A High-Efficiency Energy Harvesting Interface for Implanted Biofuel Cell and Thermal Harvesters

Abstract

A dual-source energy harvesting interface that combines energy from implanted glucose biofuel cell and thermoelectric generator is presented. A single-inductor dual-input dual-output boost converter topology is employed to efficiently transfer the extracted power to the output. A dual-input feature enables the simultaneous maximum power extraction from two harvesters, whereas a dual output allows a control circuit to perform complex digital functions at nW power levels. The control circuit reconfigures the converter to improve the efficiency and achieve zero-current and zero-voltage switching. The measurement results of the proposed boost converter, implemented in a 0.18 ${\mu }$ m CMOS process, show a peak efficiency of 89.5% when both sources provide a combined input power of 66 ${\mu }$ W. In the single-source mode, the converter achieves a peak efficiency of 85.2% at 23 ${\mu }$ W for the thermoelectric source and 90.4% at 29 ${\mu }$ W for the glucose biofuel cell. The converter can operate from minimum input voltages of 10 mV for the thermoelectric source and 30 mV for the glucose biofuel cell.