Surface mount components are used in the device to make the assembly density higher, the volume is smaller, the weight is lighter, the reliability is higher, the high frequency characteristics are better, and the electromagnetic and radio frequency interference are reduced.

2.6 PCB component layout and routing

The string between the strip line, the wire and the cable in the PCB is one of the most difficult problems in the printed circuit board circuit [7]. The radiated disturbance of the switching power supply is proportional to the product of the current in the current path, the loop area of ​​the path, and the square of the current frequency. Therefore, the layout design of the PCB will directly affect the electromagnetic compatibility of the whole machine. When designing a switching power supply printed circuit board, it is necessary to start with the optimized design of the layout and routing.

(1) Printed board wiring usually meets the following principles

1. The wires used at the input and output terminals should be as close as possible to avoid equality. It is best to add the ground wire between the wires to avoid feedback coupling.

2. The printed circuit board wire should be as wide as possible, especially the power line and the ground line;

3. The curved corner of the printed conductor generally adopts a circular arc shape;

4, dedicated zero-volt line, power line trace width (1mm, power line and ground line as close as possible.

(2) The layout of components usually meets the following principles

1. Arrange the position of each functional circuit unit according to the flow of the circuit, so that the layout facilitates signal circulation and keeps the signal as consistent as possible.

2. Center around the core components of each functional circuit and arrange it around it. Components should be evenly, neatly and compactly arranged on the PCB to minimize and shorten leads and connections between components.

3. For circuits operating at high frequencies, the distribution parameters between components should be considered. The general circuit should make the components equally arranged as much as possible.

4, the components located at the edge of the board, the distance from the edge of the board is generally not less than 2mm.

3. Conclusion

The switching power supply is getting smaller and smaller, and the power density is getting larger and larger. The EMI/EMC problem has become a key factor in the stability of the switching power supply, and it has received more and more attention. There are many electromagnetic compatibility control strategies and control technologies for switching power supplies, such as suppression of interference transmission channels, separation of space, separation of time, frequency management, and electrical isolation. In the design of the switching power supply, only the comprehensive use of various electromagnetic interference suppression technologies can effectively improve the electromagnetic compatibility of the switching power supply, and truly meet the needs of various occasions.

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