Characteristics of a 1st radial-vibration-mode-disk coupler-type piezoelectric ceramic transformer

We have already proposed a new type of piezoelectric ceramic transformer that is constructed by combining two 1st radial-vibration-mode disks with a coupling element, and have reported a basic investigation of it. In this paper, the characteristics such as input admittance, power transmission and temperature increase are dealt with and compared with those of the third-order longitudinal-mode Rosen type piezoelectric ceramic transformer of normal construction. As a result, the following has been clarified: the specific merit of this coupler type transformer is that its input impedance is effectively small and the vibration mode of this transformer is similar to that of the Rosen type transformer mentioned above. Moreover, it has been found that the step-up voltage ratio of this coupler type transformer is about 4 times larger than that of the Rosen type transformer; that is, the coupler type transformer proposed by us achieved a sufficiently low input impedance in spite of the use of a single-layer piezoelectric ceramic transformer. The efficiency and temperature increase of this transformer were found to be slightly inferior to those of the Rosen type transformer. However, 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 x 6.0 x 1.0 mm(3), the transmission power up to about 4 W could be achieved when the temperature increase was not more than 20 degrees C.