Multiple Slope Switching Waveform Approximation to Improve Conducted EMI Spectral Analysis of Power Converters

An improved and simplified electromagnetic interference (EMI) modeling method based on multiple slope approximation of device-switching transitions for EMI analysis of power converters is presented. The traditional noise source modeling method, which uses single slope for rise and fall transition, is studied, and the criteria for reasonable modeling in the frequency range is analyzed. The turn-on and turn-off dynamics are investigated by dividing the nonlinear transitions into several stages based on an insulated gate bipolar transistor (IGBT) behavior circuit model. Real device-switching voltage and current waveforms are approximated by piece-wise linear lines and modeled by multiple dv/dt and di/dt slopes. The predicted EMI spectra suggest that high-frequency EMI noise is modeled with an acceptable accuracy. The proposed method was verified experimentally for a dc-dc buck converter     

Essential-coupling-path models for non-contact EMI in switching power converters using lumped circuit elements

This paper proposes a simple lumped circuit modeling approach for describing noncontact EMI coupling mechanisms in switching power converters. The resulting model assumes a minimum number of noise sources and contains essential coupling paths that allow easy physical interpretations. Essentially, all capacitive couplings are represented by an equivalent noise voltage source and six coupling impedances, whereas all inductive couplings are represented by an equivalent noise current source and three coupling impedances. The resulting coupled noise appears as currents flowing into the terminals of the line-impedance-stabilization-network (LISN). The equivalent voltage source can be conveniently approximated as the switching-node-to-zero voltage, which is typically a rectangular pulse of a few hundred volts. The equivalent current source can be modeled as the current flowing around a loop containing the equivalent voltage source and parasitics such as winding capacitance of the power transformer, the snubber capacitance and connection inductances. Also, the coupling impedances can be estimated by making simplifying assumptions about the geometry of the components and tracks, or by direct measurements. Simulations and experiments verify how inductive and capacitive couplings through each path may produce substantial EMI measured by the LISN. Being based on a lumped circuit approach, the proposed model is easy to apply in practice for understanding, diagnosing and approximating EMI behaviors.     

Characterization of power electronics system interconnectparasitics using time domain reflectometry

The significance of interconnect parasitics of power electronics systems is their effects on power converters' electromagnetic interference (EMI)-related performances, such as voltage/current spikes, dv/dt, di/dt, conducted/radiated EMI noise, etc. In this paper, a time domain reflectometry (TDR) measurement-based modeling technique is described for characterizing interconnect parasitics in switching power converters. Experiments are conducted on power components of a prototype high-power inverter, including insulated gate bipolar transistor (IGBT) modules, busbar and bulk capacitors. It is shown that the interconnect inductance of the IGBT module can be extracted completely using TDR. It is also shown that the busbar equivalent circuit can be modeled as transmission line segments or L-C filter sections, and the bulk capacitor contains a significant equivalent series interconnect inductance     

Multilayer power printed structures suitable for controlling EMI noises generated in power converters

Electromagnetic interference (EMI) noises generated in power converters are diffused on the surface of conductors. This means influences occur from radiated EMI noises emitted from power transmission lines as well as conducted EMI noises transmitted from them. EMI noises diffusing on the surface of conductors are generally difficult to control using conventional concentrated constant theory. Thus, a new approach based on distributed constant circuit theory is needed in order to control EMI noises. A power converter structure to control EMI noises using multilayer power printed circuit technology is studied in this paper. A structure which can control EMI noises should simultaneously satisfy two conditions, i.e., one to shut down and one to attenuate EMI noises. The structure satisfying these conditions is studied through simulations using the Transmission-Line Modeling Method. The simulations show that the diffusion of EMI noises is controlled by dividing the flow of currents produced by EMI noises into the horizontal and perpendicular directions. That is, the horizontal current flow is controlled inside using the differences in the resistance produced from differences between inner and outer diameter of power transmission lines and the perpendicular current flow can be controlled by properly designing the thickness of the dielectric layer sandwiched between P-and N-power transmission lines with the symmetrical structure. Moreover, it is confirmed by simulations and experiments that the attenuation of EMI noises is affected by the width of the power transmission lines. It is expected that the results obtained in this paper can provide important rules when designing power converters with EMI noise control functions which use the multilayer power printed circuit technology.     

功率变流器传导干扰多通路频域模型研究

针对功率变流器传导电磁干扰建模与预测方法展开研究,提出了多通路并联的"干扰源-耦合通路"频域模型,研究了干扰源频谱及干扰耦合通路传递函数的建模提取方法.通过提取干扰源的端口频谱特性及干扰耦合通路的传递函数,直接在频域计算干扰噪声,具有建模方法简单,通用性强,不受具体电路结构限制的特点,可作为通用的频域建模方法应用于功率变流器传导电磁干扰建模与预测研究.通过具体实例,阐述了所提出的多通路频域模型的建模流程,验证了模型的准确性及其在变流器传导干扰建模、预测与噪声抑制过程中的指导意义.     

正态频率调制降低开关变换器电磁干扰的研究

利用正态频率调制技术从噪声产生源头上降低了开关变换器的电磁干扰。简单地分析了具有不变概率密度分布的离散随机信号频率调制降低开关变换器EMI噪声的原理,并试制了一台正态频率调制开关变换器电源样机。给出了开关管电流信号的频谱以及传导干扰测试的结果。实验结果表明该技术能有效降低开关谐波峰值,使开关变换器易于通过EMI测试,具有应用的前景。     

Improving the Characteristics of integrated EMI filters by embedded conductive Layers

Discrete electromagnetic interference (EMI) filters have been used for power electronics converters to attenuate switching noise and meet EMI standards for many years. Because of the unavoidable structural parasitic parameters of the discrete filter components, such as equivalent parallel capacitance (EPC) of inductors and equivalent series inductance (ESL) of capacitors, the effective frequency range of the discrete filter is normally limited. Aiming at improving high frequency performance and reducing size and profile, the integrated EMI filter structure has been proposed based on advanced integration and packaging technologies , . Some improvements have been made but further progress is limited by EPCs of the filter inductors, which is restricted by dimension, size and physical structure. In this paper, a new structural winding capacitance cancellation method for inductors is proposed. Other than trying to reduce EPCs, a conductive ground layer is embedded in the planar inductor windings and the structural capacitance between the inductor winding and this embedded layer is utilized to cancel the parasitic winding capacitance. In order to obtain the best cancellation effect, the structural winding capacitance model of the planar spiral winding structure is given and the equivalent circuit is derived. The design methodology of the layout and area of the embedded ground layer is presented. Applying this method, an improved integrated EMI filter is designed and constructed. The experimental results show that the embedded conductive layer can effectively cancel the parasitic winding capacitance, hence ideal inductor characteristics can be obtained. With the help of this embedded conductive layer, the improved EMI filter has much smaller volume and profile and much better characteristics over a wide frequency range, compared to the former integrated EMI filter and the discrete EMI filter.     

Differential-Mode EMI Reduction in a Multiphase DCM Flyback Converter

Switched converters are a source of electromagnetic interference (EMI) due to the hard switching and abrupt edges in the current and voltage waveforms. Multiphase converters can reduce the EMI at the source, minimizing the conducted EMI generation, without changing dramatically the normal operation of the circuit. Input filter can be greatly reduced, radiated EMI is lower, and internal EMI problems are minimized. This paper is focused on exploring multiphase converters as a topological technique to reduce conducted differential-mode EMI generation at the source, considering some nonidealities of the multiphase converter.      

A Suitable Method for Ecovehicles to Control Surge Voltage Occurring at Motor Terminals Connected to PWM Inverters and to Control Induced EMI Noise

A method that is suitable for ecovehicles, which controls the surge voltage appearing at motor terminals that are connected to a pulsewidth modulation inverter with short leads that are less than the critical cable length (i.e., the shortest length at which full reflection may occur), is described here. Also, a method to control electromagnetic interference (EMI) noise, which is induced by the surge voltage, is discussed. Ecovehicles have the problem where insulation degradation of motors occurs due to the surge voltage being repeatedly applied to motor terminals during long lifecycles. EMI noise such as the shaft current and the radiated noise, which are induced by the generated surge voltage, easily diffuse into other electric devices due to the high-density packaging structure. The diffused EMI noise may cause a malfunction of the vehicle controller. An EMI noise controller is studied, which can meet the high-density packaging requirements for ecovehicles like electric vehicles. The EMI noise controller is attached on the motor terminals and simultaneously suppresses the surge voltage and the noise. After clarifying surge voltage characteristics and a circuit model for expressing the surge phenomenon through experiments and simulations, an EMI noise controller is proposed, which uses a multilayer printed power circuit technique. It is verified through simulations and experiments that the proposed controller has the ability to simultaneously control the surge voltage and the EMI noise, such as the radiated noise and the shaft current (the bearing current), which are induced by the surge voltage.     

Low stray inductance bus bar design and construction for good EMCperformance in power electronic circuits

Ten years after the publication of the EC Directive 89/336 on electromagnetic compatibility, the impact of this directive on design and lay-out of modern electrical and electronic equipment can be observed. Many research and development studies have proposed and evaluated detailed improvements in the area of component design, component selection, circuit lay-out, shielding and active and passive filtering. New and innovative solutions to minimize noise, especially common mode conducted electromagnetic interference (EMI), in power electronic circuits continue to be developed. In this paper, the authors investigate to what extent EMI caused by power electronic devices in hard switching inverter topologies can be minimized using ultra-low inductive planar busbars. The concept followed in this study is to tackle EMI directly at the source where most EMI is generated; in other words, to reduce the parasitic magnetic energy stored in the inverter DC link to reduce high voltage spikes during switching. A planar busbar was built, tested and analyzed. Measurements show the validity of the theoretical, but simple, design procedure for planar busbars in power converters     

FDTD modeling incorporating a two-port network for I/O line EMIfiltering design

Electromagnetic interference (EMI) filters are often utilized on I/O lines to reduce high-frequency noise from being conducted off the printed circuit board (PCB) and causing EMI problems. The filtering performance is often compromised at high frequencies due to parasitics associated with the filter itself, or the PCB layout and interconnects. Finite difference time domain (FDTD) modeling can be used to quantify the effect of PCB layout and interconnects, as well as filter type, on the EMI performance of I/O line filtering. FDTD modeling of a T-type and π-type filter consisting of surface-mount ferrites and capacitors is considered herein. The FDTD method is applied to model PCB layout and interconnect features, as well as the lumped element components, including the nonlinear characteristics of ferrite surface-mount parts. The EMI filters with ferrites; are included in the modeling by incorporating the time-domain Y-parameters of the two-port network into the FDTD time-marching equations. Good agreement between the FDTD modeling and S-parameter measurements supports the new FDTD algorithm for incorporating two-port networks     

Electromagnetic Design Techniques for Liquid Crystal Display Driver ICs

A simple method of verifying electromagnetic interference (EMI) reduction effects for liquid crystal display (LCD) driver integrated circuits (ICs) is proposed. In this paper, we discuss correlations between radiated emissions and high-frequency currents of power system at three different levels: print circuit board (PCB) level, chip level, and functional circuit level. The EMI design points for LCD driver ICs are presented too. Simulated and measured results prove that our EMI design effectively reduces LCD EMI noise.     

基于新能源利用的逆变系统电磁干扰噪声解决方案

文章在对线性阻抗稳定网络内部结构和测量原理分析的基础上,针对于新能源系统的传导电磁干扰问题提出一种新的测量方法。利用该方法可以较为精确的测量新能源系统中逆变系统的传导电磁干扰噪声,并设计相应的滤波器对于传导电磁干扰噪声进行抑制。并且,根据新能源的特点,提出在直流侧加入电感电容以稳定由于直流侧电能不稳定所带来的电磁干扰噪声问题。实验结果表明该方法较为有效。     

An electromagnetic crystal power substrate with efficient suppression of power/ground plane noise on high-speed circuits

An electromagnetic crystal power substrate (ECPS) in a high-speed circuit package is proposed for suppressing the power/ground planes noise (P/GPN) and the corresponding electromagnetic interference (EMI). The ECPS is simply realized by periodically embedding the high dielectric-constant rods into the conventional package substrate between the continuous power and ground planes. With a small number of embedded rods and low rod filling ratio, the proposed ECPS design can efficiently eliminate the noise of 30dB in average within several designed stopbands. In addition, the radiation or EMI resulting from the P/GPN is also significantly reduced over 25dB in the stopbands. The excellent noise and EMI suppression performance for the proposed structure are verified both experimentally and numerically. Reasonably good consistency is seen.     

Field-Line-Circuit Coupling Based Method for Predicting Radiated Electromagnetic Emission of IGBT-PMSM Drive System

Electric drive system with Insulated gate bipolar transistor (IGBT) power device is widely used in Electric vehicle (EV), which consists of inverter, cables and Permanent magnet synchronous motor (PMSM). Due to the fast switching in di/dt and dv/dt of IGBT device, the system produces serious radiated Electromagnetic interference (EMI) through the interconnection cables. Thus, modeling of EMI source, propagation path and load PMSM is the key to accurately evaluate the system's radiation level. In addition, the system's radiated EMI involves the integrated calculation of circuit, cable and electromagnetic field, which cannot be solved by using a single circuit or electromagnetic calculation method. Therefore, this paper develops an effective field-linecircuit coupling based method to investigate the radiated EMI problems for IGBT-PMSM drive system, which is validated by experimental measurement. Besides, the impact of power cable parameters on radiated EMI is discussed. The proposed approach has guiding significance for electromagnetic compatibility design of EV.     

随机频率调制降低开关变换器电磁干扰的研究

利用随机频率调制技术从噪声产生源头上降低了开关变换器的电磁干扰。分析了具有不变概率密度分布的随机频率调制降低开关变换器EMI噪声的原理。将嵌入式系统产生的均匀分布离散随机信号加入脉宽调制芯片,开关频率随机变化,试制了一台随机频率调制开关变换器电源样机。给出了开关管电流信号的频谱以及传导干扰测试的结果。实验结果表明该技术能有效降低开关谐波峰值,使开关变换器易于通过EMI测试,具有应用前景。     

Characterization and modeling of parasitic emission in deep submicron CMOS

This paper presents a study of the parasitic emissions of a 0.18-/spl mu/m CMOS experimental integrated circuit (IC) and an accurate method for modeling the internal current switching to forecast electromagnetic interference (EMI). The effectiveness of emission reduction techniques is quantified through a set of conducted noise measurements. A simple core model is developed, based on the current switching activity. Added to a lumped-element model of the test board and the package, good agreement between simulation and measurements are obtained up to 10 GHz. The simulation methodology may be applied to forecast the impact of low emission design techniques on the EMI of ICs.     

A systematic coupled approach for electromagnetic susceptibility analysis of a shielded device with multilayer circuitry

This paper presents a systematic coupled approach for electromagnetic susceptibility (EMS) analysis of a shielded electronic device in the presence of an ambient electromagnetic interference (EMI). A full-wave electromagnetic modeling technique coupled with a circuit-based method is developed for the overall EMS performance analysis. The mixed-potential electric field integral equation (MPIE) is formulated via the method of moments to model the electromagnetic properties of an arbitrary structure consisting of wires and surfaces with any applied excitation. With numerical analysis, the effect of an ambient electromagnetic noise is characterized, and an equivalent circuit model is extracted for further analysis of EMI to internal high-speed sensitive circuits. Numerous examinations exhibit that this systematic coupled approach is a computationally efficient method to address the EMS problems at system level, in which the external EMI effects are fully considered and the circuit-based simulator is also exploited.     

混沌频率调制增强开关变换器EMC的研究

探讨了混沌频率调制技术在开关变换器中抑制电磁干扰的实际效果.分析了被调制信号的频谱与混沌系统产生的调制信号的不变密度函数之间的关系.设计了一个简单的Ber noulli映射混沌电路,并加入到工作在双环控制模式的Boost变换器,使开关频率随机变化.实验结果证明了提出的技术能有效降低开关变换器的谐波峰值和应用于开关变换器的可行性.     

Reduction of power converter EMI emission using soft-switchingtechnique

Measurements of conducted and radiated electromagnetic interference (EMI) emission from hard-switched and soft-switched buck, boost, and flyback converters of similar power ratings are presented. Results indicate that EMI emission can be substantially reduced by using a soft-switching technique in power converters. Thus, the soft-switching technique provides a practical and useful solution to reduce EMI emission from switched-mode power circuits. A comparison of EMI emission on the three classes of converters is also included. The flyback converter is found to be the least EMC friendly among the converters tested