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第 1 页 共 13 页 外文出处：Farhadi, A. (2008). Modeling, simulation, and reduction of conducted electromagnetic

interference due to a pwm buck type switching power supply. Harmonics and Quality of Power,

2008. ICHQP 2008. 13th International Conference on, 1 - 6.

Modeling, Simulation, and Reduction of Conducted Electromagnetic

Interference Due to a PWM Buck Type Switching Power Supply I

A. Farhadi

Abstract:Undesired generation of radiated or conducted energy in electrical systems is called

Electromagnetic Interference (EMI). High speed switching frequency in power electronics

converters especially in switching power supplies improves efficiency but leads to EMI. Different

kind of conducted interference, EMI regulations and conducted EMI measurement are introduced

in this paper. Compliancy with national or international regulation is called Electromagnetic

Compatibility (EMC). Power electronic systems producers must regard EMC. Modeling and

simulation is the first step of EMC evaluation. EMI simulation results due to a PWM Buck type

switching power supply are presented in this paper. To improve EMC, some techniques are

introduced and their effectiveness proved by simulation.

Index Terms:Conducted, EMC, EMI, LISN, Switching Supply

I. INTRODUCTION

FAST semiconductors make it possible to have high speed and high frequency switching in

power electronics 1. High speed switching causes weight and volume reduction of equipment,

but some unwanted effects such as radio frequency interference appeared 2. Compliance with

electromagnetic compatibility (EMC) regulations is necessary for producers to present their

products to the markets. It is important to take EMC aspects already in design phase 3.

Modeling and simulation is the most effective tool to analyze EMC consideration before

developing the products. A lot of the previous studies concerned the low frequency analysis of

power electronics components 45. Different types of power electronics converters are capable

to be considered as source of EMI. They could propagate the EMI in both radiated and conducted

forms. Line Impedance Stabilization Network (LISN) is required for measurement and calculation

of conducted interference level 6. Interference spectrum at the output of LISN is introduced as

the EMC evaluation criterion 78. National or international regulations are the references for

word the evaluation of equipment in point of view of EMC 78.

II. SOURCE, PATH AND VICTIM OF EMI

Undesired voltage or current is called interference and their cause is called interference

source. In this paper a high-speed switching power supply is the source of interference.

Interference propagated by radiation in area around of an interference source or by

conduction through common cabling or wiring connections. In this study conducted emission is

considered only. Equipment such as computers, receivers, amplifiers, industrial controllers, etc

that are exposed to interference corruption are called victims. The common connections of

elements, source lines and cabling provide paths for conducted noise or interference.

Electromagnetic conducted interference has two components as differential mode and common

mode 9.

A. Differential mode conducted interference

This mode is related to the noise that is imposed between different lines of a test circuit by a

noise source. Related current path is shown in Fig. 1 9. The interference source, path

impedances, differential mode current and load impedance are also shown in Fig. 1.

B. Common mode conducted interference

Common mode noise or interference could appear and impose between the lines, cables or

connections and common ground. Any leakage current between load and common ground could

word be modeled by interference voltage source.

Fig. 2 demonstrates the common mode interference source, common mode currents Icm1 and

Icm2 and the related current paths9. The power electronics converters perform as noise source

between lines of the supply network. In this study differential mode of conducted interference is

particularly important and discussion will be continued considering this mode only.

III. ELECTROMAGNETIC COMPATIBILITY REGULATIONS

Application of electrical equipment especially static power electronic converters in different

equipment is increasing more and more. As mentioned before, power electronics converters are

considered as an important source of electromagnetic interference and have corrupting effects on

the electric networks 2. High level of pollution resulting from various disturbances reduces the

quality of power in electric networks. On the other side some residential, commercial and

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电气工程及其自动化专业_外文文献_英文文献_外文翻译_plc方面

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1、 外文原文

A: Fundamentals of Single-chip Microcomputer

The single-chip microcomputer is the culmination of both

the development of the digital computer and the integrated

circuit arguably the tow most significant inventions of the 20th

century [1].

These tow types of architecture are found in single-chip

microcomputer. Some employ the split program/data memory of the

Harvard architecture, shown in Fig.3-5A-1, others follow the

philosophy, widely adapted for general-purpose computers and

microprocessors, of making no logical distinction between

program and data memory as in the Princeton architecture, shown

in Fig.3-5A-2.

In general terms a single-chip microcomputer is

characterized by the incorporation of all the units of a computer

into a single device, as shown in Fig3-5A-3.

Fig.3-5A-1 A Harvard type

单片机-温度控制系统-外文翻译-外文文献-英文文献-中英翻译

单片机-温度控制系统-外文翻译-外文文献-英文文献-中英翻译

1

Design of the Temperature Control System Based on AT89C51

ABSTRACT

The principle and functions of the temperature control system based on micro

controller AT89C51 are studied, and the temperature measurement unit consists of the

1-Wire bus digital temperature sensor DS18B20。 The system can be expected to

detect the preset temperature, display time and save monitoring data。 An alarm will

be given by system if the temperature exceeds the upper and lower limit value of the

temperature which can be set discretionarily and then automatic control is achieved,

thus the temperature is achieved monitoring intelligently within a certain range.

Basing on principle of the system, it is easy to make a variety of other non-linear

control systems so long as the software design is reasonably changed. The system has

3-电气工程及其自动化专业_外文文献_英文文献_外文翻译_plc方面

3-电气工程及其自动化专业_外文文献_英文文献_外文翻译_plc方面

1、 外文原文

A: Fundamentals of Single-chip Microcomputer

The single-chip microcomputer is the culmination of both

the development of the digital computer and the integrated circuit

arguably the tow most significant inventions of the 20th century

[1].

These tow types of architecture are found in single-chip

microcomputer. Some employ the split program/data memory of the

Harvard architecture, shown in Fig.3-5A-1, others follow the

philosophy, widely adapted for general-purpose computers and

microprocessors, of making no logical distinction between program

and data memory as in the Princeton architecture, shown in

Fig.3-5A-2.

In general terms a single-chip microcomputer is

characterized by the incorporation of all the units of a computer

into a single device, as shown in Fig3-5A-3.

Fig.3-5A-1 A Harvard type

电气外文文献及翻译

电气外文文献及翻译

24.437 电力电子

正弦脉宽调制

如图1所示，电压源逆变器的开关可以按要求打开和关闭。用最简单的方法，顶部的开关打开，如果每个周期打开和关闭，则方波的波形结果只有一次。但是如果改进谐波的数据则在个周期内可以实现多次打开关闭。

图1 简单的电压源逆变器

如图2所示，用最直接的执行方式，所期望的输出电压是通过比较预期的参考波形与高频率的三角载波(调制信号) 生成的，无论直流电压是正还是负，信号电压的输出只根据信号电压是否大于或小于载波波形，要注意的是，在此期间一个三角载波周期的平均电压即信号的振幅加到负载形成正比(假定不变)。

经过一段时间，三角载波的负荷是正比于幅值的信号，在这期间，由此产生的方波包含有在它低频元件所需波形的幅值，也具有较高频率分量在一个载波临近频率的幅值。需要注意的是，由于PWM使得总谐波不失真，均方根的平均交流电压波形幅值仍与直流电压相等。谐波分量只是转移到了更高的平率范围，并由电感式交流系统自动过滤。

当正弦波调制信号的振幅为Am，三角载波的振幅为Ac时，它们的调制指数就是m=Am/ Ac。因此，控制调制指数控制着输出电压的幅值。如图3所示，fc/fm=21 ，t=L/R=T/3，T为基本周期，由于感性元件的存在，高频成分不能明显的传播到交流网络(或负载)，所以具有足够高的载波频率。然而，由于具有较高的载波频率，从而导致在更多的功率损耗。所以，在电力系统的应用中，通常认为使用2-15kHz的开关频率最为合适。此外，在三相系统中，建议使用)(,3Nkkffmc，使得三个波形对称。

图2 主要的脉宽调制

图3 SPWM的fc/fm=48，L/R=T/3

如图4所示，该过程是比较合适的，因为在该图中有三角载波，其中没有交集的载体作为信号周期。然而，这种“超调”在一定量的范围内往往是允许获得更大的交流电压，使电压频谱呈现出差异。需要注意的是，使用一个额外的比率形成一个反周期超过360°的对称波形。随着偶数，有偶数阶谐波，特别是一个小的直流分量，所以，一个单相逆变器不推介使用偶数，特别是fc/fm比率。