Análise numérica de perdas em MOSFETs de potência

Abstract

This work proposes a theoretical and experimental study related to switching losses in field-effect transistor metal-oxide semiconductor (MOSFET) power devices. The work addresses a review of the main published techniques, improvement of analytical methods regarding commutation losses as well as experimental and theoretical analysis involving conventional Si and SiC MOSFETs. Initially, a comprehensive review of the technical literature concerning the main different kind of transistor losses, are shown. Three selected methods, which are focused on analytical prediction of switching losses, are revised and an experimental comparison study is presented. A new methodology is proposed aiming the estimation of MOSFETs switching losses, while considering parasitic inductances and some device nonlinear parameters, such as voltage-dependent junction capacitances. To experimentally validate the theoretical estimated switching losses, a double-pulse circuit prototype has been designed and evaluated. The device under test switching losses have been measured by means of especially adjusted oscilloscope probes. For this purpose, a de-skew probe approach has been developed seeking to mitigate asynchronous delays, which commonly arises in those experiments and could provide wrong measurements. The study reveals an agreement between the experimental estimated losses and the theoretical simulations obtained by using the proposed method. Moreover, a probabilistic method has been adopted, which is based on non-sequential Monte Carlo simulations. The model effectiveness has been evaluated by the behavior of several units of two different commercial MOSFETs brands at different voltage and current levels. The improved analytical method has resulted in errors of losses estimation below 20%. On the other hand, by using the Monte Carlo method, the errors remained 12.5%, attesting the effectiveness of losses estimation based on stochastic processes. Finally, the main contributions of this work are discussed and the proposals for future works are presented.