Power Converters for Power-Ultrasonic Transducers

High-performance power-converters in the form of single-tone class-D amplifiers are required to drive power-ultrasonic transducers in industrial applications. These must produce low-distortion, variable-frequency, and variable-amplitude sinusoidal currents to efficiently drive the piezoelectric cell and horn of transducers, and thereby vibrate materialprocessing stages. A resonant-tracking control strategy is generally used to efficiently couple and regulate output power delivery at a high-Q probe-system resonant mode. This paper reviews a number of power-converter control options suitable for such probe drivers, including quasi-squarewave (QS), naturally sampling pulse width modulation (PWM) and programmed PWM (PPWM). Typical output-waveform quality and the PSPICE models of the power-converter and piezoelectric transducer developed to assess and compare methods are presented.