FURI | Fall 2025

USB-powered Wireless Power Transfer for Low-power LED Lighting

Common 5V USB sources can power low-power LEDs if a short-range wireless link is designed to minimize reactive and conduction losses. We present a USB-powered resonant-inductive WPT architecture that co-optimizes coil geometry, compensation topology, and control under strict 5V/USB current limits. Using a coupled-mode/AC small-signal model calibrated to LTSPICE, we derive closed-form design rules for Q-factor, coupling, and impedance matching and implement a frequency-tracked transmitter with current limiting to ensure USB compliance. A benchtop prototype validates stable LED drive across lateral misalignment and separation, with measured efficiency and regulation trends aligning with theory. The result is a practical recipe, schematics, coil patterns, and control logic. For cable-free LED fixtures and sensors powered by ubiquitous USB, reducing wiring, enabling sealed luminaires, and informing low-power WPT standards.