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

A dual-source energy harvesting interface that combines energy from implanted glucose biofuel cell and thermoelectric generator is presented. A single-inductor dual-input dualoutput 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 zerocurrent and zero-voltage switching. The measurement results of the proposed boost converter, implemented in a 0.18 μm CMOS process, show a peak efficiency of 89.5% when both sources provide a combined input power of 66 μW. In the single-source mode, the converter achieves a peak efficiency of 85.2% at 23 μW for the thermoelectric source and 90.4% at 29 μW 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.