A Resonant Synchronized Switch Harvesting Rectifier with Bias-Flip Charge Recycling for Piezoelectric Energy Harvesting Achieving 13.9x Power Enhancement

Piezoelectric energy harvesting (PEH) is a promising research topic, offering a practical way to extract kinetic energy to power electronics, e.g., wearable and implantable devices. A piezoelectric transducer (PT) can be modeled as an AC current source, <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">lₚ</tex> , in parallel with an intrinsic capacitor, Cp (Fig. 1 top). To extract more power from the PT, synchronized switch harvesting (SSH) rectifiers, employing an inductor (SSHI) or capacitors (SSHC), flip the voltage across Cp at the lp zero-crossing moment. Most SSH designs aim to maximize the voltage flipping efficiency <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">(ηF)</tex> to nearly 90%; however, a high <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ηF</tex> does not always bring high output power out since the maximum power point (MPP) goes to an unachievable level, largely exceeding the standard CMOS break-down voltage. Though <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">low-ηF</tex> designs pull the MPP back to lower voltage, the large energy loss due to <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">low-ηF</tex> flipping, expressed by <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">EFlip-Loss=CP* V_S²(1-η_F²) / 2</tex> , reduces the output power significantly.