Consider The Tradeoffs When Choosing Probes For 48-V Applications

Focus:

Markets for products powered by 48 Vdc are growing quickly. Simultaneously, GaN power devices are displacing silicon MOSFETs in many applications. However, the faster rise times require about 1 GHz of oscilloscope and probe measurement bandwidth. This article looks at active and passive probe types that are candidates for measuring switching waveforms in 48-V power converters, particularly those using GaN transistors. After identifying four probe classes, where they are used, and some example models, the discussion focuses on their use in low- and high-side gate drive measurements of GaN devices. The sources of various waveform characteristics such as overshoot, dips, ringing and noise are explored with explanations of how the different probe characteristics contribute to these effects. Side-by-side comparisons of the different probe measurements illustrate the impact of probe characteristics such as bandwidth, noise performance and CMRR on the measurements. The tradeoffs in using the different probe types are weighed with respect to the requirements of gate-drive measurements in 48-V systems. Probing tips and guidelines are also provided.

What you’ll learn:

• How to understand the options and performance tradeoffs when selecting an oscilloscope probe to measure switching waveforms in 48-V power converter designs
• How to make gate drive measurements on GaN power devices in 48-V power converter designs

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Author & Publication:

Ken Johnson and Yash Gupte, Teledyne LeCroy, Chestnut Ridge, NY, How2Power Today, Nov 15 2021

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