An Improved Hybrid-Coupled Inductor Structure With Flux Reduction and Integrated Controllable Coupling Function

The design challenges to power high-performance processors require the voltage regulator to be smaller, faster, and more efficient. Compared with the noncoupled-inductor-based solution, a multiphase coupled inductor helps a buck converter achieve a smaller current ripple and a faster transient response. Among different coupled inductor structures, a hybrid-coupled inductor (HCL) is a promising candidate. Based on the proposed equivalent circuit model, this article first analyzes a conventional HCL in detail to identify its benefits and limitations. Then, an improved HCL structure with a five-leg magnetic core structure is proposed. By splitting the magnetic flux into different areas of the core plate, a thinner plate can be applied, and the inductor size is greatly reduced. Furthermore, the coupling can be flexibly adjusted by controlling the flux in different core legs. The extra inductor used to adjust the coupling in the conventional solution is eliminated in the proposed structure. With all these benefits, the proposed HCL structure can achieve a 40% inductor size reduction while maintaining a small current ripple and fast transient response, as compared with the conventional solution.