Conducted EMI noise mitigation in DC-DC converters using active filtering method | IEEE Conference Publication | IEEE Xplore

Conducted EMI noise mitigation in DC-DC converters using active filtering method

Publisher: IEEE

Abstract:

Electromagnetic interference (EMI) noise mitigation is an important issue that should be addressed and emphasized when designing DC/DC converters. These later, are known ...View more

Abstract:

Electromagnetic interference (EMI) noise mitigation is an important issue that should be addressed and emphasized when designing DC/DC converters. These later, are known to be the primary culprit of the EMI noise generation in most of the electronic systems, mainly due to the switching action of the MOSFET circuitries. Passive input EMI LC filters have been the intuitive solution for EMI noise mitigation; hence they have been integrated in almost every DC/DC converters. However, their size, weight and cost can cause a significant constraint in some applications. To overcome these constraints, an input active EMI filter is proposed. The active filter is based on the noise current phase shift and the injection of this noise current back to the DC input bus. However, the combination of the input active and the passive filters shows a substantial attenuation of the conducted emissions as compared to the passive filter only, which in turn contributes to the reduction of the size and weight of the input passive EMI filter. The proposed combination provides a design solution for compliance engineers where the PCB real-estate is an issue. Experimental results to demonstrate the performance and the effectiveness of the input active EMI filter in DC/DC converters are presented.
Date of Conference: 15-19 June 2008
Date Added to IEEE Xplore: 08 August 2008
ISBN Information:

ISSN Information:

Publisher: IEEE
Conference Location: Rhodes, Greece

I. Introduction

While DC/DC converters are well known for their significant advance in their power density per square inch, and their low thermal dissipation, the thread of generating Electromagnetic Interference (EMI) noise from the high frequencies embedded in their fast switching di/dt and dv/dt has always been a concern. As the DC/DC converters follow the new trend of power generation, their switching frequencies have increased dramatically to reduce their dimensions. Most of these DC/DC converters are PCB mount type and are installed in close proximity to microprocessors to provide DC supply to motherboards. Thus, having a DC/DC converter that can coexist with microprocessors without disturbing their operation could be a challenging design. The process of having the DC/DC converter to comply with its own environment, in terms of EMI, is referred as electromagnetic compatibility (EMC). This becomes an integrated part of the design requirements that should be addressed at the early stage of the project. Further details on EMI generation in DC switching converters can be found in [1]. EMI noise can be radiated in free space or conducted through power leads. However in this paper, only conducted noise will be discussed. There are two different modes of conducted noise, common mode (CM) and differential mode (DM) conducted EMI. It is important to discern between CM and DM noises to design a suitable passive filter. The separation of these modes is demonstrated in [2], [3]. There are some modeling techniques that have been used to predict the conducted EMI noise in switching converters [4]–[7]. These techniques can significantly contribute to the passive EMI filter design and optimization.

References

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