Common-mode Electromagnetic Interference Noise Research Articles

Suggesting a Non-Unity Turn Ratio Two-Winding Coupled Inductor for Filtering CM EMI Noise in an SRC

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.

Analysis and Modeling of the Common-Mode Conducted EMI From a Wireless Power Transfer System for Mobile Applications

Wireless power transfer (WPT) is a safe and convenient technology for battery charging thanks to the elimination of electrical contact. Despite the great advantages, the electromagnetic interference (EMI) noise generated by a WPT system coulddegrade the performance of nearby electrical circuits. In particular, common-mode (CM) EMI noise generated by the WPT system will conduct along the cable and radiate in high frequencies, thus becoming one of the concerns. In this article, the noise source and current path of the conducted CM EMI noisefrom a Qi-compliant WPT system for mobile applications are analyzed. The transfer function relating the CM EMI noise to the noise source voltage is derived analytically in the frequency domain. The noise source voltage is measured in the time domain and then converted to the frequency domain via fast Fourier transform. The conducted CM EMI spectrum is predicted by multiplying the spectrum of noise source voltage by the transfer function. The prediction matches well with measurement. The analysis and modeling explain the mechanism of the CM EMI noise and provide guidelines to reduce the CM EMI noise.

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.

Leakage Current Suppression With Capacitor Voltage Control of Three-Level Flying Capacitor Grid-Connected Inverters

Leakage current issues are worthy of attention for nonisolated grid-connected systems. This article introduces the method of eliminating common-mode (CM) voltage and reducing the leakage current based on modulation, and analyzes the correlation between actual effects of the method and the flying capacitor (FC) voltage balance in three-phase three-level FC grid-connected inverter. The proposed carrier-based modulation can balance the FC voltage by changing the transmission sequences of pulses and theoretically achieve zero CM voltage. In order to deal with the low frequency fluctuation and bias voltage of FC caused by asymmetry of actual hardware, the control method is introduced, which controls FC voltage by changing the action times’ distribution of switches, while still eliminating the CM voltage. Simulation and experimental results are provided to validate that the proposed method can control FC voltage and achieve good performance in suppressions of CM voltage, leakage, current and CM electromagnetic interference noise.

A Double-Transistor Double Primary–Winding Flyback Converter for Marine Resources Monitoring Equipment

Li, J.; Wu, H.; Xu, T., and Lin, P., 2020. A double-transistor double primary–winding flyback converter for marine resources monitoring equipment. In: Liu, X. and Zhao, L. (eds.), Today's Modern Coastal Society: Technical and Sociological Aspects of Coastal Research. Journal of Coastal Research, Special Issue No. 111, pp. 340–344. Coconut Creek (Florida), ISSN 0749-0208.The DC bus power-supply mode is the most convenient for marine resources monitoring equipment, and secondary electric power supplies at power supply nodes are featured by a wide variation range of input voltage and high electromagnetic interference (EMI) requirements. A double-transistor double primary–winding flyback converter with wide input range, low EMI noise, and active auto-starting function was designed in this study. The main circuit of this converter solves the withstanding voltage problem of switching tube via series connection of double transistors under high-voltage condition. Through the intertexture structure of the double primary windings, the main transformer reduces the drain-source voltage spike of the switch and effectively mitigates the common-mode EMI noise at output end. The large starting circuit loss is solved, and the converter efficiency is improved under wide input range through the active auto-starting circuit. The experimental results show that when the bus node voltage varies within a wide range of 100 V–1000 V, the converter efficiency is always greater than 85%, and EMI performance is superior, thus satisfying the requirements of bus power-supply system.

Conducted common‐mode electromagnetic interference suppression in the AC and DC sides of a grid‐connected inverter

Electromagnetic interference (EMI) filters are inevitable parts of power electronic systems. A novel EMI filter for single-phase grid-inverter is proposed in this study, to suppress the common-mode (CM) EMI noise. The noise source and propagation path impedances are analysed, and the interaction between AC and DC side is studied. By connecting the ground terminal of the CM capacitors to the midpoint of the DC-link, the noise coupling between AC and DC side is reduced. When compared with the state-of-the-art of EMI filter, the proposed topology has advantages: the AC and DC filters can be designed independently; the impedance of the CM loop is improved; there is a remarkable CM EMI noise suppression effect on both AC and DC sides. Simulation and experimental results verify the theoretical analysis and proposed EMI filter structure.

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.

Common-Mode Voltage Reduction for Paralleled Inverters

This paper introduces series work of common-mode (CM) voltage reduction for the paralleled inverters. The paralleled inverters’ phase-legs are connected through coupling inductors and the combined three-phase currents are provided to the load. Interleaving is an approach to reduce the CM voltage for the paralleled inverters but it cannot eliminate CM voltage. A novel pulse-width-modulation (PWM) method for paralleled inverters which can theoretically achieve zero CM voltage is developed. Considering the basic voltage vectors in each inverter, novel paralleled voltage vectors which have zero CM voltage are proposed to combine the reference voltage vector. The action time's distribution and voltage vectors’ sending sequence for each inverter are also introduced. The proposed PWM method can make sure the voltage of the two inverters are balanced in each switching cycle and limits the circulating current through small coupling inductors. Similar to interleaving space vector PWM, the proposed zero CM PWM also has the ability to reduce the output current ripple and electromagnetic interference (EMI). Simulation and experimental results are provided to show the advantage of paralleled inverters in CM voltage reduction and validate the proposed method has good performance to reduce CM current and CM EMI noise.

Analysis of common‐mode electromagnetic interference noise in a flyback converter using a self‐supply power control integrated circuit

This study analyses electromagnetic interference (EMI) noise sources generated from a new type of flyback converter which is operated from a self-supplied power control integrated circuit (IC). On the basis of analysis, a new analytical mathematical model of common-mode (CM) EMI noise path is presented. This model is easier to construct and allows researchers to better understand the impact of each parameter on CM EMI noise than former models. According to the proposed model, the capacitors from the traces connected to the ground (GND), voltage drain drain (VDD), current sense (CS) and feedback (FB) pins to the ground demonstrate the greatest impact on CM EMI. Two improved layouts are designed to verify the analysis result. The layouts were driven by the newly developed model. Test results show that they correspond with theoretical calculations supporting the analysis and the model that was developed in the course of this work.

家庭用太陽光発電用パワーコンディショナの入出力EMIフィルタ設計手法

Electro-magnetic interference (EMI) noise radiated from the DC cable of photovoltaic power conditioner systems (PCS) is a serious problem for radio transmission equipment. In order to prevent the interference, the International Special Committee on Radio Interference (CISPR) is discussing to determine a noise regulation value for this issue. To reduce the radiated noise, this paper studies the attenuation characteristics of EMI filters that are connected to both the DC- and the AC-sides of the PCS. In this paper, it is pointed out that the EMI filters do not show their own attenuation characteristic if those are connected to the PCS. In particular, when EMI filters are connected to both the DC- and AC-sides of the PCS, a specific series resonant frequency is observed and deteriorates the attenuation characteristics of both EMI filters. In order to prevent this problem, a design method for EMI filters which can reduce the common-mode EMI noise effectively, is proposed in this paper. Further, the effectiveness of the proposed method is confirmed through experiments.

Novel Techniques to Suppress the Common-Mode EMI Noise Caused by Transformer Parasitic Capacitances in DC–DC Converters

This paper proposes novel electromagnetic interference (EMI) suppression techniques for dc-dc converters. For low-voltage high-current applications, windings are paralleled and interleaved. Although low conduction loss and low leakage inductance can be achieved, the winding capacitances are considerably increased, thereby deteriorating the converter's EMI and soft-switching performances. To solve these problems, a novel balanced choke concept is proposed, as well as other techniques. The advantages of the proposed concepts and strategies are verified and demonstrated on a 1-kW 1-MHz 400-V/12-V LLC resonant converter prototype. More than 52-dB noise attenuation and 75% equivalent winding capacitance reduction are achieved. Hence, EMI and soft-switching performances are significantly improved.

The Essence of Three-Phase PFC Rectifier Systems—Part I

In the first part of this paper, three-phase power factor correction (PFC) rectifier topologies with sinusoidal input currents and controlled output voltage are derived from known single-phase PFC rectifier systems and/or passive three-phase diode rectifiers. The systems are classified into hybrid and fully active pulsewidth modulation boost-type or buck-type rectifiers, and their functionality and basic control concepts are briefly described. This facilitates the understanding of the operating principle of three-phase PFC rectifiers starting from single-phase systems, and organizes and completes the knowledge base with a new hybrid three-phase buck-type PFC rectifier topology denominated as Swiss Rectifier. Finally, core topics of future research on three-phase PFC rectifier systems are discussed, such as the analysis of novel hybrid buck-type PFC rectifier topologies, the direct input current control of buck-type systems, and the multi-objective optimization of PFC rectifier systems. The second part of this paper is dedicated to a comparative evaluation of four rectifier systems offering a high potential for industrial applications based on simple and demonstrative performance metrics concerning the semiconductor stresses, the loading and volume of the main passive components, the differential mode and common mode electromagnetic interference noise level, and ultimately the achievable converter efficiency and power density. The results are substantiated with selected examples of hardware prototypes that are optimized for efficiency and/or power density.