Wen C.-C., Wen F.-L., Lin C.-H. «Frequency adaptive driver for ultrasonic vibrators with motional current feedback» Приборы и техника эксперимента, № 1, с. 115-123 (2013)

A driving circuit of frequency adapting for an ultrasonic vibrator with motional current feedback has been presented in this paper. Via a voltage-controlled oscillator (VCO) and a digital/analog converter (DAC), the driving signal would be magnified by a linear power amplifier to actuate the vibrator. Since the vibrating velocities or displacements at the surface end of a vibrator could be predicted through the measurement of motional current, the motional current passing through the vibrator was detected by a current transformer (CT) type sensor as feedback to monitor the optimal level of output power. The calculation for phase difference and the tuning strategy for driving frequency were implemented by a microcontroller integrated with an A/D converter and a voltage comparator as well as the signal attenuation and level tuning circuit. The experiment demonstrates that the temperature effect corresponding to frequencies is at 9.75 Hz/°C shifting and the external loading reflected to frequencies is about 8.3 Hz/gm offset. The proposed circuit has the great performance in rejecting the disturbances from external loading and thermal effect.