MPPT Controled Piezoelectric Energy Harvesting Circuit Using Synchronized Switch Harvesting on Inductor

Vibration energy harvesting is attracting attention as a driving power supply for wireless sensor nodes. Piezoelectric elements arc used for piezoelectric energy harvesting (PEH). Because piezoelectric elements provide AC power, a full bridge rectifier is used to obtain DC power. However, a parasitic capacitor of the piezoelectric elements causes a power loss in conventional PEH circuits. Synchronized switch harvesting on inductor (SSHI) circuit was proposed in order to solve this problem. Output power of a rectifier used in a PEH circuit has a maximum power point (MPP). The MPP varies with the amplitude and the frequency of the vibration. Therefore, the maximum power point tracking (MPPT) control is needed. The open circuit voltage method is commonly used as the MPPT algorithm for PEH circuits, even if it takes a long time, of which the output voltage reaches the open circuit voltage in a SSHI circuit. In this study, low-capacitance filter capacitors are used to reduce the time to reach the open circuit voltage of a SSHI circuit. Thereby, the SSHI circuit is operated by the MPPT algorithm based on the open circuit voltage method. The circuit operation was confirmed by simulations and circuit experiments.