Minfan Fu

This article presents a design methodology for achieving load-insensitive operation in MHz inductive power transfer (IPT) systems based on bridge inverters. While MHz operation enables reduced coil size and improved efficiency compared with conventional kHz IPT, it also introduces challenges such as severe switching losses, junction capacitances, and harmonic distortion. To address these issues, a wide-band impedance model is established that incorporates device capacitances and transition times, from which a load-insensitive ZVS condition is analytically derived and used to guide the impedance matching network (IMN) design. A 1-kW, 6.78-MHz prototype is constructed to validate the proposed method, demonstrating nearly load-independent ZVS, stable output regulation across a tenfold load variation, and high efficiency with a peak system efficiency of 94.9% and a peak inverter efficiency of 98.8%. The results highlight the effectiveness of the proposed approach in bridging theoretical analysis and practical implementation, offering a systematic pathway toward high-power and high-efficiency MHz IPT systems.

In 48 V data-center voltage regulation, the current doubler rectifier (CDR) offers a high step-down ratio and structural simplicity but suffers from hard-switching, elevated voltage stress, and load-dependent voltage spikes. To overcome these limitations, this manuscript proposes a voltage regulator based on the current ninefold rectifier (CNR) topology. The proposed design achieves zero-voltage switching (ZVS) for all primary-side switches and employs Δ-connected primary windings to cancel circulating current, thereby reducing both switching loss and conduction loss while enhancing current-transfer capability. A 48 V/1.8 V, 180 A prototype operating at 500 kHz is built and tested. Experimental results confirm primary-side ZVS operation and demonstrate a peak efficiency of 95.86% and a full-load efficiency of 94.29%, verifying the efficiency benefits enabled by ZVS and reduced circulating current.

This article introduces a resonant gate-driven synchronous rectifier system for megahertz (MHz) wireless charger. The proposed design extracts synchronization signals directly from a voltage-sensing node within the compensated resonant tank, eliminating dedicated sensing circuits. The phase-tunable resonant gate driver concurrently enables sinusoidal gate excitation and phase compensation. Implemented in a 5 MHz prototype, the SR demonstrates 97.5% peak efficiency across a 10–50 $\boldsymbol{\Omega}$ load range.

The growing power demands of implantable medical devices, particularly brain-computer interfaces (BCIs), have driven the adoption of inductive power transfer (IPT) as a reliable and efficient energy delivery method. This paper presents a comprehensive methodology to identify, evaluate, and mitigate ECL in implantable BCIs. Starting from a practical case study, an ECL model is developed to decouple the influence of excitation current and isolate dominant loss mechanisms. A novel identification framework is introduced for efficient analysis, comparison, and measurement of ECL. Through a combination of simulation and experimental validation, both conduction and eddy current losses are optimized independently. Finally, a representative BCI system is co-optimized for coil geometry, wire selection, and phase control to minimize heat generation. This work offers a systematic solution to mitigate thermal risks in next-generation high-power implantable devices.