The Design Of Passive Planar Integrated EMI Filter Consisted Of Integrated LC Structure

The passive EMI filter is one of the most effective means for suppression of conduction interference. However, the conventional filter consists of discrete inductors and capacitors, and accounts for a very large volume in the whole power converter because of the discrete components come in different shapes and sizes and lower utilization space. Meanwhile, the high-frequency performance of EMI filter suffers from the parasitic parameters of discrete components. In order to reduce dimensional size of EMI filter and improve its performance, it is essential to carry out research on planar integrated EMI filter.The integrated LC structure, achieving the integration of inductance and capacitance, is the basic unit constituting the planar integrated EMI filter. The fundamental principle of electromagnetic integration is analyzed first in this paper, and the basic integration structure is confirmed through the analysis of electric field and magnetic field distribution in different integration structure. A generalized transmission line theory is introduced in this paper, based on which the lumped parameter model is built, and the electrical parameters of per unit length are calculated. The integrated LC structure is equivalent to a two-port network,and impedance matrix is derived using model transformation matrices.Rectangular integrated LC structure is optimized due to its defects, and the distribution of magnetic density and impedance characteristic for two structures are compared and analyzed. The achievement and design of planar integrated EMI filter based on circular integrated LC structure is focus of the paper. Stray capacitance between conductors and non-linear characteristics of the magnetic core are all considered, and then the equivalent lumped parameter circuit is built. The insertion loss is achieved through node voltage method based on the equivalent circuit, and the accuracy of the model is verified by experiment. Finally, detailed design procedure of planar integrated EMI filter based on circular integrated LC structure is discussed, and the approximate formulas used in lumped parameters are given to guide the filter design. A planar integrated EMI filter is design, and compared with the discrete one.