Development of High Power Piezoelectric Transformers

Low-profile inverter power sources are increasingly required for backlight systems of liquid crystal display. A great deal of attention has been focused on the application of miniaturized transformers to such power sources. The output performance of piezoelectric transformers, which operate in the third order longitudinal vibration mode with dimensions of l 42 mm×w 5.5 mm×t 1.4 mm, was studied. The piezoelectric ceramic material: 0.05Pb(Mn1/3Sb2/3)O3-0.48PbZrO3-0.47PbTiO3 was employed for these transformers. The values of efficiency for the transformers reach maximum when connecting a load resistance of around 100 kΩ which is assumed to be that of a cold cathode fluorescent lamp. The transformer with seven ceramic layers in the driver section, generates an output power of 3 W and shows the step-up voltage ratio over 60.