Research On Equivalent Circuit And Characteristics Of Radial Composite Disc Type Piezoelectric Ceramic Transformer

Compared with traditional transformers, piezoelectric transformers have many advantages. So, the piezoelectric transformers have attracted academic attention. Based on the derivation of the equivalent circuit and the circuit theory, the characteristic of the piezoelectric transformer has been studied:(1) Rosen type piezoelectric transformer, thickness vibration type piezoelectric transformer, and radial vibration type piezoelectric transformer have been detailed introduced in their energy transfer mode and performance characteristics. Besides, the lumped equivalent circuit of 3 kinds of different piezoelectric transformers are calculated and deduced. In this paper, the energy transfer mode of shear type piezoelectric transformer and bending mode piezoelectric transformer is also introduced. Through the analysis and study the above transformers, it can be predicted that, different shapes and different vibration modes of piezoelectric transformer will be more popular in all fields of our life. The lumped circuit diagram can make us easily to understand each transformer's characteristics. But, if structures or vibration mode is complex, we will not have a access to accurately describing its function. It is bad for design piezoelectric transformer, so in order to solve this problem must adopt distributed equivalent circuit.(2)Based on the piezoelectric equation and elastic wave equation, piezoelectric disk, piezoelectric rings and metal rings have been analyzed and deduced. Meanwhile, their distribution equivalent circuit diagrams have been derived. In order to check its correctness, compared the theoretical calculation results and finite element calculation results, the error is very small. The results show that derived the equivalent circuit is accurate. This lays a solid foundation for the study of different types of piezoelectric transformer.(3) To common dot-ring type piezoelectric transformers, do a detailed analysis. According to cascade theory, its equivalent circuit is derived. And according to Kirchhoff s law, the frequency equation, the voltage gain equation has been obtained. And the theory is verified by simulation calculation. And on this basis, discusses the influence of the thickness of piezoelectric plate of the transformer and load on the influence of frequency, voltage gain. Results show that:with piezoelectric disc radial thickness increases, the frequency of the transformer go high, but the gap between the resonance and anti-resonance frequency is getting smaller, which also led to the electromechanical coupling coefficient decreases monotonically; load increases, will indeed make voltage gain increased in a certain range, the frequency is also on the rise. However, the effective electromechanical coupling coefficient is not very stable, so find suitable load for such a transformer is very important. At the same time, it also be confirmed is that one of the drawbacks of the transformer, is poor stability, and its strength is not enough.(4) Presents a novel piezoelectric transformer structure. Using the equivalent circuit and cascade theory, based on related knowledge of electrical derived its resonance, anti-resonance frequency equation; equation of voltage gain, power efficiency equation. And the advantages of the new structure are analyzed.By various equations derived, to the metal ring thickness and the load made a detailed study on the influence of piezoelectric transformer performance. The results show that the addition of metal ring, solved the problem of piezoelectric material strength is not enough. Moreover, with the increase of metal radial width, transformer's frequency will rise. But, effective electromechanical coupling coefficient reduced, so the metal ring has an optimum thickness, to meet the needs of the normal operation of the transformer. From the whole, in the process of load from 0 to infinite, frequency, voltage gain are increased, and the effective electromechanical coupling coefficient is decreased, but when the load reaches a certain value, the change trend of slowing down. So there is an optimum load, the electrical properties of the transformer to reach an optimal state. Then, using the finite element method validates the theory, and show effect on the metal ring thickness and transformer radial stress. The result shows that theory is correctly. In the future, I hope the method and conclusions in this paper can be applied to real life.