A control system for use with an ultrasonic surgical instrument includes a generator supplying electrical energy to an ultrasonic surgical instrument, the electrical energy supplied by the generator being controlled such that power applied by the instrument is maintained constant once a predetermined pressure threshold is met. The control system operates by assigning a nominal power at which the ultrasonic instrument is to operate and adjusting the current and voltage applied to the ultrasonic surgical instrument so as to maintain the power applied by the ultrasonic surgical instrument at approximately the nominal power.
