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Electrosurgical generator power control circuit and method

  • US 5,772,659 A
  • Filed: 09/26/1995
  • Issued: 06/30/1998
  • Est. Priority Date: 09/26/1995
  • Status: Expired due to Term
First Claim
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1. A constant power control circuit for use in an electrosurgical generator having a power selection system that produces a control voltage signal to control a high voltage direct current supply which supplies a high voltage signal to an output switching radio frequency stage thereby creating an electrosurgical energy between two output electrodes, the constant power control circuit comprising:

  • a current sampling circuit inductively coupled to one output electrode, the current sampling circuit producing a sampled current signal proportional to an average current flowing through the output electrode;

    a linear conversion circuit electrically connected to the current sampling circuit for generating a linear converted signal, wherein the linear conversion circuit includes;

    a linear multiplier generating means for generating a multiplier reference signal;

    a linear offset generating means for generating an offset reference signal;

    a multiplier, electrically connected to the linear multiplier generating means, for multiplying the sampled current signal and the multiplier reference signal to produce a multiplied signal; and

    a summer, electrically connected to the linear offset generating means, for summing the offset reference signal and the multiplied signal to produce the linear converted signal; and

    a feedback correction circuit electrically connected to receive the linear converted signal from the linear conversion circuit and the control voltage signal from the power selection system for producing a feedback control signal which is supplied to the power selection system to control the amount of electrosurgical energy created, wherein the feedback correction circuit includes;

    a subtractor, electrically connected to receive the linear converted signal and the control voltage signal, for determining a difference in amplitude between the control voltage signal and the linear converted signal and producing a delta signal proportional to the difference; and

    an adder, electrically connected to receive the delta signal and the control voltage signal, for adding the delta signal to the control voltage signal and producing the feedback control signal.

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