应用于开关电源的有源共模EMI滤波器

在开关电源中,高速的开关造成了严重的共模噪声干扰.介绍了一种应用于开关电源的有源共模EMI滤波器.该有源滤波器基于电流检测、电流补偿的原理,以高速运放为核心.试验证明,该有源滤波器对共模噪声的抑制能力比无源器件高20 dB.     

FPGA在共模噪声能量评估中的应用

在电力电子开关变换器数字化共模噪声抑制系统中,一个重要环节就是共模噪声的评估。由于共模噪声电流振荡频率很高,基于DSP的采样控制很难满足要求。文章提出了用FPGA作为主要器件、以能量为指标的共模噪声评估技术。所提方案中,FPGA可完成对高速AD芯片的采样控制、读取采样值、计算共模电流的噪声能量值并将该值反馈给DSP。DSP也可以通过向FPGA写入控制字和发启动脉冲等方式对噪声电流的采样过程进行宏观层面的控制。     

一种抑制差分拐角共模噪声的补偿模型

为抑制差分传输线拐角处不对称造成的共模噪声,文中提出了一种新的45°拐角差分传输线补偿模型。该模型通过对差分拐角造成的线长差进行有效补偿,利用HFSS和ADS进行建模仿真,从时域和频域进行验证。结果证明,从S参数来看,其有效地将频率8 GHz处的差模转共模噪声降低了20 dB,同时降低了差模插入损耗;从时域来看,共模噪声比之前减小了大约90%。     

一种高共模抑制比轨到轨全差分运算放大器

针对传统全差分运算放大器电路存在输入输出摆幅小和共模抑制比低的问题,提出了一种高共模抑制比轨到轨全差分运算放大器电路。电路的输入级采用基于电流补偿技术的互补差分输入对,实现较大的输入信号摆幅;中间级采用折叠式共源共栅结构,获得较大的增益和输出摆幅;输出级采用共模反馈环路控制的A类输出结构,同时对共模反馈环路进行密勒补偿,提高电路的共模抑制比和环路稳定性。提出的全差分运算放大器电路基于中芯国际(SMIC) 0.13μm CMOS工艺设计,结果表明,该电路在3.3 V供电电压下,负载电容为5 pF时,可实现轨到轨的输入输出信号摆幅;当输入共模电平为1.65 V时,直流增益为108.9 dB,相位裕度为77.5°,单位增益带宽为12.71 MHz;共模反馈环路增益为97.7 dB,相位裕度为71.3°;共模抑制比为237.7 dB,电源抑制比为209.6 dB,等效输入参考噪声为37.9 nV/Hz^1/2@100 kHz。     

基于双重傅里叶级数的三相逆变器共模电压分析

随着电力变换器技术的不断革新和发展,三相逆变器在大功率应用场合占据了越来越重要的位置,但是在实际应用中也存在一些负面效应,比较典型的问题之一是输出共模电压影响了系统的可靠性。基于双傅里叶级数的数值计算方法,本文推导了三相逆变器共模电压的数学表达式,并根据数学表达式提出了一种抑制三相逆变器输出共模电压的方法。本文提出的共模电压分析和抑制方法具有普适性、一般性、通用性,可以推广到任意逆变器的输出共模电压分析中去,通过仿真与实验对共模电压分析方法进行了验证。     

仪表放大器及其应用（四）

仪表放大器及其应用（四）纪宗南１．概述ＡＭＰ－０１是一种低噪声、高性能、单片仪表放大器，它是为高精度数据采集和仪表应用而设计的芯片。由于采用低漂移器件、双极点补偿法、新型偏置电流补偿技术，所以该芯片具有失调电压低、稳定性好、噪声低、共模抑制比高、偏置...     

一种新的基于共模扼流圈传导干扰模态分离网络

测试传导性干扰的模态噪声,是设计电磁干扰(EMI)滤波器的前提条件。共模扼流圈能够抑制共模模态,而不影响差模电流的输出。根据共模扼流圈这一特点,设计一种由两个共模扼流圈为核心的共模/差模分离网络,实现共模电压和差模电压的同时输出。仿真结果表明,在150 kHz³0 MHz的测试频带,输入端口阻抗基本在50Ω,并且共模传递比(CMTR)、差模抑制比(DMRR)、差模传递比(DMTR)及共模抑制比(CMRR)四个结果显示了该分离网络的良好模态分离效果。     

一种用于ECG信号采集的低功耗仪表放大器

设计了一种用于心电图信号采集的电流反馈型仪表放大器。输入级采用折叠共源共栅结构,有效提高了共模抑制比。采用电流分流技术,设计了小跨导值G_m-C高通滤波器,实现了人体低频噪声的隔离和直流失调的抑制。该仪表放大器采用TSMC 0.18 μm CMOS工艺进行设计。结果表明,在1.8 V电源电压下,功耗为168.8 μW。在0.2~200 Hz带宽范围内,增益为35.7 dB,共模抑制比为142.1 dB,输入参考噪声为110 nV/Hz@202 Hz。     

抑制共模电流的变频空调系统同步PWM控制方法

为有效降低双变频空调(air conditioner,AC)系统中电压波动产生的共模电流,以便满足电磁干扰标准,提出了一种新的同步脉冲宽度调制(pulse width modulation,PWM)控制方法。在由两个逆变器驱动(主从式控制模式)的AC系统中,通过在从模逆变器的矢量空间进行信号选择,以便减小相电流的畸变。采用矢量控制的方法来抑制风扇电机的不稳定性,并利用特殊的扇区选择方法减小电压误差。理论仿真和实机测试均验证了该方法的有效性。实验结果表明,相比现有的PWM方法,提出的同步PWM方法明显减小了相位电流的畸变,并有效降低了AC系统工作过程中的传导发射噪声,在170 kHz、1 MHz和10 MHz的频率下,噪声分别可降低23 dB、6 dB和1.5 dB。     

PWM逆变器供电的电机轴电流及其防治

本文讨论了在交流感应电机中普遍存在的轴电压和轴电流问题。通过对PWM逆变器驱动电机和电网正弦波驱动电机的比较，阐明了共模电压对电机的影响，通过建立PWM逆变器和电机模型并导出共模回路的等效电路，具体分析了轴电压如何产生，轴承电流的几种路径，并在所给出不同路径电流示意图的基础上分析了它们对轴承和电机运行的影响，最后提出了不同的防治方法和采取该方法后的轴承电流的流向情况。     

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.     

Common-Mode Ripple Current Estimator for Parallel Three-Phase Inverters

For the three-phase parallel voltage source inverter systems with common dc link, several control methods were developed to suppress the common-mode circulating current. The common-mode ripple current is the main disturbance source of the common-mode circulating current control system that forms part of the parallel discontinuous pulsewidth modulation (PWM) inverter system. In this paper, a real-time analysis method for the common-mode ripple voltage of the three-phase discontinuous PWM inverter is proposed, whereby the amplitude of the common-mode ripple current can be estimated correctly, the hysteresis width of the circulating current controller can be adjusted to be as small as possible, and consequently, the rms circulating current is minimized as well. The simulation and experimental results are presented to confirm the theoretical analysis method of the common-mode ripple current and the performance of the proposed common-mode ripple current estimator.      

传导EMI的测试

在传导EMI(电磁干扰)中既存在共模电流也存在差模电流,要很好的分析传导EMI系统,就很有必要对共模干扰信号和差模干扰信号分离开来单独进行测试.这样,共模和差模噪声的分离就显得很重要了.     

Measurement of noise source impedance of SMPS using two currentprobes

Using two clamp-on current probes, a novel method for measuring the common-mode (CM) and differential-mode (DM) noise source impedance of a switched mode power supply (SMPS) is developed. With proper setup calibration, the method is capable of measuring a wide range of impedance values with good accuracy     

New methods to suppress EMI noises in motor drive systems

New methods are studied that can suppress EMI noises, especially the common-mode current produced in motor drive systems. One is a packaging technique that forms power converters using a four-layer printed power circuit board. The other is a method based on the generation mechanism of the common-mode current which was developed from experimental analyses. It is proved by experiments that the former can effectively control the common-mode current, including radiated emissions, and the latter can suppress it without any compensators between the inverter and the motor     

Common-Mode Noise Reduction for Power Factor Correction Circuit With Parasitic Capacitance Cancellation

In this paper, a method using negative capacitance to cancel the common-mode (CM) parasitic capacitance of boost power factor correction (PFC) converters is proposed. Both the theoretical analysis and experiments show that the proposed method is very easy to implement and very efficient to reduce CM noise.     

一种低漏电流七开关无变压器型光伏并网逆变器拓扑

无变压器型光伏逆变系统中的漏电流高于300mA时规定必须在0.3s内从电网中切除。为解决系统中脉动共模电压引起的漏电流问题,提出新型七开关逆变拓扑(H7),该拓扑在直流输入端引入两个高频开关管,续流阶段确保直交两侧完全解耦,维持共模电压的恒定。在调制方法上,还可以实现倍频SPWM策略,降低电流纹波。在任意模态中开关管始终交错工作,有助于热应力均衡。最后,通过2kW的样机平台验证了抑制后漏电流峰值仅为60mA,相对于传统拓扑性能更优越,提高了系统的安全裕度。     

An active circuit for cancellation of common-mode voltage generatedby a PWM inverter

This paper proposes an active common-noise canceler (ACC) that is capable of eliminating the common-mode voltage produced by a pulsewidth modulation (PWM) inverter. An emitter follower using complementary transistors and a common-mode transformer are incorporated into the ACC, the design method of which is also presented in detail. Experiments using a prototype ACC, whose design and construction are discussed in this paper, verify its viability and effectiveness in eliminating common-mode voltage in a 3.7 kW induction motor drive using an insulated gate bipolar transistor (IGBT) inverter. Some experimental results show that the ACC makes significant contributions to reducing a ground current and a conducted electromagnetic interference (EMI). In addition, the ACC can prevent an electric shock on a nongrounded motor frame and can suppress motor shaft voltage