ELECTROSURGICAL GENERATOR

• US 3,699,967 A
• Filed: 04/30/1971
• Issued: 10/24/1972
• Est. Priority Date: 04/30/1971
• Status: Expired due to Term

• Current Assignee: Robert K. Anderson
• Original Assignee: Robert K. Anderson
• Inventors: Anderson, Robert K.
• Primary Examiner(s): Goldberg, Gerald
• Application Number:
  US05/139,085
• Time in Patent Office: 543 Days
• Field of Search: 128/303.13,303.14,303.15,303.16,303.17,419R,DIG.22 321/2,4 331/61
• US Class Current: 606/37
• CPC Class Codes: A61B 18/12 by passing a current through the tissue to be heated, e.g. high-frequency current
• CPC Class Codes: A61B 18/1206 Generators therefor
• CPC Class Codes: A61B 2018/0066 without feedback, i.e. open loop control
• CPC Class Codes: Y10S 128/22 Blood coagulation

Abstract

An isolated output electrosurgical generator suitable for generating cutting and coagulation electrosurgical currents is described. The electrosurgical generator using a single power stage generates three distinct and independent currents-a coagulation current for hemostasis or tissue destruction; a pure cutting current for cutting with a minimum amount of hemostasis; and a blended cutting current with a moderate amount of hemostasis. The electrosurgical generator includes a solid state power stage driven by two discrete frequencies that provide substantially differing cutting and coagulation characteristics. The electrosurgical generator also includes a solid state control circuit that controls the operation of the power stage. More specifically, the control circuit controls whether the power stage generates a current near the resonant frequency of the LC circuit so that a coagulation current or a blended cutting current is generated or whether the power stage generates a current at another frequency whereby a pure cutting current is generated. The output from the power stage is connected through an output circuit to suitable electrosurgical instrument terminals. An indicator circuit is used to provide audio and visual indication of activation of the electrosurgical generator. In addition, the electrosurgical generator provides electrical isolation on all output connections to prevent patient burns caused by alternate return current paths.

Claims

1. An electrosurgical generator suitable for generating cutting and coagulation electrosurgical currents comprising:

a power stage means including a resonant circuit for selectively generating a cutting current at a voltage and a frequency suitable for performing a cutting electrosurgical operation and a coagulation current at a voltage and a frequency suitable for performing a coagulation electrosurgical operation, the voltage of said cutting current having a substantially constant peakto-peak value and the voltage of said coagulation current having a decaying envelope with a maximum peak-to-peak value greater than the peak-to-peak value of said cutting current, the frequency of said cutting current being different than the frequency of said coagulation current, said resonant circuit resonating at the frequency of said coagulation current but not at the frequency of said cutting current;

a control circuit means connected to said power stage means for controlling the operation of said power stage means in a manner such that the cutting current and the coagulation current are selectively generated; and

, an output circuit means connected to said power stage means for applying the cutting current and the coagulation current selectively generated by said power stage means to instruments suitable for performing cutting and coagulation electrosurgical operations.

2. An electrosurgical generator as claimed in claim 1 wherein said resonant circuit is an LC resonant circuit.

3. An electrosurgical generator as claimed in claim 2 wherein said control circuit means includes an astable multivibrator and an oscillator, said astable multivibrator and said oscillator being connected together so as to generate a combined signal, said combined signal being applied to said power stage so as to selectively control the generation of said cutting current and said coagulation current by said power stage in accordance with the nature of said combined signal.

4. An electrosurgical generator as claimed in claim 3 wherein said output circuit means is coupled to said control circuit means so as to control the nature of said combined signal.

5. An electrosurgical generator as claimed in claim 4 including an indicator circuit means connected to said control circuit means for providing an indication of the mode of operation of said electrosurgical generator.

6. An electrosurgical generator as claimed in claim 5 including a power supply means connected to said power stage means, said control circuit means and said output circuit means for receiving AC power at one level and for applying AC power at different levels to said power stage means, said control circuit means and said output circuit means.

7. An electrosurgical generator as claimed in claim 6 wherein said power stage means comprises:

a diode bridge circuit connected to said power supply means to rectify the AC power from said power supply means;

a transformer having primary and secondary windings;

a first capacitor, said first capacitor being connected across the outpUt of said bridge;

a second capacitor, the primary winding of said transformer and said second capacitor being connected in series and said series connection being connected in parallel with said first capacitor, said transformer, said first capacitor, and said second capacitor comprising said LC resonant circuit;

a plurality of power transistors connected in parallel, the emitter-collector junctions of said plurality of power transistors being connected in parallel with said second capacitor; and

, a control transistor, said control transistor having its base connected to said control circuit means and its emitter-collector junction connected to the bases of said plurality of power transistors and to the primary winding of said transformer.

8. An electrosurgical generator as claimed in claim 7 wherein said control circuit means also includes:

a capacitor;

a resistor;

a first switch, said capacitor, said resistor and said first switch being connected so as to connect said capacitor and resistor in series across the output of said astable multivibrator when said first switch is in a predetermined position;

a second switch;

a second resistor, said second resistor and said second switch being connected so as to apply said second resistance between said astable multivibrator and the output of said oscillator when said second switch is in a predetermined position;

a third switch;

a third resistor, said third switch and said third resistor being connected so that said third resistor can be connected in parallel with said second resistor when said third switch is in a predetermined position;

a transformer having its primary winding connected across the output of said astable multivibrator, said primary winding having a center tap connected to said oscillator; and

, a voltage divider connected to the secondary winding of said transformer for applying the signal on the secondary winding of said transformer to the control transistor of said power stage.

9. An electrosurgical generator as claimed in claim 8 wherein said output circuit includes a plurality of chokes connected so as to isolate the output of said power stage from the power input to said electrosurgical generator.

10. An electrosurgical generator as claimed in claim 2 wherein said power stage means comprises:

a diode bridge circuit connected to said power supply means to rectify the AC power from said power supply means;

a transformer having primary and secondary windings;

a first capacitor, said first capacitor being connected across the output of said bridge;

a second capacitor, the primary winding of said transformer and said second capacitor being connected in series and said series connection being connected in parallel with said first capacitor, said transformer, said first capacitor and said second capacitor comprising said LC resonant circuit;

a plurality of power transistors connected in parallel, the emitter-collector junctions of said plurality of power transistors being connected in parallel with said second capacitor; and

, a control transistor, said control transistor having its base connected to said control circuit means and its emitter-collector junction connected to the bases of said plurality of power transistors and to the primary winding of said transformer.

11. An electrosurgical generator as claimed in claim 1 wherein said control circuit means includes an astable multivibrator and an oscillator, said astable multivibrator and said oscillator being connected together so as to generate a combined signal, said combined signal being applied to said power stage so as to selectively control the generation of said cutting current and said coagulation current by said power stage in accordance with the nature of said combined signal.

12. An electrosurgical generator as claimed in claim 11 wherein said output circuit means is coupled to said control circuit means so as to control the nature of said combined siGnal.

13. An electrosurgical generator as claimed in claim 12 wherein said power stage means comprises:

a diode bridge circuit connected to a power supply means to rectify the AC power from said power supply means;

a transformer having primary and secondary windings;

a first capacitor, said first capacitor being connected across the output of said bridge;

a second capacitor, the primary winding of said transformer and said second capacitor being connected in series and said series connection being connected in parallel with said first capacitor, said transformer, said first capacitor and said second capacitor comprising said resonant circuit;

a plurality of power transistors connected in parallel the emitter-collector junctions of said plurality of power transistors being connected in parallel with said second capacitor; and

, a control transistor, said control transistor having its base connected to said control circuit means and its emitter-collector junction connected to the bases of said plurality of power transistors and to the primary winding of said transformer.

14. An electrosurgical generator as claimed in claim 13 wherein said control circuit means also includes:

a capacitor;

a resistor;

a first switch, said capacitor, said resistor and said first switch being connected so as to connect said capacitor and resistor in series across the output of said astable multivibrator when said first switch is in a predetermined position;

a second switch;

a second resistor, said second resistor and said second switch being connected to as to apply said second resistance between said astable multivibrator and the output of said oscillator when said second switch is in a predetermined position;

a third switch;

a third resistor, said third switch and said third resistor being connected so that said third resistor can be connected in parallel with said second resistor when said third switch is in a predetermined position;

a transformer having its primary winding connected across the output of said astable multivibrator, said primary winding having a center tap connected to said oscillator; and

, a voltage divider connected to the secondary winding of said transformer for applying the signal on the secondary winding of said transformer to the control transistor of said power stage.

15. An electrosurgical generator as claimed in claim 14 wherein said output circuit includes a plurality of chokes connected so as to isolate the output of said power stage from the power input to said electrosurgical generator.

16. An electrosurgical generator as claimed in claim 1 wherein said output circuit includes a plurality of chokes connected so as to isolate the output of said power stage from the power input to said electrosurgical generator.

17. An electrosurgical generator suitable for generating cutting and coagulation electrosurgical currents comprising:

a power stage means having frequency responsive characteristics for selectively generating a cutting current at a voltage and a frequency suitable for performing a cutting electrosurgical operation and a coagulation current at a voltage and a frequency suitable for performing a coagulation electrosurgical operation, said coagulation and cutting currents differing substantially in frequency so that said frequency responsive characteristics aid in controlling the voltage magnitude of said cutting and coagulation currents;

a control circuit means connected to said power stage means for controlling the operation of said power stage means in a manner such that the cutting current and the coagulation current are selectively generated; and

, an output circuit means connected to said power stage means for applying the cutting current and the coagulation current selectively generated by said power stage means to instruments suitable for performing cutting and coagulation electrosurgical operations in a manner that isolates said instruments from outside eleCtrical returns.

18. An electrosurgical generator as claimed in claim 17 wherein the frequency responsive characteristics of said power stage means are provided by an LC circuit that resonates at the frequency of said coagulation current.

19. An electrosurgical generator as claimed in claim 17 wherein said output circuit includes a plurality of chokes connected to provide the isolation between said instruments from said outside electrical returns.

20. An electrosurgical generator suitable for generating cutting and coagulation electrosurgical currents comprising:

a power stage means for selectively generating a cutting current at a voltage and a frequency suitable for performing a cutting electrosurgical operation and a coagulation current at a voltage and a frequency suitable for performing a coagulation electrosurgical operation;

a control circuit means connected to said power stage means for controlling the operation of said power stage means in a manner such that the cutting current and the coagulation current are selectively generated; and

, an output circuit means connected to said power stage means for applying the cutting current and the coagulation current selectively generated by said power stage means to instruments suitable for performing cutting and coagulation electrosurgical operations in a manner that isolates said instruments from outside electrical returns.

21. An electrosurgical generator suitable for generating cutting and coagulation electrosurgical currents comprising:

a power stage means having frequency responsive characteristics for selectively generating a cutting current at a voltage and a frequency suitable for performing a cutting electrosurgical operation and a coagulation current at a voltage and a frequency suitable for performing a coagulation electrosurgical operation, said coagulation and cutting current differing substantially in frequency so that said frequency responsive characteristics aid in controlling the voltage magnitude of said cutting and coagulation currents;

a control circuit means connected to said power stage means for controlling the operation of said power stage means in a manner such that the cutting current and the coagulation current are selectively generated; and

, an output circuit means connected to said power stage means for applying the cutting current and the coagulation current selectively generated by said power stage means to instruments suitable for performing cutting and coagulation electrosurgical operations.

22. An electrosurgical generator suitable for generating electrosurgical cutting and coagulation currents comprising:

a single power stage means for selectively generating a cutting current at a voltage and a frequency suitable for performing an electrosurgical cutting operation, a coagulation current at a voltage and a frequency suitable for performing an electrosurgical coagulation operation, and a blended current at a voltage and a frequency suitable for performing electrosurgical cutting with a minimum amount of hemostasis;

a control circuit means connected to said power stage means for controlling the operation of said power stage means in a manner such that the cutting current, coagulation current and blended current are selectively generated; and

, an output circuit means connected to said power stage means for applying the cutting current, the coagulation current and the blended current selectively generated by said power stage means to instruments suitable for performing cutting and coagulation electrosurgical operations.

23. In an electrosurgical apparatus wherein an electrosurgical current, generated by an electrosurgical generator connected to an external power source, is applied to an electrosurgical instrument and returns to said electrosurgical generator via an indifferent electrode electrically contacting a patient to be operated on by said electrosurgical instrument, the improvement comprising isolation means for isolating said electrosurgiCal generator from all electrical returns other than the return provided by said indifferent electrode.

24. The improvement claimed in claim 23 wherein said isolation means comprises at least one inductor connected to prevent current flow between said external power source and the output of said electrosurgical generator.