Technologies and characteristics of integrated EMI filters for switch mode power supplies

Power electronics converters are potentially large EMI noise source to there nearby electrical and electronic equipments because of the switching function. EMI filters are necessary to insure the electromagnetic compatibility. Conventional discrete EMI filters are consisted of a fairly large number of components, with different shapes, sizes and form factors, and they are manufactured by different processing and packaging technologies, of which may include labor intensive processing steps. As a result, discrete EMI filters are usually bulky, high profile, with poor space and material utilization factors. In addition to that, because of the parasitic parameters of the discrete components and the interconnection board layout, the high frequency attenuation of discrete EMI filters is reduced. Hence the effective filter frequency range is limited. Aiming at these issues, integration technologies for EMI filters are studied. Our goal is to accomplish integrated EMI filters with structural, functional and processing integration to achieved smaller size, lower profile, better performance and reduced fabrication time and cost.