Inductance Compensation of Multiple Capacitors With Application to Common- and Differential-Mode Filters

Abstract

Capacitor parasitic inductance often limits the high-frequency performance of electromagnetic interference (EMI) filters in both common-mode (CM) and differential-mode (DM) filtering domains. However, these limitations can be overcome through the use of specially-coupled magnetic windings that effectively nullify the capacitor parasitic inductance. This document explores the use of a single coupled magnetic winding to provide inductance compensation for multiple capacitors (e.g., both DM and CM capacitors) simultaneously, reducing the number of coils previously required. The substantial advantages of this method are illustrated both in a proof-of-concept test circuit and in an improved version of an existing EMI filter. The coupling between multiple inductance compensation windings in a single filter enclosure is also investigated.Index Terms-Cantilever model, capacitor parasitic inductance, coupled magnetic windings, electromagnetic compatibility (EMC), electromagnetic interference (EMI), EMI filter, inductance cancellation, inductive coupling, radio frequency interference (RFI).

A Fabrication Method for Integrated Filter Elements With Inductance Cancellation

“…INTRODUCTION F ILTERS designed to suppress electromagnetic interference (EMI) often play a critical role in meeting requirements for device compatibility. Component parasitics, such as the equivalent series inductance (ESL) of capacitors and the equivalent parallel capacitance of inductors, often limit the size and performance of these filters [1]- [14]. Recent work has addressed methods to compensate for these parasitics, thereby increasing filter performance [5]- [15] The use of coupled magnetic windings has been shown to be effective in compensating for the effects of capacitor parasitic inductance, increasing its attenuation performance and reducing the filter volume and cost [5]- [7], [14].…”

“…2. To achieve this performance, a coupled inductor structure can be inserted into the circuit to induce a voltage that counteracts the voltage due to capacitor ESL [5]- [7], [14], as illustrated in Fig. 1(b).…”

“…As developed in a previous work, a filter with inductance cancellation can be implemented with conventional capacitors and an air-core inductance cancellation winding printed on a circuit board [5]- [7], or discretely constructed [14]. These approaches are both highly effective, but each necessitates significant effort on the part of the circuit designer to design and implement the inductance cancellation winding in the context of a particular application.…”

Classification and Comparison of EMI Mitigation Techniques in Switching Power Converters - A Review

“…The inter-winding capacitance of the transformer can be reduced by a Faraday shield [1], [50]. Several articles consider the parasitic cancellation in EMI filters to improve the filtration performance, especially for high frequency noise [51], [52]. In [51], cancellation techniques for mutual parasitics, the equivalent series inductance (ESL) of capacitors and the equivalent parallel capacitance (EPC) of CM inductors are proposed.…”

Temperature dependence of magnetic behaviour in very fine grained, spark plasma sintered NiCuZn ferrites

“…In high frequency applications for filtering purposes, wideband magnetic components with tailored characteristics are usually needed 1 . Indeed, sintered MnZn and NiZn ferrites could provide an adequate response to this challenge 2,3 .…”