Finding Electrical Characteristics of a Piezoelectric Transformer through Open-Circuit Operation

Abstract

In this paper we investigate the electrical transient responses of a piezoelectric transformer (PT) under open-circuit operation and its response times. The transient responses are induced on both sides of the PT immediately after the AC voltage applied to the PT is switched off. An equivalent circuit with initial conditions is expressed first. Then, the equivalent circuit is used to derive an input voltage transient response and its response times. Moreover, an AC power supply system with a control switch is used to determine the transient responses, and an oscilloscope with a smoothing-and-filtering function is used to measure the transient responses and their DC components. Furthermore, the effects of load resistance, switching-off time and operating frequency on the transient responses are measured and discussed. From the measured results, the DC component of each output voltage transient response is almost zero and the AC response time of the output transient response is greatly decreased from 11.5 ms under an output open to 3.0 ms by adopting a 1 MΩ load resistance.