GaN technology and the potential for EMI

by Kenneth Wyatt, EDN, Jul 01 2015

Focus:
With their picosecond switching speeds GaN transistors seem likely to generate significant EMI. The author of this article, an EMC consultant, tests this assumption by performing a series of measurements on a buck converter using EPC’s eGaN transistors. He attempts to measure the transistor’s rise time, but finds his test setup is bandwidth limited, yielding “only” a 1.5-ns rise time. He does however measure the ringing of the switching waveform, the conducted EMI on the input power cable and through the load resistor (measuring harmonics out to about 600 MHz and noting that the load resistor measurements would likely fail a conducted emissions test). Finally, the author measures the near-field radiated emissions around the GaN device and the load resistor, noting some resonances that could be troublesome for compliance. Probes used to make the measurements are identified. The author concludes that more study is needed on the impact of GaN switching speeds on EMI consequences.

What you’ll learn:

• How to evaluate the impact of fast switching GaN transistors on EMI emissions and product EMC

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