Design of Electrostatic Energy Harvesting Pre charge Circuit

Abstract

An energy harvesting system uses Pre charge circuits. The need for designing circuits that consume low power is the need of the day. In this paper a pre charge circuit has been designed in 45nm CMOS technology and the output energy and average power consumption of the circuit has been computed. The cascaded double tail comparator and the gate driver circuits are designed. The pre charge circuit is energy efficient and harvests more energy as compared to the invested energy. The capacitance value for designing the pre charge circuit has been obtained from the capacitive pressure sensor in COMSOL Multiphysics 5.3. A plot of capacitance versus pressure gives the equivalent capacitance for the applied pressure. A value of 1pF has been chosen for an applied pressure of 22.5 to 25 KPa. In the pre charge circuit, the energy consumption during charging of the capacitor was computed to be $\mathbf{4.5} \mu\mathbf{W}$ and during discharging it was computed to be $\mathbf{10} \mu\mathbf{W}$ . The invested energy was $\mathbf{0.281 x 10}^{-\mathbf{9}}\mathbf{fJ}$ and the obtained energy was $\mathbf{0.781 x 10}^{-\mathbf{9}}\mathbf{fJ}$ . The net energy gain was $\mathbf{0.5 x 10}^{-\mathbf{9}} \mathbf{fJ}$ and the percentage gain was 177.94%.