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This article investigates the radiated electromagnetic interference (EMI) due to the voltage between input and output cables in a non-isolated power converter. The radiated EMI model of a non-isolated power converter is first developed and quantified based on the circuit topologies, printed circuit board (PCB) parasitics, switching waveforms, and transfer functions. Second, an antenna model is developed for converter cables based on the antenna impedance and the antenna transfer function. Third, a complete radiated EMI model is developed based on the converter's EMI model and the cable's antenna model. Fourth, the radiated EMI is analyzed based on the developed model. Finally, two radiated EMI noise reduction techniques, optimizing PCB layout and adding a cross capacitor, are proposed. The developed radiated EMI model and the proposed radiated EMI reduction techniques are verified with both simulations and experiments. The techniques are also extended to other two non-isolated power converter topologies when the radiated EMI is caused by the voltage between the input and output cables. [ABSTRACT FROM AUTHOR]

This article develops magnetic dipole moment models based on Maxwell's equations for inductor's near magnetic field evaluation and reduction in power electronics systems. In the developed model, the near magnetic field source of an inductor is composed of the magnetic dipole moments from the winding and the air gaps. The superposition of the magnetic dipole moments determines the near magnetic field. The developed model can be easily applied to inductors with different winding and air gap configurations, such as those with lumped or distributed air gaps, for near magnetic field assessment and reduction. Simulations and experiments are conducted to validate the developed theory. [ABSTRACT FROM AUTHOR]

This article first develops a radiated electromagnetic interference (EMI) model for a gallium nitride (GaN) integrated circuit (IC)-based active clamp flyback converter. Important capacitive couplings, which play a big role in the radiated EMI, are identified, extracted, and validated in the converter. The radiated EMI model is improved to characterize the impact of capacitive couplings. Based on the improved model, techniques to reduce capacitive couplings and the radiated EMI are proposed and experimentally validated. [ABSTRACT FROM AUTHOR]

In this article, the effects of the parameters of GaN HEMTs and Si mosfets and the load conditions on the radiated electromagnetic interference (EMI) are analyzed based on the compositions of the equivalent noise voltage sources. These compositions include the rising and falling edges of the switching voltages, the zero-voltage-switching voltage drops and the parasitic ringing. The radiated EMI from two identical dual-active bridge converters with GaN HEMTs and Si mosfets is investigated and compared. Experiments were conducted to validate the analysis. [ABSTRACT FROM AUTHOR]

In consumer electronics, high power density power adapters are designed to minimize the adapter size. As a result, the components are getting very close and the near-field coupling issue tends to be severe. This compromises the performance of electromagnetic interference filters, especially at high frequencies. This article investigates near-field capacitive couplings and the reduction techniques in a high power-density power adapter with a dc-bus filter. The parasitic capacitive coupling theory is developed and parasitic coupling capacitances are experimentally extracted. The common-mode (CM) noise model with parasitic capacitive couplings is developed and the techniques to reduce the CM noise due to parasitic capacitive couplings are explored. Simulation and experiments were conducted to verify the analysis and the proposed techniques. [ABSTRACT FROM AUTHOR]

In this article, the common-mode (CM) noise model is developed for an ac–dc–ac system with paralleled power modules. The CM noise contributions from both rectifiers and motor drives are analyzed. The interaction between the ac/dc rectifiers and dc/ac motor drives is explored. The CM noise reduction techniques which include a decoupling inductor technique and a CM noise balance technique are proposed to reduce the CM noise on the ac input side. Experiments and simulations were conducted to validate the developed CM noise model, rectifier and inverter interaction theory and CM noise reduction techniques. [ABSTRACT FROM AUTHOR]

The near magnetic field emitted from magnetic components may generate electromagnetic interference (EMI) and degrade EMI filter's performance. This article discussed the near magnetic field emission from toroidal inductors. The emission mechanisms are analyzed for different inductor winding structures with either common-mode (CM) or differential-mode (DM) excitation. The winding structures with low near magnetic field emission are identified. A CM inductor structure is proposed to improve inductor's high-frequency CM performance and greatly reduce its near magnetic field emission due to DM currents. The improvements are achieved with a small extra toroid. The proposed structure can also increase CM inductor's DM inductance for DM noise reduction at the expense of a reduced DM saturation current. To avoid saturation, a design procedure is developed for the proposed CM inductor to achieve desired CM inductance, minimized near magnetic field emission, high DM inductance, and optimal magnetic flux density. Three-dimensional (3-D) finite-element analysis models were developed and experiments were conducted to validate the developed theory and techniques. EMI measurement results show that the proposed CM inductor has a better performance for both DM and CM noise reduction than a conventional CM inductor. [ABSTRACT FROM AUTHOR]

EMC spectrum analyzers are popularly used for electromagnetic interference (EMI) measurement in power electronics systems. Depending on the specifications of EMI standards, the EMI measurement could be very time consuming. Conventionally, the fast Fourier transform is used to derive the EMI spectrum from the measured time-domain waveforms. However, these results may not agree with the measurement results from spectrum analyzers, and sometimes the difference could be significant. In this paper, a technique to quickly and accurately predict and analyze the EMI spectrum from time-domain waveforms is proposed. The technique is developed based on the spectrum analyzer's operating principle and the requirements of EMI standards. The EMI spectra of three modulation schemes are also analyzed. Theoretical analysis, simulations, and experiments were all conducted. The predicted peak, quasi-peak, and average EMI matches the measured EMI in whole conductive frequency range. The developed technique can accurately predict EMI using much shorter time than conventional EMC spectrum analyzers and it saves cost of expensive spectrum analyzers. [ABSTRACT FROM AUTHOR]

For the radiated electromagnetic interference pre-compliance diagnosis in power electronics systems, the measurement of common mode (CM) currents, impedances, and voltages are essentially important. In this article, two measurement issues are first identified in CM current and impedance measurement. The first is the coupling between the cables attached to a power converter and the coaxial cable connected to the measurement equipment. It degrades the measurement accuracy. The second is the coupling between the converter's attached cables and the ac grid. It degrades the repeatability of measurements. To improve the measurement accuracy and repeatability, this article proposes an improved measurement technique to address these two issues. Furthermore, for the measurement of the voltage difference between primary and secondary grounds, this article also identifies two issues. The first is the poor measurement resolution for the low noise voltage in the high-frequency range due to the high magnitude of line-frequency voltages. The second is that the loading effects of the voltage probe can reduce the measurement accuracy. This article proposed a technique to address these two issues. Finally, the proposed measurement techniques were validated on a flyback converter. [ABSTRACT FROM AUTHOR]

To analyze the radiated electromagnetic interference generated by isolated power converters, this paper proposes a technique to develop a general radiation model for the converters. The radiated electric field can be predicted from the developed model. The interaction between the impedance of the converter and the undesired antenna in the converter's power delivery paths is explored in detail based on the developed model. Moreover, a dual active bridge converter is taken as an example to demonstrate the developed modeling technique based on the converter's topology. The radiated electric field of the dual active bridge converter is predicted from the developed model. Experiments are conducted to validate the developed model and the predicted interaction between the converter impedance and the undesired antenna impedance in the power delivery paths. [ABSTRACT FROM AUTHOR]

In this paper, the models of active differential mode electromagnetic interference input filters for ac–dc converters are first investigated. The models are developed for active filters with single feedback (FB) and single feedforward (FF) configurations, which include an active filter, passive filters, and the noise model for a converter. To increase the gain of the single active filter, the models for FB–FF, FF–FB, parallel FB, and series feedback (SFB) configurations are developed and investigated. Loop gains and insertion gains for all of these configurations are derived and compared. Stability has been analyzed based on the loop gains and a compensation technique is introduced to ensure stability. Based on the comparison among all these control configurations, it has been found that the SFB configuration can achieve the highest noise reduction. The loop gains and insertion gains of an active filter prototype with the SFB configuration are measured using a network analyzer to validate the developed model and compensation technique. Finally, spectrum measurements with a commercial boost power factor correction ac–dc converter have been conducted to verify the developed modeling and control techniques as well as the predicted performance for the SFB configuration. [ABSTRACT FROM AUTHOR]

In this paper, the active differential-mode (DM) electromagnetic interference (EMI) filter topology for ac/dc converters is first briefly investigated. The active DM EMI filter model was developed based on the models of filter components including a current transformer, a high-pass filter, an operational amplifier, and a class AB amplifier. The system model including the active filter, ac/dc converter, and line impedance stabilization networks (LISNs) are explored. With the developed system model, the loop gain and insertion gain of the active filter are derived. Based on the loop gain, the stability of the active filter is investigated and the compensation is applied to achieve stability and good EMI reduction. Both simulations and experiments are conducted to validate the developed technique. [ABSTRACT FROM AUTHOR]

For isolated dc–dc power converters, the interwinding parasitic capacitance of the transformer is usually one of the main paths for common-mode (CM) noise. In order to simplify the CM noise analysis, this paper proposes a two-capacitor transformer winding capacitance model. The model is derived based on general conditions so it can be applied to different isolated converter topologies. A measurement technique is also proposed to obtain the lumped capacitance for the model. The CM noise models of several isolated converter topologies are analyzed with the proposed two-capacitor transformer winding capacitance model to achieve simplicity. Finally, the proposed transformer winding capacitance model and measurement technique are verified by simulations and experiments. [ABSTRACT FROM AUTHOR]

This paper develops a common-mode (CM) electromagnetic interference noise model for a three-level neutral point clamped topology. Compared with existing modeling techniques with only one CM noise source, two extra important CM noise sources and their characteristics are identified and derived for an accurate CM noise model. The impedances of CM noise path are also extracted. Based on the developed CM noise model, the CM noise spectrum can be well predicted. The effect of CM noise paths on CM noise is discussed based on two different LCL filters. A CM noise reduction technique with a balance bridge at a large impedance ratio is proposed based on the developed model. The technique can be easily implemented at low cost. Both simulations and experiments validate the developed theory and technique. [ABSTRACT FROM PUBLISHER]

Hybrid electromagnetic interference (EMI) filters (HEFs), which are composed of an active filter and a passive filter, have been proposed to reduce the size and weight of conventional passive EMI filters in literatures. However, accurate models that can be used to predict the stability and performance of HEFs have not been developed. To cope with this, this paper presents a modeling technique for a hybrid common-mode (CM) filter. The technique can be applied to the modeling of other HEFs. Critical component models were first developed for the HEF. HEF's overall model was further developed based on these individual component models. Experimental results validated that the developed model can successfully predict the stability and performance of active/hybrid CM filters. [ABSTRACT FROM AUTHOR]

This paper proposes a stacked common-mode (CM) inductor for electromagnetic interference (EMI) attenuation. The proposed stacked CM inductor consists of two CM inductors with identical cores and the same number of winding turns but with opposite winding directions. The proposed stacked CM inductor has three advantages. First, it is much less susceptible to external magnetic field interference than conventional CM inductors. This suppresses the EMI due to the near-magnetic-field coupling to the CM inductor. Second, the proposed winding structure effectively increases the leakage inductance of the CM inductor, which enhances its ability to suppress differential-mode (DM) noise. Third, the magnetic field generated by the DM current in the stacked CM inductor is partially canceled outside of the inductor. As a result, the stacked CM inductor has lower magnetic field emission than that of a conventional CM inductor. Simulation and experimental results validate the advantages of the proposed CM inductor, which show the proposed technique greatly improves the performance of CM inductors. [ABSTRACT FROM AUTHOR]

Some special electronic equipment not only need to avoid the interference of external electromagnetic waves (EMWs), but also need to transmit effective signals. Therefore, the development of directional electromagnetic interference (EMI) shielding materials has a great prospect. The asymmetric structure, consisting of the porous magentic rGF (reduced graphene oxide and Fe 3 O 4) layer and the dense electrical conductivity rGM (reduced graphene oxide and MXene) layer, was constructed by dual-needle 3D printing technology. After encapsulation and curing with polydimethylsiloxane (PDMS), the rGF/rGM/PDMS composites were prepared. When the ratio of rGF and rGM layers is 6:4, the SE values of rGF-6/rGM-4/PDMS composites are 38.75 dB and 30.79 dB respectively when EMWs are incident on the rGF layer and rGM layer respectively, and the ΔSE of which is about 8 dB. The results showed that the asymmetric structure composed of porous magnetic layer and dense deeply electric conductive layer could generate a special process of "weak reflection-absorption-strong reflection-reabsorption" for incident EMW. At the same time, the simulation results of the waveguide method validated the experimental results, and further explained the directional EMI shielding mechanism of asymmetric structure. For the first time, this work designs an asymmetric structure based on the double needle 3D printing technology, which provides useful inspiration for the structural design and potential application of directional EMI shielding materials. [Display omitted] [ABSTRACT FROM AUTHOR]