Revisit of series-SSHI with comparisons to other interfacing circuits in piezoelectric energyharvesting

Abstract

SSHI (synchronized switch harvesting on inductor) techniques have been demonstrated tobe capable of boosting power in vibration-based piezoelectric energy harvesters. However,the effect of frequency deviation from resonance on the electrical response of an SSHIsystem has not been taken into account from the original analysis. Here an improvedanalysis accounting for such an effect is proposed to investigate the electrical behavior of aseries-SSHI system. The analytic expression of harvested power is proposed and validatednumerically. Its performance evaluation is carried out and compared with the piezoelectricsystems using either the standard or parallel-SSHI electronic interfaces. The result showsthat the electrical response of an ideal series-SSHI system is in sharp contrast to thatof an ideal parallel-SSHI system. The former is similar to a strongly coupledelectromechanical standard system operated at the open circuit resonance, while the latteris analogous to that operated at the short circuit resonance with different magnitudes ofmatching impedance. In addition, the performance degradation due to non-idealvoltage inversion is also discussed. It shows that a series-SSHI system avails againstthe standard technique in the case of medium coupling, since its peak power isclose to the ideal optimal power and the reduction in power is less sensitive tofrequency deviation. However, the consideration of inevitable diode loss in practicaldevices favors the parallel-SSHI technique, since the frequency-insensitive feature ismuch more pronounced in parallel-SSHI systems than in series-SSHI systems.