Modelling of the absolute capacitance of a planar inductor for EMI mitigation purposes

Due to the large surface area of the conductors of planar magnetic components, they exhibit a large intra and interwinding capacitance. In addition they have a large absolute capacitance to the surroundings. In order to predict the behaviour of the magnetic component with respect to the parasitic absolute capacitance, it is necessary to be able to accurately model it. This is difficult as the conductor of the magnetic component, which can be considered to be one of the plates of the capacitor, is not an equipotential surface. The absolute capacitance is a distributed effect along the length of the winding. In this paper an equivalent model of the absolute capacitance of the structure is derived. The model is verified experimentally through direct capacitance measurements on the planar structure under operating conditions.