A Note On A Loaded Piezoelectric Transformer

Abstract

Due to the coupling of mechanical and electrical quantities in a piezoceramic material, it is possible to transform a harmonic input voltage to a harmonic output voltage by using a piezoceramic transformer. The advantage of such a transformer is the avoidance of magnetic fields and the very simple assembly. The piezoelectric transformer considered here consists of several parts. Three brass and two piezoceramic rods, that are glued together. The purpose of the system is to transform a determined input voltage to a determined ouput voltage with a high efficiency. Therefore, one of the piezoceramics is excited harmonically with a frequency close to a resonance frequency of the system. According to the electromechanical coupling in piezoceramics, the transformer oscillates with the excitation frequency. Due to the piezoelectric effect an electric displacement or an electric voltage is generated between the electrodes of the second piezoceramic. The amplitude of the output voltage depends on the geometry and the load connected between the electrodes of the second piezoceramic. In this paper a theoretical model to determine the gain and input impedance for such a transformer is derived and the results are compared with experiments.