Electromagnetic compatibility design analysis of switching power supply system
With the rapid development of electronic technology, electronic equipment is also developing in the direction of functional integration and miniaturization, which brings us a lot of convenience. However, the electromagnetic coupling between various electronic equipment has also become a problem that engineers face. the main problem. Electronic environmental pollution is no less harmful than traditional environmental pollution. As a part of environmental pollution, electromagnetic pollution has also been put on the agenda. When electronic equipment is working normally, it will withstand various electromagnetic interferences, including mutual interference from its own internal components and interference from other surrounding electronic equipment. It will also cause electromagnetic interference to other surrounding electronic equipment. Electronic equipment has very different requirements in different application environments (household, industrial control, electric power). In this regard, you can refer to the general standard IEC/EN61000-6 series or the industry requirements of corresponding products.
This electromagnetic interference mainly includes two aspects in the transmission path: one is transmission along the wire harness, which mainly includes transmission along the power port and signal port; on the other hand, it is mainly transmitted along the space.
Electromagnetic interference:
The power supply must meet the corresponding minimum emission energy requirements in its application environment, otherwise it will cause interference to the equipment in the surrounding environment. The standard IEC/EN61000-6 is divided into industrial environment equipment requirements and residential and commercial equipment requirements according to the general type requirements. Emission requirements for regional and light industrial environments; for general-purpose products such as power supplies, electromagnetic interference positioning in the early design stage will be designed in accordance with IEC/EN61000-6-3 or IEC/EN61000-6-4 unless it is a special model.
As the size of the power supply continues to be miniaturized and the power density continues to increase, the electromagnetic interference design of the power supply itself continues to become more difficult. All AC-DCs currently on the market from MORNSUN not only have built-in filters, but also transformer shielding, A large amount of design costs have been invested in noise absorption of power devices to meet the promised index requirements; R2 generation low-power DC-DC products are all designed with a six-sided shielding structure to meet the CLASS A of the industry EN55022/CISPR 22 and EN55011/CISPR 11 requirements and meet the grade requirements of basic industries.
Although a lot of design cost has been invested in the electromagnetic interference of the power supply itself, and it meets the promised index requirements, the problem of excessive electromagnetic interference in the market application of the power supply is inevitable; at this time, many design engineers will think that the root of the problem is Regarding the power supply, there is actually a misunderstanding in this regard, because the electromagnetic interference conducted disturbance test project is mainly aimed at the power port, so the power port becomes its transmission path, and all electromagnetic interference will reach the target through the power port. However, in addition to the electromagnetic interference measured by the test equipment from the power supply itself, the main part also includes electromagnetic interference generated by other parts of the whole machine, as well as electromagnetic interference generated by the resonance of parasitic parameters inside the equipment. This type of electromagnetic interference It will be coupled to the test equipment through the power port. The filter inside the power supply cannot filter this part of the electromagnetic interference. The application environment of the power supply varies greatly. The filter part of all power supply designs is to solve its own interference as the primary consideration. , the filter attenuation characteristics and spectrum characteristics will be reserved as much as possible, but it is impossible to be compatible with all applications; then this requires our complete machine designers to follow the application circuit recommended by the power supply manufacturer when designing the power supply front-end Make a design.
