Dielectric elastomer generator with a voltage-difference-type output circuit and its circuit analysis

Abstract

This study considers electric circuits for dielectric elastomer generators (DEG) supplying to low-voltage devices such as sensors for wireless networks. The DEG convert the mechanical energy to the electrical one owing to their capacitance change according to the deformation, and they are expected as the generators utilizing low-frequency vibrations. To supply the electric charge to the DEG for power generation, the self-priming circuit (SPC) comprising capacitors and diodes is widely used. To use the DEG as the power source for the low-voltage devices, voltage step-down elements such as Zener diodes are conventionally introduced, however, the energy loss caused by the elements deteriorates the efficiency. Moreover, to quickly boost the voltage to the operational region from the initial state, smaller capacitors are usually used in the SPC. However, the choice makes the generators sensitive to the leakage charge flowing through the dielectric layers, which is problematic especially when the DEG are operated by low-frequency vibrations. This study proposes a DEG with a voltage-difference-type output circuit that utilizes a rectifier as the output circuit elements connected serially between the DEG and SPC, instead of the step-down elements connected parallel to them. The current flow to the load is governed by the voltage difference between the DEG and SPC, hence we can choose larger SPC capacitors because the quick voltage boost is not required. The output charge as well as the voltage increment and the acceptable leakage charge per cycle is precisely analyzed, from which a systematic way to choose the SPC parameters is also deduced. Experimental results show the validity of the derived formulae and the efficiency of the proposed circuit.

Keywords

• energy harvesting
• vibration generator
• dielectric elastomer generator
• self-priming circuit
• leakage charge