Electric vehicles (EVs) are becoming increasingly popular as an environmentally friendly and sustainable mode of transportation. With the development of EVs, low-voltage DC-DC converter (LDC) systems are now required to supply more auxiliary loads, and the power demand has reached levels of up to 5 kW. In addition, researchers are constantly working on new technologies to improve the performance and extend the driving range of electric vehicles. One of these technologies is the 800 V battery architecture. High-voltage systems are becoming more common in today’s EV architectures because they offer benefits such as faster charging, lower power losses, and thinner cabling. This project aims to design a high-efficiency DC-DC converter with high and variable input voltage for electric vehicle applications. Instead of using traditional (wound) transformers, planar transformers will be used to achieve a compact, lightweight, and high power density design. Furthermore, wide bandgap (WBG) semiconductors (SiC, GaN) will be used to reduce switching losses and improve system efficiency. Within the scope of the project, the most suitable circuit topology will be selected, magnetic components will be optimized, and both electromagnetic and circuit analyses will be carried out using various simulation tools. The main goal is to develop a high-power converter prototype that can operate with a nominal input voltage of 800 V and provide a low-voltage output. In this way, the project is expected to offer a compact and reliable solution to efficiently meet the energy demands of low-voltage loads in electric vehicles.