The fast development of modern processors requires the voltage regulator to be more efficient, faster and smaller. 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, the detailed analysis of a HCL and the performance difference between an ICL and a HCL is unclear so far. This paper proposes an optimal design process of a HCL with a comprehensive analysis. Then, a detailed design comparison of an ICL and a HCL to quantify their difference are presented with a hardware verification. The experiment shows that a HCL can realize 38 % inductor footprint reduction under the same circuit performance constraint, as compared with an ICL. The analysis in this paper provides a powerful design tool for a HCL to meet the power design requirements for future microprocessors.
