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The Engineer’s Guide To EMI In DC-DC Converters
by Timothy Hegarty, Texas Instruments, Phoenix, Ariz.

Although the emergence of faster-switching power devices for dc-dc converters provides an opportunity for increased switching frequency and smaller size, the higher switch voltage and current slew rates that occur during switching transitions often exacerbate EMI, causing problems in the overall system. EMI filters are inevitably part of a power electronic system, but since filtering adds unwanted size and cost, it’s incumbent on the power designer to focus on system EMI noise reduction and mitigation.

Originally, published in the HOW2POWER TODAY newsletter, this multi-part article series addresses all aspects of EMI relevant to the design of board-level dc-dc converters with the goal of enabling designers to meet requirements for electromagnetic compliance (EMC) in automotive and industrial applications. It introduces and explains the relevant standards and measurement techniques required to perform pre-compliance EMC testing and the electrical and mechanical design techniques required to minimize or mitigate a dc-dc converter’s emissions.

Part 1: Standards Requirements And Measurement Techniques

Part 2: Noise Propagation And Filtering

Part 3: Understanding Power Stage Parasitics

Part 4: Radiated Emissions

Part 5: Mitigation Techniques Using Integrated FET Designs

Part 6: Mitigation Techniques Using Discrete FET Designs

Part 7: Common-Mode Noise Of A Flyback

Part 8: Common-Mode Noise Mitigation In Isolated Designs

Part 9: Spread-Spectrum Modulation

Part 10: Input Filter Impact on Stability

Part 11: Input Filter Impact On Dynamic Performance

Part 12: Predicting The Differential-Mode Conducted Noise Spectrum