System and method for augmented impedance sensing

• US 7,956,620 B2
• Filed: 08/12/2009
• Issued: 06/07/2011
• Est. Priority Date: 08/12/2009
• Status: Active Grant

• Current Assignee: Covidien LP (Medtronic Plc)
• Original Assignee: Tyco Healthcare Group LP (Medtronic Plc)
• Inventors: Gilbert, James A.
• Primary Examiner(s): Velez; Roberto
• Application Number:
  US12/540,190
• Publication Number:
  US 20110037484A1
• Time in Patent Office: 664 Days
• Field of Search: None
• US Class Current: 324/649
• CPC Class Codes: A61B 18/1206 Generators therefor
• CPC Class Codes: A61B 18/1233 with circuits for assuring patient safety
• CPC Class Codes: A61B 18/1445 at the distal end of a shaft, e.g. forceps or scissors at the end of a rigid rod
• CPC Class Codes: A61B 18/16 Indifferent or passive electrodes for grounding
• CPC Class Codes: A61B 2018/00875 Resistance or impedance
• CPC Class Codes: A61B 2018/1286 having a specific transformer

Abstract

An impedance monitoring circuit for an electrosurgical generator is disclosed. The monitoring circuit includes an isolation transformer coupled to at least one of an active terminal and a return terminal of an electrosurgical generator, wherein the isolation transformer includes a primary winding coupled to a reference resistor and a secondary winding coupled to a load. The monitoring circuit also includes a driver configured to transmit a sensor signal to the reference resistor and the load, a primary converter coupled to the reference resistor and the load and configured to detect a primary converted signal as a function of the sensor signal passing through the reference resistor and the load. The monitoring circuit further includes a secondary converter coupled to the driver and configured to detect a secondary converted signal as a function of the sensor signal prior to passing through the reference resistor and the load and a controller configured to determine a fault condition based on the primary and secondary converted signals.

Claims

1. An impedance monitoring circuit for an electrosurgical generator, the monitoring circuit comprising:

an isolation transformer coupled to at least one of an active terminal and a return terminal of an electrosurgical generator, wherein the isolation transformer includes a primary winding coupled to a reference resistor and a secondary winding coupled to a load;

a driver configured to transmit a sensor signal to the reference resistor and the load;

a primary converter coupled to the reference resistor and the load and configured to detect a primary converted signal as a function of the sensor signal passing through the reference resistor and the load;

a secondary converter coupled to the driver and configured to detect a secondary converted signal as a function of the sensor signal prior to passing through the reference resistor and the load; and

a controller including a preprogrammed offset value, wherein the controller is configured to determine a fault condition based on the primary and secondary converted signals and the offset value.

2. The impedance monitoring circuit according to claim 1, wherein the driver is a level shifter driver chip coupled to an oscillator configured to supply an oscillator signal thereto, and wherein the driver is configured to increase at least one of voltage and current of the oscillator signal.

3. The impedance monitoring circuit according to claim 2, wherein the controller is configured to determine existence of a fault condition with at least one of the driver and the oscillator when an amplitude of both of the primary and secondary converted signals is approximately 0 V.

4. The impedance monitoring circuit according to claim 2, wherein the controller is configured to determine existence of a short circuit condition when an amplitude of the primary converted signal is approximately 0 V.

5. The impedance monitoring circuit according to claim 1, wherein the reference resistor has a predetermined resistance from 1 kΩ

to 10 kΩ

.

6. The impedance monitoring circuit according to claim 5, wherein the controller is configured to determine existence of an open circuit condition when a resistance of the load is larger than the predetermined resistance of the reference resistor.

7. An impedance monitoring circuit for an electrosurgical generator, the monitoring circuit comprising:

an isolation transformer coupled to at least one of an active terminal and a return terminal of an electrosurgical generator, wherein the isolation transformer includes a primary winding coupled to a reference resistor and a secondary winding coupled to a load;

a driver configured to transmit a sensor signal to the reference resistor and the load;

a primary converter coupled to the reference resistor and the load and configured to detect a primary converted signal as a function of the sensor signal passing through the reference resistor and the load;

a secondary converter coupled to the driver and configured to detect a secondary converted signal as a function of the sensor signal prior to passing through the reference resistor and the load; and

a controller configured to determine a fault condition based on the primary and secondary converted signals.

8. The impedance monitoring circuit according to claim 7, wherein the driver is a level shifter driver chip coupled to an oscillator configured to supply an oscillator signal thereto, and wherein the driver is configured to increase at least one of voltage and current of the oscillator signal.

9. The impedance monitoring circuit according to claim 8, wherein the controller is configured to determine existence of a fault condition with at least one of the driver and the oscillator when an amplitude of both of the primary and secondary converted signals is approximately 0.

10. The impedance monitoring circuit according to claim 8, wherein the controller is configured to determine existence of a short circuit condition when an amplitude of the primary converted signal is approximately 0.

11. The impedance monitoring circuit according to claim 7, wherein the reference resistor has a predetermined resistance from 1 kΩ

to 10 kΩ

.

12. The impedance monitoring circuit according to claim 11, wherein the controller is configured to determine existence of an open circuit condition when a resistance of the load is larger than the predetermined resistance of the reference resistor.

13. A method for detecting a fault in an impedance monitoring circuit, the method comprising the steps of:

transmitting a sensor signal to a reference resistor coupled to a primary winding of an isolation transformer and a load coupled to a secondary winding of the isolation transformer;

detecting a primary converted signal as a function of the sensor signal passing through the reference resistor and the load;

detecting a secondary converted signal as a function of the sensor signal prior to passing through the reference resistor and the load; and

determining a fault condition based on the primary and secondary converted signals.

14. The method according to claim 13, wherein the transmitting step further includes the step of supplying an oscillator signal from an oscillator to a driver, wherein the driver is configured to increase at least one of voltage and current of the oscillator signal.

15. The method according to claim 14, wherein the determining step further includes the step of determining existence of a fault condition with at least one of the driver and the oscillator when an amplitude of both of the primary and secondary converted signals is approximately 0.

16. The method according to claim 14, wherein the determining step further includes the step of existence of a short circuit condition when an amplitude of the primary converted signal is approximately 0.

17. The method according to claim 13, wherein the reference resistor of the transmitting step has a predetermined resistance from 1 kΩ

to 10 kΩ

.

18. The method according to claim 17, wherein the determining step further includes the step of determining existence of an open circuit condition when a resistance of the load is larger than the predetermined resistance of the reference resistor.