Abstract
Inductive devices are extensively employed in power electronic systems due to their magnetic energy storage and power transfer capabilities. The current trend is towards increasing the frequency of operation in order to reduce the size of the magnetic components, but the main drawback is that the parasitic capacitance effect can become significant, and degrade the performance of the system. This work analyses the influence of this stray capacitance, and considers how to improve the performance of the device. In general, the impact of the stray capacitance on a magnetic component can be reduced by two methods: reducing the parasitic capacitance between turns of the winding or, alternatively, modifying the arrangement of the connection between turns. To evaluate the last option, an approximated expression of the first self-resonant frequency of the magnetic device is proposed. This gives a rapid assessment of the performance of different devices maintaining the overall equivalent inductance. The proposed expression accounts for the influence of the connection between turns in the bandwidth of the component. Finally, some numerical results are verified with planar coils manufactured on two-layer printed circuit boards.
Highlights
Planar coils are often selected for power electronics systems because these components are well adapted to the geometry of many applications and are convenient for integrated applications
The present tendency towards higher operation frequencies has led to an interest in modelling parasitic capacitive effects because, among other reasons, this stray capacitance can be used as the resonant element in converters or determines the bandwidth of the magnetic component
The remainder of the paper is organised as follows: in Section 2, the distributed circuit model for inductors including stray capacitances is described; the behaviour of these system are explained in Section 3; in Section 4, the procedure to calculate the distributed circuit element is given; experimental validation of the proposed model is drawn in Section 5 and Section 6 concludes
Summary
Planar coils are often selected for power electronics systems because these components are well adapted to the geometry of many applications and are convenient for integrated applications. The preceding methods are valuable by themselves, the applicability of the results is limited to the prototypes studied In these simplified lumped equivalent circuits it is assumed that all turns are driven by the same current and depending on the device or the frequency, the accuracy could be affected and some alternatives have been proposed. These alternatives include distributed circuits [23,24,25,26,27,28,29] and transmission line approaches [30], which are mainly focused on obtaining selfresonant frequencies associated with the parasitic capacitances and inductances of the system. The remainder of the paper is organised as follows: in Section 2, the distributed circuit model for inductors including stray capacitances is described; the behaviour of these system are explained in Section 3; in Section 4, the procedure to calculate the distributed circuit element is given; experimental validation of the proposed model is drawn in Section 5 and Section 6 concludes
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