Separating Common Mode and Differential Mode Noise in EMI Measurement

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.

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.

Accurate measurement of common mode (CM) and differential mode (DM) noise is crucial for electromagnetic interference filter design. With the application of wide bandgap devices, the measurement results require higher accuracy at high frequency. This letter proposes a novel CM and DM noise separation method where a 20 dB attenuator is integrated to allow the measured results less sensitive to the parasitic parameters in the 150 kHz-30 MHz frequency range. The proposed method improves the flatness of the noise separator in the 150 kHz-30 MHz frequency range, which is 0.3 dB for common mode transmission ratio and 0.6 dB for differential mode transmission ratio. Simulation and experimental results are provided to validate the effectiveness of the proposed method.

EMI measurements and the design of proper filter to mitigate the EMI noise is very important, since the EU Directive 336/89 has been published. For conduction emission noise, the separation of the common and the differential mode noise is important for determining whether the differential or common mode component is dominant. Therefore, it will be possible determine whether an anticipated change in a value of an element in the power supply filter will be effective on the considered component. Two devices for the separation of the conducted EMI noise into the common and the differential mode components have been realized and tested. In this paper the authors show the design considerations that have to be taken into account for the realization of the two devices.

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.

An ultra-wideband bidirectional absorptive common mode filter (A-CMF) using a defected ground structure was proposed and measured. In order to achieve high-speed digital communication while maintaining compatibility with older standards, common mode filters are required to cover high-frequency and wide-band ranges. However, it is difficult to suppress the common mode (CM) noise in a wide band while reducing the impact on the differential mode (DM) signals. In particular, CMFs that can be adapted to frequencies over 15 GHz have not been studied until now. While reflective CMFs (R-CMFs) that return CM noise to the input side have been studied, absorptive CMFs (A-CMFs) that absorb common mode noise within the filter have begun to be studied in recent years. An ultrawideband bidirectional A-CMF that attenuates CM by 10 dB over a wide frequency band from 2.5 GHz to 20 GHz and suppresses DM attenuation to less than 3 dB was proposed. Moreover, a prototype was manufactured and measured to confirm that their performance matched the design performance.

Common mode electronic noise in differential circuits

A new test method is described which separates common (asymmetrical) and differential (symmetrical) mode noise and yields quantitative data about each mode from 100 kHz to 20 MHz. The essential feature of this method is a modified r-f current probe combined with a high pass filter. The purpose of the high pass filter is to enhance the rejection of the power frequency current in the output of the current transformer.

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.

This paper presents a method to model a back-to-back converter and the additional passive filter system. The mathematical modeling method followed the step of converting the three-phase system to single phase systems by separating the differential mode (DM) and common mode (CM) noise circuit for the design of the filter components separately. The model accounts for parasitic components in the converters and presents an indirect method of estimating parasitic capacitance for CM filter design. Design rules for the different components are summarized. Results from a lab prototype are presented and show good correspondence to the model.

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.

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.

This E-Book focuses on conducted and radiated emission noise generated by different power converters such as Switch Mode power Supplies and DC-AC Inverters. EMI filter design and different approaches to predict common mode and differential mode noise are illustrated in detail. Common mode and surge voltage issues in AC machines have also been addressed and discussed in this E-book. The E-book is intended for helping engineers and students to analyze EMI problems in electrical and electronic systems.

A new method is proposed to estimate power line communication radiated EMI noise. By using the noise separation to extract common mode (CM) noise current, the radiated EMI noise can be estimated according to the relationship between the radiated EM field and the CM noise current. The experiment results show that the radiated EMI noise is decreased obviously, while the CM current is suppressed by using ferrite core.

With the recent development in power electronic technologies, designers and manufacturers intend to increase the switching frequencies to achieve smaller size of the converter. However, the high currents gradient di/dt and high voltage gradient du/dt in the circuits will generate high differential mode (DM) noise and common mode (CM) noise, which seriously affect the normal operation of the equipment and adjacent other equipment. So it is necessary to study the methods of conducted disturbance suppression in drive system. The methods are broadly classified based on two criteria. One is the reduction of the conducted disturbance after generation. The other is the reduction of the conducted disturbance at the generation stage itself. This paper also discusses the characteristics and application prospects of the above suppression methods. In the end, this paper clarifies the principles that should be considered when adopting different conducted disturbance suppression methods in practice. The study in this paper can contribute to the further development and practical application of the conducted disturbance suppression methods of drive system.