[Go] 1th what is EMI filter

Ext.: HTTP://WWW.MURATA.COM/ZH-CN/PRODUCTS/EMICONFUN/EMC/2010/10/28/EN-20101028-P1

< preface >

EMI is an acronym for Electro Magnetic Interference, which means electromagnetic interference. In other words,EMI Filter is a filter to eliminate electromagnetic interference . However, the light is a bit difficult to understand, let me start with the EMI filter manufacturing background.

Recently, electronic devices have become more and more widely used in our daily life. These electronic devices use digital circuitry, and when high-frequency currents pass through a circuit board or route, the path becomes an antenna that radiates noise outwards. When there are other electronic devices nearby, this radio wave interferes with the normal operation of other electronic devices. For example, when a computer is placed next to the radio, the audio of the radio will be mixed with noise. This is the noise emitted by the computer's digital circuitry, which interferes with the radio's receiving antenna and generates noise. When the serious noise enters the digital circuit, it can cause the digital signal distortion, even causes the digital circuit to fail. The propagation of noise is not limited to the transmission of radio waves by space, but also through the transmission of power lines to connected devices.

1. What are the conditions for noise disturbance?

< How to solve the noise problem?>

There are 2 ways to solve the noise problem. One is to suppress noise sources of equipment emission noise, known as radiation countermeasures . The other is to prevent the device from being affected by noise or cause a malfunction, called an anti-disturbance countermeasure . "Anti-disturbance" has the meaning of "immunity". and pathological immunity, it refers to the immunity of the noise, that is affected by the noise and will not produce any problems of the countermeasure. Radiation countermeasures and anti-disturbance measures together are called EMC (Electro Magnetic Compatibility: Electromagnetic compatibility) countermeasures.

2. Two fundamental measures of noise suppression

In addition to the special circumstances, the noise problem can be solved as long as one of the radiation countermeasures and anti-disturbance countermeasures is solved. Radiation countermeasures are a measure of what is known about the position and type of noise, and the anti-disturbance strategy is based on the situation where the noise is from and how it enters, so it is more difficult than the radiation countermeasure. To this end, the market today focused on radiation countermeasures to solve the problem of noise focus. In order to solve the noise problem, countries set up the standard, which limits the radio wave and propagation noise above certain numerical value. (also required for partial immunity)

[Go] 1th what is EMI filter