Reducing EMI Noise with Common Mode and Passive LC Filters.
This Coilcraft paper explains field interactions, unintended transmitters and receivers, and EMI mitigation techniques used in electromagnetic compliance testing.
The world is increasingly relying on the use of electronics and electrical devices at home, at work, and in every aspect of daily life. This increased use of devices — such as televisions, cell phones, notebook computers, and IoT devices — combined with technology such as appliance motors, lights, fans, and HVAC units running in the background has led to an environment full of competing signals and noise sources of various frequencies. This can lead to increased field interactions, current loops, ground loops, crosstalk, and other potential sources of electromagnetic interference (EMI), or undesired electrical disturbance (noise) that interferes with other devices.
Electronic devices and gadgets are also smaller, lighter, and faster today than ever before, while also providing the benefits and convenience of longer battery life and continuously improving processing ability. Although these smaller devices have the advantage of reducing some types of EMI, with a compact design comes smaller spacing between parts, which can also contribute to other potential sources of EMI. Understanding how fields interact to create intentional and unintended transmitters and receivers and applying EMI mitigation strategies can help devices meet electromagnetic compliance for electromagnetic compatibility (EMC), or the ability of electronic equipment to function properly without interference from noise sources (immunity/susceptibility) and without causing disturbances to other electronic equipment (emissions).
We will discuss several EMI solutions in this eBook. These include designing common-mode filters to prevent excessive noise by calculating specific filter alignments by manipulating the transfer function coefficients (component values) of a filter to achieve a specific damping factor. Another solution involves designing the right passive LC filter to block noise through modeling and analysis utilizing free design programs and models available online. Further, using a communication standard allows you to select the optimal common mode filter choke within the signal frequency that will not adversely attenuate, so that you can maintain high-speed communications free of EMI.
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Courtesy of Coilcraft
