EMI filter and frequency filters having capacitor with inductance cancellation loop
US7180389B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Dec 17, 2004 |
| Grant date | Feb 20, 2007 |
| Priority date | — |
| Expiry date | Jan 17, 2025 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03H2001/005
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
An electromagnetic interference (EMI) filter or frequency filters (e.g. bandpass or band reject filters) in which a capacitor has an inductance cancellation loop. Inductive coupling between capacitors can allow undesired high frequencies to propagate across a filter. This is particularly a concern when the capacitors are oriented in parallel. In the present invention, the inductance cancellation loop is disposed adjacent to one capacitor so that mutual inductance between the capacitors is reduced. The attenuation of the filter at high frequencies is thereby increased. The loop can increase voltage attenuation of an EMI filter by about 20 dB. In another aspect, inductors in the filter are oriented horizontally relative to a circuitboard. Horizontal orientation reduces leakage inductance coupling between the inductors and circuitboard traces, and between the inductor and capacitors, thereby preventing unwanted propagation of high frequencies. Both measures in combination can provide a voltage attenuation increase of 30 dB.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.