EMI Considerations in Selecting AC/DC Switching Power Supplies

Focus:

Switched-mode power supplies can be a source of EMI in a system and are also vulnerable to EMI to the point where their operation is affected. Even power supplies that have passed EMC testing on their own can cause a system to fail EMC tests. The ways in which switched-mode power supplies contribute to system-level EMI are discussed. The elements of power supply design that influence the generation of EMI such as transformer design, PCB layout, use of capacitors and inductors as filters, also discussed with an eye toward helping the system designer select an appropriate power supply. Also addressed are other power supply selection issues such as the need to verify EMI compliance on an actual power supply sample unit, the issue of unit-to-unit variation in production, the need to test EMI performance with the power supply in system, and the issue of power supply immunity.

What you’ll learn:

• How to select ac-dc power supplies to achieve EMI compliance in your system designs
• How to minimize EMI when designing ac-dc power supplies

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Author & Publication:

Ryan Gordon Benhard, Medical Electronics Manufacturing, Sep 01 2005

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