A subthreshold digital maximum power point tracker for micropower piezoelectric energy harvesting applications

Utilizing piezoelectric energy harvesting to power autonomous wireless sensors has garnered significant attention recently. However, because the generated power for small form-factor piezoelectric devices is on the order of 10 µW, the use of maximum power point tracking (MPPT) is imperative. Moreover, minimizing the power consumption of the maximum power point tracker is essential to increase the available power for the wireless sensor. To resolve this challenge, a digital MPPT controller is presented in this paper that is designed using subthreshold operation techniques. The MPPT controller is implemented and verified using a CMOS 0.35-µm process. The maximum power point tracker operates with a 1-V supply, consuming 3.71 µW while active. In addition, the proposed MPPT controller operates with 99.5% tracking efficiency.