A Single-Stage Bias-Flip Regulating Rectifier With Fully Digital Duty-Cycle-Based MPPT for Piezoelectric Energy Harvesting

Piezoelectric energy harvesting (PEH) has been considered a promising solution for replacing conventional batteries to power wireless sensors. A complete PEH system typically includes three stages: ac-dc rectification, maximum power point tracking (MPPT), and output voltage regulation to power the load circuits. Unfortunately, most prior works focus only on the first one or two stages. A few employ three, but unfortunately, they are in cascaded stages, which results in cascaded power efficiency loss. This article proposes a single-stage bias-flip MPPT regulating rectifier (BMRR), which integrates the active bias-flip rectification, MPPT, and output voltage regulation into one stage. The proposed BMRR transfers energy from the piezoelectric transducer (PT) directly to the output capacitor by employing fewer switches, removing the conventional bridge rectifier, and eliminating cascaded energy loss. In addition, the design was implemented in a fully digital fast-MPPT technique based on an improved duty-cycle-based (DCB) algorithm to let the PT voltage jump to the maximum power point (MPP) in only one step. The proposed BMRR rectifier was fabricated in a 180-nm BCD process. The measured results show 930% power enhancement compared to a full bridge rectifier (FBR) and 92.5% end-to-end (E2E) efficiency.