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Summarize some common methods for EMC rectification

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2022-06-15 10:27

EMC (electromagnetic compatibility) refers to the ability of equipment or system to operate as required in its electromagnetic environment without causing intolerable electromagnetic interference to any equipment in its environment. Therefore, EMC rectification 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 electrical appliances have a certain degree of immunity to electromagnetic interference of the environment, namely electromagnetic sensitivity.

The interference between various operating electronic equipment is mainly related to and affected by electromagnetic conduction, electromagnetic induction and electromagnetic radiation. Under certain conditions, it will cause interference, impact and harm to equipment and personnel in operation. In fact, there are many articles about specific EMC rectification. I compiled the six steps of EMC rectification proposed by predecessors for reference and learning by colleagues. The six steps of EMC rectification are as follows: find and confirm the radiation source; wave filtering; Wave absorption; Grounding; shield; Disperse energy.
1. The methods to find and determine the radiation source include the elimination method, the frequency search method of the spectrum analyzer, and the natural frequency analysis method of components. The elimination methods include pull wire method, partition operation elimination method, low voltage small current human touch method, and area shielding elimination method. The natural frequency analysis method of components refers to the analysis and classification of the fixed frequencies and their multiples of some components, such as the working frequencies of crystal and DDR components are fixed. 2. Filtering is generally divided into capacitance filtering, RC filtering and LC filtering. 3. The electromagnetic wave absorbing methods include the series magnetic bead method, the passing through magnetic ring method and the sticking absorbing material method. When using the electromagnetic wave absorption method, special attention shall be paid to: the frequency of the electromagnetic wave with excessive radiation shall be within the range of the electromagnetic wave frequency absorbed by the absorbing material used, otherwise the absorption method will become invalid. 4. The grounding mode is generally divided into single point grounding mode and multi-point grounding mode. 5. Generally, shielding methods include shielding, housing shielding and PCB layout shielding. 6. The energy dispersion method refers to that the control software of some tested objects uses spread spectrum, frequency hopping and other technologies to broaden the frequency bandwidth, so that the frequency band with concentrated energy will jump, thereby reducing the energy attached to the single point frequency, that is, reducing the electromagnetic wave intensity radiated by the single point frequency. Therefore, this method has obvious effect on the frequency radiation of the peak burr waveform exceeding the standard, but not on the frequency radiation of the envelope waveform exceeding the standard.
The above EMC rectification methods are more suitable for the rectification of common electronic equipment, but although the above methods help to improve the efficiency of EMC rectification, save cycle, and quickly pass the EMC test, they are not the basis for solving EMC problems. A better solution to EMC problems is to consider the design side, rather than using some "containment" solutions afterwards.