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。     

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。     

单片机实现的超声频SPWM逆变器的研究

文章介绍了一种适合于超声换能器的ＳＰＷＭ（正弦脉宽调制）逆变器。本系统控制电路采用最新单片机技术与正弦脉宽调制技术相结合，功率开关管采用速度极高的ＶＤＭＯＳ器件，从而实现了逆变调制频率为１８０ｋＨｚ～２７０ｋＨｚ，输出正弦波频率为２０ｋＨｚ～３０ｋＨｚ满足了负载换能器的要求。同时也突破了国内报道的调制频率几十千赫，输出正弦波频率几千赫的现有水平     

PWM逆变器采样通路传导噪声的分析与抑制

提高开关管的开关频率,可以提高输出电压的电能质量,增强PWM变换器的动态调节性能。然而,较高开关频率的应用使得开关过程引起的高频噪声对控制系统的采样产生更加深刻的影响。本文主要针对PWM逆变器传导噪声产生源和采样调理电路的传导通路进行分析,并利用实验测得噪声传导等效电路中各无源器件的参数。通过对该等效电路进行时域分析,采用一种简单的传导噪声抑制方法。仿真结果与实验结果基本一致,证明了共模传导等效电路模型及其分析的正确性。     

频率调制抑制DC／DC变换器EMI的研究

开关电源是采用高速半导体器件来进行电能转换的,开关切换过程中产生的电压电流尖峰造成了严重的EMI问题。常规的DC／DC变换器工作在频率固定的PWM模式下,频谱是离散的,开关频率和低次谐波的能量尖峰很高。文章研究了频率调制技术抑制DC／DC变换器EMI噪声的效果,通过对一台Boost变换器样机进行周期频率调制,证明了频率调制技术对抑制DC／DC变换器EMI的有效性。     

用于W—CDMA手机的CoolPAM HBT功放模块

凌特公司(Linear Technology)推出具集成扩频频率调制功能的降压型同步DC／DE控制器IXC3808，主要面向需要低EMI和低噪声的电源系统。LTC3808通过在460kHz～635kHz范围内随机改变开关频率，最大限度地降低了对EMI屏蔽和滤波器的需求；LTC3808也可工作在一个恒定的开关频率下。从而将DE／DE控制器的峰值辐射和传导噪声降低20dB以上。该器件提供两种选择：用户可选300kHz、500kHz、750kHz工作频率或250kHz—750kHz锁相环(PLL)工作。     

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.     

基于模型预测变开关频率PWM的EMI主动抑制技术

脉宽调制(PWM)是电力电子技术的重要基础领域,是当前电力电子变换器实现交直流电能变换与控制的主要方式。模型预测变开关频率PWM技术是经典脉宽调制技术理论在电力电子变换器领域的重要发展,也是扩频调制技术的一个新兴分支,融合了微秒级时间尺度的开关纹波时域预测模型,可主动控制PWM开关频率自由度,在实现电磁干扰主动抑制的同时,综合权衡了电力电子变换器开关纹波、开关损耗等重要因素。文章综述了基于模型预测变开关频率PWM的传导电磁干扰主动抑制技术的研究进展,回顾了基于不同预测模型的变开关频率PWM技术的实现方法,探讨了模型预测变开关频率PWM技术应用过程中的关键共性问题,进而展望了此技术在电力电子变换器领域的发展方向与机遇。     

基于噪声调制的薄膜电阻加热温度控制系统

基于脉宽调制（PWM）技术的控制系统广泛应用于工业和日常生活中,随机脉宽调制（RP-WM）技术也已提出.利用耦合到系统的环境噪声和系统本身的噪声经加工处理后调制控制信号,由噪声信号的自相关函数和功率谱密度函数给出噪声调制脉冲的平均开关频率和平均加热功率的计算方法.利用模拟器件设计了一个简单的基于噪声调制的薄膜电阻加热温度控制系统.实验表明：控制系统能够稳定地运行,在一定范围内能抑制噪声,实现了高精度温度控制.     

基于BiCMOS工艺的180GHz信号产生、调制与探测电路

在常规SiGe工艺下,设计了太赫兹频段的180 GHz信号产生、调制与探测电路。正交振荡器产生了四路相位相差90°的正弦信号,每路频率为45 GHz,线性叠加之后频率可达到180 GHz,开关交叉耦合结构在提高振荡器频率的同时,改善了振荡器的相位噪声;采用控制差分尾管电流的跨导切换式的调制方式,对180 GHz信号进行了10 MHz的幅度调制,输出功率为-27 dBm;探测电路主要为肖特基势垒二极管直接检波电路,实现对已调制的180 GHz信号解调。采用IBM 180 nm SiGe BiCMOS工艺进行流片验证,芯片面积为1 000μm×450μm,测试结果表明探测器能够成功解调太赫兹信号。     

无Y电容开关电源的EMI抑制方法研究

在要求低漏电流的电子设备中使用的开关电源不能采用Y电容,但无Y电容的开关电源往往难以通过EMC测试。文中通过分析开关电源中造成电磁干扰问题的原因和解决方法,提出利用吸收电路来抑制无Y电容情况下开关电源的电磁干扰。测试表明,这种方法可以有效解决无Y电容的开关电源中EMI问题。     

Use of sigma-delta modulation to control EMI from switch-mode powersupplies

Conducted electromagnetic interference (EMI) is a major cause of concern in switch-mode power supplies (SMPSs) which commonly use standard pulsewidth modulation (PWM). In this paper, sigma-delta (ΣΔ) modulation is proposed as an alternative switching technique to reduce conducted EMI from an SMPS. The result of using ΣΔ modulation is a spread in the spectrum of the conducted emissions so that large concentrations of power at discrete frequencies are avoided. Experimental time-domain waveforms and spectra of the switching function of first-order and second-order ΣΔ modulators are presented to prove the viability of the scheme for EMI mitigation. These modulators are then applied to a DC-DC converter in an off-the-shelf computer power supply and experimental results show a reduction of roughly 5-10 dB·μV in EMI emissions over standard PWM modulators     

PFC full bridge rectifiers EMI modeling and analysis-common mode disturbance reduction

Switched mode power supplies must comply with electro-magnetic interference (EMI) regulations. Due to technological improvements, switching frequencies have been increased leading to reduced passive component values but also greater EMI levels, especially conducted common mode disturbances. This paper presents a simple and effective EMI forecast method to study and to analyze the conducted EMI effects before prototype testing. The methodology is validated and applied to the single phase full bridge power factor correction (PFC) rectifier. Several techniques to reduce common mode current (CMC) levels created by the converter are presented. The study is based on high frequency models and understanding of phenomenon. Looking at the control strategies and/or the propagation paths, it is demonstrated that EMI levels may be reduced. It is shown that with symmetrical EMI propagation paths, synchronized control strategies such as bipolar pulse width modulation (PWM) are preferred and lead to reduced CMC levels. On the other hand, with asymmetrical propagation paths, unipolar and half bridge control strategies may be preferred to reduce both differential mode current (DMC) and CMC levels. Results are validated using practical experiments performed under EMI regulation testing conditions.     

反激式开关电源传导干扰的Saber建模仿真

针对目前反激式开关电源传导干扰问题较为严重的现象,分析了反激式开关电源的工作原理以及电路产生传导干扰的原因。利用Saber软件建立了电路的传导干扰仿真模型,得到了电路的传导干扰仿真波形。通过软件仿真结果与硬件电路的传导干扰波形测试结果相对比,验证了模型的适用性。     

Viability of active EMI filters for utility applications

The application of active circuitry to increase the performance per size and cost of utility-side EMI filters is considered. The major problems are power line frequency (60 Hz) rejection and the compensation of the feedback loop, which is influenced by the wide-ranging utility impedance. While analysis and simulations show that these problems prevent the practical application of active filtering to power supplies switching at around 75 kHz, results at 450 kHz demonstrate potential for substantial improvement of EMI filters for switching frequencies of a few hundred kHz, although with the cost of a complex compensation     

An innovative EMI reduction design technique in power converters

The present paper deals with the problem of reducing electromagnetic interference (EMI) of switched-mode power converters using gate controlled devices such as IGBTs and power MOSFETs. In order to reduce power losses, these systems rely on fast on/off time pulses, thus producing emissions due to the high-frequency spectral content of pulses. An original design method for switched-mode power supplies is developed allowing to obtain an acceptable compromise between power losses and EMI. Emphasis is placed on the analysis of the commutation cell of the switching static converter in order to demonstrate that it is possible to control the emissions of the device by handling the parameters of the driver circuit. Theoretical analysis is discussed and compared with experimental results of the investigation on the spectrum amplitude of the emissions     

开关电源EMI滤波器设计

分析了一种典型的开关电源电路,利用Pspice软件对其传导电磁干扰进行仿真研究,以TDK公司提供的元器件模型,提出了一种二阶无源EMI滤波器,完全消除了电路输出信号中的尖峰干扰,抑制了开关电源电路中的共模、差模噪声。同时,研究源和负载理想、非理想阻抗特性对滤波器插入损耗的影响,具有一定的意义。     

开关电源电磁干扰滤波器插入损耗的研究

研究了电磁干扰(EMI)滤波器的共模和差模插入损耗(IL)，并进行理论分析和测量；分析了影响IL的各种原因及改进方法。最后，测量了EMI滤波器插入损耗，为了检验EMI滤波器对开关电源的电流(电压)谐波的抑制效果，测量了开关电源的电流(电压)谐波分量，列出了测量数据，并对测量结果进行分析，总结出开关电源传导干扰的特点。测量结果验证了理论计算和分析的正确性。