A Calibration Technique for P-SSHI-Phi Interface for Piezoelectric Energy Harvesting

This work presents the design and implementation of a P-SSHI-phi interface circuit for piezoelectric energy harvesting along with a calibration technique. The proposed design can operate in either energy-extraction mode or reverse-charging calibration mode. In calibration mode, the system is at rest, and the reverse-charging method operates the interface in a backward manner which drives the transducer with an AC voltage source. The interface voltage and current are then recorded and further processed to derive the operation parameters that lead to the maximum power point. An interface circuit is implemented in a 0.25-μm HV CMOS process to validate the efficacy of the proposed calibration technique at both resonant and off-resonant frequencies. Measurement results with an in-house piezoelectric transducer at 3 different operating frequencies show that the energy harvester is able to extract more than 96.58% of the maximum power with the proposed calibration, out-performing the conventional V
OC
/2 method by at least 13.46%.