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Rem output stage topology

  • US 5,695,494 A
  • Filed: 12/22/1994
  • Issued: 12/09/1997
  • Est. Priority Date: 12/22/1994
  • Status: Expired due to Term
First Claim
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1. An electrosurgical return electrode circuit for developing an impedance measurement between two contact pads, comprising:

  • an isolation transformer in the electrosurgical return electrode circuit, the isolation transformer having a driving winding and a driven winding having two driven ends and, the driving winding having two driving ends and having a signal terminal and a ground terminal each connected to one driving end thereof;

    a first electrical conductor and a second electrical conductor each attached to one driven end of the driven winding;

    a first patient contact pad and a second patient contact pad electrically coupled to the first and second electrical conductors, respectively, and the driven winding for resonating at a monitoring frequency;

    a voltage detection circuit connected to the signal terminal of the driving winding for producing an electrical phase signal of the voltage across the driven winding;

    a voltage shaping circuit included in the voltage detection circuit and in electrical communication therewith;

    a current detection circuit connected to the signal terminal of the driving winding for producing an electrical phase signal of the current flowing in the driving winding;

    a current shaping circuit included in the current detection circuit and in electrical communication therewith;

    a phase detector connected to the voltage shaping circuit and the current shaping circuit for providing an electrical signal indicating a phase difference signal between the voltage across the signal terminal and current at the signal terminal;

    a phase filter connected to the phase detector for providing a response characteristic of the phase difference signal, anda phase locked oscillating voltage source for operating at the monitoring frequency of oscillation, the phase locked oscillating voltage source connected between the phase filter and the signal terminal of the driving winding for producing an electrical driving signal upon receipt of the response characteristic of the phase difference signal so that the monitoring frequency of oscillation is continuously adjusted to keep the phase difference between the voltage and the current at the signal terminal substantially zero thereby delivering a maximum voltage signal to the voltage detection circuit, the electrical driving signal used to develop the impedance measurement.

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