How to layout PCB when designing switching power supply
The electromagnetic interference generated by the switching power supply often affects the normal operation of electronic products, so the correct PCB layout of the switching power supply becomes very important.
In many cases, a power supply that is perfectly designed on paper may not work properly when it is first commissioned, because there are many problems with the PCB layout of the power supply.
In the design of switching power supply, PCB design is a very critical step, which greatly affects the performance, EMC requirements, reliability and manufacturability of the power supply.
With the development of electronic technology, the volume of switching power supply is becoming more and more compact, the performance is more powerful, the switching frequency is getting higher and higher, and the density of devices is getting higher and higher, which requires more and more anti-interference requirements for PCB layout and wiring. The stricter it is, so a reasonable and scientific PCB layout becomes very important. This article will give advice on how to achieve a good PCB layout the first time.
General PCB layout should follow a few points
1. The first principle of layout is to ensure the completion rate of wiring. When moving devices, pay attention to the connection of flying wires, and put the devices with connection relationship together;
2. Determine the position of the switching power supply module on the PCB. The switch is a strong source of EMI radiation. It should be placed away from sensitive components such as clocks and interfaces, and should be placed as close as possible to the power terminal, while considering factors such as heat dissipation and assembly;
3. Determine the difference between the main power supply channel and ground in the schematic block diagram (power ground, signal ground, and other signal ground). Red is the main current channel; purple is the difference between ground; blue is the feedback channel;
4. Take the core components of each functional circuit as the center and make layout around it. Components should be evenly, neatly, and compactly arranged on the PCB, so that it is not only beautiful, but also easy to assemble and weld, and easy to mass produce. Minimize and shorten the leads and connections between components, decoupling capacitors should be as close as possible to IC pins, and ground wires should be short;
5. When placing devices, consider future welding and maintenance. Try to avoid placing short components between two high-height components.
6. When laying out components, the loop area of high-frequency pulse current and high current should be given priority, and the area of high-frequency loop should be reduced as much as possible to suppress the radiation interference of switching power supply;
7. Arrange the position of each functional circuit unit according to the circuit flow, make the layout convenient for signal circulation, and keep the signal in the same direction as possible;
8. The placement of via holes should not destroy the path of high-frequency current on the formation;
9. The layout of heating elements (such as transformers, switching tubes, rectifier diodes, etc.) should consider the effect of heat dissipation, so that the heat dissipation of the entire power supply is uniform, and key components that are sensitive to temperature (such as IC) should be kept away from heating elements. There should be a certain distance between the device and the electrolytic capacitor and other devices that affect the life of the whole machine.
