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In this paper, models that account for the duty cycle and phase shift angle of the applied phase voltages in coupled stripline microinductors are presented and are shown to have a significant impact on harmonic current amplitudes and therefore microinductor efficiency. The impact of a high coupling factor between two windings surrounded by a single core is also investigated. The models are validated using finite-element analysis and measurements. A three-phase-coupled microinductor has been fabricated with a Ni45Fe55 core and analyzed for a number of operating conditions. A prototype 1.6 W, three-phase converter utilizing this inductor has also been measured and is discussed in detail. The coupled microinductor is predicted to have a peak efficiency of 86.6% at 20 MHz in the prototype circuit. [ABSTRACT FROM AUTHOR]

This paper examines the process challenges in developing high aspect-ratio copper structures for improving microinductor performance. With increased miniaturization, increasing windings losses become a major challenge limiting the microinductor efficiency. It was also identified that within constraint footprints coil thickness to spacing ratio increase can reduce dc resistance significantly. In this paper, we present a reliable process for developing high aspect ratio ( $\sim 5.8$ ) resist moulds for copper electrodeposition. This resist provided coil spacings 10 $\mu $ m for 58 $\mu $ m resist thickness; this in turn reduces the dc resistance of a typical microinductor by more than 17% when compared with a similar device reported previously. [ABSTRACT FROM AUTHOR]

Microfabricated inductors experience increasing interest and research activity because of their high potential in buck converters for power supply in package and power supply on chip applications. This paper details the modeling and optimization of microfabricated racetrack inductors. The analytical expressions derived characterize inductance, efficiency, and power density based on geometrical parameters, inductor current, and switching frequency. An accurate analysis of the inductor current that includes the impact of losses is performed to determine the switching frequency, the ac copper losses, and the core losses. The presented model is compared to finite element method simulations and reported results of three microfabricated inductors. Finally, the optimum tradeoff between efficiency and power density is identified using the Pareto front, which results from the evaluation of a large number of microfabricated inductors in the design space defined by the application. [ABSTRACT FROM AUTHOR]