General analysis and optimization of a two-stage power management circuit for electrostatic/triboelectric nanogenerators

Triboelectric nanogenerators (TENGs) generate high AC voltages that are often rectified using stable charge pumps. This paper provides for the first time a comprehensive general theory that determines the optimal electrical bias conditions for this class of rectifiers. In this work, the proposed generic formulas have been applied to full-wave and half-wave diode bridges. Key figures have been demonstrated like for instance the optimal bias voltage or the maximum converted energy. It is confirmed that half-wave rectifiers always have a higher saturated voltage, as well as higher maximum energy per cycle, but at the cost of longer start-up time. On the contrary, full-wave rectifiers perform better only when the output voltage is much lower than the internal triboelectric voltage of the TENG. These rectifiers followed by a buck DC-DC converter have also been studied in details, often required to provide a low output voltage. We showed that the optimal buck’ switch activation is between .5 and .7 of the charge-pump saturation voltage, depending on the hysteresis of the switch, and that the charging time of the output capacitor is at least twice as fast with a half-wave rectifier than with a full-wave rectifier. The theoretical results were confirmed by simulations and experiments using a plasma switch.