The Engineer’s Guide To EMI In DC-DC Converters (Part 1): Standards Requirements And Measurement Techniques
by Timothy Hegarty, Texas Instruments, Phoenix, Ariz, How2Power Today, Dec 15 2017
Focus:
Although faster-switching power devices for dc-dc converters enable increased switching
frequency and smaller size, the higher switch voltage and current slew rates that occur during
switching transitions often exacerbate EMI. Although EMI filters are inevitably part of the
solution, they add size and weight. Therefore the power designer must focus on system EMI noise
reduction and mitigation to design dc-dc converters that meet electromagnetic compliance (EMC)
standards. Part 1 in this article series reviews the EMC standards for industrial and
automotive end equipment and describes how to measure conducted EMI in pre-compliance testing.
After discussing the relevant standards such as EN 55022, FCC Part 15, EN 55032 and CISPR 25,
part 1 explains the role of the line impedance stabilization network (LISN) and details of its
use. The article then describes a CISPR 25 test setup for measuring conducted emissions of
power converters for automotive applications. Photos of an example test setup and example
measurement results are included.
What you’ll learn:
- How to understand which EMC standards apply to power converters targeting industrial and automotive applications
- How to measure conducted EMI of power converters for automotive applications
- How to perform conducted EMI precompliance testing per CISPR 25
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