Testing electrostatic energy harvesters: A new topology for accurate characterization

Small autonomous devices using low power techniques can be supplied by energy harvesters. In this paper we focus on electrostatic energy harvesters using a variable capacitor as transducer. The capacitance, charge and voltage vary in a loop process. Many different setups are known. The aim of this paper is to show a method to characterize the harvested energy of the intrinsic harvester. Due to the very low currents in the range of nA, it is difficult to do exact measurements without influencing the harvesting process. A new improved topology is used to ensure the autonomous operation of the harvester circuit. This topology makes it possible to measure the converted energy more accurately, even if there are resistive losses in the variable capacitor. Thus we can obtain comparable results on the efficiency of the harvester itself. The amount of harvested energy can be determined easily by processing the measured values.