Design and experiment research of integrated EMI filter based on flexible multi-layer foils

As an important role in electromagnetic interference (EMI) solving of switching power supply, the EMI filter’s performance and integrated design are of great significance to improve the power density of switching power supply. This paper combines the basic means of magnetic integration and electrical integration of the filter and utilizes the integration advantages of flexible multilayer foils (FMLFs) to integrate the common and differential mode inductor and Y capacitor of the filter into a unit module. At the same time, the design value of the differential mode inductor is increased through the decoupling design of the common and differential mode inductor. Compared with the traditional discrete filter, the integrated filter omits the Y capacitance and reduces the X capacitance, which can effectively reduce the board area of the EMI filter on the premise of consistent performance. Combined with the design process of the integrated filter, to improve the integration, this paper mainly discusses the process of core selection, performance prediction, and performance modeling, and finally verifies the feasibility and effectiveness of this scheme through a noise comparison experiment.

This paper studies the conducted electromagnetic interference (EMI) problems in a DC/DC switched-mode power supply (SMPS) with semi-isolated topology. A high frequency circuit simulation model is firstly established to predict the conducted emissions of this power supply. Then the common mode (CM) and the differential mode (DM) conducted emission mechanisms of this power supply are analyzed in detail according to its working principle and structure. The voltage of the rectifier diodes at the transformer's secondary is founded to be the main CM EMI sources. A DM noise coupling phenomenon from the voltage ripple of output port is discovered and its role on EMI emission is explained too. Based on conduced emission paths analysis, three kinds of EMI filters, including traditional input EMI filter, high frequency input and output port EMI filters and a new DM topology filter are proposed to restrain the conducted emissions respectively. Their effectiveness is verified with experiments and the merits and drawbacks of different designs are also introduced.

This paper presents a systematic and comprehensive approach for differential mode (DM) electromagnetic interference (EMI) filter design in a three-phase boost-type power factor correction (PFC) rectifier. Since the DM EMI filter forms a significant portion of the overall filter as well as converter volume, the reduction of DM filter component size is kept as a major objective in the filter design process in order to improve the power density. In addition to the objectives of volume optimization and conducted emission attenuation requirement to comply with the EMI standard, the filter design process also ensures a near-unity power factor operation with the optimal set of EMI filter parameters. To accomplish this, the paper analyzes the effect of EMI filter component selection on the overall lower order (1-100 kHz) frequency response, which is important for evaluating the dynamic response and stability. The results from the proposed design approach are validated through simulation, the DM Bode plot, and frequency response of the input current with and without EMI filter. As a proof-of-concept verification, the proposed EMI filter is implemented in a 4-kW three-phase boost-PFC prototype, which demonstrates minimal phase displacement (<;5°) of the input current.

Active electromagnetic interference (EMI) filter is a feasible and effective suppression technology for switching mode power supply (SMPS) system. The traditional active EMI filter (AEF) suppresses EMI by sensing EMI signal and generating cancelation EMI by the controlled high-frequency operational amplifier. The filtering performance not only depends on the high-open-loop gains of the operational amplifier but also on its low-output impedance of AEF. However, obtaining sufficiently low-output impedance of AEF is very difficult in a controlled filtering frequency band. To cope with it, a filtering topology of AEF based on impedance modulation for SMPS is proposed in this article. The proposed active trap EMI filter (ATEF) can trap the EMI current at the filtering frequency band with a sufficiently low-output impedance by introducing a negative impedance circuit. Finally, the impedance and the filtering performance are evaluated on a 48 W SMPS, and experimental results show that the proposed ATEF can effectively suppress the conducted EMI generated by SMPS.

A unique design technique of power line filter is being proposed. It is based on the conventional technique of composite low pass filter. The equivalent circuit of the composite low pass filter is being presented in the two different modes by considering the modal propagation of noise. The consideration of composite LPF is taken into account in the design technique of power line filter. In order to accurately predict the insertion loss of the filter the effects of non-ideal behaviour of the passive lumped components are considered. It is based on the parasitic effect of the passive lumped elements. The filter is then characterized using S-parameters. The response of the filter's circuits is simulated using advanced design software (ADS). Keywords: Conducted emission, Composite filter, electromagnetic compatibility, lumped elements, and power line filter. I. Introduction Switching and modulation techniques are used for efficient use of electrical power. Widely used Switched mode power supplies (SMPS) for powering today's electronics loads is a most common example. Unfortunately, all the power control techniques deliberately distort sinusoidal wave form of power frequency and generate unwanted interfering signals. Obviously, they all are often cited as one of the main source of conducted emission (CE). Usually the power supplies which are using controlling techniques cannot comply with the strict electromagnetic compatibility (EMC) regulations. In order to meet the limit set for conducted EMI, power supplies require a filter at its input. Conducted EMI generated through particular equipment gets coupled into other equipments mostly through power line cables. CE can be controlled by using filters and increasing line impedance. Conducted EMI has two components: The common mode (CM) interference and differential mode (DM) interference. The coupling mechanisms of these interferences are different (4). The difference in the direction of propagation of these coupling currents along the phase and neutral line, leads to differential mode ( ) current and common mode ( ) current. Therefore design of EMI filters demand decoupling of these two modes (2). This paper attempts to describe a design technique for Power Line filter using classical design technique. 1.1 Characterization of common mode & differential mode currents

This paper proposes an EMI filter design and optimization method for both AC and DC side in a DC-fed motor drive system. Based on the noise generation and propagation mechanism, the analysis of common mode (CM) and differential mode (DM) EMI noise equivalent circuits is provided. Based on those equivalent circuits, this paper investigates the system EMI noise between AC and DC side, which shows the interaction between DM and CM noises and the interaction between adding AC and DC side filters. With these considerations, an optimized EMI filter design procedure is proposed to design CM and DM filters for both AC and DC sides. To minimize the impact on the EMI noise of one side caused by adding filter on the other side, certain order must be followed to design AC and DC CM and DM filters. Moreover, the EMI filter weight optimization method is also discussed to get the minimum weight of EMI filter and improve system power density. Simulation and experimental results verify the interaction between AC and DC filters and show that EMI filters can be designed to suppress both AC and DC EMI noise to meet the standard with the proposed EMI filter design method.

EMC filters consist of passive components mainly. The insertion loss and type of filter define the appropriate values of these components. However, the volume of EMI filters is usually defined by the common-mode (CM) and differential mode (DM) inductors. In order to reduce the total volume, in this paper the Coupled Common-Differential Inductor (CCDI) is proposed. In addition, two aspects are presented: the influence of the packaging and the winding strategy in the high frequency CCDI impedance. The CCDI is manufactured using two types of magnetic materials. Nanocrystalline ring core for CM impedance and iron powder for DM impedance. The experimental results highlight the advantages and disadvantages of the packaging and winding strategy of CCDI.

Switched-mode power supplies (SMPS) are the source of both conducted and radiated electromagnetic interference (EMI) noise. Resonant converters are popular due to the possibility of switching loss reduction using zero voltage switching (ZVS) or zero current switching (ZCS) and also attenuating conducted EMI noise. Conventionally, a common-mode (CM) choke with a single core and two identical windings is used to suppress the CM noise in an EMI filter. This paper introduces an effective and cost-efficient method for mitigating the CM EMI noise in SRCs. The proposed method benefits a two-winding coupled inductor instead of the simple resonant inductor in the SRC. While a unity turn ratio does not meet the desired resonance inductance, the suggested two windings coupled inductor with an unequal number of turns deals with the EMI noise as well as the normal operation of an inductor in the resonant tank. Applying the proposed method significantly achieves up to 20 dB attenuation in the noise amplitude both at the input and output terminals of the converter. Simulations are used for investigating the analysis of the method. Moreover, a series resonant converter is designed and implemented to verify both analysis and simulations.

In literature, the use of passive electromagnetic interference (EMI) filters is extensively researched to not only restrain the common-mode (CM) noise but also the differential-mode (DM) noise. Although the CM and DM chokes are simple to design, reliable, and do not need an auxiliary power supply, they increase the overall volume and reduce the power density of a power converter. Hence, this paper presents a novel integrated choke that offers higher DM impedance than the traditional CM choke by maintaining the same volume, when compared to the traditional CM choke. The calculation of CM inductance, as well as DM inductance of the proposed integrated filter topology, is presented along with a small signal measurement using an impedance analyzer. The proposed EMI filter performance is verified on a three-phase silicon carbide (SiC) fed brushless dc (BLdc) motor.

This paper analyzes the electrical parameters of differential-mode (DM) and common-mode (CM) inductors used in EMI filters. To design an EMI filter, it is necessary to identify the various parameters of the passive elements: inductors and capacitors. Because of their major impact on filter efficiency, these elements must be identified with accuracy. In this study, a high frequency model of coupled inductors is proposed. Simulation results of the proposed model are compared to the experimental data obtained using a specific experimental setup. These results made it possible to validate the filter model in frequency range varying from 9 kHz to 30 MHz. The proposed high frequency coupled inductors model will be very helpful for EMI filter optimization design.

Along with the increasing price of copper material, there is more demanding on cost price of switching power supplies due to those weighty inductors such as common-mode (CM) chokes. The total capacitance of CM filter is usually limited by safety standard. As a result, large bulky CM inductor is usually required. In some applications, such as silver-box power supply, wherein the CM noise is not mainly from PFC part, the dc-dc will dominant the CM noise level. For the purpose of reducing CM filter, bare CM noise of typical dc-dc converters was investigated and the effect of duty cycle on EMI noise is discussed in detail. Presuming the corner frequency of EMI filter and its size as well is determined by the low-frequency bare noise, by optimizing the noise spectrum in the most sensitive frequency range and creating a valley in the vicinity of 150 kHz for the noise spectrum, the frequency of critical noise spectrum to be attenuated can be increased and so does the corner frequency of CM filter. Experiments are performed to verify the benefits in a typical power supply design.

This paper proposes an analytical method based on two ports network to analyze the conducted electromagnetic emission interference of typical airborne full bridge AC/DC Switch Mode Power Supply (SMPS) in tow modes, which are common mode and differential mode respectively. According to the analysis results, the SPICE circuit model of the SMPS is established. The model is simulated and obtained the time domain results. The results are processed by an algorithm that considered intermediate frequency bandwidth influence. The frequency domain calculated results are compared with the practical measurement data. The compare results verify the feasibility and reliability of the above methods.

This paper deals with a high frequency modeling method of the common and differential mode inductors used in EMI filters. These filters are intended to reduce conducted emissions generated by power static converters towards power network. To model the EMI filters, it is necessary to identify the various parameters of the passive elements: inductors and capacitors. Because of their major impact on filter efficiency, these elements must be identified with accuracy. In this study, high frequency model of common mode coupled inductors is proposed. Simulation results of the proposed model are compared to the experimental data obtained using the specific experimental setup. These results made it possible to validate the proposed filter model and its robustness in a frequency range varying from 9 kHz to 30 MHz. The proposed high frequency inductor models will be very helpful for design optimization of EMI filters, since the high frequency behaviour of the filter mainly depends on magnetic materials used and on the geometrical characteristics of winding.

The switching frequency of the boost power factor correction (PFC) converter operating in critical conduction mode (CRM) varies in a line cycle, making the conducted electromagnetic interference (EMI) spectra of the converter appear great differences under different input voltage and load conditions. The EMI filter should be designed according to the worst conducted EMI spectrum of the converter, so as to suppress the conducted EMI of the converter to be lower than the standard limits under all working conditions. This paper analyzes the characteristics of the common-mode (CM) and differential-mode (DM) noise spectra of the CRM boost PFC converter, and discusses the effects of the varied switching frequency on the peak, quasi-peak (PK), and average (AV) conducted EMI spectra. It is revealed that, for the conducted EMI limits defined in EN55022 class B, which are specified within 150 kHz to 30 MHz, the EMI filters required for suppressing the QP spectra of the conducted EMI of the CRM boost PFC converter are larger than that for suppressing the AV spectra, and the QP values of the conducted EMI under all working conditions are lower than a certain maximum boundary. The input voltage and load conditions for the worst CM and DM noise spectra of the converter are derived in this paper, thus the repetitive measurements and numerical calculations are avoided. A CRM boost PFC converter prototype is fabricated, and the evaluation of the measured conducted EMI spectra and the EMI filter design example verified the theoretical analysis.

High-frequency grid-tied inverters in vehicle-to-grid (V2G) systems often produce lots of high-frequency harmonics and electromagnetic interference (EMI) noise. Therefore, a filtering module, which consists of a harmonic filter and an additional EMI choke, is typically required to effectively restrain the aforementioned noises, but this passive module will inevitably raise size and cost of the converter, which goes against high-power density demand of electric vehicles (EVs). To address this issue without impairing the filter’s performance, this article proposes a decoupled electromagnetically integrated structure of a symmetrical <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCL</i>-EMI filter for grid-tied converters in V2G applications. EE-shape magnetic core and flexible multilayer foil (FMLF) technique are employed in the integration design, the FMLF windings for achieving a symmetrical <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCL</i> filter are wound on side limbs of the EE core, and the EMI choke windings are arranged on the central limb. The used proper terminal configuration of the windings can almost realize function-decoupling between the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCL</i> unit and EMI choke. Moreover, magnetic decoupling can be achieved between converter- and grid-side inductors of the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCL</i> unit through air-gap design in the EE core’s side limbs, which can preserve the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCL</i> unit’s satisfactory harmonic attenuation performance. Performance analysis and design principles of the integrated module are introduced, and the experimental results from a 1-kW SiC-MOSFET high-frequency grid-tied converter confirm the feasibility and validity of the approach.