Design method of electromagnetic interference filter capable of suppressing resonance

Abstract

The invention discloses a design method of an electromagnetic interference filter capable of suppressing the resonance. The method comprises the steps of obtaining difference/common mode interferencevoltage and interference source internal resistance of the inverter through an inverter interference source model; calculating to obtain insertion loss required by a system, then selecting a filter topology, extracting element parameters of a differential/common mode filter by adopting an optimization algorithm, and simulating to obtain an optimal filter element value under the condition of considering high-frequency equivalent parasitic parameters of a filter device. According to the invention, filter manufacturing and experimental verification are carried out according to element parameter values obtained by simulation; analysis of filtering effect, high-frequency equivalent model combined with filter, finding out a filter self-resonance frequency point; the problem that common-mode EMIof part of frequency points exceeds the standard is solved by adding damping resistors, the trial and error cost in the filter design process is reduced, quantitative design of the EMI filter is achieved, key parts causing EMI exceeding the standard are accurately positioned by analyzing a system high-frequency equivalent model, and the optimal design of the filter is achieved.

Description

technical field [0001] The invention belongs to the technical field of filter design, and in particular relates to a design method of an electromagnetic interference filter capable of suppressing resonance. Background technique [0002] EMI (electromagnetic interference, electromagnetic interference) filter, as an important part of the electromagnetic compatibility design of the converter device, is widely used in high-frequency power electronic products. [0003] The topology of the filter is divided into single-stage and multi-stage structures. There are two types of single-stage filters: L-type and π-type. The multi-stage topology is formed by cascading multiple single-stage filters. The topology of the EMI filter is selected according to the internal resistance of the interference source and the load resistance. The traditional design method often assumes that the source impedance and the load impedance are 50 ohms, and the filter is designed according to the principle o...

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Problems solved by technology

However, after the filter components calculated by the above method are put into practical application, the circuit resonance will still cause the problem of EMI exceeding the standard at some frequency points, which will affect the filtering effect.

On the one hand, in order to ensure that the filter can have the proper filtering effect after it is put into use, engineers often leave enough margin for the filter in the pre-design to meet the requirements of electromagnetic compatibility, which leads to the filter On the other hand, after the system is put into use, if the EMI still exceeds the standard after the system is connected to the filter, it is generally necessary to redesign the filter, which costs a lot of money. Human and material resources

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