Differential Mode Electromagnetic Interference Research Articles

Output DM EMI Noise Prediction for MHz TCM-Based Single Phase Inverter

Conventional fast Fourier transform analysis is limited in conducted electromagnetic interference (EMI) prediction for triangle current mode (TCM) based converters. Several prediction strategies based on EMI receiver modeling have been published for this issue, but the prediction range was below 1 MHz. Such a narrow frequency range cannot meet the demands of EMI prediction for MHz converter. In this article, a more accurate differential mode (DM) EMI prediction is proposed for MHz TCM-based single-phase inverter. The accurate drain-to-source voltage model considering the TCM resonant transition is established for different TCM-derived strategies at first. Passive components of the propagation path are also modeled with the measured impedance for more accurate transfer gain. An improved envelope detector model of the EMI receiver is proposed for an accurate quasi-peak spectrum. The prediction range can be extended to 5 MHz. Moreover, the EMI of TCM, hybrid triangle current mode, and sinusoidal triangle current mode are analyzed and compared with the established prediction strategy. The worst spectrum can be determined, and the DM filter can be designed without repetitive measurements. Finally, A 500 W MHz single-phase inverter prototype is built, and the evaluation of the measured conducted EMI spectrum and the EMI filter design can verify the theoretical analysis.

Degradation monitoring of SiC MOSFET gate-oxide based on differential mode conducted interference spectrum

The gate-oxide degradation of power devices has an important impact on the normal operation of electrical equipment. Therefore, the research on the condition monitoring of gate oxide is of great significance to improve the operation reliability. In this article, a new monitoring method for the gate oxide in silicon carbide (SiC) metal-oxide-semiconductor field-effect transistors (MOSFETs) is proposed. Firstly, the degradation mechanism of gate oxide and its influence on the change rate of drain current (di/dt) during device switching are analyzed. Secondly, taking the Buck converter composed of SiC MOSFET as the research object, combined with the EMI equivalent model and conducted interference coupling path of the converter, the relationship between differential mode electromagnetic interference (DM EMI) signal and gate-oxide degradation is established. Finally, the amplitude of DM interference signal is used as the characteristic parameter to monitor the condition of SiC MOSFET gate oxide, and the effectiveness of the monitoring method is verified by experiments. The monitoring method proposed in this paper is applicable to different switching frequencies and load currents, and can monitor the healthy state of gate oxide in SiC MOSFET under laboratory environment and actual working conditions, which has strong practicability.

Analysis of time‐frequency characteristic parameters of electromagnetic interference sources in the basic commutation unit

Establishing accurate electromagnetic interference (EMI) sources of the basic commutation unit is the key to accurately predicting the EMI of the converter equipment. To compensate for the insufficiency of the reported works, that is to use asymmetric trapezoidal waveforms (ATW) as common mode (CM) and differential mode (DM) EMI sources, this paper analyzed the switching transient process of insulated gate bipolar transistor (IGBT) device in the basic commutation unit, and then proposed the equivalent waveform of EMI sources with multi-polylines-damped oscillation waveform (MP-DOW). The spectrum envelop characteristic parameters of MP-DOW were obtained by the frequency domain analysis method, and its correctness was experimentally verified. Comparison with the reported works shows that the proposed spectrum envelope of MP-DOW can take into account the voltage and current overshoot during the switching transients of IGBT devices, and the spectrum characteristic parameters are more accurate. This paper is beneficial to the prediction of EMI for the converter already in operation, and can also provide theoretical guidance for the converter to be designed in conjunction with the analytical formula of the EMI source.

Design method of wide‐band high‐current air‐core inductor EMI filter for high voltage DC power of motor inverter of electric vehicle

Passive filters are often used for electromagnetic interference (EMI) suppression of high voltage (HV) DC power supplies of electric vehicle (EV) motor controllers. The high current of the DC bus saturates the differential mode (DM) magnetic ring, while the leakage inductance of common mode (CM) inductor used as the DM inductance is usually very small, resulting in almost no suppression of DM EMI. A design method of broadband high-current air-core inductor passive filter is proposed. By using the air-core inductor as DM inductor, the problem of easy saturation of the DM inductor core and the small leakage inductance of the CM inductor is solved, and improves the low frequency DM EMI suppression. Through the calculation and selection of the turning frequency point of the multi-stage filter circuit, the effective frequency band can be improved. By analysing the influence of parasitic parameters, the problem of insufficient insertion loss of the filter at high frequency is solved. The experimental verification shows that the proposed air-core inductor filter achieves 50 dB of CM and DM insertion loss in frequency range of 150 kHz–108 MHz, and meets the requirements of system conducted disturbance voltage specified in CISPR25-2016Rd level 3.

EMI Mitigation of a Ćuk-Based Power-Electronic System Using Switching-Sequence-Based Control

Switching-sequence-based control (SBC) laws when designed based on topological switching behavior can have positive effects on slow- and fast-scale dynamics of a power-electronic system (PES). The slow-scale control can encompass fast PES state regulation and tracking, based on predefined objective, while fast-scale control can address differential-mode (DM) and common-mode (CM) spectral-peak energy associated with PES switching operation. Such control laws may offer enhanced programmability to conventional PES design where bulky electromagnetic interference (EMI) filters have been traditionally used to reduce EMI of switching power converters to meet EMI regulatory standards. An EMI filter is always a less programmable solution since it is usually designed for the worst-case EMI mitigation and usually overkill for a PES operating under reduced load condition. The control scheme outlined in this article offers EMI mitigation across wide operating regions without compromising PES regulation. Moreover, it does so by use of switching sequences that guarantee the reachability of the PES dynamics using an advanced Lyapunov-function-based approach. SBC is a powerful tool to generate control actions for a PES based on multivariate PES state constraints. Hence, contemporary EMI regulatory standards are used as constraints in the SBC formulation to operate the PES under wide operating regime while autonomously mitigating the EMI levels. The work may be of paramount importance for operating the ultra-fast-transition recent wide-bandgap semiconductor devices like GaN-FET and SiC MOSFET under higher power with increasing switching frequencies, which is usually desirable for increased power density and reduced switching losses. Here, a hardware Ćuk-PES operated with GaN-FETs is fabricated and is used for case illustration. It is shown by experimental results how SBC mitigate DM and CM EMI noise of the PES while maintaining regulation even for the higher order nonminimum phase PES, while reducing sensor requirements using state observer derived from the switching model of the PES.

Differential Mode Noise Estimation and Filter Design for Interleaved Boost Power Factor Correction Converters

Interleaved power factor correction (PFC) is widely used circuit topology due to good efficiency and power density for single-switch boost PFC. As the differential mode (DM) electromagnetic interference (EMI) noise magnitude depends upon the input current ripple, this research details a comprehensive study of DM EMI filter design for interleaved boost PFC with the aim of minimizing the component size. It is also demonstrated that the different numbers of interleaved stages and switching frequency influence the filter attenuation requirement and, thus, the EMI filter size. First, an analytical model is derived on the basis of the Norton equivalent circuit model for the differential mode noises of interleaved boost PFC within the frequency range of 9–500 kHz. The derived model can help identify the proper phase shifting among the interleaved boost converters in order to minimize the considered differential mode noises at the filter design frequency. So, a novel phase-shift method is developed to get a minimized attenuation required by a filter in Band B. Further, a volume optimization of the required DM filter was introduced based on the calculated filter attenuation and volumetric component parameters. Based on the obtained results, unconventional and conventional phase shifts have demonstrated a good performance in decreasing the EMI filter volume in Band B and Band A, respectively. A 2-kW interleaved PFC case study is presented to verify the theoretical analyses and the impact of phase-shifting on EMI filter size.

Aging Monitoring of Bond Wires Based on Differential Mode Conducted Interference Spectrum for IGBT Module

This article presents a method for monitoring the aging of insulate gate bipolar transistor (IGBT) module bond wires based on the spectrum characteristics of differential mode (DM) interference signals. The buck converter composed of IGBT modules is used as the device under test. The path of DM current in buck converter passes through the IGBT module, so the DM current is more suitable for monitoring the status of the module. The DM electromagnetic interference (EMI) in buck converter is mainly generated by the rapid decrease of the collector current, and the aging degree of bond wires is directly related to the DM EMI signal. The aging degree of bond wires inside IGBT module is monitored by the peak value of DM EMI signal in low frequency band. The experimental results show that the DM EMI amplitude of buck converter with aging IGBT module is larger than that of the buck converter with healthy IGBT module. The main advantage of the method proposed in this article is that it is independent of temperature and can realize the on-line accurate monitoring of the aging of the bond wires inside the IGBT module through the current probe under the actual working conditions.

EMI Noise Reduction for the Single-Phase Grid-Connected Inverter With A Modified Harmonic Filter Design

Harmonics and conducted electromagnetic interference (EMI) are two main issues in grid-connected inverter system. In this article, a modified LCL-LC harmonic filter is structured to strengthen its EMI suppression ability. Considering the common mode and differential mode EMI propagation paths, the traditional LCL-LC filter is split into a symmetrical topology, and with the midpoint of the split filtering capacitors connected to the midpoint of the dc-link capacitor. Compared to the traditional LCL-LC filter, the modified one can maintain the satisfied harmonic attenuation ability and strengthen the EMI suppression. Also, a double closed-loop control strategy is employed to solve the severe resonance problem caused by the harmonic filter. Moreover, a system calibration method is proposed and introduced to design the controller parameters to improve the high-order grid-connected system's stability. A comprehensive analysis and discussions concerning the traditional and modified LCL-LC filters are conducted in simulation and experiment on a 2 kW/220 V/50 Hz single-phase grid-connected inverter. The results have verified the feasibility of the proposed design method, and shown the superiority of the modified LCL-LC filter and active damping strategy in EMI mitigation. Besides, the weight and volume of the harmonic filter can be significantly reduced through this strategy.

Analysis of the Influence of Measurement Circuit Asymmetries on Three-Phase CM/DM Conducted EMI Separation

Electromagnetic interference (EMI) conducted emissions (CE) are of increasing concern in power electronics due to the high switching frequency and fast switching speeds of the latest generation of wide-bandgap semiconductors. The decomposition of the total conducted EMI noise into its common-mode (CM) and differential-mode (DM) part by means of a CM/DM noise separator is a useful tool that allows for a systematic EMI filter design. Carefully designed realizations achieve a CM rejection ratio and DM rejection ratio of 50 dB at 30 MHz. However, a very high-performance CM/DM noise separator is not sufficient. It is theoretically analyzed and experimentally proven that asymmetries in the EMI test setup result in an unwanted conversion between CM and DM EMI noise, and therefore significantly influence the CM/DM EMI separation. In particular, three main influences are identified: the line impedance stabilization network (LISN), the connection cables between LISN and the equipment under test (EUT), and the converter EMI filter. The unwanted noise conversion is pronounced for frequencies in the MHz range, where parasitic resonances occur. Experimental results show a CM-to-DM conversion of up to -30 dB at 30 MHz (a degradation by 20 dB or a factor of 10 compared to a high-performance separator alone) considering a connection cable length mismatch of roughly 5 cm. Values as high as -21 dB result when standard commercial LISNs are used for the measurement. The impact of asymmetries in the EMI filter is most severe, and clearly limits the EMI noise splitting at high frequencies. A high-performance noise separator can, however, be used to investigate such filter asymmetries (component tolerances and/or layout), and therefore helps to improve the filter design process and facilitates the modeling of EMI noise sources. [COMP: Change bullet list to numbered].

Active Bridge Rectifier With DM EMI Reduction Based on Linear Reverse Operation of MOSFETs

A new linear control scheme for operating power MOSFETs in the third quadrant (i.e., synchronous rectifier (SR) operation) is proposed and applied to electromagnetic interference (EMI) mitigation of switching converters. MOSFETs operating in the third quadrant exhibit electrical characteristics equivalent to a voltage-controlled voltage source between the gate-source and the drain-source voltages. Such operation is an alternative to typical SR mode, allowing fast control of the ac drain-source voltage. It is applied to active bridge rectifiers (ABRs) that can produce the necessary high-frequency voltage compensation signal to reduce differential-mode EMI. The ABR can then play the role of ac line rectification and EMI reduction at the same time. Its characteristics are modeled, and experimental verifications are carried out on a boost-type power factor corrector (PFC). The EMI performance of the PFC is improved with the proposed technique. The proposed technique facilitates the reduction of passive filter size and gives the potential of integrating active filtering function into the ABR as a solid-state front-end module. The idea can, thus, help increase the power density of power converters.

A new analytical conducted EMI prediction method for SiC motor drive systems

Abstract Although silicon carbide (SiC) devices can greatly improve the energy efficiency of electric motor drive systems and increase the power density of inverters as well in electric vehicle applications, fast switching and high-frequency operations of the devices bring more serious electromagnetic compatibility (EMC) problems. It is very important to predict the electromagnetic interference (EMI) level of SiC motor drive systems at design phase. However, since the megahertz resonances caused by the system parasitic parameters can’t be ignored, conventional EMI prediction methods need to be improved. In this paper, the fast switching transient of SiC devices, the power module parasitic parameters, and other detailed circuit parameters are modeled into the EMI sources and propagation paths. In the differential mode (DM) and common mode (CM) EMI sources modeling, both the equivalent switching current sources and the equivalent switching voltage sources of SiC devices are simultaneously taken into account. The proposed analytical method can accurately predict conducted EMI in the SiC motor drive system in frequency range from 150 kHz to 30 MHz. Compared with the previous conventional methods, the proposed method improves DM EMI prediction accuracy of the SiC motor drive system in high frequency range.

An Integrated EMI Filter Scheme for Paralleled Inverter With Zero-CM PWM Algorithm

Motor drive system generates harmful differential mode (DM) and common mode (CM) electromagnetic interference (EMI) when it is working. To solve this problem, the integrated EMI filter scheme for paralleled inverter using zero-CM pulsewidth modulation (PWM) algorithm is proposed in this article. The zero-CM PWM algorithm and the coupled inductor constitute a holistic solution for the ac side EMI suppression. By using the zero-CM PWM algorithm, the CM leakage current of the system can be suppressed without adding additional CM EMI filter and only DM EMI needs to be considered. In addition, the DM inductor is naturally integrated in the coupled inductor, leakage inductance of the coupled inductor instead of the discrete DM inductor is used as the DM inductor which has less restrictions on the inductor material. The DM EMI filter can be constructed by just adding DM capacitors. Thus, using the integrated EMI filter scheme has advantageous over traditional scheme since the CM EMI filter is omitted and only DM capacitor is added which can simplify and reduce the size of EMI filter in the ac side and has the potential to increase the power density of the system since other solutions require both the DM and CM EMI filter.

Analysis and Modeling of Conducted EMI from an AC–DC Power Supply in LED TV up to 1 MHz

Critical conduction mode (CRM) boost power factor correction (PFC) converter is widely used in ac–dc power supplies to achieve high power factor. The switching frequency varies in a half-line cycle. In this article, both the differential-mode (DM) and common-mode (CM) electromagnetic interference (EMI) noises below 1 MHz from the ac–dc power supply in a LED TV are analyzed and modeled. The power supply consists of two parts: CRM boost PFC converter and LLC resonant converter. The conducted EMI noise and noise source voltages are measured in the time domain and then converted to the frequency domain via short-time fast Fourier transform (STFFT). Through the joint time-frequency analysis using STFFT, the drain-to-source voltage of the power MOSFET in the PFC converter is identified as the dominant noise source of both CM and DM EMI noises below 1 MHz from the power supply. The EMI current path is different during different periods of a cycle of the line voltage. During most time of a cycle, two diodes of the bridge rectifier are forward biased, and the bridge rectifier can be treated as short circuit. The current paths of DM and CM EMI noises are explained and modeled by a linear equivalent circuit model. Three parasitic capacitances need to be considered to model the CM EMI noise in this device under test. From the circuit model, transfer functions relating DM and CM EMI spectra to noise source voltage spectrum are obtained. The conducted EMI spectra are predicted by multiplying the spectrum of noise source voltage by the transfer functions. The prediction matches with measurement. The effects of parasitic capacitances on CM EMI noise are analyzed by simulation and then validated by measurement. The analysis results can help with EMI design to reduce the CM EMI.

DC-AC Isolated Power Converter Array. Focus on Differential Mode Conducted EMI

This paper introduces the implementation of a DC–AC step up isolated converter from associations of bidirectional Conversion Standard Cells (CSCs). The designed multi-cell converter is an array of standardized converter cells. It is described and then compared to a reference converter with respect to differential mode conducted electro-magnetic interference (EMI). The paper outlines the motivation for developing a generic multi-cell approach before underlining the benefits from the point of view of conducted EMI when implementing power converter arrays (PCAs). In particular, it is shown that in PCAs, the differential mode (DM) EMI filter can advantageously utilize distributed CSCs, making it possible to use very low value AC inductors to filter the AC current ripple. Experimental results are provided to validate the analysis carried out in the paper.

High Frequency Conducted EMI Investigation on Packaging and Modulation for a SiC-Based High Frequency Converter

Silicon carbide (SiC) devices have the advantages of high switching speed and high switching frequency, which can increase the power density, but electromagnetic interference (EMI) will increase along with higher switching frequency thus it can become a challenge for high-frequency converters. In order to clarify the influence factors of EMI noise in SiC converters and find the suppressing method, this paper investigated the conducted EMI in SiC-based high power density electronic systems from two aspects: packaging structures and modulation methods. For packaging investigation, this paper introduced parasitic parameters of power module into EMI analytical model, then defined transfer functions of EMI noise to analyze the influence of parasitic parameters on noise propagation path and further studied the impact of parasitic parameters on noise source by analyzing switching transient and frequency spectrum. Analysis and simulation are carried out based on a hybrid structure SiC power module and discrete SiC devices to verify the analysis. The influence of modulation on EMI is studied by analyzing and comparing two modulations: continuous current modulation (CCM) and triangle current modulation (TCM). To certify the analysis study, two 1.6-kW, 300-kHz switching-frequency synchronous buck converters are designed and tested. One is based on the hybrid packaging power module and the other is based on TO-247 packaged SiC devices, respectively. The result shows that the hybrid packaging module can suppress the common mode (CM) EMI by 10 dB, and has a suppression on differential mode (DM) EMI between 10 and 20 MHz. Moreover, TCM can increase DM EMI in low-frequency range but suppress it in the high-frequency range.

Suppressing Conducted DM EMI in an Active Power Filter via Periodic Carrier Frequency Modulation

Active power filters (APF) aim at solving the harmonic problem originated by the nonlinear load in power systems. However, the high dv/dt and di/dt outputs from power electronic devices in a voltage source converter on APF introduced unwanted conducted electromagnetic interference (EMI) when compensating for the low-frequency harmonic components. Hence, this paper develops a spectrum analysis approach to investigate and quantify the source differential-mode (DM) voltage of a single-phase shunt APF to suppress the DM EMI via periodic carrier frequency modulation (PCFM). In this scheme, the analytical expressions of source DM voltage in the APF using the PCFM scheme are obtained with a double Fourier series. In addition, the influence of PCFM parameters on the source DM voltage spectrum is predicted based on the analytical expression. As a result, the PCFM parameters, which have the best suppression effect on the DM EMI are obtained. The experiment results proved the validity of the sawtooth PCFM APF with the maximum frequency deviation equal to 800 Hz in alleviating the APF DM EMI.

Integrated Magnetic Circuits for Differential-mode and Common-mode Chokes of EMI Filters


 In this paper, two magnetic circuits to integrate common-mode (CM) and differential-mode (DM) chokes of an electromagnetic interference (EMI) filter are proposed. The DM and CM chokes are integrated by using UIU and EI ferrite core shapes. To evaluate the EMI reduction performances of proposed approaches, the conducted EMI reduction performances of proposed integrated DM and CM chokes are compared with the conventional CM choke and traditional separated DM and CM chokes. From the experimental results, it ensures the advantages of the use of proposed approaches. Although some magnetic parts are eliminated by proposed approaches, the amount of DM and CM EMI attenuation rate is comparable to the case of traditional separated DM and CM chokes, except the highest peak is located at different frequencies.

EMI filter design of single-phase SiC MOSFET inverter with extracted noise source impedance

This paper presents an electromagnetic interference (EMI) filter design procedure for a single-phase SiC MOSFET inverter. To ensure the EMI filter performance is both accurate and effective, the equivalent noise source impedances of common mode (CM) and differential mode (DM) noise models are extracted. Then the CM and DM EMI filters can be designed based on the known CM and DM noise source impedances, respectively. The EMI filter design based on the proposed method is validated both through simulation and experiments. The simulation and experiment results have verified the effectiveness of the proposed method.

Modeling and Stability Analysis of Active Differential-Mode EMI Filters for AC/DC Power Converters

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.

A Comprehensive Design and Optimization of the DM EMI Filter in a Boost PFC Converter

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.