Design Approach of Planar Transformer-Based 2-TR Phase-Shift Full-Bridge Converter for High Efficiency and High Power Density in LDC

The recent focus on greenhouse gas emissions from fossil fuel usage has led to strengthened regulations on carbon emissions. Consequently, research on electric vehicles (EV), which have higher energy efficiency compared to internal combustion engine vehicles, is actively being pursued. With advancements in the technology of electronic components in electric vehicles, there is a growing trend in the demand for higher-rated capacities of Low DC-DC Converter (LDC) that possess a wide input-output voltage range. Furthermore, the restricted space within vehicles and the emphasis on high energy utilization necessitate converters with high power density and efficiency. Currently, in electric vehicles, the Active Clamp Forward Converter (ACFC) and the Phase Shift Full-Bridge Converter (PSFB) are commonly applied, as they readily achieve a wide input-output voltage range and high power density. However, ACFC and PSFB encounter difficulties in achieving high efficiency and power density due to the requirement for output inductors with high current specifications. To address these challenges, this study proposes a Two-Transformer Phase Shift Full-Bridge Converter (2-TR PSFB) based on planar transformers, which can replace conventional ACFC and PSFB. The proposed converter achieves high efficiency and power density without the need for high-current output inductors. Additionally, the utilization of GaN power semiconductors allows for a high switching frequency, enabling a significant reduction in the volume of magnetic components. This research presents the operational principles of the 2-TR PSFB and provides design directions. To validate the design, a 2.5 kW prototype was manufactured and tested.