Electromagnetic Interference of Power Adapters

　　Electromagnetic interference (EMI) is a significant concern when it comes to power adapters. Power adapters, especially those with switching power supplies, can generate electromagnetic emissions that may interfere with other electronic devices.

　　The switching power supply in a power adapter works by rapidly switching the input voltage on and off. This high - speed switching process can produce electrical noise in the form of electromagnetic waves. These waves can radiate out from the power adapter and interfere with nearby devices such as radios, Wi - Fi routers, and even other power adapters. For example, if a power adapter is placed too close to a Wi - Fi router, the electromagnetic emissions from the adapter may disrupt the router's signal, causing intermittent disconnections or slower network speeds.

　　There are two main types of EMI associated with power adapters: conducted EMI and radiated EMI. Conducted EMI travels along the power lines and can affect other devices that are connected to the same electrical circuit. This can be a problem in a home or office environment where multiple electronic devices are plugged into the same power strip. Radiated EMI, on the other hand, is emitted into the air as electromagnetic waves. It can affect devices that are in the vicinity of the power adapter, even if they are not connected to the same electrical circuit.

　　To mitigate electromagnetic interference, power adapter manufacturers employ several techniques. One common method is to use shielding. The power adapter's internal components are enclosed in a metal shield, which helps to contain the electromagnetic emissions and prevent them from radiating out. Another technique is the use of filters. Input and output filters are added to the power adapter's circuitry to reduce the electrical noise. These filters can block the high - frequency components of the EMI, both in the input power line (to prevent external EMI from entering the adapter) and in the output line (to prevent the adapter's generated EMI from reaching the connected device).

　　In addition, power adapters are often designed to comply with international EMI standards, such as the FCC (Federal Communications Commission) regulations in the United States or the CE (Conformité Européene) standards in Europe. These standards set limits on the amount of electromagnetic emissions that a power adapter can produce. By adhering to these standards, manufacturers ensure that their power adapters are safe to use in a variety of environments without causing excessive interference to other electronic devices.

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The EU has published new LVD (2014/35/EU) and EMC (2014/30/EU) directives