Noise Source Impedance Research Articles

EMI filter design for single‐phase grid‐connected inverter with noise source impedance consideration

It is well known that noise source impedance plays a significant role in designing conducted electromagnetic interference (EMI) filters. However, the noise source impedance in a switched-mode power supply is not easy to extract. In this study, the noise source impedance in a single-phase inverter is extracted under operating conditions based on a two-probe approach. First, the noise source modelling and analysis are implemented for the inverter system to illustrate the importance of impedance. Furthermore, the proposed two-probe method is introduced and then validated by several passive components. Proper and straightforward premeasurement calibrations are needed to eliminate the influence of the probes and cables. The approach can accurately extract the common-mode and differential-mode noise source impedances with different configurations according to the characteristics of their propagation paths. Compared with a traditional EMI filter design, the experimental results show that the one designed by the proposed approach can effectively attenuate the conducted EMI noises to meet the requirements with more appropriate and optimised parameters.

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.

Study on conducted EMI noise source modelling applied in electromagnetic compatibility analysis based on GA in cooperation with LM

In this study, a new method employing scattering parameters (SPs) method, genetic algorithm (GA) and Levenberg–Marquardt algorithm (LM) is proposed for modelling conducted electromagnetic interference (EMI) noise source impedance. On the basis of the impedance information extracted by traditional SP method, GA is adopted to optimise the impedance information by taking advantage of the fast convergence speed. The obtained values of the RCL parameter are used as a set of initial values. Then, by using the advantage of the high precision of the LM, the initial values obtained by the GA are iteratively calculated. Better results can be obtained by using this combination method. This method improves the processing accuracy while ensuring the processing speed and contributes to the design of conduction EMI filter.

Systematic Common-Mode Filter Design for Inverter-Driven Motor System Based on In-Circuit Impedance Extraction

Inverter-driven induction machines often suffer from premature bearing failure due to high-frequency common-mode (CM) voltage and induced CM current. One effective remedy is adding a CM filter to suppress the CM current. Optimal CM filter design requires prior knowledge of both noise source and termination impedances. With an improved in-circuit impedance measurement setup, the CM noise source impedance of a high-power inverter-driven motor system with strong background noise can be extracted. The setup also protects the measurement instruments from surges and transients from the harsh operating environment. The extracted noise source impedance allows a CM filter to be designed systematically without overdesigning. In the evaluation of the first-order single-inductor and second-order LC filters, it is found that the second-order CM filter is prone to differential-mode to common-mode (DM-to-CM) conversion, especially at the resonant frequency caused by the leakage inductance of the CM choke and the equivalent DM capacitance of the line-to-ground capacitors. Therefore, an additional DM inductor is necessary to curb the mode conversion, which may not necessarily result in final size reduction as compared to that of first-order single-inductor filter.

Novel Measurement Procedure for Switched-Mode Power Supply Modal Impedances

The measurement of modal impedances of switching-mode power supplies (SMPSs) is of paramount importance in electromagnetic compatibility applications, especially when designing electromagnetic interference filters to suppress the conducted and radiated electromagnetic emissions is the target. A novel measurement technique that makes use of an impedance analyzer and a coupling transformer and allows extracting the complex value of common- and differential-mode noise source impedance of an SMPS is proposed. The measurement procedure is first studied from the theoretical point of view, then experimentally validated with passive components, and eventually implemented in a CISPR-25 conducted emission test setup to measure the magnitude and phase of modal impedances of an automotive SMPS under different operation conditions.

Investigation on conducted EMI noise source impedance extraction for electro magnetic compatibility based on SP‐GA algorithm

A new approach employing scattering parameters (SPs) and genetic algorithm (GA) (SP-GA) is proposed for modelling conducted electromagnetic interference (EMI) noise source impedance. Based on the principle of SPs, the source impedance is measured through transmission and reflection parameters from a vector network analyser when the circuit is shorted and loaded with noise source impedance, respectively. Moreover, amplitude-frequency performance and phase-frequency performance are optimised by using GA, and therefore the equivalent resistance, capacitance, and inductance are attained following the usual formula of the phase and amplitude of source impedance. This work made contribution for the design of the conducted EMI filter.

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.

Practical papers, articles and application notes

With the rapid development of high-speed wide band-gap (WBG) semiconductor devices, electromagnetic interference (EMI) in power converters has become a major design issue that cannot be ignored. The first paper "EMI Filter Design of Single-Phase SiC MOSFET Inverter with Extracted Noise Source Impedance" authored by Yitao Liu, Shiqi Jiang, Huaizhi Wang, Guibin Wang, Jian Yin and Jianchun Peng from Shenzhen University, China, describes a systematic procedure to design effective common-mode (CM) and differential-mode (DM) EMI filters for a power grid connected SiC MOSFET inverter system.

Investigating CM Voltage and Its Measurement for AC/DC Power Adapters to Meet Touchscreen Immunity Requirement

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.

A Noise Source Impedance Extraction Method for Operating SMPS Using Modified LISN and Simplified Calibration Procedure

A noise source impedance extraction method for switched-mode power supply (SMPS) under operating condition is proposed and validated in this letter. First, a simplified precalibration method using several known impedances is introduced to eliminate the influence of measurement instruments and other parasitic effects. Second, the configuration of the proposed method is presented and the calculation methods of common-mode and differential-mode noise source impedances using microwave transmission analysis are described, respectively. The experimental results show that the proposed method can extract the noise source impedance of SMPS in wide frequency band with sufficient accuracy. Compared with traditional methods, the complex calibration process can be simplified, and no more additional equipment is required. Moreover, a novel multiple-function line impedance stabilization network (MF-LISN) with the function of electromagnetic interference measurement and noise source impedance extraction is designed according to the proposed method. Since only MF-LISN is used, it can be more convenient to extract the noise source impedance of SMPS for electromagnetic compatibility pretest.

Error analysis in conductive electromagnetic interference noise source impedance extraction: A simulation and experimental study

Error analysis in conductive electromagnetic interference noise source impedance extraction: A simulation and experimental study

Modelling of a Filter using EMI/EMC Considerations

There are so many Filters are available in the nature of communication. The modern communications are purely depends on the diversity of the signals. The signaling systems are fairy major problem with the noise that occurs internally or externally. The standard measuring of electromagnetic pulse problems can reduce the problems of noise in the modern digital systems. The present work is to overcome the problems of noise that occurs internally or externally and malfunctions of the circuit with the measurement of EMI/EMC considerations. In Digital Signal Processing system consists of devices such as Phase Shifters and Power Dividers and Filters as well as Multiplexers which are used to transmit and adjust the amplitude and phase of the electrical signals in such a way is to form desire signal. After forming the desire beams of a system and then malfunctions of the system with the measurement of EMI/EMC consideration and observes the beams without any noise in the Digital signal processing system and compared both performances. By using the stimulation and synthesis can be carried out to Digital Signal processing System. The different standard methods to reduce insertion loss are proposed to measure the noise source impedance to particular systems. The information obtained through the proposed method enables the prediction of EMI filter performance and the design of a suitable filter for a switch mode power supply.

The Input Impedance of Common-Mode and Differential-Mode Noise Separators

This paper discusses the $\Delta$ -networks and other circuits designed to separate the conducted electromagnetic interference (EMI) into its common mode (CM) and differential mode (DM) components. The input impedances of CM/DM separators must be 50 $\Omega$ resistive in the measurement frequency range, and they must be independent of the values of the noise signals and noise source impedances. The conditions for achieving such input impedances are derived. It is shown that many of the proposed separators, including the $\Delta$ -network suggested in the International Special Committee on Radio Interference (CISPR) 16-1-2 standard, do not fulfill the input impedance requirement. This leads to unreliable CM and DM measurements and, consequently, to the oversizing of EMI filters and design by trial and error.

Исследование акустических характеристик глушителей шума выпуска автотранспортных двигателей внутреннего сгорания

The main acoustic characteristic of noise muffler–"brought losses", which shows the decrease of noise created by its source, in particular by exhaust system of internal-combustion engine, in a control point as a result of muffler use is considered. The explanation of essence of this characteristic and its mathematical description are offered; the empirical dependences for calculation of sound radiation impedance by exhaust system end opening are given. The offered way of release noise source impedance definition seems to be more reliable in comparison with already known ones as it allows to consider oscillatory processes in the exhaust manifold of internal-combustion engine thanks to which the calculation accuracy of muffler’s brought losses in course of its development at motor transport engines design stage is increased. The analytical dependences for calculation of frequencies at which the extreme values of this characteristic are observed are also received.

EMI filter design: Part III: Selection of filter topology for optimal performance

In the first two parts of the electromagnetic interference (EMI) filter design series, the conducted EMI generation mechanism and the method on the measurement of noise source impedances of a switched-mode power supply were described. In this final part, the selection of filter topology for optimal performance is explained. With good accuracy of both amplitude and phase of termination impedances, an EMI filter can be designed systematically to give optimal performance.

EMI filter design: Part II: Measurement of noise source impedances

In the first part of the EMI filter design series, the conducted EMI generation mechanism was explained. In this second part, a method on the measurement of noise source impedance of SMPS will be described. The proposed measurement method allows accurate extraction of the common-mode and differential mode equivalent noise source impedances of a SMPS under it actual operating conditions.

A new CMOS wideband low noise amplifier with gain control

In this paper, a new CMOS wideband low noise amplifier (LNA) is proposed that is operated within a range of 470 MHz–3 GHz with current reuse, mirror bias and a source inductive degeneration technique. A two-stage topology is adopted to implement the LNA based on the TSMC 0.18-μm RF CMOS process. Traditional wideband LNAs suffer from a fundamental trade-off in noise figure (NF), gain and source impedance matching. Therefore, we propose a new LNA which obtains good NF and gain flatness performance by integrating two kinds of wideband matching techniques and a two-stage topology. The new LNA can also achieve a tunable gain at different power consumption conditions. The measurement results at the maximum power consumption mode show that the gain is between 11.3 and 13.6 dB, the NF is less than 2.5 dB, and the third-order intercept point (IIP3) is about −3.5 dBm. The LNA consumes maximum power at about 27 mW with a 1.8 V power supply. The core area is 0.55×0.95 mm 2.

Systematic Electromagnetic Interference Filter Design Based on Information From In-Circuit Impedance Measurements

Based on a two-probe measurement approach, the noise source and noise termination impedances of a switched-mode power supply (SMPS) under its normal operating condition are measured. With the accurate noise source and noise termination impedances, an electromagnetic interference (EMI) filter can be optimally designed. A practical example of the design of an EMI filter to comply with a regulatory conducted EMI limit using the proposed procedure is demonstrated and compared with the cases, where the noise source and noise termination impedances are not taken into account, or coarse estimates of them are considered. Although all approaches allow filtered SMPS to pass the regulation limits, designing EMI filters with the accurate noise source and termination impedances leads to optimal component values and avoids overdesign.

Accurate Extraction of Noise Source Impedance of an SMPS Under Operating Conditions

An accurate measurement method to extract the common mode (CM) and the differential mode (DM) noise source impedances of a switched-mode power supply (SMPS) under its operating condition is developed and validated. With a proper premeasurement calibration process, the proposed method allows extraction of both the CM and the DM noise source impedances with very good accuracy. These noise source impedances come in handy to design an electromagnetic interference filter for an SMPS systematically with minimum hassle.

Effects of X Capacitors on EMI Filter Effectiveness

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> The suppression mechanism of the differential-mode noise of an X capacitor in offline power supplies is, for the first time, attributed to two distinct concepts: 1) impedance mismatch (regarding a line impedance stabilization network or mains and the equivalent power supply noise source impedance) and 2) <formula formulatype="inline"><tex> $C(dv/dt)$</tex></formula> noise current balancing (to suppress mix-mode noise). The effectiveness of X capacitors is investigated with this theory, along with experimental supports. Understanding of the two aforementioned mechanisms gives better insight into filter effectiveness, which may lead to a more compact filter design. </para>