Greatly Improving EMI Filter High Frequency Performances Through the Cancellation of Inductive Couplings and Equivalent Series Inductance (ESL) of Capacitors

Because EMI standards are enforced by governments in the world, all electronic equipment uses EMI filters. The parasitics, including parasitics of components and parasitic couplings between components, affect EM1 filter performance significantly. At high frequency range, these parasitics determine filter performance. Usually, in order to reduce couplings between components, companies place components far away to each other, which makes larger filter size but the performance is still not so good. Therefore, it is very necessary to control these couplings to improve EMI filter performance. This invention proposed a novel technique to efficiently control all these parasitic parameters. Because all parasitics are controlled to very small values, filter has nearly ideal performance. The experiments show the insertion voltage gain of the prototype (minus insertion loss) is even beyond the measurement limit (-90dB) of network analyzer from 1MHz to 30MHz. The measured prototype is a one stage pi filter with corner frequency at 73kHz. The prototype achieves at least 45dB improvement compared with the products from the companies. The cost is very low.
Patent Information:
App Type Country Serial No. Patent No. File Date Issued Date Patent Status
US Utility *United States 11/013,930 7,180,389 12/17/2004 2/20/2007 Abandoned
For Information, Contact:
Li Chen
Licensing Associate
Virginia Tech Intellectual Properties, Inc.
(540) 443-9217
Shuo Wang
Fred Lee
Willem Odendaal