Electromagnetic Interference Issues in Power Electronics and Power Systems

The separation of differential mode and common mode noise in EMI analysis is a well known procedure which is useful especially for the analysis and the understanding of interference phenomena of power converters. However, separating both components is rarely done during measurements. Therefore, two different approaches are developed and evaluated in this paper to realize separated common mode and differential mode measurements.

This paper describes the investigation of Common Mode (CM) noise and Differential Mode (DM) noises in Dual Active Bridge (DAB) converter applied in Electric Vehicle (EV) in order to reduce the Electromagnetic Interference (EMI) that occurs in EVs. The DAB converter is designed and simulated using a spice simulator and the CM and DM noises from the converter circuit were measured as per the CISPR 25 EMI Standard. Based on the simulated results, the attenuation level of noise was calculated and used to design the components of the EMI filter. The design was validated using the simulation findings after the converter are created, tested and the experimental results compared. Based on the results and discussion, recommendations are made in this paper to reduce EMI in converters used in EV. Especially, suggestions to reduce the common mode and differential mode noises produced by Dual Active Bridge converters employed in EV were given as per the CISPR 25 standard.

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.

Common-mode (CM) noise cancellation method is an attractive approach to reduce the original CM noise in power converters, which helps to shrink the size of electromagnetic interference filter. Traditional CM noise cancellation method cancels the CM noise current by adding a branch consisted of a compensation voltage source and a compensation capacitor, which generates a cancellation current and nullifies the noise current. As the duality, the voltage cancellation method is also feasible for reducing the CM noise, which has not been investigated in dc–dc converters. In this article, a common-mode voltage cancellation (CMVC) method is proposed, which cancels the CM voltage of the converter by inserting compensation voltage source into the input power cord. The requirement for achieving CMVC is that the cancellation voltage and the parasitic capacitances in the circuit are matched. The applications of CMVC method in basic nonisolated and isolated dc–dc converters are presented, and the considerations for practical applications of this method are discussed. Finally, a buck converter and a half-bridge LLC resonant converter prototype are built, and the proposed method is verified by experiment, respectively.

The common-mode (CM) noise at the output of ac/dc power adapters can interfere with touchscreen's normal operation in consumer electronic products. Existing power adapter's output CM voltage measurement used in power electronics industry does not align with the touchscreen's sensitivity test used by touchscreen manufacturers. This paper first reviews existing measurement setups and identifies the technical issues in the tests. The CM noise source impedance of ac/dc power adapters and the characteristics of touchscreens are investigated. A new measurement setup is proposed based on both the characteristics of CM noise source of power adapters and touchscreens. A CM voltage limit is also proposed with industry companies. A measurement device is developed for the proposed measurement setup and procedure. The experimental results validate the proposed techniques.

The common-mode (CM) noise in nonisolated dc-dc converters is mainly caused by the displacement current through the high <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dv/dt</i> node in the circuit and the associated parasitic capacitance, and it may cause electromagnetic interference (EMI) to the surrounding equipments. To reduce the original CM noise and shrink the EMI filter size of non-isolated dc-dc converters, CM noise cancellation methods have been proposed, including the symmetry circuit, balancing technique, passive cancellation and CM voltage cancellation. In these methods, additional components or windings are required for reducing the CM noise. In this article, a new CM noise cancellation method in non-isolated dc–dc converters is proposed by adopting a split-winding configuration. Compared to the existing CM noise cancellation methods which require additional components, the proposed method in the buck, boost and single-ended primary-inductor converter (SEPIC) converters which runs in voltage step-up mode has the identical volume as their conventional circuit configurations. The proposed method is verified for a buck converter by experiment.

Switch Mode Power Supplies (SMPS) are extensively employed in fields such as telecommunications, information technology, and electric vehicles, where energy efficiency is increasingly demanded. Modern SMPS designs prioritize compact size, high power density, and optimal efficiency to meet these requirements. The LLC resonant topology, commonly utilized in the DC/DC conversion stage with planar transformers, enables operation at high frequencies (hundreds of kHz) and facilitates soft switching across the full load range. However, a significant drawback of this topology is electromagnetic interference (EMI), particularly common-mode (CM) noise, which arises from high switching frequencies and parasitic capacitance in the components. This challenge is further exacerbated by the use of planar transformers. This study presents a CM noise model for the Half-Bridge LLC (HB-LLC) converter based on a two-capacitor transformer representation, aiming to analyze CM noise behavior and investigate practical, cost-effective methods for its reduction.

The common mode (CM) current in differential circuits generates CM noise which radiates in the environment and causes electromagnetic interference (EMI) with electronic devices in proximity. This noise is generated due to imbalance in the charging and discharging paths of the driver circuit and asymmetric equalization. A systematic study of how asymmetric equalizer increase the CMnoise is still lacking. Few active on-chip solutions are proposed for wireline transmitters up to 20-Gbps speed. However, these solution does not suppress CM noise by the equalizer and they could not support four-level pulse amplitude modulation (PAM-4) optical transmitters. This paper analyzes two potential sources of EMI-related CM noise, the common mode logic (CML) driver and feed forward equalization (FFE) circuit, and presents a novel on-chip active circuit technique for automatic CM noise cancellation in high-speed PAM-4 transmitter. This solution provides the benefits of small size and low cost by eliminating the need for discrete components to suppress EMI. The post-layout simulation demonstrates that the CM noise cancellation circuit (CMNC) efficiently mitigate the EMI by suppressing the CM noise up to 90% and consumes 5 mW, with core area of 17 mu m x 9 mu m.

For flyback converters with long cables attached, radiated common mode (CM) current is the dominant radiation source. Radiated CM current is caused by the CM voltage driving the CM noise propagation loop including the converter and the antenna. This paper proposes a radiated CM current model to quantify the relationship between the CM voltages, impedance and currents. It is discovered that the significant impact from the transformer on radiated CM current is primarily from the CM voltage transformation. To characterize the CM voltage transformation, a transformer CM model extraction method is proposed. Based on the model, for radiated CM current reduction, this paper reviews transformer structures and proposes an interwinding capacitive coupling minimized coaxial shielding technique. And this paper also studies on the EMI filter design for radiated CM current reduction. The proposed modeling and reduction techniques are verified through experiments performed on a flyback converter with cables attached.

Electromagnetic interference (EMI) signals, which radiate in the environment and cause the malfunction of electronic devices in proximity, are generated due to the common mode (CM) noise in differential circuits. This CM noise is produced because of the imbalance in the charging and discharging paths of the driver and equalizer circuits in the transmitter. However, the effects of the equalizer on CM noise have not been examined. This paper systematically investigates the effect of different feed forward equalizer (FFE) configurations on EMI-related CM noise in a 56-Gbps four-level pulse-amplitude modulation (PAM-4) optical transmitter, aiming to provide an optimized configuration with low CM noise and power consumption, while providing high compensation. The simulation results show that an asymmetric equalizer significantly improves the compensation performance. However, the offset in differential pair of output stage should be minimized to decrease the CM noise generated from the FFE.

Common mode electronic noise in differential circuits

This paper investigates the power module design for better common-mode (CM) noise and thermal performance. A high-frequency full-bridge diode rectifier is selected as a case study. The most influential factors in CM noise generation and mitigation are first identified with a simplified CM equivalent model and a comprehensive parametric study. Studies show proper parasitic value and parasitics symmetry can improve CM noise performance. The analysis of packaging structures indicates the vertical module has better CM noise and thermal performance than the traditional lateral wire-bonded module. To validate this, both modules are designed and prototyped for verification. The thermal simulation shows the vertical module exhibits a 25.5% lower thermal resistance from junction to case and a 51% increase of power density in a force-air-cooled condition. Experiments also reveal 15 dB of CM noise reduction from 150 kHz to 6 MHz and a 32% improvement of power density in a force-air-cooling condition. Finally, a case study demonstrates the vertical power module CM noise performance in a typical unsymmetrical topology. This results in a 30 dB CM noise reduction up to 6 MHz.

SiC devices can upgrade the inverter performance to a new level by its potentially more than ten times higher switching speed compared to its Si counterpart. However, the high switching frequency and dv/dt, di/dt worsen the electromagnetic interference. Reduction of the common mode (CM) noise of the non-isolated photovoltaic (PV) inverters is addressed by many researchers through adding filters or balancing the circuit. However, most methods rely on the certainty of the parasitics in the system in advance. It is usually not practical for a PV inverter because the parasitic capacitance of PV panels that are to be installed in plants varies from case to case and further can be seriously affected by the damp environment. This article proposes a practical way to reduce the CM noise of the three-level active neutral point clamped (ANPC) inverters with uncertain parasitic capacitance of PV panels. First, the CM model of ANPC inverters with all parasitic capacitances is established. Next, most existing hardware-based reduction methods of the CM noise are summarized based on a unified mathematical model and further compared with each other. After the comparison, a practical method is proposed to reduce the CM noise of the ANPC inverter with uncertain parasitic capacitances, which just adds little volume and cost to the whole system. Finally, the simulation and experiments are conducted to validate the proposed method.

A multiphase DC-DC converter consisting of a coupled inductor and fast switching devices enables power electronics equipment to achieve a high power density. However, with such devices, the fast voltage transition generates substantial common mode (CM) noise. However, there are very few studies on CM noise reduction for multiphase converters using a coupled inductor. Therefore, in this paper, a CM noise reduction method is proposed for a multiphase DC-DC converter that hardly lowers the power density.

This paper deals with Electro Magnetic Interference in switching power supplies. The EMI consists of mainly common mode and differential mode noises. Due to interference, the efficiency of the equipment reduces and some times the equipment may be damaged. A procedure to design a novel topology of EMI Filter to suppress these two noises is presented in this paper.