Impedance matching in electrosurgery

Abstract

A system and method for performing impedance matching to improve surgical outcomes in electrosurgical systems is described. An impedance matching network is positioned along the RF energy path and dynamically matches the output impedance of the electrosurgical generator to the input impedance of the tissue load by varying the inductance of a resonant cell. As a result, adjustments are made to the output phase of the electrosurgical generator to ensure optimal matching of the source and load impedance based on the tissue sealing, fusing, or cutting cycle. This results in a resonant condition that provides a zero-degree phase shift between the RF output voltage and current of the electrosurgical generator. The inductance of the resonant cell is proportional to the magnitude of the current flowing through the DC winding of the saturable core reactor or the size of the air gap in the inductor core material.

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims priority to and the benefit of U.S. Provisional Patent Application Serial No. 63 / 426,066, entitled "Impedance Matching in Electrosurgery," filed November 17, 2022, which is expressly incorporated herein by reference in its entirety for all purposes.

[0002] (Technical field) The present invention relates generally to electrosurgical systems and, more particularly, to systems and methods for controlling the efficiency of energy transfer between an electrosurgical generator and a tissue impedance load or tissue load. [Background technology]

[0003] Electrosurgery is a surgical procedure using electrosurgical energy that involves applying high-voltage, high-frequency electrical energy, e.g., radio frequency (RF) energy, to tissue for the purpose of sealing, fusing, and / or cutting tissue or blood vessels. Electrosurgery typically involves the use of an electrosurgical generator to generate the RF energy and an electrosurgical hand device or instrument to direct the RF energy toward the target tissue. Electrosurgical instruments are generally classified into two types: monopolar and bipolar. Monopolar instruments deliver electrical energy to one or more electrodes on the instrument at a high current density, and a separate return electrode is often electrically coupled to the patient and designed to minimize current density. Bipolar electrosurgical instruments operate without a separate return electrode, allowing electrical signals to be delivered to a focused tissue region with reduced risk.

[0004] A common concern in electrosurgical energy management is impedance matching. To maximize power transfer from the power source to the load, the output impedance of the power source must be equal to the input impedance of the load. Failure to match impedances can lead to signal reflections and inefficient power transfer. Excessive power loss, heat dissipation, and circuit failures can all result from improper impedance matching. In these cases, reduced efficiency is the result of improper matching, causing excessive power loss. On the other hand, accurate and balanced impedance matching can result in the desired maximum power transfer and / or power efficiency.

[0005] During electrosurgery, while RF energy is applied to a target tissue, the target tissue is affected and its characteristics, i.e., input impedance load, change as a result of the application of RF energy. When the load impedance changes, a large portion of the power can be reflected, resulting in a substantial impedance mismatch and inefficient power transfer. Under high RF output power conditions during an electrosurgical sealing event, the efficiency of energy transfer from the electrosurgical generator to the tissue is less than desirable. Efficient energy transfer to the tissue can improve seal quality and seal consistency and can be useful for reducing the power requirements for sealing tissue. Accordingly, embodiments of the present invention are intended to maximize or at least improve power transfer efficiency between an electrosurgical generator and a tissue load during a surgical procedure. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] U.S. Patent Application Serial No. 16 / 562,122 Summary of the Invention

[0007] According to various embodiments, the present disclosure describes systems and methods for performing impedance matching to improve surgical outcomes. The systems and methods enable matching of source and load impedances under all dynamic conditions, such as variable load, procedure, and / or operating conditions, thereby ensuring optimal matching based on tissue sealing, welding, or cutting cycles, thereby achieving improved surgical outcomes.

[0008] According to one aspect of the present invention, an electrosurgical system for performing a surgical procedure is provided. The electrosurgical system can include an electrosurgical generator configured to deliver RF energy to a surgical site and an electrosurgical instrument. The electrosurgical instrument has at least one active electrode adapted to treat tissue with the delivered RF energy. The electrosurgical system can further include an impedance matching network. In various embodiments, the impedance matching network can include an adjustable resonating cell disposed along a path of the RF energy and positioned to provide maximum power transfer from the electrosurgical generator to the electrosurgical instrument. In various embodiments, this maximum power transfer is achieved by dynamically varying the inductance of the adjustable resonating cell to create a resonant condition, thereby adjusting the phase of the delivered RF energy to a predetermined phase value.

[0009] According to a second aspect of the present invention, there is provided a method of performing impedance matching in an electrosurgical procedure, the method including the steps of providing an electrosurgical generator for delivering RF energy to a surgical site via an electrosurgical instrument, positioning an adjustable resonating cell along a path of the RF energy to provide maximum power transfer from the electrosurgical generator to the surgical instrument, and selectively controlling the inductance of the adjustable resonating cell to adjust the phase of the delivered RF energy to a predetermined phase value.

[0010] According to a third aspect of the present invention, an electrosurgical system is provided. The electrosurgical system may include an electrosurgical generator configured to deliver RF energy and an electrosurgical instrument operably coupled to the electrosurgical generator to treat target tissue. The electrosurgical system further includes an impedance matching network coupled between the electrosurgical generator and the electrosurgical instrument. According to embodiments of the present invention, the impedance matching network may include a first E-shaped magnetic core having a central leg and two outer legs, and a second E-shaped magnetic core having a central leg and two outer legs. In various embodiments, the first and second E-shaped magnetic cores are arranged in a mirror image configuration such that the central leg and the two outer legs from each of the first and second E-shaped magnetic cores are aligned and facing each other.

[0011] According to a fourth aspect of the present invention, an electrosurgical system is provided that includes a controller and an impedance matching network. In various embodiments, the controller is configured to receive measured voltage and current values ​​of the delivered RF energy and calculate a phase difference between these measurements. The controller is further configured to determine a phase error relative to a predetermined phase value and output an impedance matching control signal in response to the determined phase error. The impedance matching network is configured to receive the impedance matching control signal. In various embodiments, the impedance matching network can include a saturable core reactor (SCR) having a pair of E-shaped magnetic cores arranged in a mirror image configuration. The impedance matching network further includes an AC winding wound around a central leg of the pair of E-shaped magnetic cores and configured to have a variable inductance in accordance with the impedance matching control signal.

[0012] According to a fifth aspect of the present invention, an electrosurgical system is provided having an electrosurgical generator configured to deliver RF energy and an electrosurgical instrument operably coupled to the electrosurgical generator to treat target tissue. The electrosurgical system further includes an impedance matching network coupled between the electrosurgical generator and the electrosurgical instrument. In various embodiments, the impedance matching network can include a first E-shaped magnetic core having a central leg and two outer legs, and a second E-shaped magnetic core having a central leg and two outer legs. The first and second E-shaped magnetic cores are arranged in a mirror image configuration such that the central leg and the two outer legs from each of the first and second E-shaped magnetic cores are aligned and opposite. This arrangement, in various embodiments, forms a symmetrical structure with two identical halves separated by an air gap.

[0013] According to a sixth aspect of the present invention, an electrosurgical system is provided having a controller and an impedance matching network. In various embodiments, the controller is configured to receive measured voltage and current values ​​of the delivered RF energy, calculate a phase difference between the measured voltage and current values ​​of the delivered RF energy, determine a phase error relative to a predetermined phase value, and output an impedance matching control signal in response to the phase error. In various embodiments, the impedance matching network can include a variable core inductor (VCI) having a pair of E-shaped magnetic cores arranged in a mirror image configuration. The impedance matching network further includes a single winding wound around a central leg of the pair of E-shaped magnetic cores and configured to have a variable inductance in accordance with the impedance matching control signal. The impedance matching network is further configured to receive the impedance matching control signal.

[0014] According to another aspect of the present invention, an impedance matching circuit for use in an electrosurgical system is provided. The impedance matching circuit can include a first E-shaped magnetic core having a central leg and two outer legs, a second E-shaped magnetic core having a central leg and two outer legs, and a plurality of windings. In various embodiments, the first and second E-shaped magnetic cores are arranged in a mirror image configuration such that the central leg and the two outer legs from each of the first and second E-shaped magnetic cores are aligned and opposite each other. The plurality of windings can include one AC winding wound around the mirror-image central leg and two DC windings, one DC winding wound around each of the mirror-image outer legs. In embodiments of the present invention, the inductance of the AC winding can be selectively controlled based on the DC current flowing through the two DC windings.

[0015] According to another aspect of the present invention, an impedance matching circuit for use in an electrosurgical system is provided. The impedance matching circuit can include a first E-shaped magnetic core having a central leg and two outer legs, a second E-shaped magnetic core having a central leg and two outer legs, and a single winding wound around the central leg in a mirror image configuration. The first and second E-shaped magnetic cores are configured as mirror images such that the central leg and the two outer legs from each of the first and second E-shaped magnetic cores are aligned and opposed, forming a symmetrical structure with two identical halves separated by an air gap. In various embodiments, the inductance of the single winding can be selectively controlled based on variations in the size of the air gap achieved by moving one of the two identical halves relative to the other.

[0016] Many of the attendant features of this invention will be more readily understood by reference to the foregoing and following descriptions when considered in conjunction with the accompanying drawings.

[0017] The present disclosure is described in conjunction with the accompanying drawings. [Brief explanation of the drawings]

[0018] [Figure 1]1 shows a perspective view of an electrosurgical generator, according to various embodiments of the present invention; [Figure 2] 1 shows a perspective view of an electrosurgical hand device according to various embodiments of the present invention. [Figure 3] 1 shows a block diagram of an electrosurgical generator, according to various embodiments of the present invention; [Figure 4] 1 is a schematic diagram of an electrosurgical system showing one embodiment of an impedance matching network in greater detail, in accordance with an embodiment of the present invention; [Figure 5] FIG. 1 is a schematic diagram illustrating one embodiment of a saturable core reactor (SCR), in accordance with an embodiment of the present invention. [Figure 6] FIG. 2 is a block diagram of an electrosurgical system showing in greater detail one embodiment of a control system and one embodiment of an impedance matching network within the electrosurgical generator, in accordance with various embodiments of the present invention. [Figure 7] FIG. 2 is a schematic diagram illustrating the operation modes and functional blocks of a PID controller according to an embodiment of the present invention. [Figure 8] FIG. 2 illustrates the characteristics of a saturable core reactor (SCR) according to an embodiment of the present invention. [Figure 9] FIG. 2 illustrates the characteristics of a saturable core reactor (SCR) according to an embodiment of the present invention. [Figure 10] 10A-10C are experimental results illustrating the phase and impedance changes of a saturable core reactor (SCR) across a capacitive load according to an embodiment of the present invention. [Figure 11] 10A-10C are experimental results illustrating the phase and impedance changes of a saturable core reactor (SCR) across a capacitive load according to an embodiment of the present invention. [Figure 12] 10A-10C are experimental results illustrating the phase and impedance changes of a saturable core reactor (SCR) across an inductive load according to an embodiment of the present invention. [Figure 13] 10A-10C are experimental results illustrating the phase and impedance changes of a saturable core reactor (SCR) across an inductive load according to an embodiment of the present invention. [Figure 14] FIG. 2 illustrates an alternative embodiment of a saturable core reactor (SCR) in accordance with an embodiment of the present invention. [Figure 15A] FIG. 10 illustrates an alternative embodiment of an impedance matching network, in accordance with an embodiment of the present invention. [Figure 15B] FIG. 10 illustrates an alternative embodiment of an impedance matching network, in accordance with an embodiment of the present invention. [Figure 16] 1 illustrates a schematic implementation of a variable core inductor (VCI) module, according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0019] In the accompanying drawings, similar components and / or features may have the same reference label. Furthermore, various components of the same type may be distinguished by following the reference label with a dash and a second label that distinguishes between the similar components. When only a first reference label is used in this specification, the specification applies to any one of the similar components having the same first reference label, regardless of the second reference label.

[0020] The description that follows provides exemplary embodiments only and is not intended to limit the scope, applicability, or configuration of the present disclosure. Rather, the subsequent description of exemplary embodiments will provide those skilled in the art with an enabling description for practicing exemplary embodiments of the present disclosure. It should be understood that various changes can be made in the function and arrangement of elements without departing from the spirit and scope of the invention.

[0021] The present disclosure relates generally to electrosurgery and electrosurgical systems, and more particularly to systems and methods of impedance matching for controlling energy transfer efficiency between an electrosurgical generator and target tissue.

[0022] Embodiments of the present invention are directed to systems and methods for improving surgical outcomes by providing an impedance matching network that can accommodate changes in tissue impedance that occur during an electrosurgical procedure. The present invention, in various embodiments, allows for matching the source impedance to the load impedance under all dynamic conditions, such as changes in the tissue impedance load due to the electrosurgical procedure or tissue impact, and any operating conditions and commands determined by the surgeon, surgical procedure, and / or device script. An impedance matching network, in accordance with embodiments of the present invention, is positioned along the path of the RF energy to dynamically match the output impedance of the source energy, e.g., an electrosurgical generator, to the load, e.g., the tissue impedance load or the input impedance of the tissue load.

[0023] To achieve maximum power delivery, any reactive component present at the load should be equal in magnitude to the source impedance but opposite in sign. In other words, to achieve maximum power delivery and improve power efficiency, the source impedance and the load impedance should be complex conjugates of each other. An impedance matching network according to various embodiments of the present invention can include an LC resonant circuit with a tunable inductor. In various embodiments, the tunable inductor can include a saturable core reactor (SCR) coupled in series with one or more capacitors electrically connected to each other. The SCR according to embodiments of the present invention not only allows for pre-matching of the source impedance to the load impedance, but also allows for accommodating constantly changing tissue load impedances under any changing conditions during electrosurgical surgery.

[0024] Electrosurgical systems and methods according to various embodiments of the present invention are described in detail below with separate sections describing the electrosurgical generator, the electrosurgical hand device or instrument, and the control systems and methods used for power transfer and / or impedance matching to maximize power transfer efficiency between the electrosurgical generator and the target tissue.

[0025] 1-2, an exemplary embodiment of an electrosurgical system according to various embodiments of the present invention is shown. As shown in these figures, the electrosurgical system can include an electrosurgical generator 10 and a removably connectable electrosurgical tool or instrument 20. The electrosurgical tool or instrument 20 can be electrically coupled to the generator 10 via a cable connection having a device key or connector 21 extending from the instrument 20 to a device connector or access port 12 on the generator 10. The electrosurgical instrument 20 can include audio, tactile, and / or visual indicators to alert the user to certain or predetermined states of the instrument 20, such as, for example, the start and / or end of a fusion operation. In some embodiments, a manual controller, such as a hand switch or foot switch, can be connectable to the generator 10 and / or the instrument 20 to enable certain selective control of the instrument, such as initiating a fusion operation.

[0026] According to various embodiments, the electrosurgical generator 10 includes a display 14 that can indicate the status of the electrosurgical system, including, among other information, the status of one or more electrosurgical instruments and / or accessories, connectors or connections thereto, the status or operation of the generator, and error indicators. The electrosurgical generator 10 according to various embodiments of the present invention can include a user interface, such as, for example, a plurality of buttons 16. The plurality of buttons 16 allows for user interaction with the electrosurgical generator 10. This user interaction can include, for example, requesting an increase or decrease in electrical energy supplied to one or more instruments 20 coupled to the electrosurgical generator 10. In various embodiments, the generator 10 further includes a user-accessible power-on switch or button 18 that, when activated, applies power to the generator 10 and activates or initiates a generator self-verification system test. In other embodiments, the display 14 can be a touchscreen display, thus integrating data display and user interface functions.

[0027] According to various embodiments, when the generator 10 is powered up by actuation of the power-on switch 18, the generator 10 initiates or initiates a power-on self-verification system test. During the self-verification system test, the generator 10 verifies the adjustment of the RF output power in one or more RF modes and / or one or more RF resolution settings. According to various embodiments, the RF adjustment modes include voltage, current, and power adjustment modes, and the RF resolution settings include low, normal, and high voltage settings. In various embodiments, the self-verification system test allows for the rapid identification of potential generator problems or errors prior to use of a connected electrosurgical instrument or delivery of RF energy to tissue or a vessel via the electrosurgical instrument 10. To this end, one or more internal impedance loads are incorporated into the electrosurgical generator 10. The internal impedance loads, having multiple configurations, are utilized to verify generator voltage, current, power, and / or phase measurements across multiple RF adjustment modes and multiple RF resolution settings. For details of the self-verification system testing of the electrosurgical generator 10, reference may be made to U.S. Patent Application No. 16 / 562,122, filed September 5, 2019, the contents of which are incorporated herein by reference in their entirety.

[0028] In various embodiments, the electrosurgical generator 10 of the present invention is configured to output radio frequency (RF) energy via a connectable electrosurgical instrument or hand device 20 to seal, fuse, and / or cut tissue or vessels via one or more electrodes. According to an embodiment of the present invention, the electrosurgical generator 10 is configured to generate RF energy up to 300 V, 8 A, and 375 VA and is configured to determine the phase angle or difference between the generator's RF output voltage and RF output current during activation or delivery of RF energy. In this manner, the electrosurgical generator 10 regulates voltage, current, and / or power and monitors the RF energy output (e.g., voltage, current, power, and / or phase). In one embodiment, the generator 10 can stop, terminate, or otherwise interrupt the RF energy output under predetermined conditions. By way of example, these predetermined conditions may be when a device switch is deasserted (e.g., when a fuse button is released), when a time value is met, and / or when the active phase angle and / or phase change is greater than or equal to a phase and / or phase change termination value indicating the end of an operation such as fusing or cutting tissue.

[0029] According to an embodiment of the present invention, the electrosurgical instrument 20 can include an elongate shaft 26 having a proximal end coupled to and extending from the actuator 24 and a distal end coupled to and extending from the jaws 22. A longitudinal axis extends from the proximal end to the distal end of the elongate shaft 26. In one embodiment, the actuator 24 can include a movable handle 23 pivotally coupled to a stationary handle or housing 28. The movable handle 23 is coupled to the stationary handle or housing 28 via a central or main floating pivot. In actuation, the movable handle 23 is manipulated by a user, e.g., a surgeon, to selectively open and close the jaws 22 by actuating the jaws 22 at the distal end of the elongate shaft 26. Once tissue or a vessel is grasped between the jaws 22, a switch or button 29 is actuated by the surgeon to seal, fuse, and / or cut the tissue / vessel between the jaws 22. When the button 29 is actuated, the associated circuitry or contacts are connected to connect the appropriate electrodes on the jaws with the associated connections on the generator 10 to deliver RF energy to tissue grasped between the jaws 22 or otherwise in contact with one or more electrodes on the jaws.

[0030] In various embodiments, the electrosurgical instrument 20 further includes a mechanical or electrical cutting blade that can be coupled to a blade actuator, such as a blade lever or trigger 25 on the stationary handle or housing 28. The cutting blade is actuated by the blade trigger 25 to divide or cut tissue between the jaws 22. In various embodiments, a blade slider is connected to the blade trigger 25, and a protrusion extends from the proximal end of the blade slider into an opening at one end of the blade trigger, connecting the components together. The other end of the blade trigger is exposed and accessible to the user, and the blade trigger 25 is pivotable about a trigger pivot at or near the midpoint of the blade trigger. In this manner, when the blade trigger 25 is pulled or rotated proximally by the user, the distal end of the blade trigger, connected to the blade slider, slides or moves the blade slider distally. Integral to or attached to the distal end of the blade slider is a cutting blade, knife, or cutting edge or surface. In this manner, longitudinal translation of the blade slider through the blade channel of the jaws cuts tissue grasped between the jaws 22.

[0031] In one embodiment, the cutting edge or surface is angled to facilitate cutting of tissue between the jaws 22. In various embodiments, the cutting blade is a curved blade, hook, knife, or other cutting element sized and configured to cut tissue between the jaws 22. In various embodiments, the elongate shaft 26 comprises an actuation tube or rod that couples the jaws 22 to the actuator. In one embodiment, the actuator includes a rotating shaft assembly including a rotation knob 27 disposed on the outer cover tube of the elongate shaft 26. The rotation knob 27 allows the surgeon to rotate the shaft of the device while gripping the actuator. In various embodiments, the elongate shaft 26 is rotatable 360 ​​degrees, and in other embodiments, the rotation of the elongate shaft 26 is limited to 180 degrees, i.e., 90 degrees clockwise and 90 degrees counterclockwise.

[0032] Referring now to FIG. 3 , a block diagram of an electrosurgical generator 10 is shown in accordance with an embodiment of the present invention. As shown in this figure, the electrosurgical generator 10 includes a power input module 31, e.g., an AC mains input, coupled to a power supply module, e.g., two 48V DC power supplies 32, 33. The power supply module converts AC voltage from the AC mains input to DC voltage and supplies power to various circuits of the generator 10 via a housekeeping power supply 34, particularly to an RF amplifier 40, which generates or outputs RF energy. In one embodiment, the RF amplifier 40 includes a combination of a buck circuit and an H-bridge circuit to convert the DC voltage input to an RF output, or in another embodiment, a variable amplitude 350 kHz sine wave. The DC voltage input is a 96V DC input generated by two 48V DC power supplies 32, 33 coupled in series. One of the 48V DC power supplies 32, 33 is configured to generate a low-voltage rail, specifically, a standby voltage for powering the generator 10.

[0033] The RF output, and in various embodiments, the amplitude of the RF waveform output, is controlled and regulated by an electrosurgical control system, or digital integrated servo control system 100, incorporated or integrated into the electrosurgical generator 10. As shown in FIG. 3 , the control system 100 can include an RF amplifier 40, a primary microcontroller 50, and a feedback system 60. The control system 100 varies between regulating the voltage, current, or power of the RF output generated by the RF amplifier 40. In various embodiments, the feedback system 60 measures the RF output and processes the measured data before digitally providing the real and imaginary components of the RF output to the primary microcontroller 50. The primary microcontroller 50, according to embodiments of the present invention, processes the data received from the feedback system 60 and adjusts the output of the RF amplifier 40 to meet desired adjustment targets. In various embodiments, the feedback system 60 includes an analog input, digital processing, and a digital output.

[0034] According to various embodiments of the present invention, the electrosurgical generator 10 is further configured to provide RF power in three resolution settings or modes: low voltage, medium voltage, and high voltage range. During the high voltage range or resolution setting, the RF power can reach up to 300 V or 4 A and is primarily used for tissue cutting. During the medium or normal voltage range or resolution setting, the RF power can reach a maximum of 150 V or 8 A and is primarily used for tissue sealing. During the low voltage mode or resolution setting, the RF power is limited to 10 V and 100 mA and is primarily used for passive tissue impedance assessment and measurement at a level that does not produce a physiological response in tissue but is sufficient to detect openings and / or short-loading of the RF power path upon activation of the electrosurgical hand device, e.g., instrument 20.

[0035] In various embodiments, a device script stored or located on a connectable electrosurgical hand device, e.g., instrument 20, and / or a connector coupled thereto, e.g., device key 21, is used to determine or set the RF power or voltage mode. In various embodiments, the device script represents a walkthrough of a surgical procedure, which may include the application and termination of RF energy to tissue. In various embodiments, the electrosurgical generator 10 records all RF power data to an internal memory device, e.g., a secure digital (SD) or non-volatile memory card. The memory device is configured to be read via an interface port 35 on the electrosurgical generator 10, e.g., a universal serial bus (USB) port (best shown in FIG. 3 ). In various embodiments, the generator 10 is configured to copy data from the internal memory device to a connectable portable storage device, e.g., a USB flash drive, via the generator's interface port.

[0036] In various embodiments, the electrosurgical generator 10 is configured to alert the surgeon when the vessel has reached a treatment completion state, e.g., a sealed completion state, or if an error or fault condition occurs. In various embodiments, the electrosurgical generator 10 can include visual, tactile, and / or audible outputs to provide such alerts or other indicators or information to the surgeon as dictated by the surgical procedure, the device script, or health or operational information regarding the device 20 and / or the generator 10. In one embodiment, the generator 10, via a front panel interface 38, alerts the surgeon via an LCD display 14 integrated into the generator's front panel, and in various embodiments, provides specific audible alarms or informational tones via a speaker 36 also integrated into the generator's front panel. In various embodiments, the generator 10 can include a front panel overlay 39 that provides a user interface or access, including navigational pushbuttons to allow the user to access system settings such as volume and display brightness. The front panel overlay 39 can also include a system power button or connection. In various embodiments, a fan system 37 is provided to assist with heat dissipation. Additionally, as shown in Figure 3, signal or sig refers to a connection consisting of, for example, digital signals used to communicate information between systems and / or printed circuit boards, power refers to a connection consisting of, for example, voltage rails used to power systems and / or printed circuit boards, and RF refers to a connection consisting of, for example, high voltage, high current RF energy used to seal, fuse, or cut tissue or blood vessels.

[0037] 4, a schematic diagram of an electrosurgical system is shown depicting an embodiment of an impedance matching network 300 in more detail in accordance with an embodiment of the present invention. As can be seen in this figure, the impedance matching network 300 is disposed along the path of RF energy between the electrosurgical generator 10 and a composite tissue impedance load or tissue load, e.g., Z_load 20-1, which is the equivalent electrical circuit of the contact between the instrument 20 and the patient's body or surgical site. Because the tissue impedance load or tissue load Z_load 20-1 continuously changes due to various tissue conditions, operating conditions, and commands determined by the surgeon, surgical procedure, and / or device script, in embodiments of the present invention, the impedance matching network 300 is designed and configured to dynamically match the output impedance of the electrosurgical generator 10 to the input impedance of the tissue load, e.g., Z_load 20-1. To this end, in various embodiments, the impedance matching network 300 may include an LC resonant circuit, e.g., a series LC tank circuit 30, having a tunable inductor (L_Ser) coupled in series with a capacitor bank (C_Ser). In various embodiments, the adjustable inductor may include a saturable core reactor (SCR) 302 electrically coupled with one or more capacitors 304 (not shown in FIG. 4 ) to form an adjustable resonant cell, such as a series LC tank or resonant circuit 30. In various embodiments of the present invention, the inductance of the saturable core reactor (SCR) 302 is dynamically adjusted to control the efficiency of energy transfer between the electrosurgical generator 10 and the tissue impedance load or tissue load Z_load 20-1.

[0038] Referring now to FIG. 5, a schematic diagram of an embodiment of a saturable core reactor (SCR) 302 is shown in various embodiments of the present invention. As can be seen from this diagram, the saturable core reactor 302 can include a pair of E-shaped magnetic cores or E-cores. Each E-shaped magnetic core or E-core consists of one center leg and two individual outer legs. In various embodiments, the two E-shaped magnetic cores or E-cores are positioned so that the center leg and the two outer legs from each core are aligned and opposite each other. This results in a symmetrical or mirror-image configuration formed by two identical magnetic core halves. In various embodiments, the saturable core reactor (SCR) 302 can have three windings: one AC load winding and two DC control windings. As shown in FIG. 5, the two DC control windings and one AC load winding are interconnected by the paired E-shaped magnetic cores or E-cores so that the magnetic cores form a continuous magnetic path in the assembly. The use of E-shaped magnetic cores strengthens the magnetic field and provides a more symmetrical solution, creating a closed magnetic system. The amount of magnetic field enhancement provided by an E-core may depend on the magnetic permeability of the core material. In various embodiments, the E-core material is made from ferrite or silicon steel. In some embodiments, a powder core consisting of metal grains mixed with a suitable organic or inorganic binder and pressed to a desired density is used as the E-core material. In other embodiments, carbonyl iron powder is used as the E-core material.

[0039] According to various embodiments of the present invention, an AC load winding is wound around the center leg of an E-shaped magnetic core pair or E-core. In various embodiments, the AC load winding is designed to act as the inductor (L_Ser) of a series LC tank or resonant circuit 30 disposed along the RF energy path between the electrosurgical generator 10 and the composite tissue impedance load or tissue load Z_Load 20-1. Meanwhile, two DC control windings are designed and configured to control the inductance of the AC load winding. For this purpose, one DC control winding is wound around each outer leg of an E-shaped magnetic core pair or E-core. As can be seen in FIGS. 4-5 , the two DC control windings are wound in opposite directions, resulting in opposite polarities. This configuration serves to avoid or at least mitigate electromagnetic interference. Furthermore, the two DC windings are electrically connected in series and linked to a DC current source. It should also be noted that the distance or air gap between the two E-shaped magnetic cores (E-cores) is designed to enhance magnetic isolation, thereby preventing magnetic interference between the windings of each core.

[0040] Despite constant changes in the tissue impedance load, the saturable core reactor (SCR) 302 tends to maintain a predetermined magnitude of current in the AC load winding. This is achieved by adjusting the magnitude of the DC current passing through the DC control winding. When the current through the two DC control windings reaches a certain current threshold, the E-core of the saturable core reactor (SCR) begins to saturate. As the E-core is driven further into saturation, the relative permeability μ of the magnet material decreases, thereby decreasing the inductance of the AC load winding (i.e., L_Ser). Therefore, the inductance of the AC load winding (L_Ser) is directly proportional to the magnitude of the current passing through the DC control winding. During operation, the inductance of the AC load winding is constantly adjusted as a function of the current passing through the DC control winding to match the tissue impedance load or the impedance of the tissue load to the impedance of the electrosurgical generator. Thus, the source impedance or output impedance of the electrosurgical generator depends on the series LC tank or resonant circuit 30 of the impedance matching network 300.

[0041] Meanwhile, the tissue impedance load or tissue load Z_Load 20-1 continuously changes under various surgical procedures, operations, or treatment conditions. In various embodiments, the dynamically changing tissue impedance load or tissue load may be more inductive or capacitive in nature due to the influence of electrosurgical tissue, for example, during tissue sealing, welding, or cutting cycles, or any other operational or treatment conditions. Thus, during any tissue sealing cycle, a difference in impedance value occurs between the electrosurgical generator and the tissue impedance load. This difference in impedance value translates into a phase difference between the generator's RF output voltage and current. In various embodiments, the electrosurgical generator 10 is configured to continuously monitor and measure the phase difference between the voltage and current supplied across the tissue impedance load or tissue load Z_Load 20-1. A positive phase difference (current-lagging voltage) indicates a more inductive tissue impedance load or tissue load, while a negative phase difference (current-leading voltage) signifies a more capacitive tissue load.

[0042] The saturable core reactor (SCR) 302, according to various embodiments of the present invention, continuously matches the output impedance of the electrosurgical generator to the input tissue impedance load. By varying the inductance of the saturable core reactor (SCR), the source impedance of the electrosurgical generator is dynamically adjusted under all surgical, operational, or procedural conditions to offset inductive or capacitive tissue loads. Thus, if the load impedance or tissue impedance load is capacitive, the source impedance becomes more inductive, and vice versa. When the source impedance and load impedance are matched, the tissue impedance load seen by the electrosurgical generator 10 is purely resistive. In various embodiments, this matched condition results in a resonance condition of the series LC tank circuit 30, which provides a zero-degree phase shift between the generator's RF output voltage and current.

[0043] Table I summarizes theoretical calculations showing the relationship between power efficiency and impedance matching for an exemplary electrosurgical system with and without an impedance matching network 300, e.g., a series LC tank or resonant circuit 30 with SCR 302, in an embodiment of the present invention. In this exemplary embodiment, electrical properties, e.g., impedance, current, various powers: active, reactive, and apparent power, and power factor, are calculated for an exemplary inductive tissue impedance load or tissue load (i.e., Z_Load = 50 Ω + 20 μH). As can be seen from Table I, without the impedance matching network, the calculated tissue impedance load is approximately 67 Ω, resulting in a substantial mismatch with a 50 Ω electrosurgical generator. Power factor is defined as the ratio of active power (RF power output by the electrosurgical generator to a resistive tissue load) to apparent power (RF power output by the electrosurgical generator to a complex tissue load). A high power factor (i.e., unity or close to "1") is an indicator of high efficiency with low power losses. As can be seen from Table I, when no impedance matching is performed between the source impedance and the load impedance, the calculated power efficiency is about 74.5%. [Table 1]

[0044] In various embodiments, the inductance of the saturable core reactor (SCR) 302 in the LC tank or resonant circuit 30 of the impedance matching network 300 is dynamically adjusted so that the source impedance of the electrosurgical generator is equal to and inverse (complex conjugate) of the 20 μH tissue inductive load. This creates a resonant condition where the tissue impedance load seen by the electrosurgical generator is purely resistive, i.e., the desired 50 Ω target tissue load, resulting in a power factor or power efficiency of 100%. Note that these calculations assume no losses in the cables and connectors in the RF path. Thus, assuming ideal lossless conditions, power efficiency increases from a theoretical value of 74.5% without the SCR to 100% with the SCR impedance matching network.

[0045] In operation, to achieve this exemplary purpose, but not by way of limitation, a proportional-integral-derivative (PID) controller is used in combination with a saturable core reactor (SCR) 302 to form an impedance matching control module in various embodiments of the present invention. The focus of this control module is the dynamic control of the inductance in the series LC tank or resonant circuit 30 to control the efficiency of energy transfer between the electrosurgical generator 10 and the tissue impedance load or tissue load Z_load 20-1. The proportional-integral-derivative (PID) controller ensures optimal matching of impedance based on the tissue impedance load or tissue load, e.g., if the load impedance is capacitive, the source impedance becomes more inductive, and vice versa. Additionally, in various embodiments, the speed and accuracy of the impedance matching process are ensured by utilizing a PID (proportional-integral-derivative) control algorithm, circuit, or system.

[0046] FIG. 6 is a block diagram of an electrosurgical system illustrating in more detail an embodiment of an electrosurgical generator control system 100 and an embodiment of an impedance matching network control system 500, according to an embodiment of the present invention. In this embodiment, the impedance matching network 300-1 functions as a self-contained impedance matching module that operates independently of the electrosurgical generator 10. According to various embodiments, the control system 100 provides RF output adjustment under dynamically changing impedance loads due to electrosurgical operation or electrosurgical tissue influences and / or impedance matching effects, and control conditions, e.g., device script or user manipulation. As such, the control system 100, according to various embodiments, is designed to adjust for different load impedances and output voltages and is therefore not limited to ideal conditions. The control system 100 is also configured to account for over-damping of the system as impedance increases, which can result in suboptimal phase margin and dynamic or unpredictable behavior, thus affecting the control system 100's ability to track or comply with dynamic commands, e.g., device script manipulation. The generator control system 100 in combination with the impedance matching network 300-1 ensures that tissue electrosurgical effects, such as sealing, fusing, or cutting, are optimized through the critical response of the control system to dynamically changing tissue impedance conditions and operating conditions and commands determined by the surgeon, surgical procedure, and / or device script.

[0047] The servo control system 100 of the electrosurgical generator 10, according to various embodiments, can include an RF amplifier 40, a feedback system 60, and a primary microcontroller 50. The feedback system 60 forms a closed-loop system path between the RF amplifier 40 and the primary microcontroller 50. In various embodiments, the feedback system 60 can include three channels: a main channel, a redundant channel, and a verification channel (not shown in FIG. 6 ). In various embodiments, the primary channel and the redundant channel can include separate but identical components. Furthermore, the primary channel and the redundant channel follow separate but identical electrical paths and, in embodiments, are both connected to the RF amplifier 40 and the RF output. Similarly, the components of the verification channel are separate but similar to those of the primary channel and the redundant channel. In one embodiment, the verification channel can include the same components as the primary channel and the redundant channel, but the components of the verification channel have a higher rating, e.g., higher resolution and / or lower drift, and are often more expensive. In another embodiment, the verification channel can include the same components as the primary channel and the redundant channel. The verification channel also follows a separate but identical electrical path to the primary and redundant channels and, in an embodiment, is connected to an RF amplifier 40 and RF output.

[0048] In various embodiments, feedback system 60 measures the analog RF output and digitizes the measurements. Feedback system 60 is configured to measure and digitize the RF output via at least one channel, e.g., a main channel. In this embodiment, feedback system 60 via the main channel measures the analog RF output via a front-end circuit. In various embodiments, feedback system 60 collects the voltage and current measurements from RF amplifier 40 and digitizes the measurements via an analog-to-digital converter (ADC). Feedback system 60 is further configured to process the digitized values ​​to derive real and imaginary components of the voltage and current RF output and communicate or transmit the real and imaginary components to primary microcontroller 50 and PID controller 500, e.g., serially.

[0049] According to various embodiments, the primary microcontroller 50 receives the digital real and imaginary components of the voltage and current measurements and calculates the magnitudes of the voltage, current, and power. In various embodiments, the primary microcontroller 50 further calculates individual error values ​​for the voltage, current, and power and determines or selects an adjustment mode based on the error values. Thus, the primary microcontroller 50 determines which of three adjustment modes, e.g., voltage, current, and power, should be enhanced or activated by the electrosurgical generator 10. In various embodiments, the primary microcontroller 50 is further configured to generate a cumulative error value over time for a selected RF adjustment mode and calculate variable gain factors for each of multiple RF adjustment modes based on previously calculated values ​​to provide dynamic adjustment of the variable or changing RF output of the generator 10. Additionally, as switching occurs between voltage, current, and power adjustment modes, the primary microcontroller 50 also performs special preload calculations to enable a gradual and seamless transition of the RF output. For a detailed discussion of the control system 100 of the electrosurgical generator 10, reference may be made to U.S. patent application Ser. No. 16 / 562, filed September 5, 2019, the contents of which are incorporated herein by reference in their entirety.

[0050] 6, an impedance matching network 300-1 is operably coupled between the electrosurgical generator 10 and the electrosurgical device 20. As further described above, in various embodiments, the impedance matching network 300-1 can include a series LC tank or resonant circuit (tunable resonant cell) 30 and an impedance matching controller or PID (proportional integral derivative) controller 500. In various embodiments, the series LC tank or resonant circuit 30 is comprised of a saturable core reactor (SCR) 302 coupled in series with a capacitor bank (C_Ser). The capacitor bank (C_Ser) can include one or more capacitors connected in series, in parallel, or any combination thereof to provide various load configurations or values. In embodiments of the present invention, the PID controller 500 may include a field programmable gate array (FPGA) that processes received data from the feedback system 60, e.g., the real and imaginary components of the voltage and current RF output, and adjusts the DC current through the DC control winding of the SCR in the series LC tank or resonant circuit 30 to meet the desired resonant condition for matching the source and load impedances. This is achieved by continuously calculating an error value e(t) as the difference between the desired output value or setpoint and the measured variable value, and applying corrections based on proportional (P), integral (I), and derivative (D) terms. In some embodiments, the desired output value or setpoint may be provided by a device script. In other embodiments, an advanced reduced instruction set machine (ARM) processor may be configured to establish the desired output value or setpoint. According to various embodiments, the desired output value or setpoint is a zero-degree phase shift, and the measured value represents the phase measured between the generator's RF output voltage and current.

[0051] 7 is a schematic diagram illustrating the operating modes and functional blocks of a PID controller 500 of impedance matching network 300-1, in accordance with embodiments of the present invention. In various embodiments, the FPGA of PID controller 500 receives measured real and imaginary voltage and current components or values ​​from feedback system 60 and calculates phase using these components. The FPGA is further configured to calculate a relative error and, based on the error value, determine or select a control output u(t) for adjusting the phase between the RF output voltage and current. Thus, in various embodiments, the control output u(t) sets a DC current through a DC control winding of saturable core reactor (SCR) 302 of series LC tank or resonant circuit 30, thereby controlling the inductance of SCR 302 and creating a resonant condition for maximizing energy transfer efficiency between electrosurgical generator 10 and a composite tissue impedance load or tissue load (i.e., the equivalent electrical circuit of the contact between instrument 20 and the patient's body or surgical site). In various embodiments, the PID controller 500 ensures that tissue electrosurgical effects, such as sealing, fusing, or cutting, are optimized through the critical response of the PID control system to dynamically changing tissue impedance conditions and operating conditions and commands determined by the surgeon, surgical procedure, and / or device script. This is achieved by utilizing only the proportional (P) and integral (I) terms of a PID algorithm, circuit, or system to derive a control output u(t) for adjusting the DC current through the DC control winding of the saturable core reactor (SCR) 302, thereby adjusting the inductance of the SCR 302. By varying the inductance of the saturable core reactor (SCR) 302, the source impedance of the electrosurgical generator is dynamically adjusted under any surgical, operational, or procedural condition to offset inductive or capacitive tissue impedance loads or current loads, such as Z_load 20-1. This results in an LC resonance condition that provides a zero-degree phase shift between the RF output voltage and current. In this way, in various embodiments, total power is delivered only across the resistive load, thereby maximizing RF energy transfer.Thus, the impedance matching network 300-1, and in particular the PID controller 500, according to various embodiments of the present invention, functions as a phase control loop and / or phase adjuster and can provide a critical step response to all impedance load conditions or any changes thereto.

[0052] In an alternative embodiment, the electrosurgical generator 10 may include an impedance matching network 300. In this alternative embodiment, the impedance matching network 300 may be included in or integrated with the control system 100 of the electrosurgical generator 10. In some embodiments, the SCR (saturable core reactor) module or series LC tank / resonant circuit 30 may be included on or integrated with the RF amplifier 40 on the same circuit board. In other embodiments, the SCR module 30 may be included on or integrated with a separate circuit board placed in series with the RF output circuit. In yet another embodiment, the SCR module 30 may be included on or integrated with the feedback system 60 on the same circuit board. In this alternative embodiment, if an impedance matching network, e.g., the SCR module 30, is implemented in the electrosurgical generator 10, e.g., the control system 100, the control loop algorithm, circuit, or system depicted in FIG. 7 of the present disclosure would be included in the primary microcontroller 50. In this manner, a separate control mechanism, e.g., the microcontroller 500, for regulating the DC current through the DC control winding of the SCR module 30 is no longer required. In this manner, and in various embodiments, the electrosurgical generator 10 generates the required RF output energy after initiating the complete device script. The feedback system 60 continuously monitors and measures the electrical characteristics, such as current and voltage, of the RF energy being delivered across one or more or all channels of the feedback system 60 and digitally provides the measured data to the primary microcontroller 50. The primary microcontroller 50, in various embodiments, is configured to calculate a phase difference between the measured RF current and the measured RF voltage. A PID control algorithm, circuit, or system contained within the primary microcontroller 50 in this embodiment uses this phase to calculate an error, apply a gain, and set a new output to control the DC current through the DC control winding of the SCR module 30.The new set of digital controls is communicated to the SCR module 30, which can be located on the same circuit board as the RF amplifier 40, on a separate circuit board placed in series with the RF output circuitry, or on the same circuit board as the feedback system 60.

[0053] The experimental results of the impedance matching network 300-1 in accordance with an embodiment of the present invention are described in more detail below. To this end, an open-loop characterization of the SCR (saturable core reactor) module 30 is first performed using a 10 Ω resistive load and a 20 Vrms RF output voltage. In various embodiments, the DC current through the DC control winding of the SCR module 30 is varied, and the impedance of the AC winding of the SCR module 30 and the phase difference between the output RF voltage and current of the electrosurgical generator 10 are measured. Figures 8 and 9 are graphs showing the SCR phase profile and SCR inductance profile, respectively, as a function of the applied DC current in the DC control winding of the SCR module 30. As can be seen from these figures, when the applied DC current is approximately 0 A, the SCR phase profile indicates a highly inductive load. As the applied DC current increases, the inductance of the AC winding of the SCR module 30 begins to gradually decrease, resulting in a gradually decreasing inductive phase angle. The phase angle, or phase difference, between the RF output voltage and current becomes zero degrees at approximately 2.7 A, where the RF output power is fully transferred across the 10 Ω resistive load. As the applied DC current increases further beyond this value, the inductance of the AC windings of the SCR module 30 decreases further, causing a gradual increase in the capacitive phase angle. As shown in Figure 8, with an applied DC current of approximately 3.5 A, the SCR phase profile exhibits a highly capacitive load. Note that the inductance varies from approximately 50 μH to approximately 20 μH.

[0054] Next, closed-loop characterization of the SCR (saturable core reactor) module 30 is performed using two different impedance loads. For this purpose, the SCR module 30, combined with a PID controller 500, is connected between the electrosurgical generator 10 and a composite tissue impedance load or tissue loads. The tissue site in each of the impedance loads is modeled using a resistive load, such as a capacitive or inductive load, connected in series with a reactive load bank. The electrosurgical generator 10 generates the required RF output energy and continuously measures the phase between the RF output voltage and current at 1-millisecond intervals. The PID microcontroller 500 determines the error between the measured phase and a set value for the phase (e.g., zero degrees phase). Based on the error value, the PID microcontroller 500 applies a gain and sets a new output to control the DC current through the DC winding of the SCR (saturable core reactor) module 30. This new set of outputs is then digitally communicated to the SCR module 30 to adjust the inductance of the series LC tank or resonant circuit 30 to move in a direction that has zero servo control error, which indicates that the desired target set point, e.g., zero degrees phase, has been reached and the impedance of the electrosurgical generator 10 has matched the tissue impedance load or the complex conjugate of the tissue load.

[0055] 10-11 illustrate the characteristics of a closed-loop SCR servo control system using an impedance load of Z_Load=100 Ω + 13.6 nF and an RF output voltage of 20 Vrms. More specifically, the closed-loop response of the SCR servo to achieve a setpoint of zero degrees phase is shown in FIG. 10, and the closed-loop impedance response of the SCR servo to match the source and load impedance is shown in FIG. 11. As can be seen from these figures, a substantial impedance mismatch is observed at the initial measurement point, where the phase shift between the output RF voltage and current is approximately -10.6° and the measured load impedance is approximately 112.7 Ω. Due to the resonant condition created by the SCR module 30, the phase shift between the RF output voltage and current gradually increases toward zero degrees phase, which is achieved at approximately -1.1 degrees. Simultaneously, the impedance load seen by the electrosurgical generator 10 gradually decreases, changing from a capacitive load to a purely resistive load (where the source impedance matches the complex conjugate of the load impedance), which is achieved at approximately 105.3 Ω. Note that the unwanted additional impedance at the final measurement point, for example 5.3 Ω, may be due to the impedance of cables, measurement lines, connectors and / or other components in the test setup.

[0056] Figures 12-13 show the characteristics of a closed-loop SCR servo control system using an impedance load of Z_Load=100 Ω + 4.35 μH and an RF output voltage of 20 Vrms. Similar to the previous experimental results, the SCR servo control loop response to achieve a zero-degree phase setpoint is shown in Figure 12, and the SCR servo closed-loop impedance response to matching the source and load impedances is shown in Figure 13. These results differ from those of Figures 10-11 in that the substantial impedance mismatch observed at the initial measurement point (22.8°, 122.4 Ω) remains nearly constant for a longer period (approximately 1 second) before gradually decreasing toward the zero-degree phase shift and purely resistive tissue impedance load achieved at the final measurement point (1.3°, 109.9 Ω). In addition, the unwanted additional impedance at the final measurement point is slightly higher, e.g., 9.9 Ω, compared to the previous measurement results. It should be noted that the impedance load seen by the electrosurgical generator 10 changes from an inductive load at its initial measurement point to a purely resistive load at its final measurement point.

[0057] Table II summarizes the measured and calculated electrical characteristics of both impedance loads at the initial and final measurement points. As can be seen from Table II, for the capacitive complex impedance load, the power efficiency improved from 89% of the initial value to 95% of the final value. Similarly, for the inductive complex impedance load, the power efficiency improved from 83% of the initial value to 92% of the final value. It should be noted that higher power efficiency may be achieved by implementing the entire test setup on a single PCBA (printed circuit board) or circuit board. This can reduce or eliminate the unwanted additional impedance seen at the final measurement point due to the impedance of measurement lines, connectors, and / or other components. It should also be noted that in these experimental results, the measured AC current based on the connected tissue impedance load was less than 1 A. Therefore, for high-power applications requiring higher RF currents, the power efficiency improvement may be even higher. [Table 2]

[0058] Due to inconsistencies in the manufacturing process and the impedance matching network topology itself, such as in a saturable core reactor (SCR), some unwanted power components may couple from the AC load winding to the DC control winding, resulting in unpredictable nonlinearities in the inductive response. In alternative embodiments, one or more filters, such as low-pass filters, bandstop filters, or any other type of suitable filtering, may be added to the DC control winding and / or the AC load winding of the SCR module 30 to reduce or eliminate these nonlinearities in the response. In this alternative embodiment, unwanted bands or portions of interfering frequencies may be selectively filtered. In some embodiments, one or more filters may be added only to the DC control winding of the SCR module 30 to suppress high-frequency components that may couple from the AC load winding to the DC winding. FIG. 14 illustrates an alternative exemplary embodiment of a saturable core reactor (SCR) incorporating one or more additional filters in accordance with embodiments of the present invention. Such alternative exemplary embodiments are contemplated as being within the scope of the present disclosure.

[0059] 15A-15B, another alternative embodiment of an impedance matching network 400 according to an embodiment of the present invention is shown. In this alternative embodiment, the impedance matching network can include a variable core inductor (VCI) 402. According to various embodiments of the present invention, the variable core inductor (VCI) 402 is designed to dynamically adjust the inductance of a resonant cell 30, such as a series LC tank / resonant circuit 30. This is achieved by moving a magnetic core in and out of the inductor. In essence, the VCI serves to change the inductance of the resonant cell 30 through manipulation or displacement of the magnetic core within the inductor. FIG. 15A shows a schematic diagram of the variable core inductor (VCI) 402 according to an embodiment of the present invention. As can be seen from this diagram, the magnetic core used in this alternative embodiment can include two Economic Transformer Design (ETD) cores arranged in a symmetrical pair or mirror-image configuration, with the two ETD cores forming two identical halves. The ETD core has a characteristic E-shape with a cylindrical or circular central leg to maximize the magnetic flux path and facilitate efficient winding of the coil. In various embodiments, a single central coil (best shown in FIG. 15A and referred to as the "inductor bobbin / winding" in FIG. 16) is wound around the central legs of the two ETD cores to form a tunable inductor. To affect the inductance of the tunable inductor, e.g., VCI (variable core inductor) 402, an air gap (i.e., distance D in FIG. 15A ) can be formed between the two identical halves of the ETD core. By changing the position of one of the two identical halves, e.g., the top half, relative to the other identical half, e.g., the bottom half, the air gap or distance D between the two ETD cores changes, thereby changing the inductance of the variable inductor or VCI 402.By adjusting the inductance, the no-load impedance and source impedance can be dynamically adjusted under any surgical, operative or procedural condition to provide a zero degree phase shift between the generator's RF output voltage and current, thus resulting in a resonant condition that maximizes RF energy transfer, according to various embodiments of the present invention.

[0060] The inductance and air gap created between the two halves of the ETD core is related by the effective permeability μ of the magnetic material as follows:

number

[0061] FIG. 15B is a graph illustrating the inductance of a variable core inductor (VCI) as a function of air gap in an embodiment of the invention. As shown in this figure, the inductance of the VCI (variable core inductor) inductor 402 gradually decreases as the distance, or air gap, between the two identical halves of the ETD core increases. Note that the inductance variation ranges from about 16 μH to about 1.6 μH for a core displacement of about 1 cm. As further described above, and in various embodiments, by varying the inductance of the variable core inductor (VCI) 402, the source impedance of the electrosurgical generator is dynamically adjusted under any surgical, operational, or procedural condition to offset inductive or capacitive tissue loads or tissue impedance loads. Thus, if the load impedance or tissue impedance load is capacitive, the source impedance will become more inductive, or vice versa. When the source impedance and load impedance are matched, the tissue impedance load seen by the electrosurgical generator is purely resistive. In various embodiments, this matching condition results in a resonance of the series LC tank or resonant circuit 30, resulting in a zero degree phase shift between the RF output voltage and current.

[0062] Referring to FIG. 16 , a schematic implementation of a variable core inductor (VCI) module is shown, according to an embodiment of the present invention. As depicted in this figure, air gap variation is achieved by separating two identical halves of the ETD core. This further involves moving the top half of the ETD core relative to its bottom half to adjust their position within or outside the single central coil of the VCI inductor, identified by the inductor's bobbin / winding 404. In various embodiments, precise control of core positioning is achieved by connecting a solenoid plunger 70 to a leaf spring 72, which in turn connects to the two ETD core top halves of the VCI inductor 402. This assembly is secured within an inductor core holder 74. According to various embodiments, a solenoid 76 is provided as a control mechanism for positioning or displacing the two ETD core top halves. In various embodiments, the position of the solenoid plunger is adjusted by a solenoid current, which is a direct current flowing through the solenoid. Additionally, a permanent magnet located at the center of the solenoid plunger 70 contributes to controlling its position. The permanent magnet serves the purpose of introducing a constant or permanent position offset. As a result, the magnetic field generated by the current flowing through the solenoid 76 counteracts the permanent offset, ensuring precise position control of the solenoid plunger 70. In various embodiments, the leaf spring 72 provides a predetermined stiffness to the system. This stiffness can increase as the solenoid plunger 70 is pushed closer and closer to the VCI inductor cores, e.g., two ETD cores.

[0063] As further explained above, in various embodiments, the inductance of the VCI (variable core inductor) 402 is varied by adjusting the air gap (i.e., distance D) between the two ETD cores. As a result, the phase difference between the RF voltage and current can also be varied. Adjusting the inductance therefore allows matching the source and load impedances (complex conjugates) and achieving higher power efficiency. In this embodiment, the control parameter is the DC current through the solenoid 76, which adjusts the position of the solenoid plunger 70. This movement adjusts the position of the upper halves of the two ETD cores of the VCI inductor 402. Note that successful operation of this alternative embodiment may be highly dependent on the mechanical alignment of various components, which may change over time due to various factors, such as vibration and / or mechanical alignment.

[0064] The above description is provided to enable any person skilled in the art to make and use an electrosurgical device or system and to practice the methods described herein, and represents the best mode contemplated by the inventors for carrying out the invention. However, various modifications will still be apparent to those skilled in the art. These modifications are contemplated to be within the scope of this disclosure. Different aspects or features of such embodiments may be shown in the various figures and described throughout the specification. However, it should be noted that each embodiment and its aspects, although shown or described separately, can be combined with one or more other embodiments and its aspects, unless expressly stated otherwise. The fact that each combination has not been explicitly described is solely to facilitate the readability of the specification.

[0065] While the present invention has been described in terms of specific embodiments, many additional modifications and variations will be apparent to those skilled in the art. It is therefore understood that the present invention can be practiced otherwise than as specifically described, including various changes in size, shape, and materials, without departing from the scope and spirit of the invention. The present embodiments, therefore, are to be considered in all respects as illustrative and not restrictive.

Claims

1. 1. An electrosurgical system for performing a surgical procedure, comprising: an electrosurgical generator configured to deliver RF energy to a surgical site; an electrosurgical instrument having at least one active electrode adapted to treat tissue with the delivered RF energy; an impedance matching network having an adjustable resonant cell disposed along a path of RF energy and configured to provide maximum power transfer from the electrosurgical generator to the electrosurgical instrument by adjusting the phase of the delivered RF energy to a predetermined phase value by dynamically varying the inductance of the adjustable resonant cell to create a resonant condition; An electrosurgical system comprising:

2. The electrosurgical system of claim 1 , wherein the predetermined phase value is a zero degree phase.

3. The electrosurgical system of claim 1 or 2, wherein the inductance of the tunable resonant cell varies based on the saturation state of a magnetic core or the size of an air gap formed in the magnetic core.

4. 4. The electrosurgical system of claim 1, wherein the tunable resonant cell comprises an inductive element electrically coupled to a capacitive element, the inductive element and the capacitive element being coupled in series.

5. The electrosurgical system according to claim 4, wherein the inductive element comprises a saturable core reactor (SCR) having a pair of E-shaped magnetic cores arranged in a mirror image configuration to form a symmetrical structure.

6. 6. The electrosurgical system according to claim 5, wherein each core of the pair of E-shaped magnetic cores includes a central leg and two outer legs, the central leg and the two outer legs from each magnetic core being aligned and facing each other in the mirror image configuration.

7. The electrosurgical system according to claim 5 or 6, wherein the saturable core reactor (SCR) comprises multiple windings, the multiple windings including one AC winding and two DC windings.

8. The electrosurgical system according to claim 7, wherein the one AC winding is wound around a center leg of the mirror image configuration and one DC winding is wound around each outer leg of the mirror image configuration.

9. 9. An electrosurgical system according to claim 7 or 8, wherein the two DC windings are wound in opposite directions and thereby have opposite polarities.

10. 10. An electrosurgical system according to claim 5, wherein the inductance of the SCR (saturable core reactor) is adjustable in response to variations in the magnitude of DC currents flowing through the two DC windings.

11. The electrosurgical system according to claim 10, wherein the DC current is supplied by a controller coupled to the impedance matching network.

12. The electrosurgical system according to claim 11, wherein the controller is configured to selectively adjust the magnitude of the DC current based on an error value that exists between a measured phase of delivered RF energy and a predetermined phase value.

13. 13. The electrosurgical system of claim 11 or 12, wherein the controller receives measured voltage and current values ​​of the delivered RF energy from a feedback system of the electrosurgical generator and calculates a phase difference between the measured voltage and current values ​​of the delivered RF energy.

14. 14. The electrosurgical system according to claim 13, wherein the controller is configured to determine a phase error relative to the predetermined phase value to correct for a phase shift between the voltage and current of the delivered RF energy, and set an output to adjust the magnitude of the DC current accordingly.

15. The electrosurgical system according to claim 4, wherein the inductive element comprises a variable core inductor (VCI) having a pair of E-shaped magnetic cores arranged in a mirror image configuration forming a symmetrical structure having two identical halves.

16. 16. The electrosurgical system according to claim 15, wherein each core of the pair of E-shaped magnetic cores includes a central leg and two outer legs, the central leg and the two outer legs from each magnetic core aligned and facing each other in a mirror image configuration.

17. The electrosurgical system of claim 15 or 16, wherein the central leg of each core of the pair of E-shaped magnetic cores is cylindrical.

18. The electrosurgical system of any one of claims 15 to 17, wherein the variable core inductor (VCI) comprises a single winding wrapped around the central leg of the mirror image configuration.

19. The electrosurgical system of claim 15 , wherein an air gap is formed between the two identical halves of the mirror image configuration.

20. 20. The electrosurgical system according to claim 19, wherein the inductance of the VCI (variable core inductor) is adjustable by varying the size of the air gap achieved by moving one of the two identical halves relative to the other.

21. The electrosurgical system of claim 20, further comprising a position adjustment mechanism that ensures precise control of the relative position of one of the two identical halves relative to the other.

22. 22. The electrosurgical system according to claim 21, wherein the position adjustment mechanism includes a solenoid having a solenoid plunger connected to one of the two identical halves with a leaf spring.

23. 23. The electrosurgical system of claim 22, wherein the leaf spring imparts a particular level of initial stiffness to the position adjustment mechanism, the stiffness increasing as the solenoid plunger approaches the other of the two identical halves.

24. 24. The electrosurgical system of claim 22 or 23, wherein the solenoid has a permanent magnet located at the center of the solenoid plunger to provide a constant positional offset between the two identical halves when direct current (DC) is passed through the solenoid.

25. 25. The electrosurgical system according to claim 24, wherein the direct current (DC) generates a magnetic field that cancels the fixed position offset between the two identical halves to achieve precise position control of the solenoid plunger for displacing one of the two identical halves.

26. 26. The electrosurgical system of claim 24 or 25, wherein the direct current (DC) is provided by a controller coupled to the impedance matching network.

27. 27. The electrosurgical system according to claim 26, wherein the controller is configured to selectively adjust the size of the air gap between the two identical halves by varying the magnitude of direct current (DC) flowing through the solenoid based on an error value that exists between a measured phase of the delivered RF energy and a predetermined phase value.

28. 28. The electrosurgical system of claim 26 or 27, wherein the controller receives measured voltage and current values ​​of the delivered RF energy from a feedback system of the electrosurgical generator and calculates a phase difference between the measured voltage and current values ​​of the delivered RF energy.

29. 29. The electrosurgical system according to claim 28, wherein the controller is configured to determine a phase error relative to the predetermined phase value to correct for a phase shift between the voltage and current of the supplied RF energy and thereby vary the size of the air gap between the two identical halves by setting an output to adjust a magnitude of a direct current (DC) voltage.

30. 30. The electrosurgical system of any one of claims 1 to 29, wherein the capacitive element comprises one or more capacitors connected in series, parallel or any combination thereof.

31. The electrosurgical system of any one of claims 1 to 30, wherein an electrosurgical generator includes the impedance matching network.

32. The electrosurgical system of any one of claims 1 to 31, wherein the impedance matching network operates independently from the electrosurgical generator and functions as a self-contained module.

33. 1. A method of performing impedance matching in an electrosurgical procedure, comprising: providing an electrosurgical generator for delivering RF energy to a surgical site via an electrosurgical instrument; positioning an adjustable resonating cell along a path of RF energy to provide maximum power transfer from the electrosurgical generator to the surgical instrument; selectively controlling the inductance of the tunable resonant cell to adjust the phase of the delivered RF energy to a predetermined phase value; A method comprising:

34. 34. The method of claim 33, wherein the predetermined phase value is a zero degree phase.

35. 34. The method of claim 33, wherein selectively controlling the inductance comprises varying the inductance of a tunable resonant cell based on a saturation state of a magnetic core or a size of an air gap formed in the magnetic core.

36. 34. The method of claim 33, wherein the tunable resonant cell comprises an inductive element electrically coupled in series with a capacitive element.

37. 34. The method of claim 33, further comprising providing the tunable resonant cell with an inductive element comprising a storage core reactor (SCR).

38. 38. The method of claim 37, wherein the saturable core reactor (SCR) comprises a first E-shaped magnetic core having a center leg and two outer legs, and a second E-shaped magnetic core having a center leg and two outer legs, the first and second E-shaped magnetic cores being arranged in a mirror image configuration such that the center leg and the two outer legs from each of the first and second E-shaped magnetic cores are aligned and opposite, forming a symmetrical core structure having a common center leg and first and second common outer legs.

39. 39. The method of claim 38, wherein the saturable core reactor (SCR) further comprises a first DC winding wound around the first common outer leg, a second DC winding wound around the second common outer leg, and an AC winding wound around the common center leg.

40. 40. The method of any one of claims 37 to 39, wherein selectively controlling the inductance of the adjustable resonant cell comprises dynamically adjusting the magnitude of DC current through the first and second DC windings.

41. the tunable resonant cell further comprising a controller; The step of selectively controlling the inductance of the tunable resonant cell further comprises: determining a phase error for said predetermined phase value; correcting a phase shift between the voltage and current of the supplied RF energy; 41. The method of claim 40, comprising:

42. Selectively controlling the inductance of the tunable resonant cell comprises: receiving measured voltage and current values ​​of the delivered RF energy; calculating a phase difference between the measured voltage and current values ​​of the delivered RF energy, wherein the receiving and calculating steps are performed by the controller before the determining and correcting steps; 42. The method of claim 41 further comprising:

43. 43. The method of claim 42, wherein the measured voltage and current values ​​of the delivered RF energy are continuously transmitted to a controller of the tunable resonant cell from a feedback system of the electrosurgical generator, the feedback system continuously monitoring an electrical characteristic of the delivered RF energy and generating a digital RF signal related thereto.

44. an electrosurgical generator including said tunable resonant cell; the electrosurgical generator further comprising: a feedback system for continuously monitoring an electrical characteristic of the delivered RF energy and generating a digital RF signal related thereto; a microcontroller that adjusts the delivered RF energy of the electrosurgical generator in response to the digital RF signal generated from the feedback system; 41. The method of any one of claims 37 to 40, comprising:

45. Selectively controlling the inductance of the tunable resonant cell comprises:

45. The method of claim 44, further comprising:

46. 34. The method of claim 33, further comprising providing the tunable resonant cell with an inductive element comprising a variable core inductor (VCI).

47. 47. The method of claim 46, wherein the variable core inductor (VCI) comprises a first E-shaped magnetic core having a center leg and two outer legs, and a second E-shaped magnetic core having a center leg and two outer legs, the center leg of each of the first and second E-shaped magnetic cores being cylindrical.

48. 48. The method of claim 47, wherein the first and second E-shaped magnetic cores are arranged in a mirror image configuration such that the center leg and the two outer legs from each of the first and second E-shaped magnetic cores are aligned and opposite, forming a symmetrical core structure having two identical halves.

49. 49. The method of claim 48, wherein the variable core inductor (VCI) further comprises a single winding wound around the central leg of each of the first and second E-shaped magnetic cores.

50. 50. The method of any one of claims 46 to 49, wherein an air gap is formed between two identical halves of the variable core inductor (VCI), and wherein selectively controlling the inductance of the adjustable resonant cell comprises dynamically adjusting the size of the air gap by moving one of the two identical halves relative to the other.

51. The adjustable resonant cell further comprises a position adjustment mechanism and a controller, and the step of selectively controlling the inductance of the adjustable resonant cell comprises: adjusting the position of one of the two identical halves using the position adjustment mechanism; determining a phase error for said predetermined phase value; correcting a phase shift between the voltage and current of the delivered RF energy; 51. The method of claim 50, further comprising:

52. Selectively controlling the inductance of the tunable resonant cell comprises: receiving measured voltage and current values ​​of the delivered RF energy; calculating a phase difference between the measured voltage and current values ​​of the delivered RF energy, wherein the receiving and calculating steps are performed by the controller before the determining and correcting steps; 42. The method of claim 41 further comprising:

53. 53. The method of claim 52, wherein the measured voltage and current values ​​of the delivered RF energy are continuously transmitted to a controller of the tunable resonant cell from a feedback system of the electrosurgical generator, the feedback system continuously monitoring an electrical characteristic of the delivered RF energy and generating a digital RF signal related thereto.

54. an electrosurgical generator including said tunable resonant cell; the electrosurgical generator further comprising: a feedback system for continuously monitoring an electrical characteristic of the delivered RF energy and generating a digital RF signal related thereto; a microcontroller that adjusts the delivered RF energy of the electrosurgical generator in response to the digital RF signal generated from the feedback system; 51. The method of any one of claims 46 to 50, comprising:

55. the adjustable resonant cell further comprises a position adjustment mechanism; Selectively controlling the inductance of the tunable resonant cell comprises: adjusting the position of one of the two identical halves using the position adjustment mechanism; receiving the measured voltage and current values ​​of the delivered RF energy from the feedback system; calculating a phase difference between the measured voltage and current values ​​of the delivered RF energy; determining a phase error for said predetermined phase value; correcting a phase shift between the voltage and current of the supplied RF energy, wherein the receiving, calculating, determining, and correcting steps are performed by the microcontroller; and 55. The method of claim 54, further comprising:

56. 56. The method of claim 51 or 55, wherein the position adjustment mechanism comprises a solenoid having a solenoid plunger connected to one of the two identical halves with a leaf spring.

57. 57. The method of claim 56, wherein the solenoid has a permanent magnet for providing a constant position offset between the two identical halves when direct current (DC) flows through the solenoid, the permanent magnet being located at the center of the solenoid plunger.

58. 58. The method of claim 57, wherein the direct current (DC) generates a magnetic field that cancels the constant position offset between the two identical halves to achieve precise position control of the solenoid plunger to displace one of the two identical halves.

59. 59. The method of claim 58, wherein the direct current (DC) is supplied by a controller of the tunable resonant cell or a microcontroller of the electrosurgical generator.

60. 60. The method of claim 59, wherein adjusting the position of the one of the two identical halves comprises dynamically adjusting a magnitude of direct current (DC) flowing through the solenoid based on an error value that exists between a measured phase of the delivered RF energy and the predetermined phase value.

61. 1. An electrosurgical system comprising: an electrosurgical generator configured to supply RF energy; an electrosurgical instrument operably connected to the electrosurgical generator for treating target tissue; an impedance matching network coupled between the electrosurgical generator and the electrosurgical instrument; Equipped with The impedance matching network comprises: a first E-shaped magnetic core having a center leg and two outer legs; a second E-shaped magnetic core having a center leg and two outer legs; wherein the first and second E-shaped magnetic cores are arranged in a mirror image configuration such that the center leg and the two outer legs from each of the first and second E-shaped magnetic cores are aligned and opposite. Electrosurgical system.

62. 62. The electrosurgical system according to claim 61, wherein the impedance matching network further includes an AC winding wound around the central legs of the first and second E-shaped magnetic cores.

63. 63. The electrosurgical system according to claim 62, wherein the impedance matching network is adapted to be disposed along a path of RF energy with the AC winding electrically connected in series with one or more capacitors.

64. 64. The electrosurgical system of claim 62 or 63, wherein the AC winding is configured to have a variable inductance based on a saturation state of the first and second E-shaped magnetic cores.

65. 65. The electrosurgical system of any one of claims 61 to 64, wherein the impedance matching network further includes two DC control windings, one DC control winding wound around each of the two outer legs of the first and second E-shaped magnetic cores.

66. 66. The electrosurgical system of claim 65, wherein the two DC control windings are wound in opposite directions and thereby have opposite polarities, and the two DC windings are connected in series and linked to a DC current source.

67. 67. The electrosurgical system according to claim 66, wherein the inductance of the AC winding is selectively adjustable based on DC currents flowing through the two DC control windings.

68. 67. The electrosurgical system according to claim 66, wherein the inductance of the AC winding is adjustable in response to variations in the magnitude of DC currents flowing through the two DC control windings.

69. 69. The electrosurgical system of claim 67 or 68, wherein the impedance matching network is configured to provide maximum power transfer from the electrosurgical generator to the electrosurgical instrument by dynamically adjusting the inductance of the AC winding to create an LC resonant condition.

70. 70. The electrosurgical system according to claim 69, wherein the LC resonant condition results in adjusting the phase of the delivered RF energy to a predetermined phase value.

71. The electrosurgical system of claim 70, wherein the predetermined phase value is a zero degree phase.

72. 1. An electrosurgical system comprising: receiving measured voltage and current values ​​of delivered RF energy; calculating a phase difference between the measured voltage and current values ​​of the delivered RF energy; determining a phase error for a predetermined phase value; and outputting an impedance match control signal in response to the phase error; a controller configured to: an impedance matching network configured to receive the impedance matching control signal; Equipped with The impedance matching network comprises: a saturable core reactor (SCR) having a pair of E-shaped magnetic cores arranged in a mirror image configuration; an AC winding wound around a central leg of the pair of E-shaped magnetic cores and configured to have a variable inductance in response to the impedance matching control signal; Equipped with Electrosurgical system.

73. 73. The electrosurgical system according to claim 72, wherein the AC winding is electrically connected in series with a capacitor bank and disposed along a path of RF energy.

74. 74. The electrosurgical system of claim 72 or 73, wherein the inductance of the AC winding varies based on the saturation state of the E-shaped magnetic core pair.

75. 75. The electrosurgical system according to any one of claims 72 to 74, wherein the impedance matching network further includes a first DC control winding and a second DC control winding.

76. 76. The electrosurgical system according to claim 75, wherein the first and second DC control windings are wound around first and second outer legs, respectively, of the E-shaped magnetic core pair.

77. 77. The electrosurgical system of claim 76, wherein the first and second DC control windings are wound in opposite directions and thereby have opposite polarities.

78. 78. The electrosurgical claim of any one of claims 75 to 77, wherein the first and second DC control windings are connected in series and linked to a DC current source.

79. 79. The electrosurgical system of claim 75, wherein the magnitude of the DC current through the first and second DC control windings of the SCR is selectively variable in response to the impedance match control signal to dynamically adjust the inductance of an AC winding of the SCR.

80. 80. The electrosurgical system of any one of claims 75 to 79, wherein the controller is further configured to provide a zero degree phase shift between the voltage and current of the delivered RF energy in combination with the impedance matching network.

81. 1. An electrosurgical system comprising: an electrosurgical generator configured to supply RF energy; an electrosurgical instrument operably connected to the electrosurgical generator for treating target tissue; an impedance matching network coupled between the electrosurgical generator and the electrosurgical instrument; Equipped with The impedance matching network comprises: a first E-shaped magnetic core having a center leg and two outer legs; a second E-shaped magnetic core having a center leg and two outer legs; wherein the first and second E-shaped magnetic cores are arranged in a mirror image configuration such that the center leg and the two outer legs from each of the first and second E-shaped magnetic cores are aligned and opposite to form a symmetrical structure having two identical halves separated by an air gap. Electrosurgical system.

82. 82. The electrosurgical system according to claim 81, wherein the impedance matching network further includes a single winding wound around the central legs of the first and second E-shaped magnetic cores.

83. 83. The electrosurgical system according to claim 82, wherein the central leg of each of the first and second E-shaped magnetic cores is cylindrical.

84. 83. The electrosurgical system according to claim 82, wherein the inductance of the single winding is selectively controllable based on the size of the air gap, the size of the air gap being adjustable by moving one of the two identical halves relative to the other.

85. 85. The electrosurgical system according to claim 84, wherein the impedance matching network further comprises a position adjustment mechanism configured to control the relative position of one of the two identical halves.

86. 1. An electrosurgical system comprising: receiving measured voltage and current values ​​of delivered RF energy; calculating a phase difference between the measured voltage and current values ​​of the delivered RF energy; determining a phase error for a predetermined phase value; and outputting an impedance match control signal in response to the phase error; a controller configured to: an impedance matching network configured to receive the impedance matching control signal; Equipped with The impedance matching network comprises: a variable core inductor (VCI) having a pair of E-shaped magnetic cores arranged in a mirror image configuration; a single winding wound around a central leg of the pair of E-shaped magnetic cores and configured to have a variable inductance in response to the impedance matching control signal; Equipped with Electrosurgical system.

87. 87. The electrosurgical system according to claim 86, wherein the imaging mirror arrangement has a symmetrical magnetic core structure with an air gap formed between two identical halves.

88. 88. The electrosurgical system according to claim 87, wherein the inductance of the single winding is selectively controllable based on the size of the air gap, the size of the air gap being adjustable by moving one of the two identical halves relative to the other.

89. 89. The electrosurgical system according to claim 88, wherein the impedance matching network further comprises a position adjustment mechanism configured to control the relative position of one of the two identical halves.

90. 87. The electrosurgical system of claim 86, wherein the controller is further configured to provide a zero degree phase shift between the voltage and current of the delivered RF energy in combination with the impedance matching network.

91. 1. An impedance matching circuit for use in an electrosurgical system, comprising: a first E-shaped magnetic core having a center leg and two outer legs; a second E-shaped magnetic core having a center leg and two outer legs; a plurality of windings including one AC winding and two DC windings; Equipped with the first and second E-shaped magnetic cores are arranged in a mirror image configuration such that the center leg and the two outer legs from each of the first and second E-shaped magnetic cores are aligned and opposite; the one AC winding is wound around the center leg of the mirror image configuration and the one DC winding is wound around each outer leg of the mirror image configuration; the inductance of the one AC winding is selectively controllable based on the DC current flowing through the DC winding; Impedance matching circuit.

92. 1. An impedance matching circuit for use in an electrosurgical system, comprising: a first E-shaped magnetic core having a center leg and two outer legs; a second E-shaped magnetic core having a center leg and two outer legs; a single winding wound around the central leg in a mirror image configuration; Equipped with the first and second E-shaped magnetic cores are arranged in a mirror image configuration such that the center leg and the two outer legs from each of the first and second E-shaped magnetic cores are aligned and opposite to form a symmetrical structure having two identical halves separated by an air gap; the inductance of the single winding is selectively controllable based on variation in the size of the air gap achieved by moving one of the two identical halves relative to the other; Impedance matching circuit.

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