Power generator for a piezoelectric ultra-sonic transducer

Claim 1

A power generator for an ultrasonic transducer comprising variable-controlled oscillator means; power amplifier means receiving the output of said variable-controlled oscillator means; a transformer having three windings, said transformer having a first winding connected to said ultrasonic transducer; coupling means coupling the output of said power amplifier means and said variable controlled oscillator means to said ultrasonic transducer through said first winding of said transformer; phase measuring means having first and second inputs and an output, said first input being derived from the output of said coupling means, said second input being derived from the load current flowing through said ultrasonic transducer and said first winding by connecting said second input to a third winding of said three windings transformer, said second input being a current porportional to a reactive current component of said load current flowing in a second winding of said three winding transformer caused by the lead capacitance and rest capacitance of said ultra-sonic transducer, said second winding being connected to the output of said coupling means, said first and second windings being poled so that their magnetic effects are subtracted from each other; said phase measuring device producing an output to said variable controlled oscillator proportional to the phase difference of said first and second inputs to adjust the frequency of said variable controlled oscillator means to a resonant frequency of said ultrasonic transducer determined by the load applied to said transducer.