EMI filters are essential for power electronics to meet conducted emission standards such as EN 55032, CISPR 11, and FCC Part 15. A well-designed filter ensures compliance while maintaining efficiency.
Basic EMI Filter Topology
A typical EMI filter consists of a common-mode (CM) choke, X-capacitors between line and neutral, and Y-capacitors from line/neutral to ground. The CM choke suppresses high-frequency noise present on both lines in phase.
Design Steps
- Measure conducted noise spectrum with a LISN
- Identify differential-mode (DM) and common-mode (CM) noise peaks
- Select CM choke inductance based on target attenuation
- Choose X and Y capacitors rated for safety voltage
- Verify filter performance with final product testing
Common Design Mistakes
- Insufficient grounding causing poor CM attenuation
- Parasitic inductance in capacitor leads reducing effectiveness
- CM choke saturation under DC bias
Custom EMI Filters
SIRUI-Tech designs and manufactures custom EMI filters and common-mode chokes for industrial, automotive, and renewable energy applications. We support RoHS, REACH, and AEC-Q200 requirements.
About Shaanxi SiRui Technology Co., Ltd
Shaanxi SiRui Technology Co., Ltd (Sirui-Tech) is a professional magnetic components manufacturer specializing in electrical transformers, power inductors, current sensors and magnetic cores. We offer OEM & ODM services with free samples, fast lead times and 100% pre-shipment inspection. Browse our products or contact us for a quote.