Inverter topologies for ultrasonic piezoelectric transducers with high mechanical Q-factor

Piezoelectric ultrasonic transducers are often used in well known applications such as ultrasonic cutting or cleaning processes. A novel application is the utilization of transducers in ultrasonic standing wave atomizers. Here, the transducers produce an ultrasonic field resulting in high alternating excess pressures, used to disintegrate polymer melts for powder lacquer. The power supplies stimulating the transducer have to provide output voltages at ultrasonic frequencies and output power levels at several kW. Besides the output filter circuit of an inverter is strongly influenced, especially when driving piezoelectric transducers with a high mechanical quality factor. In this contribution, two resonant converter concepts and a pulse width modulated converter (PWM converter) feeding ultrasonic transducers are analyzed and compared. In this comparison focus is laid on: sensitivity of the output filter to varying load conditions, potential of miniaturization and cost savings and the frequency range, in which different transducers can be fed by the power supply. The results are summarized in a benchmark matrix. Based on these results, a flexible PWM converter was developed and realized. This laboratory power supply is part of a rapid prototype system (dSpace). Measurements are presented in the last part of this contribution.