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Design of fully integrated milliwatt thermoelectric energy harvesting interface circuit for wireless body sensor networks

Demir, Süleyman Mahircan
Wireless body sensor networks have drawn significant attention for providing out-of-hospital diagnosis and remote abnormality monitoring, which are vitally important for millions of people suffering from chronic diseases. Batteries powering these sensor networks hurt their mobility and longevity due to their bulkiness and down-time during charging or replacement. Therefore, this study focuses on thermoelectric energy harvesting from body heat, and targets eventual replacement of batteries by generating power levels above 1 mW using a fully integrated interface circuit component. The 180nm standard CMOS circuit, designed using Cadence IC design suite, contains the first optimized implementation of a previously developed quadrupling oscillator concept, a charge-pump based DC-DC converter, and a maximum power point tracking circuitry. Simulations using the electrical model of a commercial TEG module show that the DC-DC converter is capable of up to 1.5 mW output power, and 2 V output voltage, with 37% interface circuit efficiency when the TEG voltage is 500 mV. Minimum input voltage for the converter startup is found as 92 mV in the post-layout simulations. The interface circuit simulations with MPPT achieve 1.24 mW output power and 1.5 V output voltage for the TEG voltage of 500 mV. In the corresponding circumstance, the interface circuit efficiency is recorded as %20. The optimized interface circuit can be utilized to power up WBSN and enables batteryless sensor network operations.