This study investigates a terminal transient response of a Langevin-type PZT vibrator theoretically and experimentally to quantify an electrical shock and refine an equivalent circuit of the vibrator. The shock is induced immediately after an AC sinusoidal voltage of the vibrator is switched off. Then, the transient response involves a DC part and an AC part, which approach zero at the DC and AC times, respectively, and the vibrator is placed on a sponge in air. To do so, we should propose an open-circuit test to find the AC and DC times in addition to the maximum amplitude of the transient response. Thus the DC times exceeds the AC time, and the AC and DC times are used to estimate the resistances in the equivalent circuit presenting the real mechanical and dielectric losses, respectively. Therefore, the resistances in the equivalent circuit are sensitive to the vibration amplitude, but the inductance and capacitances are not. Furthermore, the maximum amplitude is required to cause the shock, and depends on the frequency of the source and the open-circuited time, and is about 65 times the amplitude of the source.

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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.

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