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Abstract

A driving circuit for ultrasonic tools which uses a piezoelectric transducer to convert ultrasonic electric signals into ultrasonic mechanical vibrations including a voltage-controlled oscillator which produces an output signal at a frequency that is proportional to an input voltage, a power amplifier stage having its input coupled to the output of the voltage-controlled oscillator, the power amplifier stage including an output transformer which couples the output of the power amplifier stage to the piezoelectric transducer, the power output transformer further acting as both an insulating transformer and a boosting transformer for the driving circuit and a feedback transformer coupled in series with the secondary side of the output transformer and the piezoelectric transducer, the feedback transformer having a secondary side through which a current flows which is proportional to the current flowing through the piezoelectric transducer, a phase comparitor which detects the phase difference between two signals applied to two inputs of the phase comparitor, the two inputs being respectively coupled to the output signal of the voltage controlling oscillator and the secondary side of the feedback transformer and a low pass filter which blocks high frequency components to pass therethrough connected between an output of the phase comparitor and the input of the voltage controlled oscillator.

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First Claim