A sub-µA stand-by current synchronous electric charge extractor for piezoelectric energy harvesting

In the field of energy harvesting there is a growing interest in power management circuits with intrinsic sub-µA current consumptions, in order to operate efficiently with very low levels of available power. In this context, integrated circuits proved to be a viable solution with high associated non-recurring costs and design risks. As an alternative, this paper presents a fully autonomous and battery-less circuit solution for piezoelectric energy harvesting based on discrete components in a low cost PCB technology, which achieves a comparable performance in a 32x43 mm2 footprint. The power management circuit implements synchronous electric charge extraction (SECE) with a passive bootstrap circuit from fully discharged states. Circuit characterization showed that the circuit consumes less than 1 μA with a 3 V output and may achieve energy conversion efficiencies of up to 85%. In addition, the circuit is specifically designed for operating with input and output voltages up to 20 V, which grants a significant flexibility in the choice of transducers and energy storage capacitors.