In-Depth Review of Planar Transformer Modeling and Optimization: Challenges and Perspectives

The increasing demand for compactness, predictability and repeatability in manufacturing is driving the adoption of planar transformers (PTs) as an alternative to conventional wire-wound transformers. However, the capabilities of PTs, particularly for high-power transformation, is still not fully unfolded. Therefore, this in-depth review paper provides a comprehensive overview of PT applications, types, modeling techniques, and optimization approaches, opening up the potential for high-power PTs. The modeling and optimization of power losses, thermal performance and parasitics are highlighted to facilitate application-tailored design of PTs and overcome their challenges. Methods for integrating leakage inductance are reviewed and compared, enabling dedicated design. The effects of parasitic capacitance, which cause high-voltage spikes and common-mode noise, are evaluated, and methods for reducing these effects are compared. The different types of PTs are discussed, and their application range in terms of frequency and power levels is presented in a compact overview. A case study demonstrating the optimization of a low and high power PT is demonstrated, showcasing the different challenges related to the power levels. Lastly, an overview of the challenges and perspectives of PTs is provided.