The most complete summary of EMC knowledge about switching power supplies
As early as the early 1980s, the infant mortality rate in the obstetrics ward of a hospital in New Jersey, USA was quite high. At night, the warning lights on the monitors monitoring babies always go out for no reason. The nurses were very angry about this, so they turned off the monitor and patrolled back and forth one by one.
After a preliminary investigation, the professor found out the truth of the matter. It turned out that the transmitter of a nearby television station had obtained permission from the US Communications Commission to increase its output power significantly after around midnight, but it must be restored to its original level before 6am or other designated time. The connection cable between the nurse station and each baby's monitor resonates at these interference frequencies, inducing voltage and causing the monitor warning light to turn off. Before the hospital discovered this issue, about six children had already died.
Another example: There was a customer complaint that when a power switch was turned on in the computer room, the company's 100M speed local area network experienced a speed drop and stopped, while the 10M speed network was not affected. Turn off the power and restore the network to normal.
After experimentation, it was found that the high-frequency interference signal of the switching power supply was coupled to the network line, causing the network to malfunction.
The history of EMC development: EMC was actually born with the rapid development of the modern electronics industry. By the end of the last century, with the rapid increase of electronic and electrical equipment. EMC has expanded into numerous fields, and it can be said without exaggeration that wherever there are electronic products, there are EMC issues. The requirements of Western countries are becoming increasingly stringent, and EMC has become one of the trade barriers for developing countries' electronic products to enter the Western market.
For enterprises, different EMC design concepts can lead to different costs and time wastage.
