Jaw position impedance limiter for electrosurgical instrument

[0001] Electrosurgical devices are used in many surgical operations. Electrosurgical devices apply electrical energy to tissue in order to treat tissue. An electrosurgical device may comprise an instrument having a distally-mounted end effector comprising one or more electrodes. The end effector can be positioned against tissue such that electrical current is introduced into the tissue. Electrosurgical devices can be configured for bipolar operation. During bipolar operation, current is introduced into and returned from the tissue by active and return electrodes, respectively, of the end effector. Bipolar devices may also have an end effector consisting of two or more jaws each having at least one of the active and or return electrodes. At least one of the jaws is moveable from a position spaced apart from the opposing jaw for receiving tissues to a position in which the space between the jaws is less than that of the first position. Movement of the moveable jaw compresses the tissue held between. Heat generated by the current flow through the tissue in combination with the compression achieved by the jaw movement may form hemostatic seals within the tissue and/or between tissues and thus may be particularly useful for sealing blood vessels, for example. The end effector of an electrosurgical device sometimes also comprises a cutting member that is movable relative to the tissue and the electrodes to transect the tissue.

[0002] Electrical energy applied by an electrosurgical device can be transmitted to the instrument by a generator. The electrical energy may be in the form of radio frequency (“RF”) energy. The electrical energy may be in the form of radio frequency (“RF”) energy that may be in a frequency range described in EN 60601-2-2:2009+A11:2011, Definition 201.3.218—HIGH FREQUENCY. For example, the frequency in monopolar RF applications are typically restricted to less than 5 MHz. However, in bipolar RF applications, the frequency can be almost anything. Frequencies above 200 kHz can be typically used for MONOPOLAR applications in order to avoid the unwanted stimulation of nerves and muscles which would result from the use of low frequency current. Lower frequencies may be used for BIPOLAR techniques if the RISK ANALYSIS shows the possibility of neuromuscular stimulation has been mitigated to an acceptable level. Normally, frequencies above 5 MHz are not used in order to minimize the problems associated with HIGH FREQUENCY LEAKAGE CURRENTS. However, higher frequencies may be used in the case of BIPOLAR techniques. It is generally recognized that 10 mA is the lower threshold of thermal effects on tissue.

[0003] During its operation, an electrosurgical device can transmit RF energy through tissue compressed between the two or more jaws. Such RF energy may cause ionic agitation in the tissue, in effect producing resistive heating, and thereby increasing the temperature of the tissue. Increased temperature of the tissue may lead to tissue cauterization. In some surgical procedures, RF energy may be useful for removing, shrinking, or sculpting soft tissue while simultaneously sealing blood vessels. RF energy may work particularly well on connective tissue, which is primarily comprised of collagen and shrinks when contacted by heat. Because a sharp boundary may be created between the affected tissue and the surrounding tissue, surgeons can operate with a high level of precision and control, without sacrificing un-targeted adjacent tissue.

[0004] In one aspect, an electrosurgical system may include an RF current generator, a handle body, an end effector having a first jaw including a first energy delivery surface in electrical communication with a first terminal of the RF current generator, and a second jaw including a second energy delivery surface in electrical communication with a second terminal of the RF current generator. The first jaw and the second jaw may form a jaw angle. The electrosurgical system may also have a shunt impedance circuit including a shunt impedance element having a pre-determined shunt impedance value, in which the shunt impedance element is reversibly placed electrically in parallel with the first energy delivery surface and the second energy delivery surface when the jaw angle is at least a pre-determined angle. The electrosurgical system may also include an impedance detector in electrical communication with the first energy delivery surface and the second energy delivery surface.

[0005] In one aspect of the electrosurgical system, first jaw that may be movable when a force is applied to the end effector.

[0006] In one aspect of the electrosurgical system, the second jaw may be movable when a force is applied to the end effector.

[0007] In one aspect of the electrosurgical system, the shunt impedance circuit may include a contactor in electrical communication with the shunt impedance element.

[0008] In one aspect of the electrosurgical system, the contactor may be configured to form an electrical contact with one or more electrical components of the first jaw or one or more electrical components of the second jaw.

[0009] In one aspect of the electrosurgical system, the contactor may be a spring-loaded contactor.

[0010] In one aspect of the electrosurgical system, the shunt impedance element may be one or more of a resistive element, a capacitive element, and an inductive element.

[0011] In one aspect the electrosurgical system, the pre-determined shunt impedance value may be an impedance value of a cauterized tissue.

[0012] In one aspect of the electrosurgical system, the shunt impedance circuit may include a shunt switch in electrical communication with the shunt impedance element.

[0013] In one aspect of the electrosurgical, the end effector may include the shunt impedance circuit.

[0014] In one aspect of the electrosurgical system, the handle body may include the shunt impedance circuit.

[0015] In one aspect, the electrosurgical system may further include an elongated shaft having a proximal end in mechanical communication with the handle body and a distal end in mechanical communication with the end effector.

[0016] In one aspect, the electrosurgical system may further include a scissor style device, in which the end effector is in mechanical communication with the handle.

[0017] In one aspect, an end effector for an electrosurgical device may include a first jaw having a first energy delivery surface designed to be in electrical communication with a first terminal of an RF current generator and a second jaw having a second energy delivery surface designed to be in electrical communication with a second terminal of the RF current generator. The first jaw and the second jaw may form a jaw angle, in which the first jaw, the second jaw, or the first jaw and the second jaw is/are movable. The end effector may also include a shunt impedance circuit including a shunt impedance element having a pre-determined shunt impedance value, in which the shunt impedance element may be reversibly placed electrically in parallel with the first energy delivery surface and the second energy delivery surface when the jaw angle is at least a pre-determined angle.

[0018] In one aspect of the end effector, the shunt impedance circuit may include a contactor in electrical communication with the shunt impedance element.

[0019] In one aspect of the end effector, the contactor may be a spring-loaded contactor.

[0020] In one aspect of the end effector, the contactor may be designed to form an electrical contact with one or more electrical components of the first jaw or one or more electrical components of the second jaw.

[0021] In one aspect, of the end effector, the shunt impedance element may be designed to form an electrical contact with one or more electrical components of the first jaw or one or more electrical components of the second jaw.

[0022] In one aspect of the end effector, the shunt impedance element may be one or more of a resistive element, a capacitive element, and an inductive element.

[0023] In one aspect of the end effector, the pre-determined shunt impedance value may be an impedance value of a cauterized tissue.

[0024] In one aspect of the end effector, the shunt impedance circuit may include a shunt switch in electrical communication with the shunt impedance element.

[0025] In one aspect, a method of controlling an RF current delivered to an end effector of an electrosurgical system may include providing an electrosurgical system that may include an RF current generator, a handle body, an end effector, a shunt impedance circuit, an impedance detector, and a controller of the RF current generator; The end effector may include a first jaw having a first energy delivery surface in electrical communication with a first terminal of the RF current generator and a second jaw comprising a second energy delivery surface in electrical communication with a second terminal of the RF current generator. The first jaw and the second jaw may form a jaw angle therebetween. The shunt impedance circuit may include a shunt impedance element having a pre-determined shunt impedance value and the shunt impedance element may be reversibly placed electrically in parallel with the first energy delivery surface and the second energy delivery surface when the jaw angle is at least a pre-determined angle. The impedance detector may be in electrical communication with the first energy delivery surface and the second energy delivery surface. The method may also include sourcing an RF current from the RF current generator to the first energy delivery surface via the first terminal of the RF current generator and receiving an RF current by the RF current generator from the second energy delivery surface via the second terminal of the RF current generator. The method may further include measuring an impedance between the first energy delivery surface and the second energy delivery surface by the impedance detector, and causing the controller of the RF current generator to disable sourcing the RF current to the first energy delivery surface when a measured impedance between the first energy delivery surface and the second energy delivery surface is greater than a pre-determined impedance limit.

[0026] In one aspect of the method, the RF current generator may include the impedance detector.

[0027] In one aspect of the method, the RF current generator may generate an RF current of about 100 kHz to about 1 MHz.

[0028] In one aspect of the method, the pre-determined impedance limit may be an impedance of a cauterized tissue.

[0050] Reference will now be made in detail to several aspects, including example implementations of electrosurgical medical instruments for cutting and coagulating tissue. Wherever practicable similar or like reference numbers may be used in the figures and may indicate similar or like functionality. The figures depict examples of the disclosed surgical instruments and/or methods of use for purposes of illustration only. One skilled in the art will readily recognize from the following description that alternative examples of the structures and methods illustrated herein may be employed without departing from the principles described herein.

[0051] Various aspects of surgical instruments that utilize therapeutic and/or sub-therapeutic electrical energy to treat tissue or provide feedback to the generators (e.g., electrosurgical instruments). The various aspects are adapted for use in a manual or hand operated manner, although electrosurgical instruments may be utilized in robotic applications as well.

[0052] FIG. 1 is a perspective view of one example of a surgical instrument system 100 comprising an electrical energy surgical instrument 110. The electrosurgical instrument 110 may comprise a proximal handle 112, a distal working end or end effector 126 and an introducer or elongated shaft 114 disposed in-between. Alternatively, the end effector may be attached directly to the handle as in scissor style devices such as the electrosurgical instrument described in U.S. Pat. No. 7,582,087.

[0053] The electrosurgical system 100 can be configured to supply energy, such as electrical energy, ultrasonic energy, heat energy, or any combination thereof, to the tissue of a patient either independently or simultaneously, for example. In one example, the electrosurgical system 100 may include a generator 120 in electrical communication with the electrosurgical instrument 110. The generator 120 may be connected to the electrosurgical instrument 110 via a suitable transmission medium such as a cable 122. In one example, the generator 120 may be coupled to a controller, such as a control unit 125, for example. In various aspects, the control unit 125 may be formed integrally with the generator 120 or may be provided as a separate circuit module or device electrically coupled to the generator 120 (shown in phantom to illustrate this option). The control unit 125 may include automated or manually operated controls to control the amount of current delivered by the generator 120 to the electrosurgical instrument 110. Although as presently disclosed, the generator 120 is shown separate from the electrosurgical instrument 110, in some aspects, the generator 120 (and/or the control unit 125) may be formed integrally with the electrosurgical instrument 110 to form a unitary electrosurgical system 100, where a battery located within the electrosurgical instrument 110 may be the energy source and a circuit coupled to the battery produces the suitable electrical energy, ultrasonic energy, or heat energy.

[0054] In one aspect, the generator 120 may comprise an input device located on a front panel of the generator 120 console. The input device may comprise any suitable device that generates signals suitable for programming the operation of the generator 120, such as a keyboard, or input port, for example. In one example, one or more electrodes in the first jaw 164a and one or more electrodes in the second jaw 164b may be coupled to the generator 120. The cable 122 may comprise multiple electrical conductors for the application of electrical energy to a first electrode (which may be designated as a + electrode) and to a second electrode (which may be designated as a − electrode) of the electrosurgical instrument 110. It may be recognized that + and − designations are made solely for convenience and do not indicate an electrical polarity. An end of each of the conductors may be placed in electrical communication with a terminal of the generator 120. The generator 120 may have multiple terminals, each configured to contact one or more of the conductors. The control unit 125 may be used to activate the generator 120, which may serve as an electrical source. In various aspects, the generator 120 may comprise an RF source, an ultrasonic source, a direct current source, and/or any other suitable type of electrical energy source, for example, which may be activated independently or simultaneously.

[0055] In various aspects, the electrosurgical system 100 may comprise at least one supply conductor 131 and at least one return conductor 133, wherein current can be supplied to the electrosurgical instrument 110 via the at least one supply conductor 131 and wherein the current can flow back to the generator 120 via the at least one return conductor 133. In various aspects, the at least one supply conductor 131 and the at least one return conductor 133 may comprise insulated wires and/or any other suitable type of conductor. As described below, the at least one supply conductor 131 and the at least one return conductor 133 may be contained within and/or may comprise the cable 122 extending between, or at least partially between, the generator 120 and the end effector 126 of the electrosurgical instrument 110. The generator 120 can be configured to apply a sufficient voltage differential between the supply conductor 131 and the return conductor 133 such that sufficient current can be supplied to the end effector 126 to perform the intended electrosurgical operation.

[0056] FIG. 2 shows a perspective view of one example of the end effector 126 with the jaws 164a, 164b open, while FIG. 3A shows a perspective view of one aspect of the end effector 126 with the jaws 164a, 164b closed. FIG. 3B illustrates an exploded view of one aspect of the end effector 126. As noted above, the end effector 126 may comprise the upper first jaw 164a and the lower second jaw 164b, which may be straight or curved. The first jaw 164a and the second jaw 164b may each comprise an elongated slot or channel 162a and 162b, respectively, disposed outwardly along their respective middle portions. Further, the first jaw 164a and the second jaw 164b may each have tissue-gripping elements, such as teeth 163, disposed on the inner portions of the first jaw 164a and the second jaw 164b. The first jaw 164a may comprise an upper first jaw body with an upper first outward-facing surface and an upper first energy delivery surface 165a. The second jaw 164b may comprise a lower second jaw body with a lower second outward-facing surface and a lower second energy delivery surface 165b. The first energy delivery surface 165a and the second energy delivery surface 165b may both extend in a “U” shape about the distal end of the end effector 126. In some non-limiting examples, an insulator 170 may be associated with second jaw 164b. The insulator 170 may be placed in contact with second energy delivery surface 165b thereby shielding the second energy delivery surface from direct electrical contact with first energy delivery surface 165a associated with the first jaw 164a. It may be recognized that an alternatively an insulator 170 may be placed in contact with first energy delivery surface 165a thereby shielding the first energy delivery surface from direct electrical contact with second energy delivery surface 165b associated with the second jaw 164b.

[0057] The lever arm 121 of the handle 112 may be adapted to actuate the axially moveable member 178, which also may function as a jaw-closing mechanism. For example, the axially moveable member 178 may be urged distally as the lever arm 121 is pulled proximally along the path 33 via the shuttle. FIG. 4 is a perspective view of one example of the axially moveable member 178 of the surgical instrument 110. The axially moveable member 178 may comprise one or several pieces, but in any event, may be movable or translatable with respect to the elongated shaft 114 and/or the jaws 164a, 164b. Also, in at least one example, the axially moveable member 178 may be made of 17-4 precipitation hardened stainless steel. The distal end of axially moveable member 178 may comprise a flanged “I”-beam configured to slide within the channels 162a and 162b in jaws 164a and 164b. The axially moveable member 178 may slide within the channels 162a, 162b to open and close the first jaw 164a and the second jaw 164b. The distal end of the axially moveable member 178 may also comprise an upper flange or “c” shaped portion 178a and a lower flange or “c”-shaped portion 178b. The flanges 178a, 178b respectively define inner cam surfaces 167a and 167b for engaging outward facing surfaces of the first jaw 164a and the second jaw 164b. The opening-closing of jaws 164a and 164b can apply very high compressive forces on tissue using cam mechanisms which may include movable “I-beam” axially moveable member 178 and the outward facing surfaces 169a, 169b of jaws 164a, 164b.

[0058] More specifically, referring now to FIGS. 2-4, collectively, the inner cam surfaces 167a and 167b of the distal end of axially moveable member 178 may be adapted to slidably engage the first outward-facing surface 169a and the second outward-facing surface 169b of the first jaw 164a and the second jaw 164b, respectively. The channel 162a within first jaw 164a and the channel 162b within the second jaw 164b may be sized and configured to accommodate the movement of the axially moveable member 178, which may comprise a tissue-cutting element 171, for example, comprising a sharp distal edge. FIG. 3A, for example, shows the distal end of the axially moveable member 178 advanced at least partially through channels 162a and 162b (FIG. 2). The advancement of the axially moveable member 178 may close the end effector 126 from the open configuration shown in FIG. 2. In the closed position shown by FIG. 3A, the upper first jaw 164a and the lower second jaw 164b define a gap or dimension D between the first energy delivery surface 165a and second energy delivery surface 165b of the first jaw 164a and the second jaw 164b, respectively. In various aspects, dimension the D can equal from about 0.0005″ (about 13 μm) to about 0.040″ (about 1 mm), for example, and in some aspects, between about 0.001″ (about 25 μm) to about 0.010″ (about 250 μm), for example. In some non-limiting examples, the dimension D may have values of about 0.0005″ (about 13 μm), about 0.001″ (about 25 μm), about 0.002″ (about 51 μm), about 0.004″ (about 100 μm), about 0.005″ (about 130 μm), about 0.01″ (about 250 μm), about 0.02″ (about 510 μm), about 0.04″ (about 1 mm), or a range between any two of these values including endpoints. Also, the edges of the first energy delivery surface 165a and the second energy delivery surface 165b may be rounded to prevent the dissection of tissue.

[0059] FIG. 5 is a section view of one example of the end effector 126 of the surgical instrument 110. The engagement, tissue-contacting, surface 165b of the lower jaw 164b is adapted to deliver energy to tissue, at least in part, through a conductive-resistive matrix, such as a variable resistive PTC body, as discussed in more detail below. At least one of the upper and lower jaws 164a, 164b may carry at least one electrode 173 configured to deliver the energy from the generator 120 to the captured tissue. The engagement, tissue contacting, surface 165a of the upper jaw 164a may carry a similar conductive-resistive matrix (i.e., a PTC material), or in some aspects the surface may be a conductive electrode or an insulating layer, for example. Alternatively, the engagement surfaces of the jaws can carry any of the energy delivery components disclosed in U.S. Pat. No. 6,929,644, filed Oct. 22, 2001, entitled ELECTROSURGICAL JAW STRUCTURE FOR CONTROLLED ENERGY DELIVERY, the entire disclosure of which is incorporated herein by reference.

[0060] The first energy delivery surface 165a and the second energy delivery surface 165b each may be in electrical communication with the generator 120. The first energy delivery surface 165a and the second energy delivery surface 165b may be configured to contact tissue and deliver electrosurgical energy to the captured tissue thereby sealing or welding the tissue. Electrical generator 120 may include control unit 125 to regulate the electrical energy delivered by the electrical generator to the first energy delivery surface 165a and the second energy delivery surface 165b. The energy delivery may be initiated by an activation button 128 (FIG. 1) operably engaged with the lever arm 121 and in electrical communication with the generator 120 via a cable 122. In one example, the electrosurgical instrument 110 may be energized by the generator 120 by way of a foot switch 129 (FIG. 1). When actuated, the foot switch 129 triggers the generator 120 to deliver electrical energy to the end effector 126, for example. Although the foot switch 129 may be suitable in many circumstances, other suitable types of switches can be used, such as, for example, a thumb switch incorporated in the body of the electrosurgical instrument 110.

[0061] As mentioned above, the electrosurgical energy delivered by electrical generator 120 and regulated, or otherwise controlled, by the control unit 125 may comprise radio frequency (RF) energy, or other suitable forms of electrical energy. Further, the opposing first and second energy delivery surfaces 165a and 165b may carry variable resistive PTC bodies that are in electrical communication with the generator 120 and the control unit 125. Additional details regarding electrosurgical end effectors, jaw closing mechanisms, and electrosurgical energy delivery surfaces are described in the following U.S. patents and published patent applications: U.S. Pat. Nos. 7,087,054; 7,083,619; 7,070,597; 7,041,102; 7,011,657; 6,929,644; 6,926,716; 6,913,579; 6,905,497; 6,802,843; 6,770,072; 6,656,177; 6,533,784; and 6,500,112; and U.S. Pat. App. Pub. Nos. 2010/0036370 and 2009/0076506, all of which are incorporated herein by reference in their entirety and made part of this specification.

[0062] In one example, the generator 120 may be implemented as an electrosurgery unit (ESU) capable of supplying power sufficient to perform bipolar electrosurgery using radio frequency (RF) energy. In one example, the ESU can be a Force Triad™ Energy Platform sold by Medtronic of Boulder Colo. In some aspects, such as for bipolar electrosurgery applications, a surgical instrument 110 having an active electrode and a return electrode can be utilized, wherein the active electrode and the return electrode can be positioned against, adjacent to and/or in electrical communication with, the tissue to be treated such that current can flow from the active electrode, through the PTC bodies and to the return electrode through the tissue. Thus, in various aspects, the electrosurgical system 100 may comprise a supply path and a return path, wherein the captured tissue being treated completes, or closes, the circuit. In other aspects, the generator 120 may provide sub-therapeutic RF energy levels for purposes of evaluating tissue conditions and providing feedback in the electrosurgical system 100. Such feed back may be employed to control the therapeutic RF energy output of the electrosurgical instrument 110. Sub-therapeutic RF energy levels may be used for bipolar surgical procedures if a risk analysis shows the possibility of neuromuscular stimulation has been mitigated to an acceptable level. Under some conditions, frequencies above 5 MHz may not be used in order to minimize problems associated with high frequency leakage currents. However, higher frequencies may be used in the case of bipolar techniques. It is generally recognized that 10 mA is the lower threshold of thermal effects on tissue.

[0063] During operation of electrosurgical instrument 110, the user generally grasps tissue, supplies energy to the grasped tissue to form a weld or a seal (e.g., by actuating button 128 and/or pedal 129), and then drives a tissue-cutting element 171 at the distal end of the axially moveable member 178 through the grasped tissue. According to various aspects, the translation of the axial movement of the axially moveable member 178 may be paced, or otherwise controlled, to aid in driving the axially moveable member 178 at a suitable rate of travel. By controlling the rate of the travel, the likelihood that the captured tissue has been properly and functionally sealed prior to transection with the cutting element 171 is increased.

[0064] FIG. 6A is a block diagram of a surgical system electronic portion 4900 comprising a surgical instrument 110 (FIG. 1) coupled to a generator 4935, according to some aspects. The surgical instrument 110 described in the present disclosure, may be coupled to a generator 4935 configured to supply power to the surgical instrument 110 through external means, examples of which will be provided in more detail below. In certain instances, the surgical instrument 100 may include a microcontroller 4915 coupled to an external wired generator 4935. The external generator 4935 may be powered by AC mains. The electrical and electronic circuit elements associated with the surgical instrument 110 and/or the generator 4935 may be supported by a control circuit board assembly, for example. The microcontroller 4915 may generally comprise a memory 4910 and a microprocessor 4905 (“processor”) operationally coupled to the memory 4910. The surgical system electronic portion 4900 may be configured to control transmission of energy to the electrodes 173 at the end effector 126 of the surgical instrument. It should be understood that the term processor as used herein includes any suitable microprocessor, microcontroller, or other basic computing device that incorporates the functions of a computer's central processing unit (CPU) on an integrated circuit or at most a few integrated circuits. The processor 4905 may be a multipurpose, programmable device that accepts digital data as input, processes it according to instructions stored in its memory, and provides results as output. It is an example of sequential digital logic, as it has internal memory. Processors operate on numbers and symbols represented in the binary numeral system.

[0065] In some cases, the processor 4905 may be any single core or multicore processor such as those known under the trade name ARM Cortex by Texas Instruments. In some cases, any of the surgical instruments of the present disclosures may comprise a safety processor such as, for example, a safety microcontroller platform comprising two microcontroller-based families such as TMS570 and RM4x known under the trade name Hercules ARM Cortex R4, also by Texas Instruments. Nevertheless, other suitable substitutes for microcontrollers and safety processor may be employed, without limitation.

[0066] In certain instances, the microcontroller 4915 may be an LM 4F230H5QR, available from Texas Instruments, for example. In at least one example, the Texas Instruments LM4F230H5QR is an ARM Cortex-M4F Processor Core comprising on-chip memory 4910 of 256 KB single-cycle flash memory, or other non-volatile memory, up to 40 MHz, a prefetch buffer to improve performance above 40 MHz, a 32 KB single-cycle serial random access memory (SRAM), internal read-only memory (ROM) loaded with StellarisWare® software, 2 KB electrically erasable programmable read-only memory (EEPROM), one or more pulse width modulation (PWM) modules, one or more quadrature encoder inputs (QEI) analog, one or more 12-bit Analog-to-Digital Converters (ADC) with 12 analog input channels, among other features that are readily available for the product datasheet. Other microcontrollers may be readily substituted for use in the surgical instrument 110. Accordingly, the present disclosure should not be limited in this context.

[0067] In certain instances, the surgical instrument 110 may comprise one or more embedded applications implemented as firmware, software, hardware, or any combination thereof. In certain instances, the surgical instrument 110 may comprise various executable modules such as software, programs, data, drivers, and/or application program interfaces (APIs), for example.

[0068] FIG. 6B is a simplified block diagram 5000 of one form of the generator 4935. Additional details of the generator 4935 are described in commonly assigned and contemporaneously filed U.S. patent application Ser. No. 12/896,360, titled “Surgical Generator For Ultrasonic And Electrosurgical Devices,” now U.S. Pat. No. 9,060,775, the disclosure of which is incorporated herein by reference in its entirety. With reference to FIG. 6B, the generator 5000 may comprise a patient isolated stage 5034 in communication with a non-isolated stage 5002 via a power transformer 5032. A secondary winding 5036 of the power transformer 5032 is contained in the isolated stage 5034 and may comprise a tapped configuration (e.g., a center-tapped or a non-center-tapped configuration) to define drive signal outputs 5038, 5044, 5048 for outputting drive signals to different surgical devices, such as, for example, a surgical device 100 having an end effector 126 with electrodes 173 as in FIG. 5. In particular, drive signal outputs 5044, 5048 may output an electrosurgical drive signal (e.g., a 100V RMS drive signal) to a power and control assembly, with output 5044 corresponding to the center tap of the power transformer 5032.

[0069] The non-isolated stage 5002 may comprise a power amplifier 5026 having an output connected to a primary winding 5062 of the power transformer 5032. In certain forms the power amplifier 5026 may be comprise a push-pull amplifier. For example, the non-isolated stage 5002 may further comprise a logic device 5018 for supplying a digital output to a digital-to-analog converter (DAC) 5020, which in turn supplies a corresponding analog signal to an input of the power amplifier 5026. In certain forms the logic device 5018 may comprise a programmable gate array (PGA), a field-programmable gate array (FPGA), programmable logic device (PLD), among other logic circuits, for example. The logic device 5018, by virtue of controlling the input of the power amplifier 5026 via the DAC 5020, may therefore control any of a number of parameters (e.g., frequency, waveform shape, waveform amplitude) of drive signals appearing at the drive signal outputs 5038, 5044, 5048. In certain forms and as discussed below, the logic device 5018, in conjunction with a processor (e.g., a digital signal processor discussed below), may implement a number of digital signal processing (DSP)-based and/or other control algorithms to control parameters of the drive signals output by the generator 5000.

[0070] Power may be supplied to a power rail of the power amplifier 5026 by a switch-mode regulator 5004. In certain forms the switch-mode regulator 5004 may comprise an adjustable buck regulator, for example. The non-isolated stage 5002 may further comprise a first processor 5012, which in one form may comprise a DSP processor such as an Analog Devices ADSP-21469 SHARC DSP, available from Analog Devices, Norwood, Mass., for example, although in various forms any suitable processor may be employed. In certain forms the processor 5012 may control operation of the switch-mode power converter 5004 responsive to voltage feedback data received from the power amplifier 5026 by the DSP processor 5012 via an analog-to-digital converter (ADC) 5008. In one form, for example, the DSP processor 5012 may receive as input, via the ADC 5008, the waveform envelope of a signal (e.g., an RF signal) being amplified by the power amplifier 5026. The DSP processor 5012 may then control the switch-mode regulator 5004 (e.g., via a pulse-width modulated (PWM) output) such that the rail voltage supplied to the power amplifier 5026 tracks the waveform envelope of the amplified signal. By dynamically modulating the rail voltage of the power amplifier 5026 based on the waveform envelope, the efficiency of the power amplifier 5026 may be significantly improved relative to a fixed rail voltage amplifier schemes.

[0071] In certain forms, the logic device 5018, in conjunction with the DSP processor 5012, may implement a direct digital synthesizer (DDS) control scheme to control the waveform shape, frequency and/or amplitude of drive signals output by the generator 5000. In one form, for example, the logic device 5018 may implement a DDS control algorithm by recalling waveform samples stored in a dynamically-updated look-up table (LUT), such as a RAM LUT, which may be embedded in an FPGA. Because the waveform shape of a drive signal output by the generator 5000 is impacted by various sources of distortion present in the output drive circuit (e.g., the power transformer 5032, the power amplifier 5026), voltage and current feedback data based on the drive signal may be input into an algorithm, such as an error control algorithm implemented by the DSP processor 5012, which compensates for distortion by suitably pre-distorting or modifying the waveform samples stored in the LUT on a dynamic, ongoing basis (e.g., in real-time). In one form, the amount or degree of pre-distortion applied to the LUT samples may be based on the error between a computed motional branch current and a desired current waveform shape, with the error being determined on a sample-by-sample basis. In this way, the pre-distorted LUT samples, when processed through the drive circuit, may result in a motional branch drive signal having the desired waveform shape (e.g., sinusoidal) for optimally driving an ultrasonic transducer. In such forms, the LUT waveform samples will therefore not represent the desired waveform shape of the drive signal, but rather the waveform shape that is required to ultimately produce the desired waveform shape of the motional branch drive signal when distortion effects are taken into account.

[0072] The non-isolated stage 5002 may further comprise an ADC 5022 and an ADC 5024 coupled to the output of the power transformer 5032 via respective isolation transformers 5028, 5030 for respectively sampling the voltage and current of drive signals output by the generator 5000. In certain forms, the ADCs 5022, 5024 may be configured to sample at high speeds (e.g., 80 MSPS) to enable oversampling of the drive signals. In one form, for example, the sampling speed of the ADCs 5022, 5024 may enable approximately 200× (depending on frequency) oversampling of the drive signals. In certain forms, the sampling operations of the ADC 5022, 5024 may be performed by a single ADC receiving input voltage and current signals via a two-way multiplexer. The use of high-speed sampling in forms of the generator 5000 may enable, among other things, calculation of the complex current flowing through the motional branch (which may be used in certain forms to implement DDS-based waveform shape control described above), accurate digital filtering of the sampled signals, and calculation of real power consumption with a high degree of precision. Voltage and current feedback data output by the ADCs 5022, 5024 may be received and processed (e.g., FIFO buffering, multiplexing) by the logic device 5018 and stored in data memory for subsequent retrieval by, for example, the DSP processor 5012. As noted above, voltage and current feedback data may be used as input to an algorithm for pre-distorting or modifying LUT waveform samples on a dynamic and ongoing basis. In certain forms, this may require each stored voltage and current feedback data pair to be indexed based on, or otherwise associated with, a corresponding LUT sample that was output by the logic device 5018 when the voltage and current feedback data pair was acquired. Synchronization of the LUT samples and the voltage and current feedback data in this manner contributes to the correct timing and stability of the pre-distortion algorithm.

[0073] In certain forms, the voltage and current feedback data may be used to control the frequency and/or amplitude (e.g., current amplitude) of the drive signals. In one form, for example, voltage and current feedback data may be used to determine impedance phase. The frequency of the drive signal may then be controlled to minimize or reduce the difference between the determined impedance phase and an impedance phase setpoint (e.g., 0°), thereby minimizing or reducing the effects of harmonic distortion and correspondingly enhancing impedance phase measurement accuracy. The determination of phase impedance and a frequency control signal may be implemented in the DSP processor 5012, for example, with the frequency control signal being supplied as input to a DDS control algorithm implemented by the logic device 5018.

[0074] In another form, for example, the current feedback data may be monitored in order to maintain the current amplitude of the drive signal at a current amplitude setpoint. The current amplitude setpoint may be specified directly or determined indirectly based on specified voltage amplitude and power setpoints. In certain forms, control of the current amplitude may be implemented by control algorithm, such as, for example, a PID control algorithm, in the processor 5012. Variables controlled by the control algorithm to suitably control the current amplitude of the drive signal may include, for example, the scaling of the LUT waveform samples stored in the logic device 5018 and/or the full-scale output voltage of the DAC 5020 (which supplies the input to the power amplifier 5026) via a DAC 5010.

[0075] The non-isolated stage 5002 may further comprise a second processor 5014 for providing, among other things user interface (UI) functionality. In one form, the UI processor 5014 may comprise an Atmel AT91SAM9263 processor having an ARM 926EJ-S core, available from Atmel Corporation, San Jose, Calif., for example. Examples of UI functionality supported by the UI processor 5014 may include audible and visual user feedback, communication with peripheral devices (e.g., via a Universal Serial Bus (USB) interface), communication with a footswitch, communication with an input device (e.g., a touch screen display indicators 4930) and communication with an output device (e.g., a speaker). The UI processor 5014 may communicate with the processor 5012 and the logic device 5018 (e.g., via serial peripheral interface (SPI) buses). Although the UI processor 5014 may primarily support UI functionality, it also may coordinate with the DSP processor 5012 to implement hazard mitigation in certain forms. For example, the UI processor 5014 may be programmed to monitor various aspects of user input and/or other inputs (e.g., touch screen inputs, footswitch inputs, temperature sensor inputs) and may disable the drive output of the generator 5000 when an erroneous condition is detected.

[0076] In certain forms, both the DSP processor 5012 and the UI processor 5014, for example, may determine and monitor the operating state of the generator 5000. For the DSP processor 5012, the operating state of the generator 5000 may dictate, for example, which control and/or diagnostic processes are implemented by the DSP processor 5012. For the UI processor 5014, the operating state of the generator 5000 may dictate, for example, which elements of a user interface (e.g., display screens, sounds) are presented to a user. The respective DSP and UI processors 5012, 5014 may independently maintain the current operating state of the generator 5000 and recognize and evaluate possible transitions out of the current operating state. The DSP processor 5012 may function as the master in this relationship and determine when transitions between operating states are to occur. The UI processor 5014 may be aware of valid transitions between operating states and may confirm if a particular transition is appropriate. For example, when the DSP processor 5012 instructs the UI processor 5014 to transition to a specific state, the UI processor 5014 may verify that requested transition is valid. In the event that a requested transition between states is determined to be invalid by the UI processor 5014, the UI processor 5014 may cause the generator 5000 to enter a failure mode.

[0077] The non-isolated stage 5002 may further comprise a controller 5016 for monitoring input devices (e.g., a capacitive touch sensor used for turning the generator 5000 on and off, a capacitive touch screen). In certain forms, the controller 5016 may comprise at least one processor and/or other controller device in communication with the UI processor 5014. In one form, for example, the controller 5016 may comprise a processor (e.g., a Mega168 8-bit controller available from Atmel) configured to monitor user input provided via one or more capacitive touch sensors. In one form, the controller 5016 may comprise a touch screen controller (e.g., a QT5480 touch screen controller available from Atmel) to control and manage the acquisition of touch data from a capacitive touch screen.

[0078] In certain forms, when the generator 5000 is in a “power off” state, the controller 5016 may continue to receive operating power (e.g., via a line from a power supply of the generator 5000). In this way, the controller 5016 may continue to monitor an input device (e.g., a capacitive touch sensor located on a front panel of the generator 5000) for turning the generator 5000 on and off. When the generator 5000 is in the power off state, the controller 5016 may wake the power supply (e.g., enable operation of one or more DC/DC voltage converters 5060 of the power supply 5006) if activation of the “on/off” input device by a user is detected. The controller 5016 may therefore initiate a sequence for transitioning the generator 5000 to a “power on” state. Conversely, the controller 5016 may initiate a sequence for transitioning the generator 5000 to the power off state if activation of the “on/off” input device is detected when the generator 5000 is in the power on state. In certain forms, for example, the controller 5016 may report activation of the “on/off” input device to the processor 5014, which in turn implements the necessary process sequence for transitioning the generator 5000 to the power off state. In such forms, the controller 5016 may have no independent ability for causing the removal of power from the generator 5000 after its power on state has been established.

[0079] In certain forms, the controller 5016 may cause the generator 5000 to provide audible or other sensory feedback for alerting the user that a power on or power off sequence has been initiated. Such an alert may be provided at the beginning of a power on or power off sequence and prior to the commencement of other processes associated with the sequence.

[0080] In certain forms, the isolated stage 5034 may comprise an instrument interface circuit 5050 to, for example, provide a communication interface between a control circuit of a surgical device (e.g., a control circuit comprising hand piece switches) and components of the non-isolated stage 5002, such as, for example, the programmable logic device 5018, the DSP processor 5012 and/or the UI processor 5014. The instrument interface circuit 5050 may exchange information with components of the non-isolated stage 5002 via a communication link that maintains a suitable degree of electrical isolation between the stages 5034, 5002, such as, for example, an infrared (IR)-based communication link. Power may be supplied to the instrument interface circuit 5050 using, for example, a low-dropout voltage regulator powered by an isolation transformer driven from the non-isolated stage 5002.

[0081] In one form, the instrument interface circuit 5050 may comprise a logic device 5054 (e.g., logic circuit, programmable logic circuit, PGA, FPGA, PLD) in communication with a signal conditioning circuit 5052. The signal conditioning circuit 5052 may be configured to receive a periodic signal from the logic circuit 5054 (e.g., a 2 kHz square wave) to generate a bipolar interrogation signal having an identical frequency. The interrogation signal may be generated, for example, using a bipolar current source fed by a differential amplifier. The interrogation signal may be communicated to a surgical device control circuit (e.g., by using a conductive pair in a cable that connects the generator 5000 to the surgical device) and monitored to determine a state or configuration of the control circuit. The control circuit may comprise a number of switches, resistors and/or diodes to modify one or more characteristics (e.g., amplitude, rectification) of the interrogation signal such that a state or configuration of the control circuit is uniquely discernable based on the one or more characteristics. In one form, for example, the signal conditioning circuit 5052 may comprises an ADC for generating samples of a voltage signal appearing across inputs of the control circuit resulting from passage of interrogation signal therethrough. The logic device 5054 (or a component of the non-isolated stage 5002) may then determine the state or configuration of the control circuit based on the ADC samples.

[0082] In one form, the instrument interface circuit 5050 may comprise a first data circuit interface 5056 to enable information exchange between the logic circuit 5054 (or other element of the instrument interface circuit 5050) and a first data circuit disposed in or otherwise associated with a surgical device. In certain forms, for example, a first data circuit may be disposed in a cable integrally attached to a surgical device hand piece, or in an adaptor for interfacing a specific surgical device type or model with the generator 5000. The data circuit may be implemented in any suitable manner and may communicate with the generator according to any suitable protocol. In certain forms, the first data circuit may comprise a non-volatile storage device, such as an electrically erasable programmable read-only memory (EEPROM) device. In certain forms, the first data circuit interface 5056 may be implemented separately from the logic device 5054 and comprise suitable circuitry (e.g., discrete logic devices, a processor) to enable communication between the programmable logic device 5054 and the first data circuit. In other forms, the first data circuit interface 5056 may be integral with the logic device 5054.

[0083] In certain forms, the first data circuit may store information pertaining to the particular surgical device with which it is associated. Such information may include, for example, a model number, a serial number, a number of operations in which the surgical device has been used, and/or any other type of information. This information may be read by the instrument interface circuit 5050 (e.g., by the logic device 5054), transferred to a component of the non-isolated stage 5002 (e.g., to logic device 5018, DSP processor 5012 and/or UI processor 5014) for presentation to a user via an output device and/or for controlling a function or operation of the generator 5000. Additionally, any type of information may be communicated to first data circuit for storage therein via the first data circuit interface 5056 (e.g., using the logic device 5054). Such information may comprise, for example, an updated number of operations in which the surgical device has been used and/or dates and/or times of its usage.

[0084] Additionally, forms of the generator 5000 may enable communication with instrument-based data circuits. For example, the generator 5000 may be configured to communicate with a second data circuit contained in an instrument of a surgical device. The instrument interface circuit 5050 may comprise a second data circuit interface 5058 to enable this communication. In one form, the second data circuit interface 5058 may comprise a tri-state digital interface, although other interfaces also may be used. In certain forms, the second data circuit may generally be any circuit for transmitting and/or receiving data. In one form, for example, the second data circuit may store information pertaining to the particular surgical instrument 110 with which it is associated. Such information may include, for example, a model number, a serial number, a number of operations in which the surgical instrument 110 has been used, and/or any other type of information. In some forms, the second data circuit may store information about the electrical properties of an end effector 126, or attachable components including the electrodes 173. For example, the first data circuit may indicate a burn-in frequency slope, as described herein. Additionally or alternatively, any type of information may be communicated to second data circuit for storage therein via the second data circuit interface 5058 (e.g., using the logic device 5054). Such information may comprise, for example, an updated number of operations in which the instrument has been used and/or dates and/or times of its usage. In certain forms, the second data circuit may transmit data acquired by one or more sensors (e.g., an instrument-based temperature sensor). In certain forms, the second data circuit may receive data from the generator 5000 and provide an indication to a user (e.g., an LED indication or other visible indication) based on the received data.

[0085] In certain forms, the second data circuit and the second data circuit interface 5058 may be configured such that communication between the logic device 5054 and the second data circuit can be effected without the need to provide additional conductors for this purpose (e.g., dedicated conductors of a cable connecting a hand piece to the generator 5000). In one form, for example, information may be communicated to and from the second data circuit using a 1-wire bus communication scheme implemented on existing cabling, such as one of the conductors used transmit interrogation signals from the signal conditioning circuit 5052 to a control circuit in a hand piece. In this way, design changes or modifications to the surgical device that might otherwise be necessary are minimized or reduced. Moreover, because different types of communications implemented over a common physical channel can be frequency-band separated, the presence of a second data circuit may be “invisible” to generators that do not have the requisite data reading functionality, thus enabling backward compatibility of the surgical device instrument.

[0086] In certain forms, the isolated stage 5034 may comprise at least one blocking capacitor 5040 connected to the drive signal output 5044 to prevent passage of DC current to a patient. A single blocking capacitor may be required to comply with medical regulations or standards, for example. While failure in single-capacitor designs is relatively uncommon, such failure may nonetheless have negative consequences. In one form, a second blocking capacitor 5042 may be provided in series with the blocking capacitor 5040, with current leakage from a point between the blocking capacitors 5040, 5042 being monitored by, for example, an ADC 5046 for sampling a voltage induced by leakage current. The samples may be received by the logic circuit 5054, for example. Based changes in the leakage current, the generator 5000 may determine when at least one of the blocking capacitors 5040, 5042 has failed. Accordingly, the form of FIG. 8B provides a benefit over single-capacitor designs having a single point of failure.

[0087] In certain forms, the non-isolated stage 5002 may comprise a power supply 5006 for outputting DC power at a suitable voltage and current. The power supply may comprise, for example, a 400 W power supply for outputting a 48 VDC system voltage. The power supply 5006 may further comprise one or more DC/DC voltage converters 5060 for receiving the output of the power supply to generate DC outputs at the voltages and currents required by the various components of the generator 5000. As discussed above in connection with the controller 5016, one or more of the DC/DC voltage converters 5060 may receive an input from the controller 5016 when activation of the “on/off” input device by a user is detected by the controller 5016 to enable operation of, or wake, the DC/DC voltage converters 5060.

[0088] It may be recognized that external generator 4925 and exemplary external generator 5000 may all be considered non-limiting examples of generator 120 depicted in FIG. 1.

[0089] FIG. 6C is a part schematic part block diagram illustrating an RF drive and control circuitry 220 used in some aspects to generate and control the RF electrical energy supplied to the electrodes 173 described above. The drive circuitry 220 may describe part or all of the components in internal generator 4940 sufficient for providing power and control to the electrodes. As will be explained in more detail below, the drive circuitry 220 is a resonant based circuit and the control circuitry operates to control the operating frequency of the drive signal so that it is varied around the resonant frequency of the drive circuit, which in turn controls the amount of power supplied to the electrodes 173 at the end effector 126. The way that this is achieved will become apparent from the following description.

[0090] The drive circuit 220 may be configured in any suitable manner. In some aspects, the generator circuit comprises an RF drive and control circuit 240 and a controller circuit 282. FIG. 6C illustrates an RF drive and control circuit 240, according to one aspect. FIG. 6C is a part schematic part block diagram illustrating the RF drive and control circuitry 240 used in this aspect to generate and control the RF electrical energy supplied to the end effector 126. As will be explained in more detail below, in this aspect, the drive circuitry 240 is a resonant mode RF amplifier comprising a parallel resonant network on the RF amplifier output and the control circuitry operates to control the operating frequency of the drive signal so that it is maintained at the resonant frequency of the drive circuit, which in turn controls the amount of power supplied to the end effector 126. The way that this is achieved will become apparent from the following description.

[0091] As shown in FIG. 6C, the RF drive and control circuit 240 comprises the above described battery 237 are arranged to supply, in this example, about 0V and about 12V rails. An input capacitor (C_in) 242 is connected between the 0V and the 12V for providing a low source impedance. A pair of FET switches 243-1 and 243-2 (both of which are N-channel in this aspect to reduce power losses) is connected in series between the 0V rail and the 12V rail. FET gate drive circuitry 245 is provided that generates two drive signals-one for driving each of the two FETs 243. The FET gate drive circuitry 245 generates drive signals that causes the upper FET (243-1) to be on when the lower FET (243-2) is off and vice versa. This causes the node 247 to be alternately connected to the 12V rail (when the FET 243-1 is switched on) and the 0V rail (when the FET 243-2 is switched on). FIG. 8B also shows the internal parasitic diodes 248-1 and 248-2 of the corresponding FETs 243, which conduct during any periods that the FETs 243 are closed.

[0092] As shown in FIG. 6C, the node 247 is connected to an inductor-inductor resonant circuit 250 formed by inductor L_s 252 and inductor L_m 254. The FET gate driving circuitry 245 is arranged to generate drive signals at a drive frequency (f_d) that opens and crosses the FET switches 243 at the resonant frequency of the parallel resonant circuit 250. As a result of the resonant characteristic of the resonant circuit 250, the square wave voltage at node 247 will cause a substantially sinusoidal current at the drive frequency (f_d) to flow within the resonant circuit 250. As illustrated in FIG. 6C, the inductor L_m 254 is the primary of a transformer 255, the secondary of which is formed by inductor L_sec 256. The inductor L_sec 256 of the transformer 255 secondary is connected to an inductor-capacitor-capacitor parallel resonant circuit 257 formed by inductor L₂ 258, capacitor C₄ 260, and capacitor C₂ 262. The transformer 255 up-converts the drive voltage (V_d) across the inductor L_m 254 to the voltage that is applied to the output parallel resonant circuit 257. The load voltage (V_L) is output by the parallel resonant circuit 257 and is applied to the load (represented by the load resistance R_load 259 in FIG. 8C) corresponding to the impedance of the forceps' jaws and any tissue or vessel gripped by the end effector 126. As shown in FIG. 8C, a pair of DC blocking capacitors C_H 280-1 and 280-2 is provided to block any DC signal being applied to the load 259.

[0093] In one aspect, the transformer 255 may be implemented with a Core Diameter (mm), Wire Diameter (mm), and Gap between secondary windings in accordance with the following specifications:

[0094] Core Diameter, D (mm)
D=19.9×10⁻³

[0095] Wire diameter, W (mm) for 22 AWG wire
W=7.366×10⁻⁴

[0096] Gap between secondary windings, in gap=0.125
G=gap/25.4

[0097] In this aspect, the amount of electrical power supplied to the end effector 126 is controlled by varying the frequency of the switching signals used to switch the FETs 243. This works because the resonant circuit 250 acts as a frequency dependent (lossless) attenuator. The closer the drive signal is to the resonant frequency of the resonant circuit 250, the less the drive signal is attenuated. Similarly, as the frequency of the drive signal is moved away from the resonant frequency of the circuit 250, the more the drive signal is attenuated and so the power supplied to the load reduces. In this aspect, the frequency of the switching signals generated by the FET gate drive circuitry 245 is controlled by a controller 281 based on a desired power to be delivered to the load 259 and measurements of the load voltage (V_L) and of the load current (I_L) obtained by conventional voltage sensing circuitry 283 and current sensing circuitry 285. The way that the controller 281 operates will be described in more detail below.

[0098] In one aspect, the voltage sensing circuitry 283 and the current sensing circuitry 285 may be implemented with high bandwidth, high speed rail-to-rail amplifiers (e.g., LMH6643 by National Semiconductor). Such amplifiers, however, consume a relatively high current when they are operational. Accordingly, a power save circuit may be provided to reduce the supply voltage of the amplifiers when they are not being used in the voltage sensing circuitry 283 and the current sensing circuitry 285. In one aspect, a step-down regulator (e.g., LT1502 by Linear Technologies) may be employed by the power save circuit to reduce the supply voltage of the rail-to-rail amplifiers and thus extend the life of the battery 237.

[0099] FIG. 6D illustrates the main components of the controller 281, according to one aspect. As illustrated in FIG. 6D, the controller 281 is a microprocessor based controller and so most of the components illustrated in FIG. 6D are software based components. Nevertheless, a hardware based controller 281 may be used instead. As shown, the controller 281 includes synchronous I, Q sampling circuitry 291 that receives the sensed voltage and current signals from the sensing circuitry 283 and 285 and obtains corresponding samples which are passed to a power, V_rms and I_rms calculation module 293. The calculation module 293 uses the received samples to calculate the RMS voltage and RMS current applied to the load 259 (FIG. 6C; end effector 126 and tissue/vessel gripped thereby) and from them the power that is presently being supplied to the load 259. The determined values are then passed to a frequency control module 295 and a medical device control module 297. The medical device control module 297 uses the values to determine the present impedance of the load 259 and based on this determined impedance and a pre-defined algorithm, determines what set point power (P_set) should be applied to the frequency control module 295. The medical device control module 297 is in turn controlled by signals received from a user input module 299 that receives inputs from the user (for example pressing buttons or activating the control levers 114, 110 on the handle 104) and also controls output devices (lights, a display, speaker or the like) on the handle 104 via a user output module 261.

[0100] The frequency control module 295 uses the values obtained from the calculation module 293 and the power set point (P_set) obtained from the medical device control module 297 and predefined system limits (to be explained below), to determine whether or not to increase or decrease the applied frequency. The result of this decision is then passed to a square wave generation module 263 which, in this aspect, increments or decrements the frequency of a square wave signal that it generates by about 1 kHz, depending on the received decision. As those skilled in the art will appreciate, alternatively, the frequency control module 295 may determine not only whether to increase or decrease the frequency, but also the amount of frequency change required. In this case, the square wave generation module 263 would generate the corresponding square wave signal with the desired frequency shift. In this aspect, the square wave signal generated by the square wave generation module 263 is output to the FET gate drive circuitry 245, which amplifies the signal and then applies it to the FET 243-1. The FET gate drive circuitry 245 also inverts the signal applied to the FET 243-1 and applies the inverted signal to the FET 243-2.

[0101] In some non-limiting medical procedures, the electrosurgical system 100 may be used to weld or seal vessels prior to tissue resection. Such vessels may also be removed as part of procedures to resect other tissue such as cysts, tumors, or infected materials. Blood vessel sealing may reduce bleeding, thereby decreasing potential harmful effects during a resection procedure. In such procedures, the vessels may be cut at the cauterization location. It may be understood that complete sealing is required at the site of the cut to prevent bleeding. It is therefore useful to have an electrosurgical device such as the electrosurgical system 100 that is prevented from cutting the vessel until complete sealing is assured.

[0102] In some aspects, an electrosurgical system 100 may include automated features to prevent the vessel from being severed before sealing is complete. In some aspects, such an automated feature may rely on the change of tissue impedance during cauterization to determine when the vessel may be cut. It is known that normal tissue, comprising water and electrolytes, presents a low impedance to electrical current. However, the process of cauterization removes water and causes tissue to oxidize into less conductive materials. FIG. 7 depicts a graph 900 of calculated tissue impedance versus time of exposure to RF power. It may be appreciated that the tissue impedance 910 starts at a low value (at short times) due to the amount of water and ionic charge carriers present in the tissue. However, as the power deposited in the tissue increases over time, water is removed and the tissue is converted into non-conducting material, thereby increasing the tissue impedance.

[0103] A threshold value of tissue impedance 920 may be chosen as being indicative that the tissue has been cauterized sufficiently. The threshold value indicative of sufficient cauterization 920 may have an impedance value of about 100Ω to about 500Ω. In some non-limiting examples, the threshold impedance value may be about 100Ω, about 200Ω, about 300Ω, about 400Ω, about 500Ω, or any value therebetween including endpoints. In one non-limiting example, the threshold value 920 may have an impedance of about 450Ω. Therefore, in one non-limiting example, an electrosurgical system 100 may include logic, implemented in hardware and/or software, that prevents the use of a tissue cutting element 171 until the measured impedance is greater than the threshold value of tissue impedance 920. In an alternative non-limiting example, an electrosurgical system 100 may include one or more indicators to notify a physician using the electrosurgical system that the tissue has been properly sealed so that a tissue cutting knife may be deployed to sever the tissue. Such indicators may include, without limitation, an optical indicator (such as a light or an LED) or an auditory indicator (such as a tone, a buzzer, or a vocalization produced by a speech synthesizer).

[0104] Proper sealing may require that sufficient pressure is placed on the vessel to assure that the vessel walls are proximate to each other and that no intervening gap remains therebetween. In addition, proper sealing may require that sufficient power is provided to assure that the vessel walls receive sufficient heat to weld the walls together. Thus both tissue compression and tissue cauterization are required to form a proper seal.

[0105] As disclosed above, end effector 126 comprises jaws 164a and 164b that can be manipulated to compress a tissue, such as a blood vessel, between them. Jaws 164a, 164b may be closer together when the tissue is compressed compared to their relative positions when not compressing a tissue. It may be understood that the amount of movement of a first jaw (for example 164a) with respect to the second jaw (for example 164b) may depend on the thickness of the tissue (which may include a blood vessel) or the placement of the tissue between the jaws. As a result, a user of the electrosurgical system 100 may not know when the jaws 164a and 164b of the end effector 126 have sufficiently compressed the tissue or vessel to assure that a proper seal is made. If the jaws 164a and 164b do not compress the tissue sufficiently when RF energy is applied, then the impedance of the cauterized tissue may not be a sufficient indicator that the tissue has been sealed. If the logic of the electrosurgical system 100 depends solely on a measured value of tissue impedance being greater than the threshold value 920 indicative of cauterized tissue, the system may allow the tissue cutting element 171 to sever an unsealed or partially sealed blood vessel.

[0106] Presently, spring based jaw closure devices do not ensure that the jaws have sufficiently compressed the vessel walls when the impedance threshold is measured. In some non-limiting examples, a measurement of jaw proximity may include the use of additional switches, sensors, potentiometers, and contacts coupled to a signal circuit to send a signal to the generator 120 that the jaw gap is or is not adequate. Generators 120 in use in the field may not be capable of enabling the additional functionality of sensors.

[0107] FIG. 8 depicts an electrical circuit schematic that incorporates a shunt impedance circuit 350 that is reversibly placed in parallel to the capacitive circuit formed by the energy delivery surfaces 165a, 165b of the end effector 126. Generator 120 may include three terminals, an RF source terminal 310, a signal source terminal 330, and a common ground or neutral terminal 320. The first energy delivery surface 165a may receive RF current from the RF source terminal 310, and the second energy delivery surface 165b may be in electrical communication with the common ground or neutral terminal 320. The shunt impedance circuit 350 may be reversibly placed in parallel with the energy delivery surfaces 165a, 165b. The shunt impedance circuit 350 may include a shunt impedance element 360 and a shunt switch 370. Although FIG. 8 depicts the shunt impedance element 360 as a resistor, other electrical components may comprise the shunt impedance element. Such components may include, without limitation, any one or more of a fixed resistor, a fixed capacitor, a fixed inductor, a variable resistor, a variable capacitor, or a variable inductor. Other components may include a thermistor or other sensor configured to measure or respond to environmental factors such as tissue temperature, mechanical force, or jaw proximity.

[0108] When the shunt switch 370 is closed, the shunt impedance element 360 is placed in parallel to the energy delivery surfaces 165a, 165b. When the shunt switch 370 is open, the shunt impedance element is functionally removed from the circuit. An energy signal switch 2829 may be activated by a physician to signal the generator 120 to provide RF energy from the RF source terminal 310. The energy signal switch 2829 may include an energy activation button 128 located on the handle 112 of the electrosurgical device 110. Alternatively, the energy signal switch 2829 may include a foot switch 129. When a physician activates the energy signal switch 2829, current from the signal source terminal 330 may flow to the ground or neutral terminal 320. The current flow from the signal source terminal 330 may be sensed by the generator 120 which will respond by sourcing current through the RF course terminal 310. In some non-limiting examples, the current flow from the signal source terminal 330 may be sensed by a transistor. In another non-limiting example, the current flow from the signal source terminal 330 may activate a solenoid coil in a relay to close a switch thereby sourcing the RF current to the RF source terminal 310.

[0109] FIG. 9 depicts an end effector 126 configured to prevent an electrosurgical system from receiving impedance measurements consistent with a cauterized vessel from tissue that has not been cauterized. The end effector 126 may comprise a first jaw 164a that can be moved relative to a second jaw 164b, thereby forming a jaw angle α therebetween. In one non-limiting example, such a movement may require a rotation of a portion of the first jaw 164a about a pivot 1125 mechanically linked the two jaws 164a, 164b together. The first jaw 164a may comprise a first energy delivery surface 165a and the second jaw 164b may comprise a second energy delivery surface 165b. Such energy delivery surfaces (165a and 165b) may be configured to deliver RF energy to a tissue compressed by the jaws 164a, 164b. Each energy delivery surface (165a and 165b) may be in electrical communication with an electrode. Each electrode may be in mechanical communication with a jaw (164a or 164b) of the end effector 126. As one non-limiting example, supply electrode 173 may be in electrical communication with the second energy delivery surface 165b, both of which being incorporated into the second jaw 164b. Each electrode may be in electrical communication with a terminal of generator 120 via a conductor. In one non-limiting example, electrode 173 in electrical communication with the energy delivery surface 165b of second jaw 164b may be in electrical communication with a RF source terminal 310 of generator 120 via supply conductor 131. The first jaw 164a may have an electrode in electrical communication with an energy delivery surface 165a and a common ground or neutral terminal 320 of generator 120 via return conductor 133.

[0110] When the jaws (164a and 164b) contact a tissue, current supplied by generator 120 may pass along supply conductor 131 to the second jaw 164b and second energy delivery surface 165b, through the tissue, and then return via first energy delivery surface 165a, first jaw 164a, and the return conductor 133 to the generator. In this manner, the tissue contacted by the first jaw 164a and second jaw 164b forms a load for the generator 120. As depicted in FIG. 6C, a load voltage (V_L) and a load current (i_L) may be measured by the voltage sensing circuitry 283 and current sensing circuitry 285, respectively. The impedance of the load (or tissue), for example a load resistance R_load, may be determined by an impedance detector. In one non-limiting example, an impedance detector may incorporate voltage sensing circuitry 283 and current sensing circuitry 285. Alternatively, the impedance detector may be a separate element from the voltage sensing circuitry and current sensing circuitry. In one non-limiting example, the load impedance may be calculated by dividing a value of the load voltage (V_L) by a value of the load current (i_L). As disclosed above, a measured load impedance having a value similar to that of cauterized tissue may not be sufficient to indicate that a proper tissue seal has been made via compression of the tissue by jaws (162a and 162b). Therefore, a method is required to assure that the jaws (162a and 162b) are sufficiently proximate to each other to assure proper tissue compression during the cauterization process.

[0111] FIG. 9 depicts a mechanism to determine when the jaws 162a, 162b are sufficiently proximate to compress the tissue during cauterization. The mechanism may be based on removably placing a shunt impedance circuit 350 (FIG. 8) in parallel with the energy delivery surfaces 165a, 165b. The shunt impedance circuit may have a shunt impedance element having a pre-determined value. In a non-limiting example, the shunt impedance may have a value less than or equal to the threshold impedance value 920. In FIG. 9, such a shunt impedance circuit may be provided by a contactor 1370 incorporating a shunt impedance element 1360. The contactor 1370 may be configured to be in electrical communication with the electrode 173 that supplies current to the second energy delivery surface 165b at a first end, and the equivalent electrode that sinks current from the first energy delivery surface 165a at a second end. The contactor 1370 may form the only electrical connection between the first jaw 164a (or electrical components thereof) and the second jaw 164b (or electrical components thereof). The pivot 1125 may be constructed of electrically insulating materials, thereby preventing electrical shorting between the first jaw 164a (or electrical components thereof) and the second jaw 164b (or electrical components thereof).

[0112] Alternatively, the shunt impedance element may not be located on the end effector 126, but may be placed at an alternative location within the electrosurgical instrument 110. Such a shunt impedance element is represented in FIG. 9 by shunt element 1365 which may be in electrical contact via conductor 1133 (dashed line) with the return conductor 133. As noted above, in one non-limiting example depicted in FIG. 9, contactor 1370 may be electrically closed with respect to first jaw 164a, thereby placing shunt impedance element 1360 in parallel with energy surfaces 165a, 165b, when the jaws 164a, 164b are at an angle α greater than a limiting jaw angle. Similarly, contactor 1370 may be electrically open with respect to first jaw 164a, thereby removing shunt impedance element 1360 from the electrical circuit, when the jaws 164a, 164b are at an angle α less than a limiting jaw angle. In one aspect in which the shunt element is not located in the end effector 126, the contactor 1370 may be electrically open with respect to first jaw 164a, and thereby placing shunt element 1365 in parallel with energy surfaces 165a, 165b, when the jaws 164a, 164b are at an angle α greater than a limiting jaw angle. Similarly, in the aspect in which the shunt element is not located in the end effector 126, the contactor 1370 may be electrically closed with respect to first jaw 164a and thereby removing shunt element 1365 from the circuit, when the jaws 164a, 164b are at an angle α less than a limiting jaw angle.

[0113] It is well understood that the total impedance (Z_t) of a circuit composed of a variable load impedance (Z_load) and a pre-determined shunt impedance (Z_shunt) in parallel with the load impedance may be calculated according to Eq. 1.
Z_t=(Z_load*Z_shunt)/(Z_load+Z_shunt)  Eq. 1

[0114] The load impedance may be a variable value related to the impedance of tissue in contact with the end effector 126. Over the course of a cauterization procedure, the tissue impedance may vary as disclosed above. It may be recognized that as the load impedance becomes much larger than the shunt impedance, the total impedance approaches, but is never greater than, the shunt impedance. A shunt impedance in parallel with the load impedance may therefore prevent an electrosurgical system from measuring a large impedance when the end effector jaws 164a and 164b do not achieve a proper gap or the tissue is not compressed to a proper thickness. In one non-limiting example, the shunt impedance value of the connector 1370 at the operating frequency of the electrosurgical device 100 may be chosen to be about equal to the impedance threshold 920 indicative of a good cautery seal. Alternatively, the shunt impedance value of the shunt impedance element 1360 may be greater than or less than the impedance threshold 920.

[0115] A measurement of only the tissue impedance may be made when the connector 1370 is disabled, thereby removing the shunt impedance from the impedance measurement circuit. In one non-limiting example, the connector 1370 may be disabled based on a jaw angle α between the first jaw 164a and the second jaw 164b. A non-limiting example of disabling the connector 1370 based on a jaw angle α may include preventing electrical connectivity between the connector and an electrode in either of the first jaw 164a or the second jaw 164b when the jaw angle α is less than a jaw angle limit. A jaw angle limit may have a value of about 1.0° to about 10.0°. Non-limiting examples of a jaw angle limit may include about 1.0°, about 2.0° about 3.0° about 4.0° about 5.0° about 6.0° about 7.0° about 8.0° about 9.0° about 10.0°, or any value therebetween including endpoints. In some non-limiting examples, a jaw angle limit may be about 8.0° for 15 mm jaws. In some non-limiting examples, a jaw angle limit may be about 3.5° for 35 mm jaws. In another non-limiting example, a jaw angle limit may be about 5.0°. In a non-limiting example, a jaw angle limit may be chosen as one that assures that both jaws (164a and 164b) form a good electrical contact with the tissue therebetween. In another non-limiting example, a jaw angle limit may be chosen as one that assures that the walls of a vessel contacted by the jaws 164a, 164b are sufficiently proximate as to assure that a closed weld in the vessel is made. When the jaws 164a, 164b have a jaw angle α greater than the jaw angle limit, the shunt impedance of the connector 1370 may limit the impedance measured through the instrument. However, once the jaws 164a, 164b compress a tissue to a jaw angle α about equal to or less than the jaw angle limit, the electrical connection through the shunt impedance of connector 1370 may be broken, and the generator 120 may determine the impedance of the tissue directly.

[0116] FIG. 10 depicts a calculated impedance value curve 910 measured by an electrosurgical system over time for an end effector 126 lacking a parallel shunt circuit, and an impedance value curve 1230 measured over time for an end effector having a parallel shunt circuit in place. The impedance curve 910 for the system lacking the parallel shunt circuit is similar to that depicted in FIG. 7. The calculated impedance curve 1230 for an end effector 126 having 1230 a parallel shunt circuit in place can be understood in view of Eq. 1, above. Over time, the impedance of tissue subject to RF current (the load impedance, or Z_load) may increase. As a result, the impedance determined by the impedance sensor of the electrosurgical device may also increase and approach the shunt impedance value Z_shunt 1235 as a limiting value. In some non-limiting examples, Z_shunt 1235 may be about the same as the threshold value 920. In some other non-limiting examples, Z_shunt 1235 may be greater than the threshold value 920.

[0117] The time axis of FIG. 10 implies a time over which RF energy is deposited into tissue by the electrosurgical device. However, as noted above, the jaws of the end effector may also be closed over time to compress the tissue as the energy is added. Thus, the tissue may be both compressed and heated over time to form the cautery seal. As disclosed above, Z_shunt may be removed from the impedance sensing circuit for a jaw angle α less than the pre-determined jaw angle limit, thereby allowing the impedance sensor to measure the tissue impedance directly. Line 1220 depicts a possible transition point between the two impedance curves when the jaw angle α of the end effector transitions from an angle greater than the jaw angle limit to an angle smaller than the jaw angle limit. FIG. 11 depicts a calculated impedance 1300 detected by an impedance sensor over time that includes a transition impedance 1320 from a large jaw-angle impedance curve 1330 (that includes Z_shunt) to a narrow jaw-angle impedance curve 1310 (in which Z_shunt is removed).

[0118] FIGS. 12A, 12B, 13A, and 13B depict non-limiting examples of end effectors having contactors including shunt impedance elements.

[0119] FIGS. 12A and 12B depict one aspect of an end effector having a spring loaded connector 1370 contacting a separate shunt impedance element 1420. FIG. 12A illustrates the end effector having its jaws (164a and 164b) open wider than a jaw angle limit. It may be observed in FIG. 12A that the spring loaded connector 1370 is in electrical communication with an electrode associated with the second jaw 164b and is also in electrical communication with the shunt impedance element 1420 associated with the upper jaw 164a. The shunt impedance element 1420 is in electrical communication with an electrode associated with the upper jaw 162a. As depicted in FIG. 12A, the shunt impedance (Z_shunt) is enabled when the jaws form an angle greater than the jaw angle limit. Z_shunt is thus placed electrically in parallel with any load impedance (Z_load) between the jaws 164a and 164b. FIG. 12B illustrates the same end effector having its jaws (164a and 164b) open smaller than a jaw angle limit. It may be observed in FIG. 12B that a gap exists between the spring loaded connector 1370 and the shunt impedance element 1420 associated with the upper jaw 164a. Thus, as depicted in FIG. 12B, the shunt impedance (Z_shunt) is disabled when the jaws form a jaw angle α less than the jaw angle limit, and only the load impedance (Z_load) from tissue between the jaws 164a and 164b can be measured.

[0120] FIGS. 13A and 13B depict another aspect of an end effector in which the connector 1530 includes a shunt impedance element 1420 in a single unit. FIG. 13A depicts a side view of an end effector with jaws 164a and 164b having a jaw angle α larger than a jaw angle limit. FIG. 13B depicts an end view of the end effector with jaws 164a and 164b having a jaw angle α larger than a jaw angle limit. Under such a condition (large jaw angle), connector 1530 may be in electrical communication with an electrode component of second jaw 164b through a first end of the connector and in electrical communication with an electrode component of first jaw 164a through a second end of the connector comprising the impedance element 1420. Alternatively, connector 1530 may be in electrical communication with an electrode component of first jaw 164a through a first end of the connector and in electrical communication with an electrode component of second jaw 164b through a second end of the connector comprising the impedance element 1420. In one non-limiting example, when the jaws have a jaw angle α less than the jaw angle limit, the connector 1530 may remain in electrical communication with the second jaw 164b (or electrical components thereof) but may break its electrical communication with the first jaw 164a (or electrical components thereof). In another non-limiting example, when the jaws have a jaw angle α less than the jaw angle limit, the connector 1530 may remain in electrical communication with the first jaw 164a (or electrical components thereof) but may break its electrical communication with the second jaw 164b (or electrical components thereof).

[0121] In another non-limiting example, the connector 1370 may be distinct from the shunt impedance element 1420. In this second non-limiting example, the connector 1370 and the shunt impedance element 1420 may separate when the jaws form a jaw angle α less than the jaw angle limit. In a non-limiting example of such one aspect, the connector 1370 may remain in physical and electrical communication with the second jaw 164b while the shunt impedance element 1420 may remain in physical and electrical communication with the first jaw 164a. In another non-limiting example of such one aspect, the connector 1370 may remain in physical and electrical communication with the first jaw 164a while the shunt impedance element 1420 may remain in physical and electrical communication with the second jaw 164b.

[0122] It may be recognized that components required for measuring tissue impedance including, but not limited to, voltage sensing circuit 283 and current sensing circuit 285 may be conveniently located along any electrical path capable of permitting the measurement of values of i_L and V_L. Similarly, processing and controlling components configured to calculate impedance values, determine limiting values of measured tissue impedance, and/or control automated features to prevent the vessel from being severed before cauterization is complete may be incorporated in any suitable computing or control component of the system 100 including, but not limited to, the surgical system electronic portion 4900 or generator including an external generator 4935, internal generator 4940, or any non-limiting example thereof (for example, exemplary generator 5000). Alternatively, such necessary processing and control components may be found in additional electronic portions not otherwise disclosed above.

[0123] FIG. 14 depicts an alternative aspect in which a shunt impedance circuit 350 is located within the handle 112 of the electrosurgical device. As depicted in FIG. 14, the handle 112 of the electrosurgical device 100 may include mechanical components 1420 configured to actuate jaws 164a, 164b. In one non-limiting example, the mechanical components 1420 may be configured to close an angle between the jaws 164a, 164b when the mechanical components are moved to a proximate position. In such a manner, tissue placed between the jaws 164a, 164b may be compressed as a result of this proximal motion. The mechanical components 1420 may include a contactor 1470 configured to move with the mechanical components. In some non-limiting examples, the contactor 1470 may be mounted on a spring 1430 to provide mechanical compliance as the mechanical components 1420 move. The mechanical components 1420 may be sized so that the contactor 1470 contacts shunt switch 1470 when the jaw angle α is less than a limiting jaw angle. It may be recognized that spring 1430 may allow the contactor 1470 to maintain contact with the shunt switch 1470 while the mechanical components 1420 move in a further proximal direction, thereby closing jaws 164a, 164b around the tissue for improved compression. In the non-limiting example depicted in FIG. 14, shunt switch 1470 may be a normally closed switch. Thus, when contactor 1450 does not contact shunt switch 1470, the shunt switch is closed, placing shunt impedance element 1450 in parallel with the energy delivery surfaces through its connections with supply conductor 131 and return conductor 133. When contactor 1450 contacts shunt switch 1470, the shunt switch may be opened, thereby removing shunt impedance element 1450 from the circuit.

[0124] It may be understood that the aspect depicted in FIG. 14 is only one non-limiting example of an electrosurgical device having a shunt circuit incorporated in its handle. In another non-limiting example, the mechanical components 1420 may be configured to close the jaws 164a, 164b by means of a distal motion. In such one aspect, the contactor 1450 may contact a normally open shunt switch 1470 when the jaws 164a, 164b form an angle α greater than a jaw angle limit. By closing the shunt switch 1470, the contactor 1450 may thereby place the shunt impedance element 1460 in parallel with the energy surfaces. When the mechanical components 1420 move in a sufficiently distal direction so that the jaws 164a, 164b form an angle α less than a jaw angle limit, contactor 1450 may cease contacting the shunt switch 1470, thereby opening the connection to the shunt impedance element 1450. The open connection may then remove the shunt impedance element 1450 from the circuit.

[0125] It will be appreciated that the terms “proximal” and “distal” are used throughout the specification with reference to a clinician manipulating one end of an instrument used to treat a patient. The term “proximal” refers to the portion of the instrument closest to the clinician and the term “distal” refers to the portion located furthest from the clinician. It will further be appreciated that for conciseness and clarity, spatial terms such as “vertical,” “horizontal,” “up,” or “down” may be used herein with respect to the illustrated embodiments. However, surgical instruments may be used in many orientations and positions, and these terms are not intended to be limiting or absolute.

[0126] Various aspects of surgical instruments and robotic surgical systems are described herein. It will be understood by those skilled in the art that the various aspects described herein may be used with the described surgical instruments and robotic surgical systems. The descriptions are provided for example only, and those skilled in the art will understand that the disclosed examples are not limited to only the devices disclosed herein, but may be used with any compatible surgical instrument or robotic surgical system.

[0127] Reference throughout the specification to “various aspects,” “some aspects,” “one example,” or “one aspect” means that a particular feature, structure, or characteristic described in connection with the aspect is included in at least one example. Thus, appearances of the phrases “in various aspects,” “in some aspects,” “in one example,” or “in one aspect” in places throughout the specification are not necessarily all referring to the same aspect. Furthermore, the particular features, structures, or characteristics illustrated or described in connection with one example may be combined, in whole or in part, with features, structures, or characteristics of one or more other aspects without limitation.

[0128] While various aspects herein have been illustrated by description of several aspects and while the illustrative embodiments have been described in considerable detail, it is not the intention of the applicant to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications may readily appear to those skilled in the art. For example, it is generally accepted that endoscopic procedures are more common than laparoscopic procedures. Accordingly, the present invention has been discussed in terms of endoscopic procedures and apparatus. However, use herein of terms such as “endoscopic”, should not be construed to limit the present invention to an instrument for use only in conjunction with an endoscopic tube (e.g., trocar). On the contrary, it is believed that the present invention may find use in any procedure where access is limited to a small incision, including but not limited to laparoscopic procedures, as well as open procedures.

[0129] It is to be understood that at least some of the figures and descriptions herein have been simplified to illustrate elements that are relevant for a clear understanding of the disclosure, while eliminating, for purposes of clarity, other elements. Those of ordinary skill in the art will recognize, however, that these and other elements may be desirable. However, because such elements are well known in the art, and because they do not facilitate a better understanding of the disclosure, a discussion of such elements is not provided herein.

[0130] While several aspects have been described, it should be apparent, however, that various modifications, alterations and adaptations to those embodiments may occur to persons skilled in the art with the attainment of some or all of the advantages of the disclosure. For example, according to various aspects, a single component may be replaced by multiple components, and multiple components may be replaced by a single component, to perform a given function or functions. This application is therefore intended to cover all such modifications, alterations and adaptations without departing from the scope and spirit of the disclosure as defined by the appended claims.

[0131] Any patent, publication, or other disclosure material, in whole or in part, that is said to be incorporated by reference herein is incorporated herein only to the extent that the incorporated materials does not conflict with existing definitions, statements, or other disclosure material set forth in this disclosure. As such, and to the extent necessary, the disclosure as explicitly set forth herein supersedes any conflicting material incorporated herein by reference. Any material, or portion thereof, that is said to be incorporated by reference herein, but which conflicts with existing definitions, statements, or other disclosure material set forth herein will only be incorporated to the extent that no conflict arises between that incorporated material and the existing disclosure material.

[0132] Various aspects of the subject matter described herein are set out in the following numbered clauses:

[0133] Clause 1. An electrosurgical system comprising:

[0134] an RF current generator;

[0135] a handle body;

[0136] an end effector comprising:

• • [0137] a first jaw comprising a first energy delivery surface in electrical communication with a first terminal of the RF current generator, and
  • [0138] a second jaw comprising a second energy delivery surface in electrical communication with a second terminal of the RF current generator, wherein the first jaw and the second jaw form a jaw angle;

[0139] a shunt impedance circuit comprising a shunt impedance element having a pre-determined shunt impedance value, wherein the shunt impedance element is reversibly placed electrically in parallel with the first energy delivery surface and the second energy delivery surface when the jaw angle is at least a pre-determined angle; and

[0140] an impedance detector in electrical communication with the first energy delivery surface and the second energy delivery surface.

[0141] Clause 2. The electrosurgical system of clause 1, wherein the first jaw is movable when a force is applied to the end effector.

[0142] Clause 3. The electrosurgical system of any of clauses 1-2, wherein the second jaw is movable when a force is applied to the end effector.

[0143] Clause 4. The electrosurgical system of any one of clause 1-3, wherein the shunt impedance circuit comprises a contactor in electrical communication with the shunt impedance element.

[0144] Clause 5. The electrosurgical system of clause 4, wherein the contactor is configured to form an electrical contact with one or more electrical components of the first jaw or one or more electrical components of the second jaw.

[0145] Clause 6. The electrosurgical system of clause 5, wherein the contactor is a spring-loaded contactor.

[0146] Clause 7. The electrosurgical system of any one of clauses 1-6, wherein the shunt impedance element is one or more of a resistive element, a capacitive element, and an inductive element.

[0147] Clause 8. The electrosurgical system of any one of clauses 1-7, wherein the pre-determined shunt impedance value is an impedance value of a cauterized tissue.

[0148] Clause 9. The electrosurgical system of any one of clauses 1-8, wherein the shunt impedance circuit comprises a shunt switch in electrical communication with the shunt impedance element.

[0149] Clause 10. The electrosurgical system of any one of clauses 1-9, wherein the end effector comprises the shunt impedance circuit.

[0150] Clause 11. The electrosurgical system of any one of clauses 1-10, wherein the handle body comprise the shunt impedance circuit.

[0151] Clause 12. The electrosurgical system of any one of clauses 1-11, further comprising an elongated shaft having a proximal end in mechanical communication with the handle body and a distal end in mechanical communication with the end effector.

[0152] Clause 13. The electrosurgical system of any one of clauses 1-12, further comprising a scissor style device, wherein the end effector is in mechanical communication with the handle.

[0153] Clause 14. An end effector for an electrosurgical device, the end effector comprising:

[0154] a first jaw comprising a first energy delivery surface configured to be in electrical communication with a first terminal of an RF current generator;

[0155] a second jaw comprising a second energy delivery surface configured to be in electrical communication with a second terminal of the RF current generator, wherein the first jaw and the second jaw form a jaw angle, and wherein the first jaw, the second jaw, or the first jaw and the second jaw is movable; and

[0156] a shunt impedance circuit comprising a shunt impedance element having a pre-determined shunt impedance value, wherein the shunt impedance element is reversibly placed electrically in parallel with the first energy delivery surface and the second energy delivery surface when the jaw angle is at least a pre-determined angle.

[0157] Clause 15. The end effector of clause 14, wherein the shunt impedance circuit comprises a contactor in electrical communication with the shunt impedance element.

[0158] Clause 16. The end effector of clause 15, wherein the contactor is a spring-loaded contactor.

[0159] Clause 17. The end effector of clause 15, wherein the contactor is configured to form an electrical contact with one or more electrical components of the first jaw or one or more electrical components of the second jaw.

[0160] Clause 18. The end effector of any one of clauses 14-17, wherein the shunt impedance element is configured to form an electrical contact with one or more electrical components of the first jaw or one or more electrical components of the second jaw.

[0161] Clause 19. The end effector of any one of clauses 14-18, wherein the shunt impedance element is one or more of a resistive element, a capacitive element, and an inductive element.

[0162] Clause 20. The end effector of any one of clauses 14-19, wherein the pre-determined shunt impedance value is an impedance value of a cauterized tissue.

[0163] Clause 21. The end effector of 14-20, wherein the shunt impedance circuit comprises a shunt switch in electrical communication with the shunt impedance element.

[0164] Clause 22. A method of controlling an RF current delivered to an end effector of an electrosurgical system, the method comprising:

[0165] providing an electro electrosurgical system comprising:

• • [0166] an RF current generator;
  • [0167] a handle body;
  • [0168] an end effector comprising:
    • [0169] a first jaw comprising a first energy delivery surface in electrical communication with a first terminal of the RF current generator, and
    • [0170] a second jaw comprising a second energy delivery surface in electrical communication with a second terminal of the RF current generator, wherein the first jaw and the second jaw form a jaw angle;
  • [0171] a shunt impedance circuit comprising a shunt impedance element having a pre-determined shunt impedance value, wherein the shunt impedance element is reversibly placed electrically in parallel with the first energy delivery surface and the second energy delivery surface when the jaw angle is at least a pre-determined angle;
  • [0172] an impedance detector in electrical communication with the first energy delivery surface and the second energy delivery surface; and
  • [0173] a controller of the RF current generator;

[0174] sourcing an RF current from the RF current generator to the first energy delivery surface via the first terminal of the RF current generator and receiving an RF current by the RF current generator from the second energy delivery surface via the second terminal of the RF current generator;

[0175] measuring an impedance between the first energy delivery surface and the second energy delivery surface by the impedance detector; and

[0176] causing the controller of the RF current generator to disable sourcing the RF current to the first energy delivery surface when a measured impedance between the first energy delivery surface and the second energy delivery surface is greater than a pre-determined impedance limit.

[0177] Clause 23. The method of clause 22, wherein the RF current generator comprises the impedance detector.

[0178] Clause 24. The method of any one of clauses 22-23, wherein the RF current generator generates an RF current of about 100 kHz to about 1 MHz.

[0179] Clause 25. The method of any one of clauses 22-24, wherein the pre-determined impedance limit is an impedance of a cauterized tissue.