A 3D Integrated Nonlinear Inductor for Improving Light Load Efficiency of Voltage Regulator Modules

Loss reduction at light loads of voltage regulator modules (VRMs) is needed to improve efficiency. Inductor current ripple causes most of the total loss at light loads. Therefore, inductor current ripple reduction is the key to improving light load efficiency. The paper presents a 3D integrated nonlinear coupled inductor (NCI) for VRMs. The inductor is made by two permeability magnetic materials, which features very high self-inductance value at light load and low self-inductance value at heavy load. The proposed NCI can effectively reduce inductor current ripple in light load to improve light load efficiency. In addition, the NCI can be integrated into bottom of GaN-based power module to increase power density. Two 90W, 12-to-1.8 V prototype with the conventional inductor and the proposed NCI are designed to test the performances. The experimental results demonstrate that the proposed NCI has 4.8% higher efficiency at light loads compared with the conventional inductor and the integrated GaN-based power module can achieve high power density of 300W/in
³
.