Patent Description:
Electrosurgical hand devices or instruments have become available that use radiofrequency (RF) energy to perform certain surgical tasks. Electrosurgical instruments may include one or more electrodes that are configured to be supplied with electrical energy from an electrosurgical generator. The electrical energy can be used to fuse, seal, or cut tissue to which it is applied. Examples of such electrosurgical or surgical instruments may include graspers, scissors, tweezers, blades or needles.

Electrosurgical instruments typically fall within two classifications: monopolar and bipolar. In monopolar instruments, electrical energy is supplied to one or more electrodes on the instrument with high current density while a separate return electrode is electrically coupled to a patient and is often designed to minimize current density. Monopolar electrosurgical instruments can be useful in certain procedures, but can include a risk of certain types of patient injuries such as electrical burns often at least partially attributable to functioning of the return electrode. In bipolar electrosurgical instruments, one or more electrodes is electrically coupled to a source of electrical energy of a first polarity and one or more other electrodes is electrically coupled to a source of electrical energy of a second polarity opposite the first polarity. Bipolar electrosurgical instruments, which operate without separate return electrodes, can deliver electrical signals to a focused tissue area with reduced risks.

Even with the relatively focused surgical effects of bipolar electrosurgical instruments, however, surgical outcomes are often highly dependent on surgeon skill. Enhanced generators have been made to reduce this dependency and an example of such a generator is disclosed in European patent application, publication number <CIT>.

In accordance with the present invention there is provided a digital closed loop control system, as recited in claim <NUM>, for use with an electrosurgical generator that supplies electrosurgical RF energy to a surgical site.

In the appended figures, similar components and/or features may have the same reference label. Where the reference label is used in the specification, the description is applicable to any one of the similar components having the same reference label.

The ensuing description provides preferred exemplary embodiment(s) only, and is not intended to limit the scope, applicability or configuration of the disclosure.

This disclosure relates in general to electrosurgical systems. It specifically relates to a new generation of electrosurgical generators capable of regulating voltage, current and power of the RF output under dynamically changing impedance loads and control conditions.

Embodiments of the present invention are directed to systems for enhancing surgical outcomes by providing control systems for controlling generators to have optimal RF output for sealing, fusing and/or cutting tissue or vessels under all dynamic conditions such as, for example, varying tissue impedance load due to electrosurgical operations or tissue affects and any operational conditions and commands determined by the surgeon, surgical procedure and/or device script. This is achieved by implementing a digital closed-loop control system to regulate voltage, current, and power of the RF output. The digital closed-loop control system may include an RF amplifier for generating RF energy, a feedback system for constantly measuring and monitoring the electrical characteristics, e.g., voltage, current, and power, of the supplied RF energy to a connectable electrosurgical instrument and a microcontroller for processing measurement data from the feedback system and adjusting the output of the RF amplifier to meet a desired regulation target under any varying conditions.

According to the embodiments of the present invention, the feedback system measures, via at least one channel, analog RF output and digitizes the measurements. The feedback system in various embodiments collects its voltage and current measurements simultaneously from the RF amplifier and digitizes the measurements through analog to digital converters (ADC). The feedback system is configured to process the digitized values, to derive real and imaginary components of the voltage and current RF output, and to supply the real and imaginary components to the primary microcontroller.

In accordance with the embodiments of the present invention, the primary microcontroller, calculates individual error values for voltage, current and power and based on the individual error values selects a regulation mode. The primary microcontroller in various embodiments calculates, using specific algorithms, a specific variable gain factor for each regulation mode that allows the electrosurgical system according to the embodiments of the present invention to have a critically damped step response under any variable conditions, e.g., surgical, operational or procedural.

In the following, the electrosurgical system according to the present invention is explained in detail with sections individually describing: the electrosurgical generator, the electrosurgical instrument and the digital closed-loop control system and method used according to the embodiments of the present invention for providing optimal RF output under any dynamically outside changing conditions.

An electrosurgical generator may be provided that controls the delivery of electrosurgical or radiofrequency (RF) energy, adjusts the RF energy and in various embodiments measures and monitors electrical properties, e.g., phase, current, voltage and power, of the supplied RF energy to a connectable electrosurgical instrument to ensure optimal sealing, fusing and/or cutting of tissues or vessels. The generator may include a feedback system that determines such electrical properties and through a microcontroller regulates and/or controls an RF amplifier that generates the required RF energy to provide the optimal RF output for sealing, fusing and/or cutting tissue or vessels under dynamic conditions, such as for example, varying loads, procedural or operational conditions.

Referring first to <FIG>, an exemplary electrosurgical system for use in surgical procedure is illustrated. As shown in these figures, the electrosurgical system may include an electrosurgical generator <NUM> and a removably connectable electrosurgical tool or instrument <NUM>. The electrosurgical hand device or instrument <NUM> can be electrically coupled to the generator <NUM> via a cabled connection with a device key or connector <NUM> extending from the instrument <NUM> to a device connector or access port <NUM> on the generator <NUM>. The electrosurgical instrument <NUM> may include audio, tactile and/or visual indicators to apprise a user of a particular or predetermined status of the instrument <NUM> such as, for example, a start and/or end of a fusion operation. In some embodiments, a manual controller such as a hand or foot switch can be connectable to the generator <NUM> and/or instrument <NUM> to allow predetermined selective control of the instrument such as to commence a fusion operation.

The electrosurgical generator <NUM> includes a display <NUM> that may indicate the status of the electrosurgical system including, among other information, the status of the one or more electrosurgical instruments and/or accessories, connectors or connections thereto, the state or operations of the generator and error indicators. The electrosurgical generator <NUM> may include a user interface such as, for example, a plurality of buttons <NUM>. The plurality of buttons <NUM> allows for user interaction with the electrosurgical generator <NUM>. This user interaction may include, for example, requesting an increase or decrease in the electrical energy supplied to one or more instruments <NUM> that are coupled to the electrosurgical generator <NUM>. In various embodiments, the generator <NUM> further includes a user-accessible power-on switch or button <NUM> that when activated powers the generator <NUM> and activates or initiates a self-verification system test of the generator. The display <NUM> can be a touch screen display thus integrating data display and user interface functionalities.

The electrosurgical generator <NUM> may be configured to output radiofrequency (RF) energy through the connectable electrosurgical instrument or hand device <NUM> to seal, fuse and/or cut tissue or vessels via one or more electrodes. The electrosurgical generator <NUM>, may be configured to generate up to 300V, 8A, and 375VA of RF energy and it is also configured to determine a phase angle or difference between RF output voltage and RF output current of the generator during activation or supply of RF energy. In this way, the electrosurgical generator <NUM> regulates voltage, current and/or power and monitors RF energy output (e.g., voltage, current, power and/or phase). The generator <NUM> may stop, terminate or otherwise disrupt RF energy output under predetermined conditions. By way of example, these predetermined conditions may be any of the following conditions: when a device switch is de-asserted (e.g., fuse button released), a time value is met, and/or active phase angle and/or change of phase is greater than or equal to a phase and/or change of phase stop value indicating end of an operation such as fusion or cutting of tissue.

The electrosurgical instrument <NUM>, may include an elongate shaft <NUM> having a proximal end coupled to or from which an actuator <NUM> extends and a distal end coupled to or from which jaws <NUM> extend. A longitudinal axis extending from the proximal end to the distal end of the elongate shaft <NUM>. In one embodiment, the actuator <NUM> may include a movable handle <NUM> which is pivotably coupled to a stationary handle or housing <NUM>. The movable handle <NUM> is coupled to the stationary handle or housing <NUM> through a central or main floating pivot. In operation, the movable handle <NUM> is manipulated by a user, e.g., a surgeon, to actuate the jaws <NUM> at the distal end of the elongate shaft <NUM>, and thereby, selectively opening and closing the jaws <NUM>. When tissue or vessels are grasped between the jaws <NUM>, a switch or button <NUM> is activated by the surgeon to seal, fuse and/or cut the tissue/vessels between the jaws <NUM>. Once the button <NUM> is activated, associated circuitry or contacts are connected to connect appropriate electrodes of the jaws with associated connections of the generator <NUM> to supply RF energy to tissue grasped between the jaws <NUM> or otherwise in contact with the one or more electrodes of the jaws.

The electrosurgical instrument <NUM> may include a mechanical or electrical cutting blade that can be coupled to a blade actuator such as a blade lever or trigger <NUM> of the stationary handle or housing <NUM>. The cutting blade is actuated by the blade trigger <NUM> to divide or cut the tissue between the jaws <NUM>. Ablade slider may be connected to the blade trigger <NUM> and a protrusion extends from a proximal portion of the blade slider into an opening in one end of the blade trigger connecting the components together. The other end of the blade trigger is exposed and accessible by the user with the blade trigger <NUM> being pivotable about a trigger pivot at or near the mid-point of the blade trigger. As such, as the blade trigger <NUM> is pulled or rotated by the user proximally, the end of the blade trigger connected to the blade slider slides or moves the blade slider distally. Integrated with or attached to a distal end of the blade slider is a cutting blade, knife or cutting edge or surface. As such, as the blade slider translates longitudinally through a blade channel in the jaws, tissue grasped between the jaws <NUM> is cut. The cutting edge or surface may be angled to facilitate cutting of the tissue between the jaws <NUM>. The cutting blade may be a curved blade, a hook, a knife, or other cutting element that is sized and configured to cut tissue between the jaws <NUM>.

The elongate shaft <NUM> may comprise an actuation tube or rod coupling the jaws <NUM> with the actuator. The actuator may include a rotation shaft assembly including a rotation knob <NUM> which is disposed on an outer cover tube of the elongate shaft <NUM>. The rotation knob <NUM> allows a surgeon to rotate the shaft of the device while gripping the actuator. The elongate shaft <NUM> may be rotatable <NUM> degrees or rotation of the elongate shaft <NUM> limited to <NUM> degrees, i.e., ninety degrees clockwise and ninety degrees counter clockwise. <FIG> illustrates an alternative electrosurgical hand device <NUM>' connectable to the electrosurgical generator <NUM>. The electrosurgical hand device <NUM>' is similar but includes different features and has a different surgical use than the electrosurgical hand device <NUM>.

Referring next to <FIG>, a block diagram of an electrosurgical generator <NUM> is shown. As shown in this figure, the electrosurgical generator <NUM> may include a power entry module <NUM>, e.g., an AC main input, coupled to a power supply module, e.g., two 48V DC power supplies <NUM>, <NUM>. The power supply module converts the AC voltage from the AC main input to a DC voltage and via a house keeping power supply <NUM> provides power to various circuitry of the generator <NUM> and in particular supplies power to an RF amplifier <NUM> that generates or outputs the RF energy. The RF amplifier <NUM> may include a Buck and H-Bridge circuitry to convert a DC voltage input into an RF output or, alternatively, into a variable amplitude <NUM> sine wave. The DC voltage input is a 96V DC input that is generated by the two 48V DC power supplies <NUM>, <NUM> coupled in series. One of the 48V DC power supply <NUM>, <NUM> is configured to generate low voltage rails and in particular supply standby voltage to power on the generator <NUM>.

The electrosurgical generator <NUM> further includes a control system according to the present invention or a digital integral servo control system <NUM> to regulate and control the RF output. As shown in <FIG>, the control system <NUM> may include the RF Amplifier <NUM>, and does include a primary microcontroller <NUM> and a feedback system <NUM>. The RF output and in various embodiments the amplitude of the RF waveform output is controlled and regulated by the electrosurgical control system <NUM> which is embedded or integrated within the electrosurgical generator <NUM>. The control system <NUM> varies between regulating voltage, current, or power of the RF output generated by the RF Amplifier <NUM>. In all embodiments, the feedback system <NUM> measures the RF output and, after processing the measured data, digitally feeds the RF output's real and imaginary components to the primary microcontroller <NUM>. The primary microcontroller <NUM>, according to the embodiments of the present invention, processes the received data from the feedback system <NUM> and adjusts the output of the RF amplifier <NUM> to meet a desired regulation target. In various embodiments, the feedback system <NUM> comprises of analog input, digital processing and digital output.

The electrosurgical generator <NUM> may log all RF output data onto an internal memory device, e.g., a secure digital (SD) or non-volatile memory card. The memory device is configured to be read through an interface port <NUM>, e.g., a universal serial bus (USB) port, on the electrosurgical generator <NUM>. The generator <NUM> may be configured to copy the data from the internal memory device to a connectable portable storage device, e.g., a USB flash drive, through the interface port of the generator.

The electrosurgical generator <NUM> is further configured to provide RF output in three resolution settings or modes: low voltage, normal or medium voltage and high voltage ranges. In various embodiments, device scripts stored and located on connectable electrosurgical hand devices, e.g., instrument <NUM>, and/or connectors coupled thereto, e.g., device key <NUM>, are used to determine or set the RF output or voltage mode.

Reffering back to <FIG> & <FIG>, the electrosurgical generator <NUM> may be configured to alert the surgeon when the vessel has reached a completed procedure state, e.g., a completed seal state, or if an error or fault condition has occurred. The electrosurgical generator <NUM> may 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, device script or health or operational information regarding the device <NUM> and/or generator <NUM>. The generator <NUM> via a front panel interface <NUM> may alert the surgeon through the LCD display <NUM>, which is integrated into a front panel of the generator, and provide specific audible alarm or informational tones through a speaker <NUM> also integrated into the front panel of the generator. The generator <NUM> may include a front panel overlay <NUM> that provides a user interface or access including navigational push buttons to allow user access to systems settings such as volume or display brightness. The front panel overlay <NUM> may also include the system power button or connection. A fan system <NUM> may be provided to assist in heat dissipation. Additionally, as illustrated in the <FIG>, signal or sig represents connections that, for example, comprise of digital signals used to communicate information across systems and/or printed circuit boards, power represents connections that, for example, comprise of voltage rails used to power systems and/or printed circuit boards and RF represents connections that, for example, comprise of high voltage, high current RF energy used to seal, fuse or cut tissue or vessels.

<FIG> illustrates, in greater detail, a block diagram of a feedback system <NUM> within the control system <NUM> of an electrosurgical generator <NUM>. As described further above and also shown in <FIG>, the control system <NUM> may include the RF Amplifier <NUM>, the primary microcontroller <NUM> and the feedback system <NUM>. The RF amplifier <NUM> may generate an RF output and the feedback system <NUM> measures various electrical properties of the RF signal outputted from RF amplifier <NUM>. According to the embodiments of the present invention, the verification system <NUM> may include a main channel <NUM>, a redundant channel <NUM> and a verification channel <NUM>. The main channel <NUM> and redundant channel <NUM> in various embodiments may include separate but identical components. Additionally, the main and redundant channels <NUM> and <NUM> follow separate but identical electrical paths and in one embodiment are both connected to the RF amplifier <NUM> and the RF output.

Similarly, components of the verification channel <NUM> are separate from the main and redundant channels <NUM> and <NUM> but are similar. The verification channel <NUM> may include the same components as the main and redundant channels <NUM> and <NUM>, but the components in the verification channel <NUM> have higher ratings, e.g., higher resolution and/or lower drift, and are often more costly. Alternatively, the verification channel <NUM> may include the same components as the main and redundant channels <NUM> and <NUM>. The verification channel <NUM> also follows a separate but identical electrical path as the main and redundant channels <NUM> and <NUM> and in one embodiment is connected to the RF amplifier <NUM> and the RF output. The feedback system <NUM> measures analog RF output and digitizes the measurements. The feedback system <NUM> is configured to measure and digitize the RF output via at least one channel, e.g., main channel <NUM>. Here, the feedback system <NUM> through the main channel <NUM> measures the analog RF output via a front end circuitry <NUM>.

As shown in <FIG>, the front end circuitry <NUM> may include a shunt resistor <NUM> coupled to a pre-amplifier <NUM> to measure the current of the RF output. The front end circuitry <NUM> may further include a voltage divider <NUM> coupled to a pre-amplifier <NUM> to measure the voltage of the RF output. Outputs of the pre-amplifiers <NUM>, <NUM> are supplied to an analog to digital converter (ADC) <NUM>, thereby digitizing the current and voltage measurements. The digitized values are further processed to derive real and imaginary components of the voltage and current RF output. In various embodiments, the digitized values from the ADC <NUM> are supplied to a fully programmable gate array (FPGA) <NUM> of the feedback system <NUM>. The FPGA <NUM> is configured for processing the digitized voltage and current measurements values to generate real and imaginary components of the voltage and current RF output using a discrete Fourier transform. The digital real and imaginary components are then supplied to the primary microcontroller <NUM> and via a serial communication protocol.

With reference to <FIG>, a schematic illustration of an embodiment of a control system <NUM>, in accordance with the present invention, depicting, in greater detail, a block diagram of a primary microcontroller <NUM> of an electrosurgical generator <NUM> is shown. As shown in this figure, the primary microcontroller <NUM> may include a primary ARM (advanced reduced instruction set machine) processor <NUM> and a primary FPGA (fully programmable gate array) <NUM>. The primary ARM processor <NUM> is configured to establish desired output values, such as for example, voltage, current and/or power as setpoints <NUM>. The desired output values may be provided by a device script. The primary FPGA <NUM> of the primary microcontroller <NUM> receives the digital real and imaginary components of the voltage and current measurements and calculates the magnitudes of the voltage, current and power of the RF output. The magnitude of the voltage, current and power of the RF output is calculated using a VCW (voltage, current, power) calculator <NUM>, as shown in <FIG>. Individual error values for voltage, current and power are also calculated by an error processor <NUM>. The error values may be calculated by subtracting a desired voltage, current and power setpoints from the measured magnitudes.

The error processor <NUM> calculates the relative error between the main channel measurements and the setpoints values <NUM>, and based on the error values determines or selects a regulation mode. Accordingly, the error processor <NUM> determines which of the three regulation modes, e.g., voltage, current and power, should be reinforced or activated by the electrosurgical generator <NUM>. The calculated error values for the selected mode is integrated by an integrator <NUM> to generate an error signal that is directly proportional to and is used to correct the output of the RF amplifier <NUM>.

According to the present invention, the calculated error values are used to determine a variable gain factor for each regulation modes, e.g., voltage, current and power, of the generator <NUM>. The variable gain is configured to use a different predefined set of calculations or algorithm based on the selected regulation mode. As shown in <FIG>, a VG (variable gain) module <NUM> is used to compute the variable gain value (Ki) for each regulation modes, e.g., voltage, current and power. The variable gain factor, according to the embodiments of the present invention, may be computed as a function of the voltage, current and power setpoints, the calculated outside impedance load or tissue load, the Buck voltage value as well as the value of the error integral or any combination thereof. As such, the variable gain provides critical step responses for all setpoints and impedance load conditions or any changes thereto. In other words, the variable gain in a system according to the present invention allows for the electrosurgical generator <NUM> to be critically damped under any varying conditions such as, for example, surgical, operational and procedural conditions. The variable gain factor may be recalculated on a predetermined schedule or timing such as, for example, every period of the RF output.

With further reference to <FIG>, the primary microcontroller <NUM> is configured to predict the necessary output voltage of the generator <NUM> to regulate the RF amplifier <NUM>. The primary FPGA <NUM> of the primary microcontroller <NUM> may use the calculated impedance loads and the voltage, current and power setpoints to predict the necessary voltage of the generator <NUM>. The predicted value is then used by a Buck Duty Cycle calculator <NUM> to calculate a duty cycle value for a pulse width modulator (PWM) of an integrated Buck circuit of the RF amplifier <NUM>. On the other hand, the product of the error integral and the calculated variable gain factor for the selected mode (Ki * ∫ e(t)) may be used to derive a duty cycle value for an H-Bridge circuit of the RF amplifier <NUM>. As such, the control system <NUM> according to the present invention is capable of providing dynamic regulation of the variable or varying RF output of the generator <NUM>. In various embodiments, the electrosurgical generator <NUM> may be switching between voltage, current and power regulation modes. In such embodiments, the control system <NUM> is configured to perform a preload calculation or preload function, the details of which will be discussed further down below, to provide a gradual, non-disruptive transition in the RF output.

The control system <NUM>, according to the present invention, may provide regulation of RF output under dynamically changing impedance loads, e.g., due to electrosurgical operations or electrosurgical tissues affects, and control conditions, e.g., device scripts or user operations. The control system <NUM> being configured with a variable gain rather than a fixed gain allows the control system <NUM> to adjust for different load impedances and output voltages and thus not be limited to be optimized, e.g., for the lowest load impedance and/or highest output voltage. The control system <NUM> is also configured to account for the system becoming over damped as impedance increases that can result in non-optimal phase margin and dynamic or unpredictable behavior and thus affect the ability of the control system <NUM> to track or follow dynamic commands, e.g., device script operations. The control system <NUM> of the generator ensures that tissue electrosurgical effects, such as for example, sealing, fusing or cutting, are optimized through critical responses of the control system to dynamically changing tissue impedance conditions and operational conditions and commands determined by the surgeon, surgical procedure and/or device script.

As described further above, the feedback system <NUM> may include a second channel, e.g., the redundant channel <NUM>, which is nearly identical to the main channel <NUM>. The measurements from the redundant channel <NUM> and the resulting calculations are being constantly compared to the measurements and calculations of the main channel <NUM> to verify the operation of the main channel <NUM>. As such, if the main and redundant channels <NUM> and <NUM> have differing measurements or calculations, then a generator error is recognized and the supply of RF energy halted.

The feedback system <NUM> may include various other systems and circuitry, e.g., a sampler or other calculator (not shown in the figures), to provide sampling and/or other calculations as required by the electrosurgical control system <NUM> of the present invention. The feedback system <NUM> may measure analog voltage and current of the RF output of the RF amplifier <NUM> and the feedback system <NUM> may take a predetermined number of samples per each RF output cycle operating at <NUM> for each measurement of voltage and current. The feedback system <NUM> may utilize demodulations and transforms to obtain zero frequency components or filtering out unwanted higher order frequency harmonics out of the measured voltage and current values. As described further above, the feedback system <NUM> communicates or transmits, e.g., serially, the measured real and imaginary voltage and current values to the primary microcontroller <NUM>.

In what follows, operational modes and functional blocks of various circuitry and systems within the primary FPGA <NUM> will be explained in detail with sections individually describing: the VCW calculator <NUM>, the error processor <NUM>, the integrator <NUM>, the Buck Duty Cycle calculator <NUM> and the VG module <NUM>.

<FIG> is a schematic illustration of operational modes and functional blocks of various circuitry and systems within a primary microcontroller <NUM> of an electrosurgical control system <NUM> of the present invention. According to the embodiments of the present invention, the primary FPGA <NUM> receives the measured real and imaginary voltage and current components or values from the feedback system <NUM> and uses these components to calculate their respective root means square (RMS) magnitudes using the VCW calculator <NUM>. The VCW calculator <NUM> may further include a load calculator <NUM> (best shown in <FIG>). The load calculator <NUM> uses the feedback system voltage and current measurement values to calculate the impedance load or tissue load. In some embodiments, filtered voltage and current measurement values are used for calculating the impedance load.

The primary FPGA <NUM> is further configured to perform error processing using the error processor <NUM>. As shown in <FIG>, the error processor <NUM> may include an error calculator <NUM> and an error selector <NUM>. The error processor <NUM> calculates the error between the main channel measurements from the feedback system <NUM> and the setpoints values and determines which regulation mode is required for the correction of the RF output power. This is achieved by calculating the relative error between the setpoints and the measurements and in various embodiments this error calculation is performed simultaneously on voltage, current, and power by the error calculator <NUM>. The error processor <NUM> utilizes the error selector <NUM> for determining which regulation mode needs to be enforced by the electrosurgical generator <NUM>. Accordingly, the error selector <NUM> will select the regulation mode based on the most positive calculated error value. As such, the error with the most positive value will dictate which regulation mode is to be used by the electrosurgical generator <NUM>. The primary FPGA <NUM> in various embodiments also normalizes the calculated magnitudes with respect to its maximum count value and then converted to floating point values.

The integrator <NUM> is constantly integrating the error with the most positive value, e.g., selected regulation mode. In operation, since the RF amplifier <NUM> may be switching between different RF regulation modes, e.g., voltage, current and power regulation modes, the integrator <NUM> needs to be preloaded with another value that allows the RF output to stay constant while transitioning between various regulation modes. For this purpose, a preload function or preload calculator <NUM> is implemented within the primary FPGA <NUM> (best shown in <FIG>). The preload function or calculator <NUM> is configured to calculate the variable gain for the mode to which the RF amplifier is transitioning to and preload this value into the integrator <NUM> using a relay or switch <NUM> (best shown in <FIG>). The preload function is calculated using the counts for the Buck and H-Bridge circuitry of the RF amplifier and the calculated tissue impedance load. This ensures a seamless transition between various regulation modes.

The primary FPGA <NUM> provides a variable integral control system to dictate the output for the Buck and H-Bridge (best shown in <FIG>) controls of the RF amplifier <NUM>. Variables used by the variable integral control system may include, for example, impedance load or tissue load calculations, setpoints for voltage current and power as well as the calculated RMS magnitude for the voltage, current, and power. The load calculator <NUM> may use filtered voltage and current measurement values for calculating the impedance or tissue load. The variable integral control system may only directly regulate voltage and in order to regulate current or power, a corresponding voltage value must be calculated. The Buck duty cycle calculator <NUM> (best shown in <FIG>) may use the calculated impedance load and the setpoints for voltage, current and power to predict where the output voltage of the RF amplifier <NUM> should be. The predicted voltage value is then used to generate the counts for the integrated Buck PWM circuit of the RF amplifier <NUM>. The output voltage of the Buck PWM circuits of the RF Amplifier <NUM> sets the main voltage rails of the integrated H-Bridge PWM circuit of the RF amplifier <NUM>.

Using the prediction set forth by the variable integral control system, the primary FPGA <NUM> sets counts for the Buck PWM circuit of the RF amplifier <NUM> and responds quickly to reach roughly close to the desired output value, e.g., the predicted voltage value. The primary FPGA <NUM> drives PWM signals to the Buck and H-Bridge (best shown in <FIG>) configurations or circuitry of the RF amplifier <NUM>. The determination of the PWM signals for the H-Bridge configurations is used to fine tune the RF output to the desired output. The duty cycle for the H-Bridge circuit of the RF amplifier <NUM> is defined by the multiplication of the calculated variable gain factor and an integral signal or error integral for the selected mode (best shown in <FIG>). As can be seen in <FIG>, the VG (variable gain) module <NUM> may include a variable gain calculator <NUM> and a multiport selector <NUM>. The variable gain calculator <NUM> calculates the variable gain for each regulation mode, e.g., voltage, current and power, and selects the appropriate variable gain factor based on the same criteria that was used by the error processor <NUM>, e.g. the error with the most positive value. The calculated variable gain may be defined as a function of the calculated impedance load, voltage, current and power setpoints, the Buck voltage value and the integral error or accumulated error. The primary FPGA <NUM> may convert respective numerical duty cycle counts to drive the PWM signals that controls the Buck and H-Bridge configurations.

The primary ARM processor <NUM> may verify the validity of the setpoints and ensures the setpoints for voltage, current, and power meet the threshold for the mode the electrosurgical generator <NUM> is operating in. Calibration values may be stored in an EEPROM of the feedback system <NUM>. These values are specific predefined coefficients used to eliminate discrepancies or tolerances on the feedback system <NUM>. All three channels <NUM>, <NUM> and <NUM> have calibration values for voltage, current, and power for normal or medium, high, and low voltage modes with the exception of the verification channel <NUM> not having a low voltage mode. The modes as such dictates the correct calibration coefficients for voltage, current, and power being used in the servo calculations. This also is based on the regulation mode the generator is operating in.

In various embodiments, the error processor <NUM> further includes one or more constants, such as a normalization factor, error coefficient and/or point positions (useful for floating point conversions). In various embodiment, the primary microcontroller <NUM> calculates the error between the main channel measurements and the setpoint values to determine which regulation mode to be used for the correction of the servo, e.g., the output of the RF energy. In various embodiments, the primary microcontroller <NUM> uses the calculated measurements and the error processor coefficient to obtain an absolute measurement. With this absolute measurement, the primary microcontroller <NUM> uses the calibration coefficient to obtain a calibrated absolute measurement and with the normalization factor obtains a relative measurement. The primary microcontroller compares the difference between the relative measurement and the setpoint established by the primary processor <NUM> to determine the relative error.

In accordance with various embodiments, the primary microcontroller <NUM> using multiplexers provide the respective values of the relative error to be calculated for voltage, current and power and comparisons are performed between the calculated errors to output the greatest or largest positive error to determine the regulation mode for the generator.

Using the selected regulation mode and its corresponding voltage value, the primary microcontroller <NUM> calculates the voltage output needed for optimal operation of the generator <NUM>. In various embodiments, as the control system <NUM> adjusts the output voltage, current and power output targets are translated into their respective voltages at calculated loads. The regulation mode then decides which calculated output will be used in the control system <NUM>.

The control system <NUM> operates as a variable integral control loop. Variables are the voltage, current and power measurements, setpoints, and load calculations and the system operates at a predefined frequency, e.g., <NUM> frequency, with the ability to switch between integral control loops. The electrosurgical generator <NUM> as such provides a control system for voltage, current and power driving sources and thus provides a generator integral control loops for current, voltage and power. Additionally, since switching between the integral control loops occurs when regulation modes are changed, the control system <NUM> implants the preload function for each mode, i.e., voltage, current and power, to ensure a smooth transition between the regulation modes.

The feedback system <NUM> may include three channels: the main channel <NUM>, the redundant channel <NUM> and verification channel <NUM>. The main and redundant channels <NUM> and <NUM> are largely identical while the verification channel <NUM> has similar functionalities to the main and redundant channels <NUM> and <NUM>, but has higher resolution, lower tolerance, and lower drift components.

Each of the channels <NUM>, <NUM> and <NUM> of the feedback system <NUM> may include an analog portion that attenuates and amplifies the RF voltage/current measurement signals. RF voltage signals may be attenuated by a network of resistor dividers before being differentially amplified to drive the ADCs (<NUM>, <NUM>, <NUM>). In various embodiments, all three channels <NUM>, <NUM> and <NUM> have different sets of amplifier gain resistors to measure different voltage modes, i.e., a normal voltage mode and a high voltage mode. In various embodiments, the normal voltage mode includes voltages less than or equal to 166V and in high voltage mode, voltages less than or equal to 322V. In accordance with various embodiments, the main and redundant channels <NUM> and <NUM> have an alternative set of resistor configuration to more accurately measure lower voltages and in various embodiments voltages less than or equal to 10V. The verification channel's resistor dividers in various embodiments contain much lower tolerance and lower drift resistors than that of the main and redundant channels <NUM> and <NUM>.

In accordance with various embodiments, the RF current measurement signal is taken across a shunt resistor (<NUM>, <NUM>, <NUM>) from each channel of the verification system <NUM>. All shunt resistors <NUM>, <NUM>, and <NUM> in various embodiments are in series, so each channel measures the same current signal. The main and redundant channels <NUM> and <NUM> in various embodiments have an alternative set of shunt resistors to more accurately measure lower currents, e.g., currents less than or equal to 100mA. The verification channel <NUM> has shunt resistors that are lower tolerance and lower drift than that of the main and redundant channels <NUM> and <NUM>.

In accordance with various embodiments, the measured signals after the amplifiers (<NUM>, <NUM>; <NUM>, <NUM>; <NUM>, <NUM>) are passed through filters for ADC input filtering. The verification channel <NUM> has filter components with much lower tolerance and lower drift than that of the main and redundant channels <NUM> and <NUM>. In various embodiments, the filter of the verification channel has a steeper rolloff and thus has a steeper attenuation of higher frequencies.

In accordance with various embodiments, data conversion components are independent between each of the three channels <NUM>, <NUM> and <NUM>. The ADCs (<NUM>, <NUM>, <NUM>) convert the analog voltage and current measurement signals to discrete samples that are processed by the respective channel's FPGAs (<NUM>, <NUM>, <NUM>). The verification channel's ADC <NUM> has more resolution, e.g., more bits, and has lower drift than that of the main and redundant channels <NUM> and <NUM>. In various embodiments, the verification channel's ADC <NUM> also has a local generated reference voltage to accurately set the input range of the ADC <NUM>.

In various embodiments, the feedback system's FPGAs (<NUM>, <NUM>, <NUM>) performs I/Q demodulation on the discrete voltage and current measurement samples to obtain real and imaginary samples. The measured values are passed through a discrete Fourier transform to obtain the DC component of the real and imaginary values for the voltage and current measurements. In various embodiments, the verification channel <NUM> contains a locally generated digital voltage rail to accurately power its FPGA's I/O pins.

In accordance with various embodiments, each channel of the feedback system <NUM> independently communicates its data to the primary microcontroller <NUM> through independent communication connections. In various embodiments, the verification channel's data is only used by a self-verification system or process at predefined time or schedule, e.g., at the start-up of the generator <NUM>. During the self-verification process, the verification channel's data is compared with the main and redundant channel's data to verify the accuracy and functionalities of the main and redundant channels <NUM> and <NUM>. In various embodiments, throughout RF related operations, the main channel's data is the only set of data used by the control system <NUM> and the redundant channel's data is constantly compared with the main channel's data to ensure the main channel <NUM> is operating within predefined parameters and/or tolerances.

According to the embodiments of the present invention, the servo control system <NUM> of the electrosurgical generator <NUM> may include the RF amplifier <NUM>, the feedback system <NUM> and the primary microcontroller <NUM>. The feedback system <NUM> creates a path for a closed-loop system between the RF amplifier <NUM> and the primary microcontroller <NUM>. The feedback system <NUM> in various embodiments measures the voltage and current of the supplied RF signals and calculates the real and imaginary components of the measurements within one or more channels <NUM>, <NUM> and <NUM>. In one embodiment, only one channel is provided for the feedback system <NUM>, the main channel <NUM>. In another embodiment, two channels are provided, the main and redundant channels <NUM> and <NUM>. In yet another embodiment, three channels are provided, the main channel <NUM>, the redundant channel <NUM> and the verification channel <NUM>. The calculated components within the one or more channels are transmitted or communicated to the primary microcontroller <NUM>.

In accordance with various embodiments, the main and redundant channels <NUM> and <NUM> are copies of one another and are used by the primary microcontroller <NUM> to monitor the voltage and current of the RF output during operation of the electrosurgical generator <NUM>. The verification channel <NUM> is similar to the other two channels <NUM> and <NUM>, but includes components, for example, that are more drift resistant and/or uses ADCs with higher resolutions. This channel, in various embodiments, is used on startup of the generator, where self-verification of the generator is performed. The feedback system <NUM> in various embodiments collects its voltage and current measurements simultaneously from the RF amplifier <NUM>. In various embodiments, the generated RF signal produces a voltage across one or more internal loads, e.g., load <NUM> (best shown in <FIG>), disposed inside the RF amplifier <NUM> or a tissue load, e.g., electrosurgical hand device <NUM>, <NUM>'. The feedback system <NUM> in various embodiments collects current being delivered by using its own shunt resistors (<NUM>, <NUM>, <NUM>) and measures the voltage across them. To measure voltage, the feedback system <NUM> provides three voltage dividers (<NUM>, <NUM>, <NUM>) which are parallel to the load <NUM>, <NUM>. All measurements in various embodiments are converted to their real and imaginary components by the FPGAs <NUM>, <NUM>, and <NUM>. The real and imaginary components are sent to the primary microcontroller <NUM> causing the feedback system <NUM> to act as a feedback device between the primary microcontroller <NUM> and the RF amplifier <NUM>.

In accordance with various embodiments, the feedback system <NUM> measures the analog RF output via front end circuitry <NUM>, <NUM>, <NUM>. Front end circuitry may include shunts <NUM>, <NUM>, <NUM> coupled to respective pre-amplifiers <NUM>, <NUM>, <NUM> to measure the current of the RF output. In various embodiments, the front end circuitry may also include voltage dividers <NUM>, <NUM>, <NUM> coupled to respective pre-amplifiers <NUM>, <NUM>, <NUM> to measure the voltage of the RF output. Outputs of the pre-amplifiers are supplied to respective analog to digital converters (ADCs) <NUM>, <NUM>, <NUM> thereby digitizing the current and voltage measurements. The digitized values are processed to derive real and imaginary components of the voltage and current RF output. In various embodiments, the digitized values from respective analog to digital converters (ADC) are supplied to FPGAs <NUM>, <NUM>, <NUM>.

In various embodiments, the electrosurgical generator <NUM> is configured to provide RF output in a low voltage mode during a passive impedance evaluation which is automatically set by the generator <NUM>. According to the embodiments of the present invention, the electrosurgical generator <NUM> is automatically set to the low voltage mode prior to execution of any device script. The device script in various embodiments represents a procedural walkthrough of a surgical operation that may include the application and termination of RF energy to the tissue. During a medium or normal voltage mode, the electrosurgical generator <NUM> according to the embodiments of the present invention is configured for having an output RF energy up to 150V or 8A and is mainly used in tissue sealing. During a high voltage mode, the electrosurgical generator <NUM> according to the embodiments of the present invention is configured for having an output RF energy up to 300V or 4A and is mainly used in tissue cutting. During the low voltage mode, the electrosurgical generator <NUM> according to the embodiments of the present invention is configured for having an output RF energy up to 10V and 100mA and is mainly used in passive tissue impedance evaluations and measurements at a level that does not create a physiological response in tissue.

In accordance with various embodiments, specific device scripts are stored on specific electrosurgical hand devices <NUM>, <NUM>' that are optimized for a specific surgical procedure to produce consistent electrosurgical sealing and/or cutting of tissue. In various embodiments, RF output parameters or settings are defined in the device scripts and used by the electrosurgical generator <NUM> to regulate or control the RF output for the specific surgical procedure and/or electrosurgical hand device<NUM>, <NUM>'. The device script and associated RF output parameters in various embodiments are retrieved or transferred to the generator <NUM> when the electrosurgical hand device <NUM>, <NUM>' is connected to the generator <NUM>. In one embodiment, the primary ARM processor <NUM> may retrieve the device script from a memory storage attached to or integrated into the device key <NUM> that connects the electrosurgical device <NUM>, <NUM>' to the electrosurgical generator <NUM>.

Referring next to <FIG>, a block diagram of an embodiment a control system <NUM> of an electrosurgical generator <NUM> operating in a passive regulation mode is shown. In accordance with various embodiments of the present invention, the electrosurgical generator <NUM> is configured to provide a passive measurement regulation mode or low voltage mode to verify whether a connected electrosurgical hand device <NUM>, <NUM>' can be used for specific surgical procedures such as, for example, sealing, fusing and/or cutting tissues or vessels. Thus, the passive regulation mode is triggered at a predetermined time, e.g., at each activation of the connected electrosurgical hand device <NUM>, <NUM>'. The passive mode is configured to detect open and/or short loads in the RF output path. In one embodiment, an open or short condition is predetermined and in various embodiments, is an acceptable impedance range or value defined by a device script included with the connected electrosurgical hand device <NUM>, <NUM>' or otherwise associated with such electrosurgical hand devices <NUM>, <NUM>'. In various embodiments, the RF output for the passive mode has a lower static limit than other RF regulation modes and is used for a limited duration before normal RF regulation or operations of the electrosurgical generator <NUM> start. The low level RF output in various embodiments does not create a physiological response in tissue.

In various embodiments, when the electrosurgical generator <NUM> is operating in the passive mode, the RF amplifier <NUM> supplies a <NUM> RF output via relays to the connected electrosurgical instrument <NUM>, <NUM>'. As described further above, the RF output in the low voltage mode or passive mode is limited to not more than 10V rms and/or not more than 100mA rms. The control system <NUM> regulates and measures voltage and current via the feedback system <NUM>. The primary microcontroller <NUM> determines if a short and/or open condition is encountered based on the device script and the measured voltage and current data from the control system <NUM>. In various embodiments, one or more electrodes (best shown in <FIG>) are used in passive mode and position or selection of the electrodes, e.g., top, center or bottom, may vary based on the connected electrosurgical device, e.g., device <NUM>, <NUM>' and/or the position of the electrodes relative to the subject tissue or vessel.

In accordance with various embodiments, when a surgeon asserts a fuse or cut switch, the electrosurgical control system <NUM> initiates a passive impedance evaluation. The passive impedance evaluation triggers or identifies a fault, if a short or open condition is detected at the jaws <NUM> or distal working end of the electrosurgical hand device <NUM>, <NUM>'. If the passive impedance check is successful, the primary ARM processor <NUM> executes the full device script. In various embodiments, the primary ARM processor <NUM> instructs other circuitry of the electrosurgical generator <NUM> to output RF energy based on specific conditions, triggers, events and timing and according to specific settings. In various embodiments, the primary ARM processor <NUM> ensures the electrosurgical device is supplied specific RF energy according to specific output settings (voltage, current and power set points) and varies the RF output through the course of the procedure or surgical operation depending on various triggers defined by the device script.

<FIG> illustrates a flow diagram of an embodiment of a passive regulation mode operations or process according to the embodiment of the present invention. The depicted portion of the process <NUM> begins in step <NUM> where the algorithm initiates the passive mode as a starting point. In accordance with various embodiments, the passive mode is initiated or triggered at each activation of the connected electrosurgical hand device <NUM>, <NUM>' by a surgeon or other users. After initiating the passive mode, the processing goes to block <NUM> for generating RF output in the low voltage mode or passive mode and supplying RF energy to the connected electrosurgical hand device <NUM>, <NUM>'. In various embodiments, when the electrosurgical generator <NUM> operates in the passive mode or low voltage mode, the RF signal outputted from the RF amplifier <NUM> is limited to a specified voltage range (≤10V) and a specified current range (≤10mA) for a range of <NUM>-<NUM> ohms resistance.

Once the RF output for the passive mode is generated, processing flows to block <NUM> where the feedback system <NUM> measures the electrical characteristics of the RF output. The control system <NUM>, in accordance with various embodiments of the present invention, regulates the RF output to a set value as directed by the passive or low voltage mode and the feedback system <NUM> measures voltage, current, and/or phase from the main channel <NUM> and digitally feeds some or all of the measured values to the primary microcontroller <NUM>. After completion of measurements and transmission of measured data, processing flows to block <NUM> where the primary FPGA <NUM> calculates or determines other electrical characteristics of the RF output based on the received data or readings and transmits some or all of the calculated results to the ARM processor <NUM> of the primary microcontroller <NUM>. Other electrical characteristics of the RF output according to the embodiments of the present invention may include tissue impedance load and/or power. Once the calculated results are received by the primary ARM processor <NUM>, the processing flows to block <NUM> where the primary ARM processor <NUM> retrieves the device script and compares the calculated results, e.g., calculated impedance load or tissue load, to a preset range set by the device script. In one embodiment, the device script is stored into a memory attached to or integrated into the device key or connector <NUM> that connects the electrosurgical hand device <NUM>, <NUM>' to the electrosurgical generator <NUM>.

A determination of whether the comparison results has met certain criteria set by the device script is made in step <NUM>. Examples of the certain criteria may include, but not limited to, whether the comparison results or readings are within maximum and/or minimum values set by the device script. If the comparison results or readings are not between maximum and/or minimum values set by the device script, processing flows from block <NUM> to block <NUM> where an error is generated to notify the user or surgeon of an error and/or to check the electrosurgical device and/or its position relative to the tissue or vessel. In accordance with various embodiments, to supply RF energy after such a notification, the electrosurgical device <NUM>, <NUM>' must be reactivated and the passive tissue impedance evaluation, e.g., passive mode or low voltage mode, be reinitiated.

If the comparison results or readings are between maximum and/or minimum values set by the device script, processing goes from block <NUM> to block <NUM> where the primary ARM processor <NUM> initiate the full device script to provide optimized RF energy for sealing, fusing and/or cutting tissue or vessel.

As described further above and in accordance with various embodiments, the control system <NUM> of the electrosurgical generator <NUM> may include one or more resolution settings and in various embodiments it includes three settings: low, normal or medium and high voltage setting. These resolution settings are different from the regulation modes and in some embodiments they require some adjustments to the circuitry that measures the RF output. Each setting is configured to require different hardware configurations for the feedback system <NUM> and/or different normalization algorithms in the calculations performed by the primary microcontroller <NUM>. In various embodiments, the voltage measurement circuit of the feedback system <NUM> uses a different resistor selection or configuration for each of the three settings. In various embodiments, the current measurement circuit of the feedback system <NUM> uses the same resistor configuration for two of the settings, e.g., normal and high voltage settings, and a different resistor configuration for the low voltage setting.

In one embodiment, while the electrosurgical generator <NUM> is operating in the passive mode, the operations or process assigned to the primary ARM processor <NUM> may be performed via an FPGA. In other embodiments, other control systems may be incorporated therein. In yet another embodiment, a proportional, e.g., adjusting the system to reach setpoints, integral, e.g., measuring an area between error values and a time axis, prediction, e.g., predicting future errors based on a current error slope, architecture or any combination thereof may be included to supplement or replace the control system measurements, calculations and/or regulation.

In various embodiments, the electrosurgical generator <NUM> may supply an RF output having different waveform characteristics, e.g., square, providing non-sinusoidal periodic waveforms alternating between a minimum and maximum value; triangle, providing non-sinusoidal periodic waveforms with asymmetric ramps upward to a maximum value and downward to a minimum value; and/or sawtooth, providing non-sinusoidal waveforms with ramps upward to a maximum value and dropping sharply to a minimum value. In accordance with various embodiments of the present invention, the electrosurgical generator <NUM> may supply an RF output having different crest factor characteristics such as providing a ratio of peak value to effective value of a waveform, a peak amplitude divided by RMS value, and/or an ideal or perfect sine wave having a crest factor of <NUM>.

The above description is provided to enable any person skilled in the art to make and use the electrosurgical devices or systems and perform the methods described herein and sets forth the best modes contemplated by the inventors of carrying out their inventions.

Claim 1:
A digital closed-loop control system (<NUM>) for use with an electrosurgical generator that supplies electrosurgical radio frequency, RF, energy to a surgical site, the digital closed-loop control system (<NUM>) comprising:
a feedback system (<NUM>) for continually monitoring electrical properties of the supplied RF energy to the surgical site as a concurrent surgical condition and generating digital signals relating thereto; and
a microcontroller (<NUM>), responsive to the generated digital signals from the feedback system (<NUM>), the system being characterized in that the microcontroller is configured with a variable gain factor to regulate and control an RF amplifier (<NUM>) that generates the supplied RF energy across a plurality of RF resolution settings and a plurality of RF regulation modes,
wherein the microcontroller (<NUM>) is configured to compute the variable gain factor for each of the plurality of RF regulation modes and to select one of the computed variable gain factors based on relative error values calculated for each of the plurality of RF regulation modes; the variable gain factor being selected based on a most positive error value.