In this study, contour-vibration-mode Pb(Ni/sub 1/2/,W/sub 1/2/)O/sub 3/-Pb(Mn/sub 1/3/, Nb/sub 2/3/)O/sub 3/-Pb(Zr, Ti)O/sub 3/ piezoelectric transformers were fabricated in the modified filter structure with ring and dot electrodes. The transformers have been developed for application in 455 kHz AM radios. The piezoelectric transformers were fabricated to the size of 31.5/spl times/31.5/spl times/2.5mm/sup 3/ by cold isostatic pressing. Driving of the piezoelectric transformer was carried out with input region for the ring electrode and output region for the dot electrode. The electrical properties and characteristic temperature rises caused by the vibration were measured at various load resistances. Efficiencies above 90% with load resistance were obtained from the transformers. A 28 W (T5) fluorescent lamp was successfully driven by the fabricated transformer. The transformer with ring/dot electrode area ratio of 1.83 exhibited the best properties in terms of output power, efficiency and characteristic temperature rise, 30.95 W, 97.57% and 8.3/spl deg/C, respectively.
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