Optimization of V-groove inductors using multilayer Co-Zr-O thin films for 10 MHz to 100 MHz dc-dc converters

Magnetic devices, which are difficult to integrate, are the largest and most lossy components in power conversion circuits. Increasing switching frequencies enable shrinking the size of magnetics and realizing integrating magnetics on-chip, but controlling losses of the magnetics at high frequencies is challenging. Thin-film V-groove inductors have demonstrated good performance on both power density and efficiency at frequencies in the MHz range, and are promising for low-voltage high-current power conversion applications. In this paper, V-groove inductors are designed for a 7-V to 3.3-V, 1-A dc-dc converter operating above 10 MHz. The V-groove inductors use multilayer Co-Zr-O/ZrO₂ thin films to improve the performance of the magnetic core and control eddy-current losses in the core. The design results are compared with published results from the literature for other thin-film on-chip inductors, and the V-groove inductors show advantages on both power density and efficiency. In this paper, the V-groove inductor is predicted to have power density of 19 W/mm² and efficiency of 98% with converter efficiency of 85% at 117 MHz.