Regulated-current power supply and methods for resistively-heated surgical instruments

• US 5,445,635 A
• Filed: 07/06/1994
• Issued: 08/29/1995
• Est. Priority Date: 05/01/1992
• Status: Expired due to Fees

• Current Assignee: Hemostatic Surgery Corporation
• Original Assignee: Hemostatic Surgery Corporation
• Inventors: Weller, Albert E., Denen, Dennis J.
• Primary Examiner(s): Pellegrino, Stephen C.
• Assistant Examiner(s): Harris, Sonya C.
• Application Number:
  US08/271,388
• Time in Patent Office: 419 Days
• Field of Search: 606/27, 606/28, 606/29, 606/30, 606/31, 606/32, 606/33, 606/34, 606/35, 606/36, 606/37, 606/38, 606/39, 606/40, 606/41, 606/42, 606/43, 606/44, 606/45, 606/48, 606/49, 606/50
• US Class Current: 606/27
• CPC Class Codes: A61B 18/08 by means of electrically-heated probes

Abstract

A power supply for use with resistively-heated surgical instruments is provided, wherein the desired operating conditions of the surgical instrument are determined by a set-point determination circuit in combination with a set-point indicator element. The power supply includes an impedance matching circuit and current step-up transformer for reducing power loss in the cable connecting the surgical instrument to the power supply. A method of regulating the output of a power supply used with resistively-heated surgical instruments is also provided.

Claims

1. Apparatus for performing surgery comprising:

a surgical instrument having a resistively-heated heating element;

a power supply for supplying an alternating current to the heating element, the power supply comprising;

a current supply circuit having a control terminal for accepting a control signal and having a first current supply circuit output terminal and a second current supply circuit output terminal for supplying the alternating current to the heating element coupled therebetween, the current supply circuit supplying the alternating current to the heating element in response to the control signal;

a current feedback circuit coupled between the second current supply circuit output terminal and the heating element for monitoring the alternating current as it is supplied by the current supply circuit, the current feedback circuit having a current feedback terminal for supplying a current feedback signal indicative of a magnitude of the alternating current as it is monitored by the current feedback circuit;

an error amplifier having a first error amplifier input for accepting a set-point signal, a second error amplifier input for accepting the current feedback signal, and an error amplifier output terminal for coupling the control signal, indicative of a difference between the set-point signal and the current feedback signal, to the control terminal of the current supply circuit, the error amplifier output terminal being coupled to the control terminal of the current supply circuit; and

means for generating the set-point signal, the means for generating the set-point signal having a set-point output terminal coupled to the first error amplifier input, wherein the set-point signal is indicative of a predetermined magnitude of the alternating current corresponding to a predetermined heating element operating temperature and so that the alternating current supplied to the heating element is regulated to the predetermined magnitude set by the set-point generating means.

2. Apparatus for performing surgery as defined in claim 1 wherein the means for generating set-point signals further comprises:

a set-point indicator element disposed within the surgical instrument, the set-point indicator element having an impedance value indicative of a desired heating element operating temperature;

means for applying a voltage across the set-point indicator element;

means for measuring current through the set-point indicator element responsive to the voltage applied across the set-point indicator element; and

means for selecting a set-point signal in response to the measured current to substantially maintain the heating element at the desired operating temperature.

3. Apparatus for performing surgery as defined in claim 2 wherein the set-point indicator element comprises a resistor having a resistance indicative of the desired heating element operating temperature.

4. Apparatus for performing surgery as defined in claim 1 wherein the surgical instrument further comprises a handle and a current step-up transformer disposed in the handle, and first and second leads, the current step-up transformer having a primary wire winding connected to the power supply and a secondary winding connected to the first and second electrical leads, the secondary winding comprising:

a washer having a periphery and a portion defining a centrally located aperture;

an inner tube having a central bore, first and second ends and an interior surface of the inner tube and an exterior surface of the inner tube, the washer affixed to the first end of the inner tube so that the central bore registers with the centrally located aperture of the washer;

an outer tube having a central bore, first and second ends, and interior and exterior surfaces, the washer affixed to the first end of the outer tube along its periphery, so that the washer, the exterior surface of the inner tube, and the interior surface of the outer tube form an assembly defining a closed-end annulus;

a plurality of magnetic toroids disposed in the closed-end annulus, each toroid being coated with an electrically insulating material;

a first terminal affixed to the interior surface of the inner tube; and

a second terminal affixed to the exterior surface of the outer tube at a position diametrically opposing the first terminal, wherein the primary wire winding comprises a plurality of wire turns wrapped on the secondary winding so that each wire turn of the primary wire winding traverses the exterior surface of the outer tube, through the aperture in the washer, and along the inner surface of the inner tube, the plurality of primary wire turns having leads coupled to the power supply.

5. Apparatus for performing surgery as defined in claim 4 wherein the surgical instrument is coupled to the power supply by a cable so that the surgical instrument and cable present an impedance to the flow of alternating current, and wherein the current step-up transformer further comprises a series resonance capacitor disposed from the second terminal to match the electrical impedance of the surgical instrument to the power supply and cable to provide for efficient transmission of power therebetween.

6. Apparatus for performing surgery as defined in claim 1 wherein the current supply circuit further comprises:

an oscillator circuit that generates a high frequency signal of variable amplitude, the oscillator circuit having oscillator circuit input means and oscillator circuit output means, the oscillator circuit input means being the control terminal of the current supply circuit that is coupled to the error amplifier output terminal;

an oscillator buffer circuit that decouples and amplifies the high frequency signal, the oscillator buffer circuit having oscillator buffer circuit input means coupled to the oscillator circuit output means and the oscillator buffer circuit having oscillator buffer circuit output means; and

a push-pull amplifier for further amplifying the decoupled and amplified high frequency signal, the push-pull amplifier having push-pull amplifier input means and push-pull amplifier output means, the push-pull amplifier input means being coupled to the oscillator buffer circuit output means, the push-pull amplifier output means being the first and second current supply circuit output terminals.

7. Apparatus for performing surgery as defined in claim 6 wherein the oscillator buffer circuit comprises:

an isolation buffer circuit for decoupling the oscillator circuit from the push-pull amplifier, the isolation buffer circuit having isolation buffer circuit input means coupled to the oscillator circuit output means and isolation buffer circuit output means; and

a power buffer circuit for amplifying the current level of the oscillator circuit signal, the power buffer circuit having power buffer circuit input means coupled to the isolation buffer circuit output means and power buffer circuit output means coupled to the push-pull amplifier input means.

8. Apparatus for performing surgery as defined in claim 7 wherein the current feedback circuit further comprises:

a current step-down transformer for providing a stepped-down current signal, the current step-down transformer having current step-down input means coupled to the push-pull amplifier output means and current step-down output means;

a burden resistor for converting the stepped-down current signal supplied by the current step-down transformer to a corresponding voltage level signal, the burden resistor being coupled across the current step-down output means; and

a converter circuit for converting the corresponding voltage level signal from an alternating current (AC) signal to a direct current (DC) signal, the converter circuit having converter circuit input means coupled across the burden resistor and converter circuit output means coupled to the second error amplifier input.

9. Apparatus for performing surgery as defined in claim 1 wherein the means for generating set-point signals further comprises:

a microprocessor for establishing the set-point signal to substantially maintain the heating element at the operating temperature.

10. Apparatus for performing surgery as defined in claim 9 wherein:

the material of the heating element further comprises a material that exhibits a Curie transition in permeability; and

the operating temperature corresponds to an auto-regulation temperature.

11. Apparatus for performing surgery comprising:

a surgical instrument having a resistively-heated heating element;

a power supply for supplying an alternating current to the heating element, the power supply comprising;

a current supply circuit having a control terminal for accepting a control signal and having a first current supply circuit output terminal and a second current supply circuit output terminal for supplying an alternating current to the heating element coupled therebetween, the current supply circuit supplying alternating current to the heating element in response to the control signal;

a current feedback circuit coupled between the second current supply circuit output terminal and the heating element for monitoring the alternating current, the current feedback circuit having a current feedback terminal for supplying a current feedback signal indicative of a magnitude of the alternating current that is monitored by the current feedback circuit;

an error amplifier having a first error amplifier input for accepting a set-point signal, a second error amplifier input for accepting the current feedback signal, and an error amplifier output terminal for coupling the control signal, indicative of a difference between the set-point signal and the current feedback signal, to the control terminal of the current supply circuit, the error amplifier output terminal being coupled to the control terminal of the current supply circuit; and

means for generating the set-point signal, the means for generating the set-point signal having a set-point output terminal coupled to the first error amplifier input, wherein the set-point signal is indicative of a predetermined magnitude of alternating current corresponding to a predetermined heating element operating temperature and so that the alternating current supplied to the heating element is regulated to the predetermined magnitude set by the set-point generating means, wherein the means for generating set-point signals further comprises;

a set-point indicator element disposed within the surgical instrument, the set-point indicator element having an impedance value indicative of a desired heating element operating temperature;

means for applying a current across the set-point indicator element;

means for measuring a voltage drop across the set-point indicator element responsive to the current applied across the set-point indicator element; and

means for selecting a set-point signal in response to the measured voltage drop.

12. Apparatus for performing surgery as defined in claim 11 wherein the means for generating set-point signals comprises:

a high frequency choke circuit for isolating the means for generating set-point signals from high frequency components of the alternating current in the surgical instrument, the high frequency choke circuit having high frequency choke circuit input means for coupling to a cable that in turn is coupled to the set-point indicator element and high frequency choke circuit output means;

an analysis circuit for detecting a value of the set-point indicator element and supplying a set-point signal that corresponds to the value of the set-point indicator element, the analysis circuit having analysis circuit input means coupled to the high frequency choke circuit output means and analysis circuit output means; and

an isolation buffer to prevent the feedback of high frequency signals from the current supply circuit from entering the analysis circuit, the isolation buffer having isolation buffer input means coupled to the analysis circuit output means and analysis circuit output means coupled to the second error amplifier input.

13. Apparatus for performing surgery comprising:

a surgical instrument having a resistively-heated heating element;

a power supply for supplying an alternating current to the heating element, the power supply comprising;

a current supply circuit having a control terminal for accepting a control signal and having a first current supply circuit output terminal and a second current supply circuit output terminal for supplying an alternating current to the heating element coupled therebetween, the current supply circuit supplying alternating current to the heating element in response to the control signal;

a current feedback circuit coupled between the second current supply circuit output terminal and the heating element for monitoring the alternating current, the current feedback circuit having a current feedback terminal for supplying a current feedback signal indicative of a magnitude of the alternating current that is monitored by the current feedback circuit;

an error amplifier having a first error amplifier input for accepting a set-point signal, a second error amplifier input for accepting the current feedback signal, and an error amplifier output terminal for coupling the control signal, indicative of a difference between the set-point signal and the current feedback signal, to the control terminal of the current supply circuit, the error amplifier output terminal being coupled to the control terminal of the current supply circuit; and

means for generating the set-point signal, the means for generating the set-point signal having a set-point output terminal coupled to the first error amplifier input, wherein the set-point signal is indicative of a predetermined magnitude of alternating current corresponding to a predetermined heating element operating temperature and so that the alternating current supplied to the heating element is regulated to the predetermined magnitude set by the set-point generating means, wherein the means for generating set-point signals further comprises;

a set-point indicator element disposed within the surgical instrument, the set-point indicator element having an impedance value indicative of a desired heating element operating temperature;

means for applying a current across the set-point indicator element;

means for measuring a voltage drop across the set-point indicator element responsive to the current applied across the set-point indicator element; and

means for selecting a set-point signal in response to the measured voltage drop, wherein the set-point indicator element comprises a resistor having a resistance indicative of the desired heating element operating temperature.

14. Apparatus for performing surgery comprising:

a surgical instrument having a resistively-heated heating element;

a power supply for supplying an alternating current to the heating element to substantially maintain the surgical instrument at a desired operating temperature, the power supply comprising;

a current supply circuit having a control terminal for accepting a control signal and having a first output terminal and a second output terminal for supplying the alternating current to the heating element coupled therebetween, the current supply circuit supplying the alternating current to the heating element in response to the control signal;

a current feedback circuit coupled between the second output terminal and the heating element for monitoring the alternating current as it is supplied by the current supply circuit, the current feedback circuit having a current feedback terminal for supplying a current feedback signal indicative of a magnitude of the alternating current as it is monitored by the current feedback circuit; and

an error amplifier having a first input for accepting a set-point signal, a second input coupled to the current feedback terminal for accepting the current feedback signal, and an output terminal for coupling the control signal, indicative of the difference between the set-point signal and the current feedback signal, to the control terminal of the current supply circuit; and

a circuit for generating the set-point signal wherein the set-point signal is indicative of a predetermined magnitude of the alternating current corresponding to a predetermined heating element operating temperature and so that the alternating current supplied to the heating element is regulated to the predetermined magnitude set by the set-point generating means to substantially maintain the heating element at the desired predetermined heating element operating temperature.

15. Apparatus for performing surgery as defined in claim 14 wherein the means for generating set-point signals further comprises:

a microprocessor for establishing the set-point signal to substantially maintain the heating element at the operating temperature.

16. Apparatus for performing surgery as defined in claim 15 wherein:

the heating element further comprises a material that exhibits a Curie transition in permeability; and

the operating temperature corresponds to an auto-regulation temperature.

17. Apparatus for performing surgery comprising:

a surgical instrument having a resistively-heated heating element;

a power supply for supplying an alternating current to the heating element to substantially maintain the surgical instrument at a desired operating temperature, the power supply comprising;

a current supply circuit having a control terminal for accepting a control signal and having a first output terminal and a second output terminal for supplying an alternating current to the heating element coupled therebetween, the current supply circuit supplying alternating current to the heating element in response to the control signal;

a current feedback circuit coupled between the second output terminal of the current supply circuit and the heating element for monitoring the alternating current, a monitored alternating current having a magnitude, the current feedback circuit having a current feedback terminal for supplying a current feedback signal indicative of the magnitude of the monitored alternating current;

an error amplifier having a first input for accepting a set-point signal, a second input coupled to the current feedback terminal for accepting the current feedback signal, and an output terminal for coupling the control signal, indicative of the difference between the set-point signal and the current feedback signal, to the control terminal of the current supply circuit; and

a circuit for generating the set-point signal wherein the set-point signal is indicative of a predetermined magnitude of alternating current corresponding to a predetermined heating element operating temperature and so that the alternating current supplied to the heating element is regulated to the predetermined magnitude set by the set-point generating means to substantially maintain the heating element at the desired predetermined heating element operating temperature, wherein the surgical instrument further comprises a handle and a current step-up transformer disposed in the handle, and first and second leads, the current step-up transformer having a primary wire winding connected to the power supply and a secondary winding connected to the first and second electrical leads, the secondary winding comprising;

a washer having a periphery and a portion defining a centrally located aperture;

an inner tube having a central bore, first and second ends and interior and exterior surfaces, the washer affixed to the first end of the inner tube so that the central bore registers with the centrally located aperture of the washer;

an outer tube having a central bore, first and second ends, and interior and exterior surfaces, the washer affixed to the first end of the outer tube along its periphery, so that the washer, the exterior surface of the inner tube, and the interior surface of the outer tube form an assembly defining a closed-end annulus;

a plurality of magnetic toroids disposed in the closed-end annulus, each toroid being coated with an electrically insulating material;

a first terminal affixed to the interior surface of the inner tube; and

a second terminal affixed to the exterior surface of the outer tube at a position diametrically opposing the first terminal, wherein the primary wire winding comprises a plurality of wire turns wrapped on the secondary winding so that each wire turn of the primary wire winding traverses the exterior surface of the outer tube, through the aperture in the washer, and along the inner surface of the inner tube, the plurality of turns having leads coupled to the power supply.