Theoretical Design And Characteristic Analysis Of A Novel Disc - Type Piezoelectric Ceramic Transformer

The input terminal of the piezoelectric ceramic transformer under the external exciting electric filed produces mechanical vibration by inverse piezoelectric effect, which converts the electric energy into the mechanical energy, at the same time, the output terminal of the piezoelectric ceramic transformer converts the mechanical energy into the electric energy by piezoelectric transformer to change the voltage. Contrasting with traditional electromagnetic transformer, the piezoelectric ceramic has the many advantages, such as microminiaturization and integration easily, anti-interference and good stability, high power density and efficiency, simple workmanship and low material cost.Because of the prominent advantages of piezoelectric ceramic transformer in electric application, the application and research value of the piezoelectric transformer have been closely watched. In recent year, the radial vibration mode piezoelectric ceramic transformer is one important type piezoelectric transformer researched at home and abroad among various type piezoelectric transformers. The single dot-ring piezoelectric ceramic transformer for mechanical vibration coupled by the radial normal stress has been researched rarely. Based on the rot-ring disc piezoelectric transformer, the radial ladder and radial composite ladder structure are increased, which provide a new idea and method for changing and promoting the piezoelectric ceramic’s properties. In this paper, the new type of piezoelectric ceramic transformer is studied with changing the thickness ratios to increase the voltage gain, especially, the radial composite ladder structure increase the mechanical strength of the piezoelectric ceramic transformer, which is helpful for heat dissipation and easier for installation, therefor, the high efficiency and strong stability both are achieved. In addition, this paper also designs newly a radial vibration single monolithic multi-terminal output piezoelectric transformer with electrode segmentation. The manufacture craft of the new type of piezoelectric transformer is simple, and the performance of the piezoelectric transformer is perfect. Importantly, the piezoelectric transformer own the one input and two outputs, which can satisfy simultaneously the two specific impendence load and change voltage.In this paper, derived from the piezoelectric equation and wave equation of the piezoelectric transformer, and based on one-dimensional radial vibration theory, the distribution parameter equivalent circuit of the new type of piezoelectric transformers were obtained. And then, the concrete analytic expression of the piezoelectric transformer’s input impedance, voltage gain and power efficiency what were deduced, the important characteristics of the new type of piezoelectric transformer were analyzed in detail. In particular, the resonance and anti-resonance of the piezoelectric transformer were stimulated by finite element method and were tested by the experiments, the result shows that the theoretical value agrees well with the stimulation value and the experiment value.For a new type of dot-ring ladder disc piezoelectric ceramic transformer, when the transformer load an infinite and limited impendence, the maximum voltage gain can get respectively under the resonance frequency and the vicinity of resonance frequency. Under different frequency, there are different optimal load to achieve the voltage gain. The maximum power efficiency can get near the resonance frequency and anti-resonance frequency, the load and the frequency both make the piezoelectric transformer’s power efficiency to be maximal. As the radius ratio and thickness ratio increases of the piezoelectric transformer outer ring into inside dish, the maximum voltage gain and its corresponding frequency both are monotone decreasing trends. For a new type of radial composite ladder disc piezoelectric ceramic transformer, compared with the dot-ring ladder disc piezoelectric ceramic transformer, the load and frequency’s influence on the voltage gain and power efficiency appear the similar characteristics. Especially, the resonance and anti-resonance frequency, the electromechanical coupling coefficient decrease with the increasing of the thickness ratio of the outer into the inside dish. The relationship of the maximum voltage and the thickness ratio isn’t monotonous, but that can determine the optimal thickness combining with the electromechanical coupling coefficient. For a new type of dual output single piezoelectric transformer, when the thickness and second output terminal’s radius are given, if the radius ratio of the input terminal into the first output terminal increase, the resonance frequency decrease, and the anti-resonance frequency basically remains unchanged, but the electromechanical coupling coefficient increase monotonically. By the analysis of the three dimension relationship of the maximum voltage gain, frequency and load, when the load is more than tens of thousands of ohm, the maximum voltage gain occur near the resonance frequency, when the frequency is given, there is an optimal load for voltage gain.