Microfabricated Air-Core Toroidal Inductor in Very High-Frequency Power Converters

Abstract

Abstract-Miniaturization of power supplies is required for future intelligent electronic systems e.g. internet of things devices. Inductors play an essential role, and they are by far the most bulky and expensive components in power supplies. This paper presents a miniaturized microelectromechanical systems (MEMS) inductor and its performance in a very high frequency (VHF) power converter. The MEMS inductor is a siliconembedded air-core toroidal inductor, and it is constructed with through-silicon vias, suspended copper windings, silicon fixtures, and a silicon support die. The air-core inductors outperform the silicon-core inductors with higher quality factor at higher frequency. This is verified by small-signal measurements. A 20-turn air-core inductor achieved an inductance of 44.6 nH and a quality factor of 13.3 at 33 MHz, while a silicon-core inductor with the same geometry has a quality factor of 9 at 20 MHz. A DC-DC class-E boost converter is designed and implemented using the fabricated MEMS air-core inductor and a highperformance 65 V gallium nitride field effect transistor. The VHF converter achieved a peak efficiency of 78 % at the input voltage of 6.5 VDC. The MEMS inductor can carry 1 A RMS AC current at 33 MHz and delivers 10.5 W to the output.Index Terms-Microelectromechanical systems, inductor, DC-DC power converters, zero voltage switching, gallium nitride.

Optimal design of VHF resonant boost converter considering the nonlinear characteristic of parasitic capacitance

“…Further, the numerical iterative model for the state variable of the circuit in Figure 9 is established, which can be expressed as Equation (10).…”

“…For the VHF resonant boost converter, the initial value v DS (0) is taken as V P . With iteration (10), the duration Δt from v DS (0) to the first zero crossing can be calculated. The term C T is then defined as a time-equivalent capacitance, which can be expressed as Equation (13), and a comparison of C T and C R (y) is shown in Figure 10.…”

“…Set the current of inductance L R at time Δt as i LR1 (Δt), and replace C R (y) in coefficient matrix A y with C T . Then, iterative calculations are performed according to Equation (10), and the resulted current of inductance L R is set as i LR2 (Δt). Define the current correction factor K I as the ratio of i LR2 (Δt) and i LR1 (Δt), as shown in Equation (14).…”

“…VHF converters generally use air‐core magnetic components, and chip multilayer ceramic capacitors (MLCC), which can significantly reduce the size, weight, and cost, improve the transient response speed of the system 8–14 . Surface‐mounted technology (SMT) is conducive to large‐scale industrial production, greatly improving the service life and stability of products, and is of great significance to the implementation of the goal of emission peak and carbon neutrality.…”

Measurement of internal magnetic flux density distribution in air-core toroidal transformer under high-frequency excitation

“…4 An air-core configuration is an alternative solution for megahertz-class power converters. [9][10][11][12] Air-core magnetic components are free from magnetic material iron losses. However, their magnetic flux density in the high-frequency region must be considered due to the following reasons.…”