Improved SECE with Revised Harvesting Cycle to Achieve Power Enhancement for Strongly-coupled Piezoelectric Energy Harvester

To improve the efficiency of piezoelectric energy extraction, various power conditioning circuits have been proposed, among which the synchronous charge extraction (SECE) technology has attracted a great deal of attention. In the lowly coupled condition, the SECE circuit can significantly increase the harvested power compared with the standard SEH circuit. However, under highly coupled conditions, using the SECE circuit increases the damping and reduces the system displacement, thus reducing the harvested power. To improve the performance of SECE, a new energy extraction strategy is proposed based on the adjustment of energy extraction frequency through N times (N>1 or N<1) the vibration frequency. Instead of switching at the maximal displacement per cycle, in the proposed method the switch is closed beforehand or delayed, so that energy in piezoelectric capacitor is transferred to the load and damping is thus reduced. Simulation results proves that the harvested power of the proposed circuit can be improved by at least 70%. In addition, it is found that the harvested power of N>1 is superior to that of N<1. Maximally, the harvest power of N=2 is increased by 1226% compared with N=1/7 under the same situation (I-p=5mA, f=5Hz).