Electroelastic vibrations and transformation ratio of a planar piezoceramic transformer

Abstract

Piezoelectric transformers of the transverse–longitudinal type are used in small-sized electronic devices, in which the traditional electromagnetic transformers are inapplicable. A monolithic piezoceramic rectangular plate, having two sections of transverse and longitudinal polarization with transformation of an electric voltage from input to output was described almost 50 years ago. The method of equivalent electric circuits was used to derive an approximate formula for the transformation ratio for no-load conditions without accounting for the difference between elastic compliance in different sections, which may be 10–15%. In the author's previous papers, the forced vibrations of a classical transverse–longitudinal piezotransformer were analyzed. A more precise formula was derived for the transform ratio with regard to the difference between the elastic compliances in the input and output sections. It was established that the transforming ratio is inversely proportional to the squared frequency and is a good match with experimental data. It was shown that the longitudinal mechanical stresses in both sections of the transformer are axisymmetric with respect to the separating line. In the present paper, the forced vibrations of a piezoelectric transformer of a transverse–longitudinal type are considered with respect to dependence of the transformer parameters upon the difference of the elastic compliances in different sections. Experimental data are also considered. The complex function method is applied for numerical analysis. Amplitude–frequency characteristics of the piezotransformer are compared with those for a thin piezoceramic rectangular plate.