On the Optimal Choice of Electrical Conditioning Circuits for Triboelectric Nanogenerators

This work presents a generic procedure for the optimal choice of an unstable charge pump (UCP) circuit topology for electrostatic kinetic energy harvesters (e-KEH) biased by a triboelectric material, also known as a triboelectric nanogenerators (TENGs). Each UCP can be characterized by the ratio $\gamma$ that it imposes between the maximum and minimum voltage across the transducer, in every cycle of its steady-state operation. The value of $\gamma$ depends on the detailed topology of each UCP. The triboelectric transducer, on the other hand is characterized by (i) the variation ratio $\eta$ between its dynamic capacitance maximum and minimum values under mechanical actuation and (ii) its DC bias $V_{\text{TE}}$ which models the triboelectric effect. The analysis done in this paper leads to the optimal $\gamma$ as a function of the transducer parameters $\eta, V_{\text{TE}}$, and as a function of the parasitic capacitance brought by the conditioning circuit or by the setup. As such, this work presents a systematic procedure to select the UCP topology maximizing the converted power for a variety of triboelectric systems. In particular, this procedure shows which of the low capacitance variation rectifier (LCVR) or of the cascade Bennet doubler rectifier (CBDR), two popular conditioning circuit topologies for e-KEH, is optimal for any given triboelectric transducer.