EMI Bites: Why Fast Switching Converters Can Become EMI Nightmares
Switching converters are built for efficiency, but that speed may come at a cost.
To operate efficiently, their switching time must be as short as possible.
That means a large amount of energy moves in a very short time—
and that’s exactly why we need to watch out for EMI.
Why this may cause problems:
- Fast transitions compress energy into very short time frames.
- Short transition times generate a wide spectrum of high-frequency harmonics.
- Now you're not just dealing with the main switching frequency, but all its relevant harmonics.
- Each harmonic increases the chance of unwanted radiation, depending on your layout and structure.
Key Insight:
7Fast switching means more harmonics—and more ways for EMI to escape.
How to contain EMI from switching converters:
- Design the layout to minimize loop (signal-return) areas at high di/dt paths.
- Use solid return and reference planes (RRP) to keep fields contained.
- Watch out for nearby traces, as they can pick up and channel noise into antenna structures.
- Remember that power cables can also act as antennas and propagate the noise.
- Dario
P.S. Want more EMI control strategies to pass EMC?