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 simple and effective in improving light-load efficiency for multi-phase 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 4-phase 12V-to-1.8V, 80A 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%.