Magnetic-Core Integration: Fundamentals, Methodology, and Application in Electric Vehicles

Magnetic-Core (MC) integration is an effective approach to improving the efficiency and power density of power converters. Although numerous MC integration structures for inductors/transformers have been proposed, systematic MC integration methodologies, especially the design guidance for integrated core shape have rarely been studied over the years. Starting from the structure, function, and electromagnetic characteristics of magnetic components, the MCs are divided into two parts: 1) source-core, corresponding to the core surrounded by windings, 2) loop-core, corresponding to the core outside the windings. Based on the definition, it is revealed that the process of MC integration can be decomposed into two steps: 1) the realization of the coupling coefficient for source-cores, and 2) the sharing or integration design of the loop-cores. The above two steps can be unified as the regulation of flux in MCs. The regulation of source-core flux is to ensure that the coupling relationship between magnetic components before and after MC integration remains consistent with the requirements of the converter, while the regulation of loop-core magnetic flux aims to reduce the magnetic flux density, loss, and volume of the core. Based on the above theoretical foundation, the method to ensure the decoupling and regulation of coupling coefficients of sourcecores of multiple magnetic components, and the method for loopcore sharing or integration, and magnetic flux/magnetic density regulations are proposed for the MC integration design. Based on the proposed MC integration rules and methods, a CLLC resonant converter with integrated transformer/inductor is designed as an example. Feasibilities and effectiveness of the presented integrated MCs are verified with experimental results.