Electromagnetic Compatibility Directive

Release time：2017-1-18 browse：0

        In order to regulate the electromagnetic compatibility of electronic products, all developed countries and some developing countries have developed electromagnetic compatibility standards. Electromagnetic compatibility standard is to make the product in the actual electromagnetic environment to work properly the basic requirements. Is called the basic requirements, that is, even if the product meets the electromagnetic compatibility standards, in actual use may also interfere with the problem. Most of the national standards are based on the International Electrotechnical Commission (IEC) developed standards.

       IEC has two parallel organizations responsible for the development of EMC standards, namely CISPR (International Radio Interference Special Committee) and TC77 (77 Technical Committee). CISPR to develop the standard number: CISPR Pub. XX, TC77 standard number for the development of IEC XXXXX.

      China 's civil product electromagnetic compatibility standards are based on CISPR and IEC standards, has been published 57, numbered GBXXXX - XX, such as GB 9254-98.

    EN standards used in the EU is also based on CISPR and IEC standards, the corresponding relationship is as follows:

    EN55 ××× = CISPR standard

    EN6 ×××× = IEC standard

    EN50 ××× = Custom criteria

    Electromagnetic compatibility standards are divided into basic standards, common standards, product standards and special product standards.

         Basic standards: describes the EMC phenomenon, provides EMC test methods, equipment, the definition of the grade and performance criteria. The underlying standards do not relate to specific products.

         Product Standard: EMC test standard for a product line. Often quoted the basic standard, but according to the specificity of the product to make more detailed provisions.

         Common Criteria: According to the use of equipment environment, when the product does not have a specific product standards can be followed, the use of common standards for EMC testing. To make the function of the device completely normal, but also to meet the requirements of these standards.

    In order to make products with good electromagnetic compatibility, special consideration should be given to the design content related to EMC. Electromagnetic compatibility design generally includes the following aspects.

1, ground design: Many of the electromagnetic interference problem is generated by the ground, because the ground potential is the reference potential of the entire circuit, if the ground wire is not properly designed, ground potential is unstable, it will lead to circuit failure. The purpose of ground wire design is to ensure that ground potential as stable as possible, thus eliminating interference.

2, circuit board design: regardless of the device to produce electromagnetic interference emission or by external interference, or interference between the circuit, the circuit board is the core of the problem, so the design of the circuit board to ensure electromagnetic compatibility of equipment is important significance. The purpose of circuit board design is to reduce the circuit board on the electromagnetic radiation generated by the sensitivity of the external interference and reduce the circuit board on the interaction between the circuit.

3, filter design: For any device, the filter is one of the key technologies to solve the electromagnetic interference. Because the wires in the device are highly efficient receiving and radiating antennas, most of the radiated emissions from the device are realized through a variety of wires, and external interference is often first received by the wire and then stringed into the device. The purpose of filtering is to eliminate these interference signals on the wire to prevent the interference signal in the circuit to the wire, the use of wire radiation, but also to prevent the wire received interference signal into the circuit.

4, shield and overlap design: For most of the equipment, shielding is necessary. Especially with the increasing frequency of circuit work, simply relying on circuit board design often can not meet the requirements of electromagnetic compatibility standards. Chassis shielding design and the traditional structure design has many differences, generally if the structural design does not take into account the requirements of electromagnetic shielding, it is difficult to shield effect added to the chassis. Therefore, for modern electronic product design, we must consider shielding from the beginning of the problem.