As piezoelectric vibration energy harvesting (PVEH) extracts electrical energy from vibration, it is a promising portable power device. Although harvesting efficiency can be increased by using switch controls based on vibration displacement, such controls require external controllers and sensors, which consume energy and occupy space in a device. To separate external energy sources and sensors from a switch controller, we propose a measurement circuit and a digital controller for PVEH to increase autonomy, flexibility, and compactness. In the present study, switch controls are realized on a self-powered digital controller using piezoelectric voltage as an observation value, where achieves a switch-controlled PVEH independent from additional external sensors. We discuss the characteristics of the proposed circuit and evaluate the harvesting performance. The experimental results demonstrated that the proposed sensor-less harvester has a harvesting performance comparable to that of a conventional sensor-equipped harvester.
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