Piezoelectric ceramic transformer using radial vibration mode disks

In this paper, the coupler type transformer using two disks combined with a coupling element is proposed. The detailed characteristics such as its input admittance, vibration velocity, power transmission and temperature increase are dealt with and compared with those of the third-order longitudinal-mode Rosen type piezoelectric transformer. As a result, the following has been clarified: the specific merit of this coupler type transformer is that its input impedance is effectively small in spite of the use of a single-layer piezoelectric ceramic transformer and the vibration mode of this transformer is similar to that of the Rosen type transformer mentioned above, however, the efficiency and temperature increase of this transformer were found to be slightly inferior to those of the Rosen type transformer. Using the prototype transformer, in which two disks of 16.7 mm diameter and 1.0 mm thickness were combined with the coupling element of 17.5×6.0×1.0 mm, the transmission power up to about 4 W could be achieved when the temperature increase was not more than 20°C