A Study Of Some Key Design Parameters For A Piezoelectric Transformer With Contacted Heat Transfer Device

Piezoelectric transformers(PTs) are devices which can convert electric energyinto mechanical vibration by converse piezoelectric effect, and the mechanicalvibration into electric energy by direct piezoelectric effect. Compared withelectromagnetic transformers, piezoelectric transformers have many advantages suchas compact volume, electromagnetic noise free-operation, non-flammability, andhigh power to volume ratio. Because of the characters of the piezoelectric material,which has a high power density400W/cm3, and a very small coefficient of thermalconductivity2W/mk, the piezoelectric transformer cannot be used in high powerapplications. In this paper, the electrical equivalent circuits of the piezoelectrictransformer and heat transfer system have been studied. And we also proposed a newpiezoelectric transformer which based on the stress distribution of the piezoelectricceramic. Main works are stated as follow:(1) We derived the equivalent circuit model of the longitudinal vibration modepiezoelectric transformer according to the piezoelectric equation, wave equation andelectromechanical equivalent network. The equivalent circuit model had beenverified by experiments. We also analyzed and summarized the factors affecting thepiezoelectric transformer equivalent circuit parameters (PTECP).(2) By analyzing the vibration and heat transfer model of the longitudinal vibration piezoelectric transformers，we proposed and designed a heat dissipationstructure for the longitudinal vibration piezoelectric transformers, and proposed theequivalent circuit model of the piezoelectric transformer with the heat transfersystem. Then we measured the effect of the introduction of the heat transfer systemon resonance frequency of the piezoelectric transformer, power density, efficiency,and other aspects, which provide a reference for the piezoelectric transformer in theapplication of high-power applications.(3) We also proposed a new piezoelectric transformer which based on the stressdistribution of the piezoelectric ceramic. Different with the conventionalpiezoelectric transformer, the new piezoelectric transformer’s input terminal andoutput terminal have different stress distribution which results in different outputvoltage. So it can achieve the step-up or step-down of the input voltage. This designof the new PTs were simulated by multi-output PTs operating at the longitudinalvibration model and tested by experiments.