Design and Optimization of Energy Harvesting Circuits for Ultra-Low Power Wearable Electronics

Abstract

The increased usage of wearable electronics in healthcare, fitness and ambient monitoring applications has augmented the pressure to supply self-sustainable energy resources that have the capacity to operate under severe energy restrictions. The analysis introduces a single energy harvesting circuit design that is suitable to ultra-low power wearable applications so that the system can be constantly powered by not relying on traditional battery charging. The design consists of a multi-source power management unit (PMU) with thermoelectric, piezoelectric and RF transducer systems, with the following characteristics: (i) a dual-stage DC-DC converter optimized to start up at less than 300 mV, (ii) asynchronous analog maximum power point tracking (MPPT) to dynamically track energy and (iii) a hybrid storage subsystem of low-leakage thin-film batteries and supercapacitors. The implementation is at 65nm CMOS with simulation and an actual wrist-worn prototype resulted in verification. Its experimental findings show power conversion efficiency higher than 82 percent and the ability to continue more than 10 minutes at the average power of 10 umW. The proposed architecture will have an increased level of adaptability and robustness in the face of different energy inputs compared to the conventional single-source PMUs. Such results highlight the scalability and modularity of the framework as a potential basis of the future generation energy-autonomous wearable electronics.