EMC (ElectromagneticCompaTIbility)
Electromagnetic compatibility refers to the state where the performance of the equipment or system is not degraded in the electromagnetic environment. Electromagnetic compatibility, on the one hand, requires no serious interference sources in the system, on the other hand, requires the equipment or the system itself to have good resistance to electromagnetic interference. Electromagnetic compatibility is an emerging comprehensive edge subject, which mainly studies electromagnetic wave radiation, electromagnetic interference, lightning strikes, electromagnetic materials and other aspects.
EMI (ElectromagneTIcInterference)
Electromagnetic interference refers to the electromagnetic waves generated during the operation of the electronic equipment itself, which are emitted to the outside, thereby causing interference to other parts of the equipment or other external equipment. For example, the common "snowflakes" on TV screens indicate that the received signal is disturbed.
EMS (ElectromagneTIcSuscepTIbility)
Electromagnetic susceptibility refers to the sensitivity of equipment to electromagnetic interference. The more sensitive the equipment, the more likely it is to be interfered.
Because of EMI, there is EMC, and because EMS meets the standard, EMC can be realized.
EOS (Electrical overstress)
In the semiconductor environment, the term electrical overload (EOS) is used to describe a phenomenon that may occur when the current or voltage of an electronic device exceeds the device's specification limit. Electrical overload may cause thermal damage to the entire device or part of the device. Thermal damage is caused by excessive heat generation during the EOS event. When the device is subjected to high voltage or high current, resistance heating occurs in the connection within the device, which causes the temperature to be too high. Usually, too much heat is around the area where electrical stress is applied. This can cause damage to the device, and in most cases, this damage is visible to the naked eye.
EOS may be caused by a single non-repetitive event or a continuous periodic or aperiodic event. EOS events can be instantaneous events (only lasting a few milliseconds) or continuous events if the conditions are met. After the EOS energy is exhausted, the device may be permanently damaged, may not work normally, or only part of it may work normally.
ESD (Electro-Static discharge)
Electro-Magnetic Compliance (ESD) is one of the most common Electro-Magnetic Compliance (EMC) phenomena. The term "static electricity" refers to the static charge that a specific substance accumulates when it comes in contact with other substances (for example, rubbing your feet on a wool carpet). Sometimes electric sparks are generated when touching metals or cars. This is the phenomenon of electrostatic discharge (ESD). The discharge amount depends on the substance and the environment (including humidity).
The ESD phenomenon does not only occur when people come into contact with electrostatically charged materials. Machines and furniture (for example, workbenches) also accumulate static electricity and discharge when they come into contact with electrical components.
EMS = EMI + EMS
(Electromagnetic interference) (Electromagnetic sensitivity)
Principles of electromagnetic interference (EMI)
ESD, EMI, EMC design are common problems encountered by electronic engineers in their design. Electromagnetic compatibility (EMC) means that equipment or systems meet the requirements in their electromagnetic environment and do not produce intolerable electromagnetic interference to any equipment in their environment. Ability. Therefore, EMC includes two requirements: on the one hand, the electromagnetic interference generated by the equipment to the environment during normal operation cannot exceed a certain limit; on the other hand, it means that the equipment has a certain degree of electromagnetic interference in the environment. The degree of immunity, that is, electromagnetic susceptibility. The so-called electromagnetic interference refers to any electromagnetic phenomenon that can degrade the performance of a device or system.
EMC includes EMI (electromagnetic interference) and EMS (electromagnetic tolerance). The so-called EMI electromagnetic interference is the electromagnetic noise generated by the machine itself that is not conducive to other systems in the process of performing its due function; and EMS refers to The ability of the machine to not be affected by the surrounding electromagnetic environment in the process of performing its functions.
In the design of electronic products, in order to obtain a good EMC performance and cost ratio, it is important to carry out EMC design on the product; the EMC performance of the electronic product is given by the design. The test only uses a certain quantitative method to characterize the inherent EMC performance of electronic products. For EMC design:
First of all, EMC design should be considered in the early stage of research and development. If the EMC problem is not considered in the early stage of product design, only hope to solve it in the test stage (indicated by rectification to solve the EMC problem of the designed product, so a lot of manpower and material resources are invested in the later stage. Testing/verification, rectification stage). Then, even if the product rectification is successful, in most cases, the rectification involves changes in circuit principles, PCB design, and structural molds, which will greatly increase R&D costs and greatly extend the cycle. Only by considering and predicting EMC issues in the pre-product design process, turning EMC into a controllable design technology, paralleling and synchronizing with the process of product functional design, can the product be designed at once.
Secondly, EMC design should be systematically designed to improve the EMC performance of electronic products. It is definitely not given by EMC experts in the enterprise alone, because EMC is absolutely impossible to exist without product hardware, structure and other physical objects. Therefore, to make the designed electronic products achieve good EMC performance at one time, it is necessary to improve the EMC experience and awareness of product design engineers. For example, hardware engineers should master the basic knowledge of EMI and EMS anti-interference design in addition to the circuit design knowledge that they must master before; PCB design engineers need to master the corresponding device layout, stacking design, and high-speed wiring EMC design knowledge; structural engineers It is also necessary to understand the design knowledge of the shielding of the product structure. Because these engineers who participate in product design together, to realize the opinions put forward by FMC experts in the product design process, they must understand and comprehend the mystery of the suggestions put forward by EMC experts, and combine them with the design characteristics of their respective fields to combine all The germination of EMC problems is eliminated in the product design stage. Only all developers involved in product design can improve EMC quality together to design electronic products with high performance EMC.
In general, the design of electronic products does not consider EMC issues, it will lead to EMC test failure, so that it can not pass the certification of relevant laws and regulations. The following figure outlines the main points of EMC, EMI, and ESD review.
Main points of EMC, EMI, ESD improvement
Grounding, shielding, filtering
With the development of electrical and electronic technology, household appliances have become increasingly popular and electronic, radio and television, post and telecommunications, computers and their networks have become increasingly developed, and the electromagnetic environment has become increasingly complex and deteriorating. We gradually pay attention to the working environment of the equipment and the electromagnetic environment. The impact of the environment on electronic equipment, electromagnetic interference (EMI) and electromagnetic compatibility (EMC) issues of electrical and electronic products have attracted more and more attention from engineers and manufacturers. In ESD protection, it can be roughly divided into two categories.
Conductive ESD protection mainly uses some protection devices to protect the electrostatic current in the circuit, forming a protection circuit in the front of the sensitive device to guide or dissipate the current. Such protective devices include ceramic capacitors, varistors, TVS tubes, etc.
Radiation ESD protection has an impact on sensitive circuits caused by static electricity. The main protection method is to minimize field generation and energy, and improve the structure to increase the protection capacity and protect sensitive circuits. It is often difficult to protect the field, and a method called alleles has been explored in improved practice. By effectively framing, the shell forms a potential equal body to suppress discharge. Facts have proved that this method is effective and easy to implement.
There are many general methods to protect against static electricity, including reducing the accumulation of static electricity; insulating products to prevent static electricity from occurring; providing branch circuits to shunt static electricity for sensitive lines; shielding the circuits in the discharge area; reducing the loop area to protect the circuit from static electricity The influence of the magnetic field generated by the discharge. There are direct discharges, and there are couplings for the associated field.
EMC certification
The EMC certification of a product is based on the product's electromagnetic compatibility standards and corresponding technical requirements, tested and confirmed by the certification body, and issuance of certification certificates and certification marks to prove that a product meets the requirements of the corresponding standards and corresponding technologies.
In my country, EMC certification has been included in the scope of 3C certification (China Compulsory Certification, English name is "China Compulsory Certification", English abbreviation is "CCC", or "3C"), the country has mandatory electromagnetic compatibility national standards or mandatory The safety certification system shall be implemented for products with electromagnetic compatibility industry standards and the standards with mandatory electromagnetic compatibility clauses. These products with electromagnetic compatibility safety certification shall be subject to mandatory supervision and management when entering the circulation field (no electromagnetic compatibility safety certification can not enter the circulation field ).
The conformity certification system shall be implemented for products with recommended electromagnetic compatibility national standards or recommended electromagnetic compatibility industry standards, and enterprises can apply for certification to certification bodies on a voluntary basis.
EMC certification body: China Electromagnetic Compatibility Certification Committee (CEMC)
The certification test must be carried out in an EMC testing organization recognized by the National Bureau of Technical Supervision.
Electromagnetic compatibility technology includes the integration of electromagnetics, electronics, materials science, and many other aspects of knowledge. With the increasing popularity of electronic products and the gradual recognition of electromagnetic hazards, reducing electromagnetic interference has become an important topic in the current electronic science community. Today's circuits have been integrated and modularized, so current circuit analysis and design can also be Speaking of system analysis and design, I believe that the in-depth study of this technology will have a significant impact on the improvement of the performance of electronic products in the future.
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