An Efficient Autonomous Increased Input Range SSHI Interface for a Variable Amplitude Vibration

This article proposes a new interface circuit for Piezoelectric Energy Harvesters (PEHs), which improves the startup issue of the Synchronized Switch Harvesting on Inductor (SSHI) technique in variable amplitude vibration environments. In the proposed Increased Input Range Synchronized Switch Harvesting on Inductor (IIR-SSHI), once the SSHI scheme stops operating because of the change in the excitation amplitude, a low-power peak detector is activated to accumulate the charge of the parasitic capacitance of the PEH by successive bias-flipping actions, without requiring any external energy investment, i.e., energy kick start. Therefore, the proposed circuit can autonomously maintain the energy extraction procedure active at the highest performance of energy extraction, i.e., FoM_MOPIR, when the excitation amplitude is reduced considerably. The proposed circuit is simulated and verified using a 0.18-μm CMOS standard technology, ensuring energy extraction performance and robustness. Based on the post-layout simulation results, the proposed circuit can extract energy from PEH significantly for a minimum input excitation amplitude of only 800 mV. The maximum output power improvement relative to the Standard Energy Harvesting (SEH) and standard SSHI circuits is 5.5 and 2.75 in decreased input amplitude scenarios, respectively.