Inductorless Synchronized Switch Harvesting Using a Piezoelectric Oscillator

This paper proposes a preliminary investigation of a voltage inversion technique for enhancing the conversion abilities and power output of piezoelectric energy harvesting systems without requiring any inductance. Based on the use of an additional, decoupled high-frequency piezoelectric oscillator that is intermittently switched on the main harvesting piezoelectric element, the proposed scheme allows obtaining an inversion effect up to 30% experimentally (and possibly much higher) in an inductorless fashion. Such a concept is both discussed and validated theoretically and experimentally. Applied to energy harvesting, this provides an experimental gain of 30% in terms of harvested power compared to short-circuit switching. Also, the proposed scheme can be implemented in a single stage using off-the-shelf components (although being possibly integrated as well), while providing a better management of the charge transfer compared to pure switched capacitance approach, thanks to the motional branch of the oscillator. This therefore enables low-cost, integrable power boosting techniques for piezoelectric vibrational energy harvesters.