Heterogeneous Integration of Transformer Windings—Fundamentals, Principles, and Implementations

Starting from the Faraday's law of electromagnetic induction, this article reviews the operation principle of the transformer, and reveals the distribution law of the induced electromotive force on the transformer windings. It is verified that the induced electromotive force is only concentrated in the part surrounded by the magnetic field lines, and there is no induced electromotive force on the windings outside the magnetic field lines. Based on this fact, the windings are divided into two parts: 1) source windings and 2) loop windings. This facilitates the understanding of the operating principle of transformers, and provides the knowledge base with new rules and methods for heterogeneous integration of windings. Based on different rules, the loop windings and source windings can be cancelled, or be replaced by other components or switch networks, thereby achieving high-density heterogeneous winding integration. This article establishes the fundamentals of winding heterogeneous integration, explains the operating principles and characteristics of various existing and new winding integration structures. Based on the proposed winding heterogenous integration rules and methods, a low-voltage high-current output dc transformer based on fractional turns and matrix magnetic core is proposed as an example. Feasibilities and effectiveness of the proposed dc transformer are verified with experimental results.