Tunable interface for piezoelectric energy harvesting

The so called Synchronous Electric Charge Extraction (SECE) interface is an electrical circuit to extract energy from a piezoelectric transducer and to put it onto a storage device like a large capacitor. The advantage of the SECE interface is the load independent power transfer. But the maximum efficiency the SECE interface in combination with the piezoelectric transducer can achieve greatly depends on the electromechanical coupling of the transducer. The SECE interface works very well with weak to mid-range electromechanically coupled piezoelectric transducers. But with strong coupled transducer the power extracted by SECE interface decreases. This paper shows how the SECE interface can be tuned to deliver the maximum power almost independent of the electromechanical coupling factor.