How can you design a power supply with low EMI?

2 Minimize the loop area

One of the main sources of EMI is the loop area formed by the switching elements, the input and output capacitors, and the wiring. The loop area acts as an antenna that radiates electromagnetic waves when the current flows through it. The larger the loop area, the more EMI it produces. You should minimize the loop area by placing the components close to each other, using short and thick wires, and avoiding sharp bends and loops. You should also use a ground plane or a shield to enclose the loop area and reduce its radiation.

3 Filter the input and output

Another way to reduce EMI is to filter the input and output of your power supply. The input filter prevents the high-frequency noise from the power source or the power line from entering your power supply and affecting its operation. The output filter prevents the switching noise from your power supply from reaching the load and causing interference. You can use passive components, such as capacitors, inductors, and resistors, to form low-pass filters that block the high-frequency noise and pass the low-frequency signal. You should choose the filter components carefully, considering their values, ratings, parasitics, and placement.

5 Select the right components

The components you use for your power supply design can also affect the EMI level. You should select the components that have low EMI characteristics, such as low parasitic capacitance and inductance, low switching losses, low reverse recovery time, and low noise. You should also avoid using components that have high EMI susceptibility, such as long leads, ceramic capacitors, and electrolytic capacitors. You should also use decoupling capacitors, snubber circuits, and ferrite beads to suppress the noise and spikes in your power supply circuit.

These are some of the basic tips and techniques to help you design a power supply with low EMI. By following these guidelines, you can improve the quality and performance of your power supply and the devices it powers. You can also avoid EMI-related issues, such as signal degradation, data corruption, and regulatory compliance.

6 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?