Nonlinear Coupled Inductor-Based Light-Load Efficiency Boost Technique for Trans-Inductor Voltage Regulators

Trans-inductor voltage regulator (TLVR) exhibits good scalability and easy multiphase magnetic coupling, making it an optimal choice for high-current point-of-load (PoL) solutions in modern data centers. Meanwhile, data center servers work at light load for the majority of their operating time, so it is imperative to improve the light-load efficiency of PoL converters. The phase-shedding (PS) technique is a simple and effective method for improving light-load efficiency in multiphase PoL converters. However, heavy coupling between phases in TLVR degrades its effectiveness. To address this issue, we propose a novel nonlinear coupled inductor (CL) for TLVR to enhance its compatibility with PS technique, improving light-load efficiency. At light load, the nonlinear CL exhibits light coupling and increased inductance, effectively decoupling the phases and minimizing ripple current. A detailed analysis of the light-load efficiency and magnetic design considerations is provided. A four-phase 12 V-to-1.8 V, 80 A TLVR incorporating the proposed nonlinear CL is designed and tested. Experimental results demonstrate an improvement in light-load efficiency compared with systems utilizing linear CLs, with a maximum efficiency improvement of 2.5%.