Patent ID: 8236020

Claim:
An ultrasonic surgical assembly, comprising: an ultrasonic transducer operable to convert a received motional current into a movement of a cutting blade of an ultrasonic waveguide, the ultrasonic transducer having a first capacitance in a parallel configuration with a series configuration of a resistance, an inductance, and a second capacitance, wherein the motional current flows through the series configuration; a measurement circuit connected in a parallel configuration with the ultrasonic transducer and comprising a third capacitance in a parallel configuration with the first capacitance; a variable power source operable to supply current through a set of connection points to the parallel configuration and thereby create the motional current in the ultrasonic transducer, the variable power source being coupled to the third capacitance and the ultrasonic transducer; and a current controller operable to regulate the motional current by varying an output of the variable power source based upon a product of the current flowing through the third capacitance multiplied by a ratio between a value of the first capacitance and a value of the third capacitance subtracted from a total current flowing into the ultrasonic transducer, thereby maintaining a substantially constant rate of movement of the cutting blade across a variety of cutting loads.