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

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