Effects of load resistances on step-up voltage gains of Rosen-type piezoelectric transformer

This paper investigates step-up voltage gains and resonance frequencies at maximum voltage gains for a Rosen-type piezoelectric transformer (PT) at various load resistances by simulation and experiment. Also, load effects of an oscilloscope, which is applied to record waveforms of input and output voltages, on the voltage gains and resonance frequencies are studied. In doing so, equivalent circuit models of the PT and the oscilloscope are first employed to derive a formula of the voltage gain. Then, an equivalent electromechanical transformer turns ratio is determined according to measured results of the voltage gains against driving frequencies. This ratio is essential to calculating the above voltage gains and frequencies. Moreover, relationships among voltage gains, driving frequencies and load resistances are simulated and measured. Finally, load effects of the oscilloscope on maximum voltage gains and their associated resonance frequencies are calculated and discussed.