Development of high frequency equivalent electric circuits for capacitors and chokes taking into account frequency-dependent dielectric and magnetic permittivity properties of dielectric and magnetic materials

Switching of power semiconductor devices in secondary power supplies is the main source of electromagnetic interference. The level of conductive interference must be lowered to meet standards of electromagnetic compatibility. This lowering can be achieved by various methods, including radio interference filters, that are built mainly from inductor coils (chokes) and capacitors. Chokes and capacitors are key elements to design radio interference filters and knowledge of their accurate high-frequency models is required for a wide range of frequencies up to 100 MHz and higher. The article is devoted to development of high-frequency models of capacitors and chokes based on equivalent electric circuits, which parameters are expressed either through electrical-physical values, or through frequency-dependent dielectric permittivity of the dielectric material and magnetic permittivity of the core. Results of modelling are confirmed by impedance measurements of a capacitor with ferroelectric and pyroelectric material used as capacitor’s dielectric and a choke with a core made of nanocrystalline alloy based on GM414 iron. An example of radio interference filter for attenuation of balanced and unbalanced conductive interference is used to consider the negative impact of «spray inductance» of capacitors and «spray capacitance» of chokes.