Design Comparison of Different Coupled Inductor Concepts for Voltage Regulators

The fast development of modern processors requires voltage regulators to be efficient and fast with a small form factor. The introduction of a coupled inductor can greatly improve the transient response of a buck converter while keeping the inductor current ripple small. Among different coupled inductor structures, the multiphase indirect-coupled inductor (ICL) and hybrid-coupled inductor (HCL) are two promising solutions. However, a detailed analysis of an HCL and the performance difference between an ICL and an HCL are lacking so far. This paper presents a comprehensive analysis of an HCL to evaluate its performance. Then, a design comparison between an ICL and an HCL is illustrated via hardware verification to quantify their differences. This comparison shows that an HCL has a smaller inductor size under the same circuit performance constraint, as compared with an ICL. The analysis in this paper provides a powerful design tool for these two coupled inductor structures.