Multilayered unipoled piezoelectric transformers

This study describes a multi-layer piezoelectric voltage and power transformer which has one direction poling, operates in a wide-frequency range and delivers both step-up and step-down voltages by inverting the electrical connections. In this design, the input and output electrodes are on the same side of the disk and are isolated from each other by a fixed gap. Investigations were performed on a disk of diameter 29.1 mm. The electrode pattern is a ring/dot structure, where a strip connects the dots. Various ratios of input to output area were studied and it was found that area ratio in the range of 2.8-3.3 or the output diameter in range of 13-15 mm yields high power and efficiency. The power density for the optimized single layer transformer was 40W/cm³ while that for the 3-layer structure was 25 W/cm³. Though the power increased with multilayer structure, the effective power density decreased because of the interlayer constraints.