An Efficient Power Management Unit With Continuous MPPT and Energy Recycling for Wireless Millimetric Biomedical Implants

TL;DR

This paper introduces a highly efficient, fully integrated power management unit for millimeter-scale biomedical implants that optimizes wireless power transfer and energy recycling to improve device longevity and miniaturization.

Contribution

It presents a novel power management architecture with continuous MPPT, impedance matching, and energy recycling tailored for millimetric implants using magnetoelectric wireless power transfer.

Findings

Peak MPPT efficiency of 98.5% achieved

Overall system efficiency of 73.33% demonstrated

High-voltage charging up to 12V with 37.88% efficiency

Abstract

Biomedical implants offer transformative tools to improve medical outcomes. To realize minimally invasive implants with miniaturized volume and weight, wireless power transfer has been extensively studied to replace bulky batteries that dominate the volume of traditional implants and require surgical replacements. Ultra-sonic and magnetoelectric WPT modalities, which leverage low frequency acoustic electrical coupling for energy transduction, become viable solutions for mm-scale receivers. This work presents a fully integrated power management unit for ME WPT in millimetric implants. The PMU achieves load independent maximum power extraction and usage by continuously matching the impedance of the transducer, dynamically optimizing the power stage across varying input divided by load conditions, and reusing the storage energy to sustain the system when input power drops. Its parallel-input regulation and storing stages architecture prevent the cascading power loss. With the skewed-duty-cycle MPPT technique and regulation efficiency optimizer, the PMU achieves a peak MPPT efficiency of 98.5 percent and a peak system overall efficiency of 73.33 percent. Additionally, the PMU includes an adaptive high-voltage charging stage that charges the stimulation capacitor up to 12 V with an improved efficiency of 37.88 percent.