Electrosurgical instrument
An embodiment of the invention includes an electrosurgical jaw structure that carries cooperating PTC bodies in both series and parallel circuit components for controlled RF energy application to engaged tissue to effectively weld tissue.
1. A bi-polar electrosurgical instrument with first and second energy-delivery surface elements coupled in series to an RF source, the first surface element overlying and electrically coupled to a first PTC body, wherein the first surface element and the first PTC body are coupled in parallel to the RF source.
2. An electrosurgical instrument as in claim 1 , wherein the second surface element comprises a second PTC body.
3. An electrosurgical instrument as in claim 2 , wherein the first and second PTC bodies have different temperature-impedance curves.
4. An electrosurgical instrument as in claim 2 , wherein the second PTC body has a lower impedance in a temperature range of about 40° C. to 60° C. than the first PTC body in substantially the same range.
5. An electrosurgical instrument as in claim 2 , wherein the second PTC body has an impedance at about 40° C. of between about 0.1 ohm and 20 ohms.
6. An electrosurgical instrument as in claim 2 , wherein the second PTC body has an impedance at 40° C. of greater that about 10 ohms.
7. An electrosurgical instrument as in claim 2 , wherein the second PTC body has a switching range between about 80° C. and 140° C.
8. An electrosurgical instrument as in claim 2 , wherein the second PTC body has a switching range between about 90° C. and 130° C.
9. An electrosurgical instrument as in claim 2 , wherein the second PTC body has a switching range between about 100° C. and 120° C.
10. An electrosurgical instrument as in claim 1 , wherein the first PTC body has a switching range between about 60° C. and 120° C.
11. An electrosurgical instrument as in claim 1 , wherein the first PTC body has a switching range between about 70° C. and 120° C.
12. An electrosurgical instrument as in claim 1 , wherein the first PTC body has a switching range between about 80° C. and 120° C.
13. An electrosurgical instrument as in claim 1 , further comprising a sensor system coupled to the RF source for measuring impedance of the series-parallel circuitry.
14. An electrosurgical instrument as in claim 13 , wherein the sensor system includes algorithms for deriving tissue temperature from the measured impedance.
15. An electrosurgical instrument as in claim 13 , further comprising a controller coupled to the RF source.
16. An electrosurgical instrument as in claim 15 , wherein the controller is configured to modulate power delivered to the first and second surface elements in response to measured impedance of the series-parallel circuitry.
17. An electrosurgical instrument as in claim 15 , wherein the controller includes algorithms for comparing a selected time-temperature curve to a measured time-temperature curve.
18. An electrosurgical instrument as in claim 17 , wherein the controller includes algorithms for modulating power to maintain the selected temperature-time curve.
19. A bi-polar electrosurgical instrument as in claim 1 , wherein the first and second energy-delivery surface elements are carried in respective first and second openable-closeable jaws.
20. A bi-polar electrosurgical instrument as in claim 19 , wherein the first energy-delivery surface element and the first PTC body are both partly exposed in a jaw engagement surface.
21. An electrosurgical instrument for applying energy to a body structure, the instrument comprising first and second jaws defining first and second energy-application surfaces, the first surface comprising a first polarity electrode portion and an electrically coupled PTC portion within a first circuit portion connected to an RF source, the second surface comprising a second polarity electrode and an electrically coupled PTC portion within a second circuit portion connected to the RF source, wherein the first and second circuit portions are configured as parallel and series circuits respectively.
22. A bi-polar electrosurgical instrument comprising:
an RF source; and
first and second energy-delivery means coupled in series to the RF source, the first energy-delivery means overlying and electrically coupled to a first PTC component means, wherein the first energy-delivery means and the first PTC component means are coupled in parallel to the RF source.