Canceling the Winding Capacitance of Inductors to Greatly Improve its High Frequency Filtering Performance

Winding capacitance of inductors is detrimental to inductor's high frequency performance since high frequency current will bypass the inductance via winding capacitance. An inductor is no longer an inductor but a capacitor at high frequencies, so that it cannot effectively block high frequency current.  Reducing or canceling the winding capacitance of inductors is therefore the key to improve inductor's high frequency performance, so as to extend its effective operating frequency range to 10-100 times.  This is especially important to EMI filter.  This invention introduces a novel idea to cancel the effects of winding capacitance, as a result, the inductor's winding capacitance is reduced by more than 95%.  Both the winding capacitance of differential mode (DM) inductors and common mode (CM) inductors can be cancelled.  The inductor's high frequency performance is improved by 30dB and its operating frequency range is extended by more than 10-30 times.  EMI measurements show >20dB improvement.
Patent Information:
App Type Country Serial No. Patent No. File Date Issued Date Patent Status
US Utility *United States 11/552,292 7,554,423 10/24/2006 6/30/2009 Expired/Unpaid Fees
US Continuation-in-Part *United States 11/850,762 7,548,137 9/6/2007 6/16/2009 Expired/Unpaid Fees
For Information, Contact:
Li Chen
Licensing Associate
Virginia Tech Intellectual Properties, Inc.
(540) 443-9217
Shuo Wang
Fred Lee