high-power signals as much as possible to reduce crosstalk between the wiring harnesses.

　　Improve the anti-interference ability of the adapter easily interfered with

　　1. Reduce the area of the equipment receiving interference: the wiring harness should be designed with the smallest length, the smallest impedance and the smallest loop area. It is best to use the power supply mode of the twisted pair cable with the smallest loop area.

　　2. Increase the distance between the equipment and the interference source: Under the condition that the layout of the interference equipment remains unchanged, modify the installation position of sensitive components to increase the distance to the interference source.

　　3. Choose a suitable ground and ground it nearby.

　　4. Strengthen filtering design for sensitive frequency bands.

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