Comparison of the influence of Si and SiC semiconductor devices on power loss and weight of multiobjective optimal designed power converters

Abstract

This paper compares the power loss and weight of multiobjective optimal (MO) designed isolated DC-DC power converters based on Si and SiC technologies. To that end, a computer-aided design (CAD) tool previously published by the authors and dedicated to the MO design of isolated DC-DC power converters with genetic algorithms is used. The design problem requires the minimization of the power loss and the weight of the converter while ensuring the satisfaction of several constraints. The results show clearly that the wide band gap (WBG) semiconductor devices, typically the SiC technology for the power and voltage levels considered in this paper, lead to lighter converter with less power loss than classical Si devices. The use of our tool allows to precisely quantify that gain within a multiobjective optimization framework. Z. De Grève et al. / Influence of Si and SiC semiconductor devices on the losses and weight of power convertersfull-off states. They also comprise magnetic components such as inductors (harmonic filtering, etc.) and transformers (galvanic insulation, etc.). The switching frequency of the semiconductor devices affects the design of the magnetic components, which can be understood considering the following formulation of Faraday law, in the case of a simple inductor:where U is the winding voltage, i the pure imaginary number, f the frequency, B the average magnetic induction, S the core section, and where complex variables are underlined. For given U and B, it is clear that a high switching frequency f corresponds to small values of S, and thus to smaller inductors or transformers. Knowing that magnetic components can account for more than 50% of the volume and weight of the converter, we understand how crucial it is to use semiconductor devices which work fast. However, it should be kept in mind that increasing the switching frequency also increases the switching losses, which can lead to abnormally high junction temperatures and/or cooling module dimensions [14]. Currently, the switches (IGBTs and MOSFETs), as well as the diodes, are based on silicon (Si) technology. The continuously increasing demand for lightweight converters forces the engineers to operate the components at switching frequencies close to their intrinsic limits. Moreover, this maximum value is seldom reached, as a trade-off between the switching losses and speed is needed.Recently, Wide Band Gap (WBG) semiconductor devices dedicated to power electronics have appeared on the market. Silicon carbide (SiC), gallium nitride (GaN) and diamond technologies have significant advantages in terms of switching speed, switched power and energy efficiency compared to Si components [2,7]. This gives rise to new perspectives for the design of high frequency power converters: their enhanced performances should permit to reach switching frequencies and power levels which were not imaginable a few years ago.Nowadays, the scientific community agrees on the superiority of the WBG components over Si devices, in terms of their intrinsic characteristi...

Comparative Study of Optimally Designed DC-DC Converters with SiC and Si Power Devices

“…Within this framework, the present contribution aims at comparing in quantitative terms power losses and mass of optimally designed Si-vs. SiC-based isolated DC-DC power converters [11]. To that end, an adapted version of the previously mentioned MO optimization CAD tool, completed with a new database of wide band gap semiconductor devices, will be used.…”