New type of piezoelectric transformer with very high power density

A new innovative multilayer PT design for operation with high power density and frequencies up to several MHz is presented. The design is based on a ring-shaped element operating in thickness vibrational mode, where the primary and secondary sides are separated by an isolation layer. Prototypes with intricate geometry, a result of FEM simulations for maximising the effective coupling factor of the working mode and suppressing spurious modes, are presented. Initial results show power densities above 40 W/cm/sup 3/ at efficiencies above 98%. This is a clear improvement over present state-of-the-art transformers. The flexibility of the general design with respect to changing power levels and transformation ratios opens a variety of new markets in the electronics industry.