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Method for improving the start up of an ultrasonic system under zero load conditions

  • US 6,480,796 B2
  • Filed: 05/25/2001
  • Issued: 11/12/2002
  • Est. Priority Date: 10/20/2000
  • Status: Active Grant
First Claim
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1. A method for improving start up performance of an ultrasonic surgical system under zero load conditions, comprising the steps of:

  • exciting a hand piece/blade with a drive current using an ultrasonic generator at an initial drive frequency;

    setting a frequency of a direct digital synthesis circuit located in the generator to an off-resonance frequency of the hand piece/blade;

    setting the drive current to a low level;

    searching for a target 0°

    impedance phase angle;

    increasing the drive frequency to a new level;

    maintaining the target 0°

    impedance phase angle at a constant value;

    monitoring impedance and phase angle magnitude values of the drive signal at the new level to calculate a frequency correction value; and

    correcting the frequency of the direct digital synthesis circuit using the calculated frequency correction value.

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