A Self-Regulating Bias-Flip Rectifier for Piezoelectric Energy Harvesting

Piezoelectric energy harvesting (PEH) efficiently converts ambient kinetic energy into electrical power, enabling sustainable and autonomous operation of low-power electronic devices. To optimize power extraction, maximum power point tracking (MPPT) methods are commonly employed. Conventional MPPT approaches, such as perturb-and-observe (P&O) and fractional open-circuit voltage (FOCV), typically rely on incremental power measurements or theoretical voltage estimations, but suffer from high power overhead, slow convergence, and circuit complexity. Duty-cycle-based (DCB) MPPT techniques partly overcome these limitations by regulating the rectifier's duty cycle at 50%, yet they still require a dedicated MPPT stage and large external capacitors, causing additional power loss and delayed convergence. To address these challenges, this paper presents a self-regulating bias-flip rectifier that inherently integrates rectification and MPPT into a single stage, eliminating cascaded energy losses and enabling rapid convergence to the maximum power point. Fabricated in a 0.18-μm CMOS process, the proposed rectifier achieves an end-to-end efficiency of 93%, MPPT efficiency of 98%, and provides a 7.7-fold improvement in energy extraction compared to conventional full-bridge rectifiers.