An Efficient Inductive Rectifier Based Piezo-Energy Harvesting Using Recursive Pre-Charge and Accumulation Operation

Abstract

Inductor-based rectifiers have been developed to overcome the limitations of the traditional diode-based rectifiers for piezo-energy harvesting (PEH). This article proposes a new efficient method for extracting power from the piezoelectric transducer using the inductive rectifier. In the proposed method, the internal capacitance of the transducer is initially pre-charged, and the generated charges in response to the mechanical vibration are accumulated on the capacitor. When the accumulated voltage reaches a maximum allowed value ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$V_{\mathrm {MAX}}$ </tex-math></inline-formula> ), the total energy stored in the capacitor is transferred to the output, and the process is repeated. The proposed method ensures that the voltage swing across the transducer is always maximum for extracting the highest possible output power for given CMOS technology. The operational steps are self-timed, and the negative voltage swing across the transducer is avoided. The proposed inductive rectifier is realized using the buck–boost power stage of the DC energy-harvesting system for enabling efficient multi-source harvesting. Test chip is fabricated in the 180-nm CMOS technology, having a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$V_{\mathrm {MAX}}$ </tex-math></inline-formula> of 3.3 V. The proposed rectifier extracts power in a single stage, even at a lower rectified output voltage <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\le $ </tex-math></inline-formula> 1 V. For a piezo open-circuit voltage of 1 V, the proposed rectifier extracts 3.68 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times $ </tex-math></inline-formula> more power than the maximum output power of a full-bridge rectifier with ideal diodes. This is despite the voltage loss occurring during accumulation in the power stage implementation.