This article presents a novel nonlinear energy extraction technique for piezoelectric vibration energy harvesting. The proposed approach is an improvement of the previous technique, “synchronous electric charge extraction,” which is the first that optimizes the harvested power whatever the connected load. The new approach is then named as “optimized synchronous electric charge extraction.” Compared with synchronous electric charge extraction, the conversion effectiveness is enhanced while simplifying the electronic circuitry and the switch control strategy. The analytical expression of the harvested powers is derived for a classical electromechanical structure. Finally, theoretical predictions confirmed by experimental results show that optimized synchronous electric charge extraction increases the harvested power for a very large range of load resistance, which is a favorable characteristic for wideband vibration energy harvesting.

Nonlinear energy extraction techniques for piezoelectric vibration energy harvesting usually require synchronized electronic switches in their electronic interface circuits. But the difficulty to self-power their complex switching control strategies limits their performances, especially in the presence of wideband ambient excitations. This technical note presents a nonlinear energy extraction interface achieved by synchronous mechanical switches. The complex switching control strategy is dodged by taking advantage of mechanical stoppers and the moving part of the piezoelectric oscillator, which is driven by the vibration itself. As a result, the added mechanical stoppers and the self-synchronized nonlinear energy extraction circuit also make the energy harvesting device system be particularly suited to wideband ambient vibrations.