Exit spark control for an electrosurgical generator

• US 5,628,745 A
• Filed: 06/06/1995
• Issued: 05/13/1997
• Est. Priority Date: 06/06/1995
• Status: Expired due to Term

• Current Assignee: Covidien AG (Medtronic Plc)
• Original Assignee: Valleylab Inc. (Medtronic Plc)
• Inventors: Bek, Robin B.
• Primary Examiner(s): Cohen, Lee S.
• Application Number:
  US08/479,424
• Time in Patent Office: 707 Days
• Field of Search: 606/37-40
• US Class Current: 606/38
• CPC Class Codes: A61B 18/1206 Generators therefor
• CPC Class Codes: A61B 2018/00732 Frequency
• CPC Class Codes: A61B 2018/00875 Resistance or impedance

Abstract

An electrosurgical generator is disclosed that includes an exit spark control system. Exit sparking occurs when energy arcs to the patient as the active electrode is withdrawn from the patient. A basis for controlling the exit spark is to automatically change the frequency at which the final amplifier is driven whenever the conditions for an exit spark are detected. The change in frequency acts to lower the gain and efficiency in the final amplifier and dissipate energy as heat. The exit spark control system includes a frequency adjustable waveform generator and a logic capability for determining the conditions when exit sparking is likely to occur. Sensors and an algorithm in a microcontroller are preferably required to detect the conditions preceding exit sparking occurrence. It is further preferred that, the algorithm also control the sequencing of events: first stopping the electrosurgical output to prevent an arc from initiating and then changing the driving frequency appropriately to dissipate excess stored energy. The output waveform may be stopped for only a short time or the surgeon will detect drag while cutting through tissue.

Claims

1. An electrosurgical generator with an exit spark control system that suppresses exit sparking in a patient circuit, the electrosurgical generator comprising:

an adjustable waveform generator in the electrosurgical generator for producing radio frequency waveforms, and capable of adjusting the frequency of the waveforms;

a radio frequency output stage electrically connected to the adjustable waveform generator for receiving the radio frequency waveforms and for generating an output voltage and an output current for transmission to the patient circuit;

a voltage sensor connected to the radio frequency output stage for receiving the output voltage, and capable of producing a first signal that is proportional to the output voltage;

a spark control circuit electrically connected to the voltage sensor for receiving the first signal, and the spark control circuit electrically connected to the adjustable waveform generator to cause the waveform generator to temporarily stop and then to temporarily adjust the frequency of the waveforms partly in response to the first signal, wherein the adjusted frequency causes a drop in gain across the radio frequency output stage.

2. The apparatus of claim 1 wherein the spark control circuit further comprises:

a current sensor connected to the radio frequency output stage for receiving the output current, and capable of producing a second signal that is proportional to the output current, and

an impedance measuring device electrically connected for receiving the first signal and the second signal and for computing the impedance of the load in the patient circuit.

3. The apparatus of claim 2 further comprising a microcontroller which has an input electrically connected to receive the impedance of the load from the impedance measuring device, and the microcontroller has an output electrically connected to the adjustable waveform generator for enabling the spark control circuit.

4. The apparatus of claim 3 further comprising an algorithm in the microcontroller for shutting off the output stage for a time in the range of 5 milliseconds to 200 milliseconds.

5. The apparatus of claim 1 wherein the spark control circuit further comprises:

a peak detector which is connected to receive the first signal from the voltage sensor and for holding peak values from the first signal, and

a comparator which is connected to receive the peak values from the peak detector and also connected to receive a voltage threshold, the comparator generating a high signal whenever the peak value exceeds the voltage threshold;

a one-shot connected to receive the high signal from the comparator, the one-shot having an output electrically connected to the adjustable waveform generator, the one-shot set to produce a pulse in the output whenever the high signal is received from the comparator.

6. An electrosurgical generator with an exit spark control system that suppresses exit sparking through a patient circuit and to the patient when used by a surgeon, the electrosurgical generator comprising:

a surgeon panel on the electrosurgical generator which is accessible to the surgeon for setting a desired level of output power;

a microcontroller in the electrosurgical generator which is electrically connected to receive the desired level of output power from the surgeon panel, and capable of setting a voltage threshold based on the desired level of output power;

an adjustable waveform generator in the electrosurgical generator for producing radio frequency waveforms, and for adjusting the frequency of the waveforms;

a radio frequency output stage electrically connected to the adjustable waveform generator for receiving the radio frequency waveforms and for generating an output voltage and an output current for transmission to the patient circuit;

a voltage sensor connected to the radio frequency output stage for receiving the output voltage, and capable of producing a first signal that is proportional to the output voltage;

a spark control circuit electrically connected to the microcontroller for receiving the voltage threshold therefrom, and the spark control circuit electrically connected to the voltage sensor for receiving the first signal, and the spark control circuit electrically connected to the adjustable waveform generator to temporarily stop and then adjust the frequency of the waveforms partly in response to when the first signal is greater than the voltage threshold, wherein the adjusted frequency causes a drop in gain and efficiency across the radio frequency output stage.

7. An electrosurgical generator with an exit spark control system that suppresses exit sparking through a patient circuit and to the patient when used by a surgeon, the electrosurgical generator comprising:

a surgeon panel on the electrosurgical generator which is accessible to the surgeon for setting a desired level of output power;

a microcontroller in the electrosurgical generator which is electrically connected to receive the desired level of output power from the surgeon panel, and capable of setting a voltage threshold based on the desired level of output power;

an adjustable waveform generator in the electrosurgical generator for producing radio frequency waveforms, and for adjusting the frequency of the waveforms;

a radio frequency output stage electrically connected to the adjustable waveform generator for receiving the radio frequency waveforms for generating an output voltage and an output current for transmission to the patient circuit;

a voltage sensor connected to the radio frequency output stage for receiving the output voltage, and capable of producing a first signal that is proportional to the output voltage;

a current sensor connected to the radio frequency output stage of receiving the output current, and capable of producing a second signal that is proportional to the output current;

an impedance measuring circuit electrically connected for receiving the first signal and the second signal and for computing the impedance of the load in the patient circuit;

a spark control circuit electrically connected to the microcontroller for receiving the voltage threshold therefrom, and the spark control circuit electrically connected to the voltage sensor for receiving the first signal, and the spark control circuit electrically connected to the adjustable waveform generator to adjust the frequency of the waveforms in response to a condition when the impedance of the load is generally less than about 4096 ohms and the first signal is greater than the voltage threshold, wherein the adjusted frequency causes a drop in gain across the radio frequency output stage;

a peak detector in the spark control circuit which is connected to receive the first signal from the voltage sensor and for holding peak values from the first signal;

a comparator in the spark control circuit which is connected to receive the peak values from the peak detector and also connected to receive the voltage threshold from the microcontroller, the comparator generating a high signal whenever the peak value exceeds the voltage threshold; and

a one-shot in the spark control circuit, the one-shot connected to receive the high signal from the comparator, the one-shot having an output electrically connected to the adjustable waveform generator, the one-shot set to produce a pulse in the output whenever the high signal is received from the comparator.

8. A method of controlling exit spark in an electrosurgical generator with an exit spark control system that suppresses exit sparking through a patient circuit and to the patient when used by a surgeon, the method of suppressing including the steps of:

setting a desired level of output power on a surgeon panel accessible to the surgeon and located on the electrosurgical generator;

receiving the desired level of output power from the surgeon panel with a microcontroller electrically connected to the electrosurgical generator;

setting a voltage threshold based on the desired level of output power with the microcontroller;

producing radio frequency waveforms with an adjustable waveform generator in the electrosurgical generator;

receiving the radio frequency waveforms with a radio frequency output stage electrically connected to the adjustable waveform generator;

generating an output voltage and an output current for transmission to the patient circuit with the radio frequency output stage;

receiving the output voltage with a voltage sensor connected to the radio frequency output stage;

producing a first signal that is proportional to the output voltage with the voltage sensor;

receiving the output current with a current sensor connected to the radio frequency output stage;

producing a second signal that is proportional to the output current with the current sensor;

receiving the first signal and the second signal with an impedance measuring circuit electrically connected to the voltage and current sensors;

computing the impedance of the load in the patient circuit with the impedance measuring circuit;

receiving the voltage threshold from the microcontroller with a spark control circuit electrically;

receiving the first signal from the voltage sensor with the spark control circuit;

adjusting the frequency of the waveforms with the adjustable waveform generator, at least partly in response to the spark control circuit, such that the gain across the output stage is reduced, the adjustment in response to a condition wherein the impedance of the load is generally less than about 4096 ohms and the first signal is greater than the voltage threshold.