System Design and Experimental Demonstration of Spherical Piezoelectric Ceramic Transformers in Radial Vibration

As a prevalent type of transformer, piezoelectric transformers have garnered significant attention in various practical applications due to their lighter, smaller construction and absence of magnetic fields. Recent advances in the field of piezoelectric transformers have developed a variety of structure types, while the piezoelectric transformer with a spherical shape has not been researched. Here, we present a spherical piezoelectric ceramic transformer capable of achieving both step-up and step-down output characteristics in radial vibration. The resulting design is made of two layers of piezoceramic spherical shells and three layers of metal spherical shells. The basic mechanism is that the input electrical energy is converted into mechanical energy via the inverse piezoelectric effect, and then the converted mechanical energy is reconverted into electrical energy, thus realizing step-up and step-down voltage conversions. The electromechanical characteristics, voltage gain, and power gain for our proposed spherical piezoceramic transformer as functions of electric load resistance and geometry size under different dielectric and mechanical losses are analyzed. The experiments are conducted to verify the performance parameters of our proposed design, which are basically consistent with the results of numerical simulation and theoretical analysis. The power gain of our proposed spherical piezoceramic transformer can reach about 36% when the input voltage of the function generator is 20 V peak-to-peak and the load resistance is 125 Ω. The resonance frequency of the spherical piezoelectric transformer can be varied from 75 839 to 74 221 Hz by varying the thickness of the intermediate metal spherical shell from 0.2 to 3.8 mm. Our methodology will open new perspectives for the design of piezoelectric transformers, which may have prominent applications in various fields, such as portable electronic chargers and electronic ballasts for fluorescent lamps.