Investigation of electromagnetic radiation induced by conducting wire of nanometer multi-quantum well device on InGaN LED

It is known that electromagnetic interference (EMI) has a negative effect upon the performance of electronic communication systems. The present study considers the case, where EMI is induced in an conducting wire (CW), and derives equations to establish the influence of the induced EMI on InGaN material of nanometer quantum well light-emitting diodes (LED). These equations are then verified experimentally. The present results indicate that the degree of influence of the EMI upon the InGaN LED device depends upon the interference power, the interference frequency, the induced power, the input resistance of the device, the inverse saturation currents, and the ideal factor of the LED. Moreover, the greater EMI amplitude and frequency, the greater deterioration I-V curves of the InGaN LED.     

Reliable study of digital IC circuits with margin voltage among variable DC power supply, electromagnetic interference and conducting wire antenna

This paper measures the margin voltage of a digital IC circuit in order to assess the deterioration of the margin voltage caused by variations in the DC power supply, electromagnetic interference (EMI), and the corresponding power induced in a conducting wire antenna (CWA). The present results confirm that these factors may influence the margin voltage to such an extent that the operation of the digital IC circuit may fail. This paper provides a theoretical analysis of the influence of these factors upon the margin voltage, and develops corresponding equations, which are then applied with appropriate parameter values to determine an optimal circuit operation. It is shown that the deteriorated margin voltage of the IC circuit is a function of the amplitude and frequency of the EMI source, and of the parasitic capacitance of the device, i.e. the greater the EMI amplitude and frequency, and the higher the capacitance of the device, the greater the likelihood that its operation will fail when subjected to a variable DC supply voltage, or to EMI and CWA effects. Furthermore, in the case of EMI, it is shown that an increased interference frequency will reduce the margin voltage of the device. Finally, it is noted that the smaller the input impedance of the IC device, the greater the influence of EMI is likely to be.     

Conducted EMI Reduction in Power Converters by Means of Periodic Switching Frequency Modulation

Spread spectrum clock generation techniques were originally developed to reduce electromagnetic interference (EMI) in communications and microprocessor systems working in the range of hundreds of megahertz. Nowadays, the switching frequency of power converters has been increasing up to values that make worthy the application of such switching frequency modulation techniques to reduce EMI emissions in power converters. Although random modulations have been applied before to power converters, periodic patterns can provide some advantages. First, theoretical principles of frequency modulation using three periodic patterns for the modulating function are presented. The influence of some important modulation parameters on the EMI reduction is analyzed and some considerations about the EMI filters design are also presented. The effectiveness of such methods in terms of EMI reduction is demonstrated theoretically and confirmed with experimental results obtained from tests carried out on two converters. The first one is a 2.5 W buck converter that can be switched up to 1 MHz and the second one is a 600 W boost converter switching at 40 kHz. In both cases, attenuations obtained in conducted EMI are evaluated. Finally, special attention has been paid to input current and output voltage ripple in order to evaluate possible undesired side-effects produced by this technique.     

Design of integrated BiCMOS operational amplifiers with low-probability EMI-induced-failures

Electromagnetic interference may cause failures in operational amplifiers. The probability of these failures can be reduced by properly designing the opamp, once the failure mechanism has been discovered. In this paper the design of some integrated BiCMOS operational amplifiers with a very low-probability of electromagnetic interference (EMI) induced failures is reported. In particular, it is shown that opamps exhibiting good general performances as well as low EMI-susceptibility can be obtained only if their response to a large square-wave input signal is symmetric and the influence of some parasitic capacitances in the input stage is compensated. Following these guide-lines, we found possible to design BiCMOS opamp structures exhibiting EMI susceptibility of only a few mV up to several hundred MHz when they are driven with an interfering input signal of some volts.     

Improved frequency characteristics of the randomized PWM boost rectifier

A randomized pulse width modulation (RPWM) algorithm is applied in the control unit of the boost rectifier to achieve improved frequency characteristics in the wide band. First, the introduction of the RPWM switching is reflected in a smaller increase of the total harmonic distortion (THD) factor in the input current. Nevertheless, decrease of the power factor is negligibly small. Second, the power spectrum density (PSD) of the input current is estimated and measured to evaluate the influence of randomization in the high-frequency range. This approach offers an effective and credible prediction method for reduction of conductive electromagnetic interference (EMI) by using the RPWM switching.     

Numerical and experimental analysis of EMI effects on circuits with MESFET devices

This study develops theoretical formulae to model the time domain and frequency domain characteristics of the noise spectrum of a MESFET device induced by varying EMI conditions. The theoretical results are then compared with the experimental measurements. The experimental and numerical results reveal that the magnitude of the EMI-induced noise is related to the pulse height, the output load, the parasitic capacitance, the interference frequency and the interference amplitude. It is shown that a higher interference amplitude or frequency increases the harmonic noise. The theoretical method presented in this paper provides a convenient means of evaluating the EMI effects and signal-to-noise ratio (SNR) of MESFET and similar wavelength devices.     

LED显示屏驱动电流的潜在电磁干扰分析

为了控制对发光二极管(LED)显示屏亮度调制时电 源电流产生的电磁干扰(EMI),对3种脉冲宽度调制(PWM)调光方法下显示 屏的电源电流频谱进行了研究。首先比较了线性、离散和选通3种PWM的调光原理和潜在 EMI,设计了基于电流频谱分析的EMI评估法,并通过对单亮度和亮度均匀渐变图像 的仿真,验证了评 估法的有效性;最后通过对LED显示屏真实图像显示时的电流频谱分析,比较了3种调光方 法的潜在EMI。实验结果表明:线性PWM方式下,同时点亮LED会产生较大的EMI;离 散PWM对消耗电流的 延展和码制对消作用,可以有效地减小EMI;选通PWM随着选通等级的提高,最小点 亮脉冲变窄不利 于减小EMI。本文的分析结果可用于在LED显示屏产品设计时,合理进行EMI分析 与分配,预估产品的电磁兼容性。     

Critical Upsets of CMOS Inverters in Static Operation Due to High-Power Microwave Interference

The effects of electromagnetic interference (EMI) from high-power microwave signals on the operational integrity of CMOS inverters are reported. The static characteristics of inverters were measured with and without the injection of microwave signals at power levels of upto 24 dBm and frequencies between 800 MHz and 3 GHz. Voltage transfer characteristics showed significant changes in output voltages, and substantial reduction in gain with microwave interference, due to increased drain currents and reduced transconductance, respectively. The asymmetry of the MOS devices (size, mobility) designed to provide balanced current driving capability, results in significantly imbalanced current driving capabilities under interference. A substantial increase in the static power dissipation at the stand-by "ON" and/or "OFF" states, is observed. Degradation in the noise margins and severely compressed input/output voltage ranges were observed due to large changes in voltage characteristics, invalidating noise immunity of cascaded CMOS inverters, and leading to serious bit-flip errors. The load-line characteristics showed substantial shift in the quiescent point of operation, and changes in the effective "ON" resistance of the MOS devices, resulting in increased current in the inverters. The input/output voltage range-related bit-flip errors and the static power dissipation problems, represent the most critical vulnerabilities in the operational integrity of digital systems.     

Reduction of power supply EMI emission by switching frequencymodulation

Electromagnetic interference (EMI) emission is always of grave concern for power electronic circuit designers. Due to rapid switching of high current and high voltage, interference is a serious problem in switching power circuits. Here, the effect of frequency modulation on power supply EMI noise is investigated. Significant reduction of emission is possible with the proposed scheme     

飞机直流母线变换器的输入电磁干扰滤波器设计

针对飞机直流270 V至直流28 V电源变换器的应用需求,分析了电源变换器输入端的传导及辐射电磁干扰源.通过对电源变换器的电磁干扰（electromagnetic interference,EMI）频谱进行分析,确定了滤波器的参数.为了抑制滤波器振荡,提出在差模电感两端并联电阻电感网络的方法,替代使用液态铝电容的传统方法,提升滤波器的可靠性.根据差模电感中电流直流分量远高于交流分量的特点,提出采用扁铜漆包线来实现绕组的方法,使差模电感的体积降低.根据锰锌铁氧体低频磁导率高,镍锌铁氧体高频磁导率稳定的特点,提出双磁芯共模电感的设计方法,实现共模电感宽频率和小体积.实测结果证明输入电磁干扰滤波器可使电源变换器符合GJB 151中CE102要求.     

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.     

Analysis of a ripple-free input-current boost converter withdiscontinuous conduction characteristics

Coupled inductor techniques supply a method to reduce the power converter size and weight and achieve ripple-free current. The boost power converter is a very popular topology in industry. However, the input-current ripple hinders efforts to meet electromagnetic interference (EMI) requirements. In particular, the input current becomes discontinuous and pulsating when the conventional boost power converter operates in the discontinuous inductor-current mode. This paper describes a boost power converter which has the same discontinuous properties as the conventional boost power converter. However, the proposed boost topology has continuous or ripple-free input current when it operates with discontinuous inductor-current. The proposed topology is compared with traditional converter topologies, such as the Sepic and Cuk power converters. Simulation results are presented. The prototype is built to demonstrate the theoretical prediction. The proposed boost topology is simple, with straightforward control [the same as pulse-width modulation (PWM)]     

电磁干扰中元件的高频特性研究

电力电子设备产生的电磁干扰都会超过可接受的水平,所以要利用滤波电路降低他们产生的EMI,这些滤波电路由串联扼流圈和并联电容器构成低通滤波器,文章对EMI滤波元件的高频特性进行分析,给出了电容、电感、电阻等的高频特性、等效电路以及仿真曲线。得出的结论体现出与工频下不同的特性,对滤波设计有重要指导意义。     

Investigation of EMI-induced noise spectrum in an enhancement-type MOSFET

This paper models the time domain and frequency domain characteristics of the noise spectrum of a MOSFET device under varying EMI conditions. The theoretical results are compared with experimental measurements. Both sets of results reveal that the magnitude of the EMI-induced noise is governed by the pulse height, the output load, the parasitic capacitance, the interference frequency and the interference amplitude. Furthermore, it is shown that a higher interference amplitude or frequency increases the harmonic noise. The theoretical method presented in this paper provides a convenient means of evaluating the EMI effects and signal-to-noise ratio (SNR) of MOSFETs and similar wavelength devices.     

海洋平台大功率整流电源电磁兼容整改分析

海洋平台大功率整流电源满功率工作时出现了非正常停机现象,CE102传导发射及RE102辐射发射测试项目超标。综合分析发现,整流电源内部开关器件开关频率及其倍频的电磁干扰、柜体屏蔽性能欠佳是超标的主要原因。通过在整流电源的输入、输出端进行针对性的EMI滤波和屏蔽设计,有效解决了大功率整流电源的电磁兼容问题。     

Techniques for measurement of input impedances of electronicequipment in the frequency range from 1 MHz to 1 GHz

Electromagnetic interference (EMI) can couple to electronic equipment through any number of interfaces of the equipment to its external environment, e.g. power and input/output signal cables or ventilation slots. The power cable interface to the equipment's power supply is investigated. Input impedances of power supplies in various electronic equipment operating under normal active conditions were measured in the common mode (phase-ground) from 1 MHz to 1 GHz. Such a wide frequency range is useful in studies of wideband EMI such as electrostatic discharge (ESD). The results of these measurements are discussed, and the possibilities of using them in further work are suggested     

Conducted electromagnetic emissions in induction motor drivesystems. I. Time domain analysis and identification of dominant modes

Stray components distributed in a pulsewidth modulation (PWM) drive system form parts of resonant circuits which can be excited to produce radio frequency (RF) noise driven by the pulsed switching action of the power devices. The dynamic response of such circuits is complex. It is essential to identify the dominant oscillation modes in the system so that electromagnetic interference (EMI) reduction techniques can be effectively implemented. This paper (Part I) investigates the mechanisms of conducted EMI emissions associated with a typical PWM inverter induction motor drive system. A numerical model, which includes the high-frequency effects within the machine, is established to evaluate the emissions in the time domain. The dominant high-frequency current paths are identified, and this allows the oscillation frequencies to be predicted from knowledge of the component values. The analysis is confirmed using laboratory measurements. Simplified frequency domain methods for direct calculation of the emission spectra based on the dominant high-frequency current paths are discussed in Part II     

Passive cancellation of common-mode noise in power electronic circuits

It is well known that common-mode (CM) conducted electromagnetic interference (EMI) is caused by the common-mode current flowing through the parasitic capacitance of transistors, diodes, and transformers to ground in the power circuit. Because of the potential for interference with other systems it is necessary to attenuate this noise. Ordinarily this is accomplished by using a magnetic choke across the input power lines, resulting in penalties to the overall size and cost of the completed system. In order to lessen the requirement for this magnetic choke, there has been a desire to introduce noise cancellation techniques to the area of EMI. This text introduces a method of canceling the common-mode EMI by using a compensating transformer winding and a capacitor. Compared with other cancellation techniques, it is much simpler and requires no additional transistors and gate-drive circuitry since it merely adds a small copper winding and a small capacitor. By using this technique the size of the EMI filter can be reduced, especially for applications requiring high currents. In this paper, the new method for passive noise cancellation is applied to many popular converter and inverter topologies. The method, results, and ramifications of this technique are presented in order of appearance.     

开关电源输入EMI滤波器设计与仿真

开关电源中常用EMI滤波器抑制共模干扰和差模干扰。三端电容器在抑制开关电源高频干扰方面有良好性能。文中在开关电源一般性能EMI滤波器电路结构基础上,给出了使用三端电容器抑制高频噪声的滤波器结构。并使用PSpice软件对插入损耗进行仿真,给出了仿真结果。