Dear Reader,

For many years, tendencies to miniaturize electronic systems and to increase the power density dissipated in components of these systems have been observed. During the operation of electronic components, their internal temperature increases due to self-heating phenomena and mutual thermal couplings between components located on the common base. An increase in the device's internal temperature causes changes in the characteristics of electronic components, and also causes a decrease in the lifetime of these components. Therefore, one of the biggest problems in electronics at present is the accurate calculation of the values of the internal temperature of such components. Solving this task requires accurate models of the considered components and circuits, which take into account all important physical phenomena occurring in these components and circuits.

Models including both electrical and thermal phenomena are called electrothermal models. Such models have been described in the literature for the last 50 years, but the development of electronic technology also leads to the development of electrothermal models of electronic components. New versions of such a class of models have different forms and are dedicated to different software for the computer analysis of electronic circuits, and they could also make it possible to shorten the duration of calculations. An effective electrothermal analysis also requires effective methods of estimation of the parameter values that exist in the used models.

In recent years, we can observe dynamic developments in the abovementioned electrothermal models. This Special Issue of *Energies* is devoted to the latest advances in this area and contains eight articles. The first article presents the results of electro-thermal simulations of SiC power MOSFETs using a SPICE-like simulation program. The manner of automatic generation of a compact thermal model from accurate 3D mesh is described. The second article concerns the problem of modelling the thermal properties of inductors. A thermal model of an inductor proposed in this article takes into account the influence of power dissipated in the core and in the winding of the inductor, and the volume of the core, on the efficiency of heat removal. The third article deals with the problem of inserting a temperature sensor in the neighbourhood of a chip to monitor the junction temperature. The fourth article proposes a method of computations of the internal temperature of power LEDs situated in modules containing multiple-power LEDs, taking into account both self-heating in each power LED and mutual thermal couplings between each diode. The influence of the thermal pad's surface area on the device temperature is investigated. The fifth paper proposes an electrothermal averaged model of the diode–transistor switch, including an IGBT and a rapid-switching diode. This model makes it possible to quickly calculate the values of currents, voltages and internal temperatures of the mentioned semiconductor devices contained in a dc-dc converter using DC analysis in SPICE. The sixth article proposes an electrothermal model of SiC power BJTs. It is proven that this model properly describes the DC electrothermal characteristics of the considered device. The seventh article contains an analysis of the efficiency of selected algorithms used to solve heat transfer problems at the nanoscale. The case study is an MEMS structure. The eighth article presents an analysis related to thermal simulation of the test structure dedicated to heat-diffusion investigation at the nanoscale. The results of computations and measurements are presented and discussed. We hope that you find this book interesting and useful.
