EMC Question of the Week: January 27, 2020

A key advantage of moving to higher switching frequencies in switch-mode power converters is

1. improved efficiency 
2. lower EMI
3. smaller components
4. all of the above

Answer

The best answer is "c". For a given supply current/power, higher switching frequencies allow smaller inductors/transformers to be used without saturating the magnetic material. Another advantage of higher switching frequencies is that they may produce a more stable output in response to quickly changing power demands.

For a given switching device, the amount of power lost to heat is pretty much directly proportional to the switching frequency. So improved efficiency is not an advantage of higher switching frequencies.

Also, while one could make an argument that smaller components are an advantage for EMI design, the near-field coupling from these components increases with the switching frequency. Generally, higher switching frequencies result in greater challenges for meeting EMI requirements.

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