Investigation of Internal Loss and Power Transmission Characteristic of Width Shear Vibration Piezoelectric Transformer

Abstract

Piezoelectric transformers proposed by Rosen [ Proc. Electronic Components Symp. (1957) p. 205] have been studied for high-voltage step-up applications. A piezoelectric transformer using a LiNbO 3 plate proposed recently by Nakamura et al. [ Proc. Japan Acoustic Society (1990) p. 687 [in Japanese]] has low loss and a simple structure. The plate of a conventional piezoelectric transformer was supported only at the point of the node of the vibration. Rigid support is required for high-power applications. To apply a piezoelectric transformer to a power circuit, we studied internal loss of transmitting power and how to support the piezoelectric plate. Based on the studies, we proposed a piezoelectric transformer which uses energy trapping of width shear vibration in a LiNbO 3 plate. This paper describes the investigation of the spurious mode, internal loss and power transmission characteristic. Efficiency of 95% or more can be obtained above a load rasistance range of about 20 Ω and under about 1000 Ω.