Basic knowledge of EMC

If you run the PC or microwave when you are listening to the radio, do you have no noise in the sound or the electrical appliances have caused a malfunction due to static electricity?This is because electromagnetic waves (electromagnetic noise) and static electricity emitted by electrical and electronic devices affect the operation of other products.In this series, we will explain the Technology EMC to prevent such problems seven times.This time, we will introduce the outline of EMC and what kind of obstacles actually occur.

Lottery

1st: What is EMC?

1.What is EMC?

EMC is still a familiar term in Japan, but the importance of designing electronic devices is increasingly increasing.First, I will explain the outline of EMC, history, and test method.

1：EMCとは？

EMC (Electromagnetic Compatibility, electromagnetic compatibility) is "in the environment where the device or system exists, and does not give any unacceptable electromagnetic disturbance to anything, and to work satisfactorily in the electromagnetic environment.It is defined as "device or system ability" (JIS C 60050-161, IEV term for EMC).In other words, EMC has both performance of not producing electromagnetic noise that affects other products and operating normally even after receiving electromagnetic noise from the outside (Fig. 1).

The electromagnetic noise generated by electronic devices is called electromagnetic obstructions (EMI: Electromagnetic Interference) or emission.On the other hand, the resistance to electromagnetic noise (not malfunctioning) is called electromagnetic sensitivity (EMS: Electromagnetic Susceptivency) or an imunity.EMC terms have multiple names and are likely to cause confusion, so this series makes electromagnetic noise generated by electronic devices an emission and resistance to electromagnetic noise.

2：EMCの歴史

EMC has a long history and dates back to the 1930s.A phenomenon (emission) in which the reception of radio devices such as the radio is hindered by the electronic noise of an electronic device incorporating motors.In response to this, the Cispr (Special Committee for the International Disorder: COMITE INTERNATIONAL DES PERTURBATIONS RadioElectriques) was established in 1934.The purpose of Cispr is to promote international trade by internationally unifying the permissible value and measurement method regarding electromagnetic noise from various devices that cause wireless disorders.After that, as the complexity of electronic devices and low -voltage operations progress, electromagnetic noise such as static electricity and broadcasting waves also begins to become a problem in which electronic devices are malfunctioning.And the idea of EMC, which includes both emissions and systems, has become common.

3：EMCの試験方法と目的

...

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2.The importance of EMC

Let's take a look at the specific examples of electromagnetic disorders and the cause.I think the understanding of EMC's importance will deepen.We will also explain regulations.

1：事例集から見た電磁障害

The problem of electromagnetic waves has occurred in many places in our familiar places.It is required to turn off the mobile phone near the priority seat of the train.When taking off and landing of the plane, you need to turn off the electronic device or set it to an in -flight mode.These are measures to prevent electromagnetic waves that are intentionally radiated by electronic devices such as mobile phones do not adversely affect cardiac pacemakers and airplan instruments.In addition, analog TV image disturbances and AM radio noise are typical electromagnetic disorders that occur due to lack of EMC measures nearby.

総務省による電磁障害事例集では、エミッションの問題として、FAXや業務用脱毛器などの電子機器が、消防無線に影響を与えた事例が報告されています（表1）。また、...

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2nd: What is an emission?

Last time, I explained the outline of EMC and its importance.EMC (electromagnetic balance) has two performances: emissions (electromagnetic noise emitted by electronic devices) and images (resistance to electronic devices for electromagnetic noise).This time, we will focus on the emissions and explain the three elements: the noise source, which is the source of the emission, and the emissions that are important in designed in consideration of EMC.

1.Emission type

EMC is divided into two performances, emissions and systems.Emissions are also roughly divided into two.Radiation emissions and conduction emissions (Fig. 1).

放射エミッションとは、電磁ノイズが筐体（きょうたい）やケーブルから空間へと放射されることです。比較的高周波の電磁ノイズ（多くの規格では30MHz以上）が該当し、測定の際はアンテナを用いて受信します。一方、...

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2.Emission noise source

Emission is an electromagnetic noise emitted from electronic devices, causing communication obstruction of radio.However, not all electronic devices emit electromagnetic noise.For example, incandescent bulbs and LED bulbs are both emitting lights.Of these, only LED bulbs generate electromagnetic noise, and incandescent bulbs do not emit electromagnetic noise at all.

Incandescent light bulbs make the filament red and emit light by applying the voltage.Both DC and exchange are available, and AC power of 50Hz or 60Hz is usually used.In this way, incandescent bulbs that use only 60Hz low frequencies and do not have no noise source do not radiate electromagnetic noise.

一方のLEDは、...

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3.3 elements of emissions

Since electronic devices generally contain many noise sources, it is necessary to take emission measures.There are three important factors in taking measures against radiation emissions: noise source, noise propagation pathway, and antenna (Fig. 4).

Electromagnetic noise occurs from noise sources such as switching and clock.Then pass through the propagation route and radiate from the antenna.When designing EMC, it is basically effective to take measures close to the noise source.

ノイズをアンテナに伝搬する経路には、ノイズ源となるスイッチングの素子や、クロックの発生源に接続されている基板の線路、ケーブルなどがあります。ただし筐体が金属製で、かつノイズ源と金属製の筐体が接続されている場合は、筐体も伝搬経路となります。また、...

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The 3rd: What is a system?

EMC (electromagnetic compatibility) has two performances: emissions (electromagnetic noise emitted by electrical and electronic devices) and images (resistance to electrical and electronic devices for electromagnetic noise).Last time, I explained the emission.This time, I will take up the images and explain the evaluation method and the typical noise source.

1.What is a system?

In the environment where we live, there are various electromagnetic noise.In such an environment, the ability of electrical and electronic devices to operate normally and the resistance to electromagnetic noise is called the image.Electrical and electronic devices with insufficient imaging measures can cause malfunction due to electromagnetic noise, which can be a serious accident.

Electromagnetic noise varies depending on the type of noise, waveforms, and invasion methods, so in the imaging test, a typical electromagnetic noise is performed.In addition, the actual test determines the acceptable malfunctions by the type of electromagnetic noise that invades.Therefore, no matter what electromagnetic noise invades, malfunction is not allowed.

2.Evaluation of the system

When evaluating the EMC of electrical and electronic devices, you need to decide what kind of results you have.In the emission test, the tolerance of the size of the electromagnetic noise is determined according to the type of product and the environment to be used.Table 1 shows an example of a tolerant for multimedia equipment (VCCI: VCCI: VCCI: VCCI: VCCI: VCCI).If the electromagnetic noise generated from electric and electronic devices is less than the allowable value, you can evaluate it as no problem.

In contrast, the imaging test evaluates the malfunction caused by the effects of electromagnetic noise.Therefore, it cannot be evaluated by the size and tolerance of electromagnetic noise, as in the emission test.Also, even if it is malfunction, the content is ambiguous.Let's look at the LED bulb as an example as before.

LED電球の機能は発光です。想定される動作も、もちろん発光です。では、誤動作はどうでしょうか？...

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3.Loan noise source

In order to take into account imaging measures, you need to determine what electromagnetic noise exists and where to invade.A typical electromagnetic noise is divided into those that are generated by natural phenomena and artificially generated.

・自然現象による電磁ノイズ

Typical examples of electromagnetic noise generated by natural phenomena include static electricity and lightning.The test method is defined in the IEC61000-4-2 IEC61000-4-2, and the basic standards for the Surge Immediate Examination Examination, and the IEC61000-4-5 Surge Immediate Examination.

IEC61000-4-2 Static electricity defined in the Static Echard Dissonent Extension Exam is for those that are discharged from the human body, and are not discharged for products.Electromagnetic noise due to static electricity has direct discharge and indirect discharge (Fig. 2).

直接放電は、電気・電子機器に直接触れたときに発生する静電気放電です。この放電は、主に電気・電子機器の金属部(金属筐体、ねじ部やコネクタのシェルなど)に接触した際に発生するものと、スイチの隙間や液晶部などの絶縁部を通して発生するものがあります。一方、...

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4th: Emission measures

EMC (electromagnetic compatibility) has two performances: emissions (electromagnetic noise emitted by electrical and electronic devices) and images (resistance to electrical and electronic devices for electromagnetic noise).This time, we will explain the types of electromagnetic noise and typical measures with the theme of emission measures.

1.Differential mode noise and common mode noise

Electromagnetic noise generated from the noise source of electrical and electronic devices is divided into two types: a differential (normal) mode noise and a common mode noise.

・ディファレンシャルモードノイズ

In the differential mode, noise generated from the noise source is transmitted through the conductor and returns through the conductor, which is set up with the line (Fig. 1 left).If the outbound route is on the positive side, the return trip will be negative, and if the outbound route is a signal line, the return trip will be ground.This is the same route as the power supply and electrical signal of electric and electronic devices.At this time, the flow of the noise is called a differential mode (normal mode) because the direction of going and the return is reversed.

・コモンモードノイズ

一方、コモンモードでは、...

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2.Measures for electromagnetic noise

There are many types of noise measures.However, the method varies depending on the product specifications, countermeasures, and frequency you want to take countermeasures, and all products are not effective.Therefore, it is necessary to know what measures are available and select the appropriate method when designing a product.

This article describes representative measures for the noise source, propagation path, and antennas, which are the three elements of the emission, about the propagation route and antenna.Making the noise source smaller is the most effective measure, but it is difficult to practice due to cost and functional restrictions.The artwork design of the board is also effective for noise measures.If you are interested, please check it out.

・伝搬経路におけるノイズ対策

The noise countermeasure for the propagation route is to propagate by electromagnetic noise and prevent spread.The filter is effective in the bandwidth of 30MHz or less.The power filter used for power lines is combined with a condenser and a common mode chalk coil.The capacitor is called the X capacitor and the Y capacitor depending on the method (Fig. 2).

X capacitors are effective for differential mode noise measures.On the other hand, Y capacitors and common mode chokcoil are effective for common mode noise measures.By changing the capacity of the capacitor and the inductance of the chokcoil, you can change the frequency that can be taken.

In the band of radiant emissions of 30MHz or more, it is difficult to take measures with filters.This is because it is necessary to take measures not only on the power line but also to signal lines.When taking measures against the signal line, it is necessary to block only the electromagnetic noise while communicating the signal as it is.In this case, measures are taken using the difference between the frequency of the signal and the frequency of the electromagnetic noise.A typical countermeasure part is ferrite beads.Ferrite bead impedance has a frequency characteristics, so you can choose a low impedance at the signal frequency and a high impedance for other frequencies.

There is a damping resistance as a measure against data buses such as memory and clocks for digital IC (Integrated Circuit).Dumping resistance is used to suppress clock ringing (voltage vibration) due to resonance circuit or signal line and IC impedance.Clock -like square waves contain harmonic components and have very wide frequency components.Ling clocks contain even larger hyperclonem components, causing electromagnetic noise.It is important to place the damping resistance right next to the output pin of memory and digital IC.

・アンテナ部におけるノイズ対策

...

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5th: Request for EMC exams

Last time, among the EMC (electromagnetic balance), we explained the measures against emissions (electromagnetic noise generated by electrical and electronic devices).EMC standards and tests for exams vary depending on the country and region.This time, I will explain what EMC exams are required in Japan, Europe and the United States.

1.Request for EMC exams in Japan

In Japan, the required EMC exams are different between general electrical and electronic devices and medical devices used for medical use.In general electrical and electronic devices, an emission test is determined by the regulations specified by the VCCI Association (Information Processing Equipment, such as information processing devices), which provide voluntary regulation of electromagnetic sabotage waves.It is.On the other hand, for medical equipment used for medical use, the resistance of emissions and electrical and electronic devices for electromagnetic noise (law on ensuring the quality, effectiveness and safety of pharmaceuticals, medical devices, etc.).) Both exams are required.In particular, strict exams are imposed on the images.This article describes the emission test required for general electrical and electronic devices.

・電気用品安全法

The Electrical Equipment Safety Law is a law enacted to prevent the dangers of electrical equipment and the occurrence of disability.In Article 2 of the Electrical Appliance Safety Act, electrical products are defined as follows.

1. 一般用電気工作物（電気事業法（昭和39年法律第170号）第38条1項に規定する一般用電気工作物をいう。）の部分となり、またはこれに接続して用いられる機械、器具または材料であって、政令で定めるもの
2. 携帯発電機であって、政令で定めるもの
3. 蓄電池であって、政令で定めるもの

また、電気用品の中でも、構造や使用方法、その他の使用状況から見て、特に危険や障害の発生する恐れが多いものを、特定電気用品としています。また...

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2.Request for overseas EMC exams

There are also requests for EMC exams overseas, and the EMC standards applied by the country and region are different.In the United States, there is an EMC test by FCC and CE Marking in Europe.

・FCC(Federal Communications Commission:連邦通信委員会)

FCC is a government agency that manages American communication, telegraph, and radio waves.It has the role of regulating wireless communication such as radio and television in the United States and international communication.If you sell wireless frequency or sell electrical and electronic devices in the United States, you need to obtain authentication in accordance with FCC rules.In addition, FCC regulations include not only intentional radio devices but also non -intentional radioxons such as digital devices, each with an EMC test.

・CE マーキング

...

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6th: EMC standard type

Last time, we introduced the demands for typical EMC exams in Japan, the United States and Europe.This time, I will explain the type of EMC standard.There are many types of EMC tests in both emissions and images.There are a wide variety of electrical and electronic devices to be tested, and to decide which level to apply, refer to the EMC standard.The EMC standard stipulates the products and test methods to be subject to the test.

1.Types of EMC standards for each established person

EMC related standards include international standards, regional standards, national standards, and group standards.Table 1 shows a typical EMC standard.

・国際規格

Radio Interference) has enacted.The names of the standards include the abbreviation of each established organization (IEC or Cispr) (eg IEC61000-4-2, Cispr11).

・地域規格・国家規格

Regional standards and national standards are standards enacted by regions such as Europe (EU) and countries such as Japan with international standards.There are EN standards, JIS, IEC-J, etc. (eg, EN 55011, JIS C 61000-4-2, J55011).

The EN standard is a regional standard enacted by Europe for international standards.It is used as a consistency standard to confirm that the EC command is satisfied when acquiring a CE marking.

Japanese national standards include some JIS (Japanese Industrial Standards) and IEC-J standards.The IEC-J standard is based on the international standard (IEC standard) and adds a unique idea of Japan.It is the technical standard of the Electrical Appliance Safety Law.The Electrical Appliance Safety Law can be broadly divided into Japan's unique technical standards and technical standards based on international standards (based on IEC-J standards).Japan's unique technical standards are described in the Table 1 to 11 of the Electric Equipment Safety Law.The strength of the 10th noise 10th noise is Japan's unique technical standard.On the other hand, the technical standards based on the IEC-J standard are described in the standards that conform to the 12th International Standards, etc.In addition, although it is not related to EMC, many of the texts of IEC-J standards are JIS based on international standards.

アメリカにおけるEMCの規格には、...

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2.EMC standard classification

The international standard IEC GUIDE107 classifies the EMC standard into basic, product standards, product group standards, and common standards (Figure 1).The application of the standard has a priority, and it is necessary to select a standard that fits electric and electronic devices.

・基本規格

基本規格は、用語、電磁環境分類、EMC レベルの仕様、電磁エミッション・イミュニティの一般的要求事項、共通的測定・試験方法などを規定しています。基本規格は、個々の製品や製品群から独立した規格で、全ての製品に適用が可能です。ただし、...

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7th: Radiation emission test and simple measurement

Last time, I explained the EMC exam standard.This is the last round.We will discuss the radiation emission test method and simple measurement.The radiation emission test is a test that measures electromagnetic noise radiated in the space from electrical and electronic devices.Since this test is performed in a radio room, it is not easy to carry out.EMC measures may be used for simple measurements called neighboring world measurements.

1.Radiation emission test method

Radiation emissions are electromagnetic noise radiated into the space from the housing and cables of electrical and electronic devices, and is relatively high frequency (30MHz or more in many standards).In the radiant emission test, the electromagnetic noise radiated from electrical and electronic devices is measured by changing the antenna for each frequency.

・供試装置の構成

In the radiation emission test, the results may change significantly depending on the composition and movement of electric and electronic devices.For this reason, the structure, arrangement, operation, etc. of the trial device (device to be tested) (device to be tested), etc. are specified in detail according to the standard.The desktop PC that uses various devices is introduced as an example, and the measurement method of radiation emission is introduced (Fig. 1).

The test method is based on the technical standards that complies with the Cispr22 of the VCCI Association, which is the voluntary regulation of information and communication equipment (information processing devices such as information processing devices).The technical standard of VCCI specifies the configuration of the test device.Introducing only the parts necessary for the composition of the PC.

"Configure a test device in accordance with typical usage examples, combine, arrange, and operate": PC is used in combination with surrounding devices such as display, keyboard, mouse.The same combination must be made during the test.

「供試装置のインターフェースポートの各々のタイプごとに最低1つのインターフェースケーブル・疑似負荷・装置を接続しておくこと。装置の実際の代表的な使用法に従って、各ケーブルは終端すること」：PCには一般的に、USBポートやLANポート、ディスプレイポート、HDMIポート、マイク・イヤホンポートなど、複数のポートがあります。これらのポートには、実際の代表的な使用法に従い、ケーブルを接続、または終端し、試験を実施する必要があります。例えば、...

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2.Simple measurement of radiation emissions

As we have seen so far, when a radiation emission test is performed in a radio -dark room, an antenna is installed in a place that is 3m or 10m from the offer device and measure (distant measurement).On the other hand, in the EMC countermeasures, a simple method of measuring electromagnetic noise is may be adopted near the test device (local measurement).The basic system of simple measurement is a combination of spectrum analyzer and neighborhood probe.Depending on the size of the noise, it is necessary to put a preamplifier (Fig. 3).

簡易測定では一般的に、回路基板上に近傍界プローブを設置し、3軸の近傍界分布を測定し、ノイズ源を特定します。また、...

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