Finite element analysis on piezoelectric ring transformer

By using concentric electrode patterns, a ring-shaped transformer can be designed to operate at its high order radial extensional modes. In our previous study, a piezoelectric transformer (PT) using the third symmetric radial extensional mode was studied and characterized. A maximum efficiency, transformation ratio and power density of 92.3 %, 1.9 and 14.3 W/cm³ could be achieved. In this paper, three-dimensional (3D) finite element models were built to study and analyze the vibration characteristics of the PTs using higher order modes (>3). The resonance frequencies, mean electromechanical coupling effect, and other open-circuit characteristics are simulated and compared with experimental measurements. The dimensions for the PTs using higher order radial extensional modes are optimized by FEM. The ring PT offers advantages of simple structure and small size. It has good potential in making low cost PT for low voltage applications.