Open-circuit test of a piezoelectric transformer and its applications

This paper investigates the characteristics of a voltage transient response, including time constants, response times, peak voltages and oscillation frequency, for a piezoelectric transformer (PT) under open-circuit operation and their applications. This transient response is induced immediately after an AC voltage applied to the PT is switched off. The time constants can be employed to determine the quality factor and equivalent circuit constants concerning the losses consumed in the PT. Then, an equivalent circuit model of the PT with the initial conditions is used to derive a constituent function of the transient response, involving both DC and AC parts. Moreover, a driving system, including a resonant inverter and a control switch, is constructed to determine the actual transient responses and their characteristics. Furthermore, the effects of both switching-off time of the AC voltage and loading resistance on the characteristics of the transient response are measured and discussed.