Electrosurgical generator

Abstract

To provide an electrosurgical generator provided with a generation unit generating high frequency AC voltage supplied to at least two output sockets configured for simultaneous connection and actuation of the electrosurgical instrument.SOLUTION: Electrosurgical generator includes a first / second HF generation unit supplying a first / second HF alternating voltage having a first / second frequency to a first / second output which are configured for connection of a first / second electrosurgical instrument. Upon activation, a first current flows to the first electrosurgical instrument and simultaneously, a second current flows to the second electrosurgical instrument. The invention provides an observer unit configured for indirect determination of said working currents based on measured values of the total currents. The so determined working currents are used as input signals for an inverter controller, achieving improved control of the electrosurgical generator.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to an electrosurgical generator configured to output a high-frequency alternating voltage to an electrosurgical instrument. The electrosurgical generator comprises a generation unit for generating a high-frequency (HF) alternating voltage that is supplied to at least two output sockets configured for simultaneous connection and operation of electrosurgical instruments. [Background technology]

[0002] Electrosurgery or radio frequency surgery involves the application of high frequency alternating current to tissue in the human body using electrosurgical instruments such as electrocauteries. Typically, high frequencies in the radio frequency range from about 200 kHz to 4,000 kHz are used. This results in the tissue being locally heated. This allows the tissue to be cut or severed by heating, or removed by thermal ablation. The main advantage of this is that bleeding can be stopped by closing the affected blood vessels at the same time that the cut is made, and that the electrosurgical instruments can be used for other applications such as coagulation. Different types of applications require different electrosurgical instruments. Summary of the Invention [Problem to be solved by the invention]

[0003] In some applications, it may be necessary to utilize more than one, especially two, electrosurgical instruments simultaneously to perform a surgical task (dual activation). To make this feasible, separate electrosurgical generators may be used, one for each electrosurgical instrument. A typical problem encountered is that interference between the high voltage outputs produced by the generators may occur. Such interference may include undesirable low frequency beating, similar to a phenomenon encountered in the field of acoustics, when the two frequencies are close to each other but do not match exactly. Furthermore, in the body, the electrical current flowing from one of the electrosurgical instruments to the other may be a cause of electrical shock. The shunted current is the shunted current A current is generated. DiversionThe current prevents proper control of the current / power delivered to any electrosurgery procedure and therefore adversely affects operational safety. Apart from this, another costly drawback is the need to have to provide two electrosurgical generators.

[0004] A similar situation may be encountered when a single electrosurgical generator with dual inverters and output stages is used, thereby allowing dual activation of electrosurgical instruments. However, it is still difficult to avoid unwanted interference. This can be mitigated by using a single inverter that alternately provides the two outputs. However, this limits use to modulation modes with duty cycles less than 50%, which is a substantial limitation.

[0005] It was further envisaged to perform power measurements across both outputs. However, this has the drawback that it is only feasible for outputs with the same settings and modes. Furthermore, the true power distribution between each of these dual outputs remains unknown.

[0006] Another approach is to feed the dual output with voltages with two different fundamental frequencies and perform a discrete Fourier transformation (DFT) on the measurements of both outputs using a Goertzel-type filter (EP 3912580 A1). If the fundamental frequencies are not perfectly orthogonal, there will be an overlap between them, and the overlap will cause a discontinuity in the Goertzel array plot. This is used to detect if significant transconductance occurs. Above a certain threshold, HF generation and output is shut off as a safety measure. As a further variation, based on this approach, the beat amplitude can be measured to determine the magnitude of the impedance. However, this is at best a measure of the impedance magnitude. DiversionIt allows for an estimation of the current and does not allow for an accurate determination of the working current, which is the current actually injected into the working tissue by each electrosurgical instrument connected to either output. As a result, while this may be a viable safety device, the control of the energy delivered by each electrosurgical instrument still requires improvement.

[0007] It is therefore an object of the present invention to provide an improved electrosurgical generator with dual outputs that alleviates this drawback. [Means for solving the problem]

[0008] The solution according to the invention resides in the features of the independent claims. Advantageous embodiments are the subject matter of the dependent claims.

[0009] 1. An electrosurgical generator configured to output a high frequency alternating voltage to an electrosurgical instrument for performing work on tissue, the first HF generating unit providing a first high frequency alternating voltage having a first frequency to a first output, and a second HF generating unit providing a second high frequency alternating voltage having a second frequency different from the first frequency to a second output, the first and second outputs configured to connect the first and second electrosurgical instruments such that, in an activated state, a first total current flows to the first electrosurgical instrument and simultaneously a second total current flows to the second electrosurgical instrument; and a central control unit configured to control the operation of the electrosurgical generator including the simultaneous operation of the HF generating units, according to the present invention, the inverter controller is configured to receive calculated first and second working currents as input signals, the first and second working currents being obtained by a working current calculation device communicatively connected to the inverter controller, the working current calculation device comprising an observer unit configured to indirectly determine the first and second working currents based on measurements obtained by dual measurement of the first and second total currents output at the first and second outputs.

[0010] In the following, some expressions used within the context of the present invention are explained.

[0011] In the field of electrosurgical generators, "high frequency" typically refers to frequencies in the range of 200 kHz to 4000 kHz, also known as radio frequency (RF).

[0012] "High voltage" typically refers to voltages of up to 10 kV, preferably up to 4000V, and more preferably at least 10V.

[0013] In the context of the present invention, an observer unit is understood to be a device designed to determine the state of a system from measurements of its outputs. It is configured to determine variables or states that are not accessible, or at least not directly accessible, by using the parameters and other measurement variables output by the system. A variety of such observer units are known to those skilled in the art of control systems.

[0014] An inverter unit is a device that provides actual high frequency AC voltage output to a surgical instrument that is connected to an output socket. The term is fairly broad and includes inverter technologies as well as converters and amplifiers.

[0015] Diversion The current is the portion of the total current delivered by the output that flows to the other output when the electrosurgical generator is activated. The working current is the other portion of the total current that actually flows from the output through the electrosurgical instrument to the tissue to be treated (and back to the same output in a bipolar configuration, or a separate neutral electrode in a monopolar configuration). The working current and DiversionThe currents form the (total) currents of the respective outputs. The (total) currents are measured by sensors on the outputs and / or output lines. The first and second working currents are therefore different from the first and second (total) currents at the respective first and second outputs. The first and second working currents are a portion of the respective first and second (total) currents, i.e., the portion that flows from the respective first and second electrosurgical instruments (19, 19') to the tissue to be worked upon in the activated state.

[0016] The fundamental problem is that it is not possible to directly measure the actual working current delivered by the electrosurgical instrument to the tissue being worked on. This is primarily due to the fact that Diversion This is because there is an electric current.

[0017] The present invention has recognized that while the working current cannot be measured directly, by using the working current (or the resulting power) as a control signal, improved control of the outputs and the electrosurgical instruments supplied by them can be achieved. Although this may at first appear paradoxical, the present invention has recognized that the difficulties experienced with known concepts may thereby be overcome.

[0018] The essence of the invention is to form an observer unit configured for indirect determination of the working current based on the measured values ​​of either output, in particular the directly measurable (total) current output, using calculated working currents instead of measured ones, since direct measurement is not possible, and these working currents of both outputs determined thereby are then used as input signals for the inverter controller.

[0019] The present invention relates to a method for generating a first HF signal from a first output of a first HF generating unit and a second HF generating unit, the method comprising the steps of: applying a voltage having a first frequency to a first output of the first HF generating unit and applying a voltage having a different second frequency to a second output of the first HF generating unit; Diversion It takes advantage of the fact that it produces an electric current. DiversionAs soon as a current is generated, the measured current at either output will be a combination of the currents at both frequencies. Diversion It has been recognized that not only can it be used to detect the presence of current, but the dual frequency characteristic can also be used to determine the portion of the current supplied by the output that is the actual working current.

[0020] The present invention thus allows a direct determination of the individual working currents for both outputs, which allows a much improved control of the energy delivered by each electrosurgical instrument. Moreover, the uncertainties encountered in the prior art by mere estimation can be effectively avoided. The quality of control as well as the operational safety of the electrosurgical generator can be improved, and undetected or erroneously estimated overcurrents and / or Diversion The risk to the patient due to the current can be effectively reduced. Preferably, the observer unit comprises a Fourier series approximation device and an automatic coefficient determination device, the Fourier series approximation device being configured to actually calculate an approximation by a dual Fourier series, one for the first working current and the other for the second working current, and the automatic coefficient determination device being configured to calculate the coefficients of the dual Fourier series approximation based on the measurements of the dual current outputs and to communicate the coefficients to the Fourier series approximation device. The quality of the approximation can be determined by selecting at what order the Fourier series is performed, as known to those skilled in the art. A higher order provides a more accurate result, but this is often not necessary. In a preferred embodiment, an approximation to the first order, i.e. with respect to the fundamental frequency, provides an optimum between sufficiently accurate results and the required computational effort / processing power.

[0021] First, an automatic coefficient determination device is described using a simplified Fourier series that is an approximation of the first (fundamental frequency). This uses K measurement samples of the measurable (total) current output of the first output I1 to determine the offset coefficients of the Fourier series around the first frequency f1,

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[0022] Similarly, for the offset coefficient based on the measurable (total) current output of the second output I2,

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[0023] The same is performed for a second Fourier series around a second frequency f2, thereby obtaining another set of six coefficients. These coefficients, determined by the automatic coefficient determination device, are provided to the Fourier series approximation device of the observer unit.

[0024] In a system having two monopolar electrosurgical instruments, the actual working current I flowing through the electrosurgical instrument connected to the first output is w1 , as well as the current I of the actual working current flowing through the electrosurgical instrument connected to the second output. w2 The determination of is performed in an observer unit as illustrated below, where I(k) denotes a single measurement.

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[0025] Diversion current I cross According to Kirchhoff's current law, the working current I w1 (or I w2 ) from the total measured current I1 (or I2). The corresponding voltage is V cross It is.

[0026] The resistance R of each of the impedances Z is calculated according to the following, where cos(φ), abbreviated as cos(φ), u,i ) denotes the power factor, which is determined by the phase shift φ between the voltage and the current.

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[0027] Based on the current, the power signal provided by either output can be determined according to the following:

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[0028] As input and output signals of the control, the root mean squared (RMS) value of each parameter is measured with a sampling time equal to the period time of the sliding window. Due to the impedance, it is recommended to calculate the power as a function of the resistance. The average power can be calculated according to:

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[0029] For systems with two bipolar electrosurgical instruments, the determination of the actual working current is similar to that in monopolar systems. It is based on Kirchhoff's current law: Diversion Applies to electric current.

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[0030] Cross resistance R cross1 and R cross2 The sum is calculated using the following formula:

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[0031] R cross1 R cross2 Then, the corresponding voltage V cross1と V cross2 are assumed to be related according to the following:

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[0032] The average power at each instrument is determined according to the following:

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[0033] The power of each instrument can be compared to a respective reference power and controlled in a power control.

[0034] For current control, the RMS value of the output currents I1 and I2 of each instrument can be controlled by manipulating the output voltage.

[0035] For voltage control, the output voltage is compared to the voltage drop across the cross impedance(s) and the maximum is used as the control variable which is manipulated via the output voltage itself.

[0036] An important advantage of the present invention is that this is accomplished at two different frequencies, f1 and f2. This doubles the number of available coefficients and allows the observer unit to calculate not only the total measurable current output, but also the unmeasurable working current flowing through the electrosurgical instrument and into the tissue being worked on. This allows for a precision and granularity in the determination of the current that was previously unattainable.

[0037] To make it easy to understand, Voltage division Voltages and / or other currents, including voltages, preferably Diversion Further electrical parameters, such as current, can be determined taking into account the first and second working currents, as well as the root mean square (RMS) values ​​of the respective currents, voltages, and powers.

[0038] Advantageously, the observer unit further comprises a phase angle determination module configured to determine the phase angle between the voltage and the first and / or second current of the first and second outputs, respectively. This allows for proper consideration of the phase shift between the voltage and the current at either output. This is important for the assessment of the effective power and therefore the energy transferred to the tissue by the electrosurgical instrument. Furthermore, the determination of the root mean square value is facilitated by the phase angle determination module.

[0039] For efficient calculation of the Fourier transform, the observer unit advantageously comprises a sliding window device for data processing of the measured values. Advantageously, the sliding window is characterized by a variable length, which is preferably determined depending on the first frequency, the second frequency and the frequency difference between the first and second frequencies. This allows the length of the sliding window to be appropriately adapted to the frequency used. For computational efficiency, preferably a fast (FFT) or discrete (DFT) Fourier transform can be used, although this is not essential.

[0040] Preferably, the sliding window device comprises a common denominator calculation unit, and is preferably configured to use the inverse of the common denominator for the length of the sliding window. This allows the sliding window to be adapted to frequency, thereby reducing undesirable spectral leakage. It is particularly advantageous to use the inverse of the largest (or second largest) common denominator for the length of the sliding window. This results in a short window that provides optimal results in terms of frequency resolution and avoidance of spectral leakage.

[0041] Although the actual current flowing through the electrosurgical instrument is the more important parameter, Diversion It may also be beneficial to address the current. To this end, advantageously: Diversion A current detector is provided, Diversion The current detector detects a current between the first and second outputs in the activated state. Diversion The electrosurgical generator is configured to determine the current, which allows for a more accurate calculation of the total power output at the dual outputs of the electrosurgical generator. Diversion The current can be appropriately taken into account. Diversion The current detector is Diversion configured to adjust the electrical characteristics of the second HF generating unit, in particular the voltage, current and / or frequency, so as to control the current Diversion More preferably, it is operatively connected to a current regulator.

[0042] Preferably, the outputs of the first and second HF generating units are independently controlled by respective first and second HF generating controllers, preferably using respective first and second working currents, and optionally Diversion The current is also used as an input variable (and / or the respective impedance). The use of independent controllers allows the most specific response to the changing impedances in the electrosurgical instruments, especially due to the different characteristics of the tissue to which the respective electrosurgical instruments are applied. The load impedance of the treated tissue is an important parameter and can be easily calculated by dividing the measured voltage by the working current determined by the observer unit. It is advantageous if the first and second HF generation controllers are capable of applying different control laws, preferably "current control" and / or "power control", optionally "voltage control". It is particularly preferred that the different control laws are selectively used, especially depending on the load and / or power of the respective electrosurgical instruments. It is particularly preferred if two or more control laws are processed, the respective outputs are compared and one is selected. For example, the error between the actual value and the reference value should be determined for each and the control law with the smallest error is used by the selection device to determine the set point for further control. "Current control" aims to maintain the current and thus the tissue effect achieved by the electrosurgical instrument. This is particularly useful for rather low load impedances. "Power Control" allows precise control of the energy delivered to the electrosurgical instrument per time. This is achieved by controlling the working current and the power equations for P1 and P2 above. DiversionTaking into account the calculated value of the current. This is particularly useful for medium load impedances in electrosurgical instruments. In the case of rather high load impedances in electrosurgical instruments, for example, a "voltage control" is provided to ensure that the output and the applied voltage are within safe limits for the electrosurgical instrument and the patient. Various control laws, for example current control with underlying voltage control, can be used individually or in parallel. Further preferably, a decoupling controller is provided, configured for independent control of the first and second HF generating units, which decoupling controller interacts with the observer unit. This allows the separation of the control of the electrosurgical instrument at the two outputs to be achieved by the observer unit, in particular the calculated working current. This allows the first and second HF generating units to be controlled independently of each other, in a manner that is consistent with the present invention. Diversion Even though they are electrically connected by current, destructive interference between them can be minimized or avoided, which is a great advantage in applying appropriate control. It is important to note that the first and second HF generation controllers can operate independently of each other, including being configured to apply different control laws.

[0043] However, it is also possible that these first and second HF generating units are formed as a combined unit capable of outputting the first and second high frequency AC voltages independently of each other. This allows the first and second frequencies, which differ in voltage and frequency, to be generated by a single combined unit. For this purpose, the combined unit is preferably a multilevel inverter having a plurality of inverter cells, a first part of the plurality of inverter cells being configured to generate the first high frequency AC voltage and a second part of the plurality of inverter cells being configured to generate the second high frequency AC voltage. This allows the first and second frequencies for the dual output to be generated very efficiently and, in the case of supplying only one output, the same inverter can be used alternatively for all inverter cells in one group. This allows for increased versatility with minimal effort.

[0044] A multilevel inverter is an inverter unit capable of delivering output voltages at a variety of levels, as opposed to providing an on / off output with only positive and / or negative polarity. Typical topologies include, but are not limited to, cascaded H-bridge, neutral point clamp, and flying capacitor.

[0045] For practical purposes, it is beneficial if the first frequency, the second frequency, and the frequency difference between the first and second frequencies are selected such that their respective values ​​are composite, i.e., non-prime, so that a fairly large common denominator of the first, second, and different frequencies can be established, allowing for a fairly short length of the sliding window to achieve good spectral resolution and minimize spectral leakage.

[0046] The invention is explained in more detail below with reference to advantageous exemplary embodiments. [Brief description of the drawings]

[0047] [Figure 1] FIG. 1 shows a front view of an electrosurgical generator with two electrosurgical instruments attached. [Diagram 2] 1 shows a schematic diagram of multiple electrosurgical instruments in a surgical site. [Diagram 3] FIG. 2 shows a schematic functional diagram of an electrosurgical generator including two monopolar output sockets. [Figure 4] A detailed diagram of the observer unit is shown. [Diagram 5] 1 shows the equivalent circuit diagram and currents of two outputs supplying two monopolar electrosurgical instruments. [Figure 6] The currents at the output of two different frequencies and the resulting beat frequency are shown. [Figure 7] 1 shows a power diagram with different control regions. [Figure 8] 6 shows an alternative equivalent functional diagram of FIG. 5. [Figure 9] FIG. 1 shows a functional control block diagram illustrating a configuration for power control. [Figure 10] 1 shows a schematic diagram of an observer unit with a Fourier series approximation device and an automatic coefficient determination device. [Figure 11] 1 shows a schematic functional diagram of another embodiment of an electrosurgical generator including a composite radiofrequency generating unit. [Figure 12] 1 shows the equivalent circuit diagram and currents of two outputs supplying two bipolar electrosurgical instruments. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0048] An exemplary embodiment of an electrosurgical generator according to a first embodiment of the present invention is shown in Figure 1. The electrosurgical generator, generally identified by the reference numeral 1, comprises a housing 11 having at least two output sockets 16, 16' (and optionally an additional socket 17 for a neutral electrode) for connecting electrosurgical instruments 19, 19'. The electrosurgical instruments 19, 19' correspond to the first and second electrosurgical instruments according to the present invention, and the output sockets 16, 16' correspond to the first and second outputs according to the present invention. The power cable 12 is provided with a plug for connection to a power source (not shown), which may be a power grid such as the AC mains in a building, or an off-grid power energy source such as a 12 volt or 24 volt battery in a vehicle or mobile hospital. Additionally, a user interface 14 is provided with a display 15, which may be a touch screen, or there may be a knob 13 for input by a user.

[0049] The electrosurgical instrument 19 includes a cable 18 that plugs into the output socket 16 to supply high frequency alternating voltage for operation of the electrosurgical instrument 19. This is equally true for other electrosurgical instruments 19' that are connected to the output socket 16' by their own cables 18'.

[0050] The two electrosurgical instruments 19, 19' supplied by the electrosurgical generator 1 are shown in the operating field in FIG. 2. An operating table 98 is provided, configured to accommodate a patient 99 to be treated. In the illustrated embodiment, both electrosurgical instruments 19, 19' are to be used on the same patient 99 in different positions. In the illustrated embodiment, both electrosurgical instruments 19, 19' are monopolar. This requires an indifferent patch electrode 10 to be attached to the operating table 98 or, preferably, to the patient 99 forming a rather large contact area. The indifferent patch electrode 10 is connected via a cable 10' to an additional socket 17 of the electrosurgical generator 1, thereby providing a return path and closing the circuit for the HF energy supplied by the electrosurgical generator 1 to the electrosurgical instruments 19, 19'.

[0051] A schematic functional diagram of the electrosurgical generator is shown in Figure 3. Power is supplied to a power supply unit 20 of the electrosurgical generator 1 by a power cable 12. The power supply unit provides power, which in the illustrated embodiment is DC power, to the various devices, units and modules of the electrosurgical generator 1. In particular, the power supply unit 20 supplies power to a first HF generating unit 4 configured to generate a first high frequency AC voltage via a DC bus 22, which is then fed to a first output socket 16 (also referred to as output 16 for brevity) for supplying a plugged-in electrosurgical instrument 19 via a first output line 23 and a first sensor assembly 26 for voltage and current measurement. The output line 24 comprises an active electrode (AE) line 24 and a neutral electrode (NE) line 25. The high voltage is typically in the range of a few kilovolts, but may have an amplitude in the range of a few tens of volts up to 4000 volts. Further, a power supply 15 is connected to the power supply 16 via the DC bus 22. unitA second HF generating unit 4' is provided, also fed from the first HF generating unit 20, and similarly provided with a second output line 23' for outputting a voltage, comprising an active electrode wire 24' and an indifferent electrode wire 25' and a second sensor assembly 26' for voltage and current measurement at a second output socket 16'. In the illustrated embodiment, a monopolar configuration is shown, where the output sockets 16, 16' are configured as monopolar outputs for connecting monopolar instruments 19, 19' and further have a neutral electrode (NE) wire 25, 25' connected to an additional indifferent output socket 17 to which the indifferent patch electrode 10 is connected. For a bipolar output, a second embodiment is provided as shown in figures 11 and 12.

[0052] The operation of the first and second HF generating units 4, 4' is controlled by a central control unit 2, which is connected to a user interface 14 so that a user can issue instructions and commands for the operation of the electrosurgical generator 1. The central control unit 2 generates corresponding control signals and manages the associated devices, units and modules of the electrosurgical generator 1 according to these instructions and commands. In particular, the central control unit 2 comprises a common inverter controller 3 that provides command signals to the first and second HF generating controllers 41, 41', either of which controls its respective first and second HF generating units 4, 4'. The first high frequency voltage generated by the first HF generating unit 4 is conveyed to the output socket 16 via the respective output lines 23 and sensor assemblies 26. Similarly, the second high frequency voltage generated by the second HF generating unit 4' is conveyed to the output socket 16' via the respective output lines 23' and sensor assemblies 26'.

[0053] The first and second HF generating units 4, 4' generate first and second HF voltages, respectively, at voltages and frequencies defined by the respective first and second HF generating controllers 41, 41'. The voltages and frequencies of the first and second HF generating units 4, 4' can be controlled and generated independently of each other. However, the resulting currents delivered from the first and second HF generating units 4, 4' through their respective output sockets 16, 16' are determined by the impedance of the respective electrosurgical instruments 19, 19' and the tissue with which either instrument contacts. The total current I1 flowing through the first output socket 16 is determined by the first sensor assembly 26, which also determines the respective actual voltages. Similarly, the total current I2 flowing through the second output socket 16' is determined by the second sensor assembly 26', which also determines the respective actual voltages. The resulting measurement signals are applied with a signal conditioning unit 90, which may include an analog to digital converter (ADC), and further provide feedback to the central control unit 2 via the working current calculation device 5.

[0054] However, the total current I1 determined by each sensor assembly 26, 26' is not identical to the current that flows through the tissue to which the electrosurgical instrument is applied (the "working current").

[0055] As shown in FIG. 2, the electrosurgical instruments 19, 19' are typically applied to different locations on the patient's body. These different locations may be quite close to each other, especially in the case of complementary procedures, or may be quite far from each other, especially in the case of simultaneous procedures. In either case, the total current delivered by the output 16 of the electrosurgical instrument 19 not only takes the desired path through the tissue to be treated towards the neutral electrode 10, but also travels in the so-called Diversion The same applies to the other electrosurgical instrument 19' as the current. Diversion The same is true for the current delivered by the output 16' of the electrosurgical instrument 19'.

[0056] This is shown in Figure 5, which shows an equivalent circuit diagram for two monopolar electrosurgical instruments 19, 19' with a shared neutral electrode 10. In the equivalent circuit diagram, at the leftmost and rightmost sides, two voltage sources are shown, which represent a first radio frequency generating unit 4 emitting and alternating a voltage V1 with a first frequency f1, and a second radio frequency generating unit 4' emitting and alternating a voltage V2 with a second frequency f2. As a result of the radio frequency generating units 4, 4' emitting different frequencies, a beat frequency is generated.

[0057] This is also shown in Figure 6, where the first high frequency generating unit generates a voltage V1 at a first frequency f1 and the second high frequency generating unit 4' generates a voltage at a second frequency f2. The currents generated by these voltages are shown by waves with large amplitudes (both frequencies are quite similar and both have the same amplitude, so they are difficult to distinguish in the figure). The resulting beat frequency is shown by waves with smaller amplitudes. This beat frequency occurs due to cross coupling induced by the cross impedance of the patient's body 99, as will be shown below.

[0058] The total current I1 provided by output 16 and flowing through cable 18 to electrosurgical instrument 19 is shown in the upper left corner of the subfigure; power 1 The total current I2 supplied by 6' and flowing through cable 18' to the other electrosurgical instrument 19' is shown in the subfigure located in the upper right corner. As can be easily seen, the current flow is affected by the beat frequency.

[0059] Any current supplied by any of the radio frequency generating units 4, 4' flows through the cross impedance formed by the patient body 99 towards the respective other radio frequency generating unit 4', 4. cross and the respective tissue impedance Z w1 , Z w2one other part I which flows towards the shared neutral patch electrode 10 (and finally back to the radio frequency generating unit 4, 4') through w1 or I w2 For effective treatment, the (working) current I that flows through the tissue impedance must be properly controlled. w1 and I w2 However, these working currents are Diversion current I cross , it is not possible to directly measure the total current I1 and I2 provided by the respective RF generating unit 4, 4'.

[0060] In order to appropriately control the power and energy delivered by each electrosurgical instrument 19, 19' to the tissue to be treated, the respective working currents I w1 or I w2 However, as already mentioned, they cannot be measured directly. To allow for a suitable control, the invention indirectly determines I by means of an observer unit 6 that receives measurable quantities as input values. w1 or I w2 By the same token, a working current calculation device 5 is provided, which is configured to determine Diversion current I cross can be determined and then utilized for current and power control.

[0061] As shown in Fig. 2 and Fig. 4, the measured quantities of the total currents I1 and I2 of the respective outputs 16, 16' as well as the measured voltages are sensed by the respective sensor assemblies 26, 26' and the measured values ​​are provided to a signal conditioning unit 90, which in particular comprises an analog-to-digital converter (ADC), and then to the observer unit 6. The sample data are processed by a sliding window device 7. The length of the sliding window used is variable and depends on the first frequency f1, i.e. the frequency of the voltage generated by the first high frequency generating unit 4, and the second distinct frequency f2, i.e. the frequency of the voltage generated by the second high frequency generating unit 4', as well as the frequency difference Δf between the first and second frequencies. Based on these values, their common denominator is calculated by a common denominator calculation device 70. Using the common denominator determined thereby, the length of the sliding window is preferably defined by the reciprocal of the largest common denominator. An illustrative example (with exaggerated numbers for better illustration) has a first frequency f1 of 300 kHz, a second frequency f1 of 400 kHz, and Δf is 100 kHz. The greatest common denominator of these numbers is 100k, and the largest common denominator is 10 μs (10 -5 For an assumed sampling frequency of 150M / s, this results in a window length of 150M / s * This results in 10 μs=1500 samples. This allows achieving a fairly short window length that provides high spectral resolution with minimal spectral leakage. The resulting windowed data is provided to a Fourier series approximation device 61 and to an automatic coefficient determination device 62 configured to calculate the coefficients of the Fourier series approximation device 61.

[0062] The automatic determination of the coefficients for the Fourier series and the Fourier transform is achieved by a Fourier series approximation device 61 and an automatic coefficient determination device 62 as shown below.

[0063] Based on the measured total current I1 supplied by output 16 to first electrosurgical instrument 19, the working current I w1To obtain, the Fourier coefficients of the first order Fourier series with an offset are determined.

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[0064] This is performed by the automatic coefficient determination device 62. Similarly, the working current I of the second electrosurgical instrument 19' is w2 The coefficients of the corresponding Fourier series for are determined by an automatic coefficient determination device 62.

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[0065] These coefficients are fed from the automatic coefficient determination device 62 to a Fourier approximation device 61 which then calculates the working current using a first order Fourier series.

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[0066] This allows the current I w1 and I w2These currents can be obtained by a Fourier series approximation device 61 with automatically determined coefficient values ​​for . They are conveyed to the central control unit 2, in particular its common inverter controller 3, by a multi-parameter signal 69, which preferably also includes a measurement signal of the voltage measured at either output 16, 16'. This allows the power to be calculated.

[0067] The observer unit 6 is also provided with a phase angle determination module 65. It is configured to determine the phase angle φ between the voltage at the first and second outputs 16, 16' and the first and / or second current I1, I2, respectively. This allows the actual phase difference φ at any of the outputs 16, 16' to be determined, thereby allowing the phase shift between the voltage and current supplied to the electrosurgical instrument 19, 19' at the respective first and second outputs 16, 16' to be properly taken into account. This is essential for the assessment of the effective power and therefore the energy transferred to the tissue by the electrosurgical instrument. Furthermore, a root mean square value can be determined using the phase angle φ provided by the phase angle determination module 65.

[0068] The common inverter controller 3 further includes: Diversion A current regulator 8 is provided, which is fed with the data of the observer unit 6, in particular its Fourier series approximation device 61. Diversion The current detector 80 is communicatively connected to the current detector 80. Diversion current I cross It can detect the presence of Diversion It can be fed to a current regulator 8 . Diversion The current regulator 8 cooperates with the common inverter controller 3 to Diversion To control the output of the high frequency generating units 4, 4', in particular their respective HF generating controllers 41, 41', their drive is modified in consideration of the current. This is because, for example, the effect on the tissue is dependent on the working current and DiversionCurrent control can be achieved by current control, since the total power acting on the tissue is determined by the total current, which is the sum of the powers delivered to the body impedances Zw1 and Zw2, and the cross body impedance Zcross, respectively. Diversion Further, for voltage control, the tissue is affected by the maximum of the voltage drop across the body impedance Zw1 or Zw2, respectively, and Zcross.

[0069] The work current I determined here w1 and I w2 Using the above, various control laws are implemented in the common inverter controller 3 and the first and second HF generation controllers 41, 41'. With the working current determined by the observer unit 6, the actual load impedance of any electrosurgical instrument 16 is obtained as the respective voltage measured for the electrosurgical instrument 16 as V1 and is then converted to the determined working current I w1 (For the second electrosurgical instrument 19', the voltage V2 is set to the working current I w2 The power can be easily determined by dividing the power by the power (divided by the power). Figure 7 shows a power diagram with different control regions. Three embodiments are shown in which up to three control laws are implemented. It is particularly preferred that the various control laws are used sequentially, in particular depending on the load and / or power of the respective electrosurgical instrument 19, 19'. It is noted that due to the independent first and second HF generation controllers 41, 41' both high frequency generation units 4, 4' can be operated with different control strategies and control laws.

[0070] In the first embodiment, shown by the upper solid line, for fairly low load impedances, in the illustrated embodiment, for example, less than about 200 Ω, "current control" may be beneficial as it strives to achieve the prescribed working current. For medium load impedances, in the illustrated embodiment, for example, in the range of about 200 Ω to about 500 Ω, "power control" may be beneficial to maintain the prescribed power delivered by the working current. For higher load impedances, greater than about 500 Ω (up to about 2000 Ω, where the control law ends), "voltage control" should preferably be used to avoid overvoltage. This set of control laws is applicable when the electrosurgical generator is capable of operating at full power. If the power is limited (e.g., to "half power"), the lower solid line is applicable, having "power control" for any load impedance less than about 1000 Ω, above which it switches to "voltage control".

[0071] For example, in a second embodiment, shown by the long dashed line, which is used for different generator modes for different surgical applications, "current control" is performed for load impedances below about 200 Ω, switching to "voltage control" above this threshold.

[0072] For example, in a third embodiment shown in dotted lines, which is used for yet another generator mode for further different surgical applications, "current control" is performed for load impedances below about 200 Ω, then switches briefly to "power control" where the power decreases linearly with increasing load impedance, and then switches to "voltage control" at about 300 Ω for any higher load impedance.

[0073] FIG. 9 shows a functional control block diagram illustrating the configuration for power control. As already mentioned above, by "power control" the control system strives to maintain a set power. Therefore, a PID controller is provided which varies the voltage supplied to the respective electrosurgical instrument 19, 19' in order to maintain the set power. The actual power supplied is determined by the voltage and the respective working current, determined by the above-mentioned observer unit 6 and fed back to the input of the PID controller. The PID controller can be parameterized by known standard procedures, for example the Ziegler-Nicol method, or by modern computer-aided tools such as the Control Design Toolbox in Matlab / Simulink®.

[0074] In Figure 8, an alternative functional equivalent diagram to that shown in Figure 5 is shown. It shows an additional effect, namely the appearance of a common path to a shared neutral electrode. In this configuration, the impedances are shown arranged in a "T" shape, unlike the diagram in Figure 5 where the impedances are shown as "π" (pi) shapes. Both models can be used to describe different effects, but can be converted into one another using the following relationship:

number

number

number

[0075] A schematic diagram of an observer unit with a Fourier series approximation device and an automatic coefficient determination device is shown in Fig. 10. Thus, the measured total currents I1 and I2 are provided via a buffer 60 to the input of an automatic coefficient determination device 62, which also receives a clock signal of the sampling frequency. Based on the above formula, the automatic coefficient determination device 62 calculates the working current I W1 and I W2 The coefficient a for the first-order Fourier approximation for both 1、0a 1、1 b 1、1 and a 2、0 a 2、1 b 2、1 The values ​​of these coefficients are supplied to a Fourier series approximation device 61 which is arranged to determine the working currents Iw1, Iw2 by first order Fourier approximation, as already mentioned above.

[0076] A schematic functional diagram of another embodiment of an electrosurgical generator is shown in Figure 11. This embodiment features a bipolar configuration for bipolar electrosurgical instruments, with output sockets 16, 16' configured as bipolar outputs for connecting bipolar instruments 19, 19', with each output socket 16, 16' being supplied by output lines 23, 23' having its own pair of active electrode (AE) and neutral electrode (NE) wires.

[0077] The equivalent circuit diagram for each of these configurations using two bipolar electrosurgical instruments is shown in Figure 12. As with the configuration shown in Figure 5, there is a cross resistance Zcross1 between the active electrodes of each electrosurgical instrument, Diversion A current Icross1 flows. However, since each of the bipolar electrosurgical instruments features its own neutral electrode, unlike FIG. 5, there is no shared neutral electrode. However, as a result, an additional current path appears between the respective neutral electrodes, forming a cross resistance Zcross2, resulting in an additional Diversion This may result in a current Icross2.

[0078] As a further difference with the embodiment of FIG. 3, the embodiment of FIG. 11 includes a combined radio frequency generating unit 4 , 4 ′ replacing the two separate radio frequency generating units 4 , 4 ′. * It is characterized by: The complex high frequency generating unit 4 * corresponds to the composite unit according to the present invention.This is embodied as a multilevel inverter with a number of inverter cells 4-1, 4-2, 4-3, 4-4. The inverter cells 4-1, 4-2, 4-3, 4-4 are cascaded in a first state and divided into two groups (e.g. two inverter cells each, but other distributions between the groups are possible), each group connected to one of the outputs 16, 16'. The inverter cells of either group thereby generate a high frequency AC voltage on their respective outputs 16, 16'. The HF generation for both groups is controlled by a combined HF generation unit 4 which consequently performs the functionality of the first and second HF generation controllers 41, 41'. * However, the complex high frequency generating unit 4 * The provision of the complex high frequency generating unit 4 is independent of the bipolar configuration. * can be similarly configured for a monopolar configuration of output sockets, as shown in Fig. 3, and a bipolar configuration can also be applied to the separated dual radio frequency generating units 4, 4', as shown in Fig. 3. Furthermore, mixed arrangements are possible, with one monopolar and one bipolar output socket and respective electrosurgical instruments.

[0079] As an added benefit, this complex high-frequency generating unit 4 * further enables (in its first state) the degrouping and configuration of all of the inverter cells 4-1, 4-2, 4-3, 4-4 into one cascade, thereby providing only one output 16 with twice the voltage range and power. Switching between this first and second state is controlled by a cell configuration governor 45, which is controlled by the central control unit 2.

Claims

1. 1. An electrosurgical generator configured to output a high frequency alternating current voltage to an electrosurgical instrument, comprising: A first HF generating unit (4) supplying a first high frequency AC voltage having a first frequency to a first output (16), and a second HF generating unit (4') supplying a second high frequency AC voltage having a second frequency different from the first frequency to a second output (16'), a first HF generating unit (4) and a second HF generating unit (4') configured to connect the first and second electrosurgical instruments (19, 19') such that, in an activated state, a first total current flows to the first electrosurgical instrument and simultaneously a second total current flows to the second electrosurgical instrument; a central control unit (2) configured to control the operation of said electrosurgical generator (1), including an inverter controller (3) for the operation of said first and second HF generating units (4, 4'); The inverter controller (3) is configured to receive the calculated first and second working currents as input signals, and the first and second working currents are obtained by a working current calculation device (5) communicatively connected to the inverter controller (3); 1. An electrosurgical generator, characterized in that the working current calculation device (5) comprises an observer unit (6) configured for indirect determination of the first and second working currents based on measurements obtained by dual measurement of the first and second total currents outputted at the first and second outputs (16, 16').

2. the observer unit (6) is provided with a Fourier series approximation device (61) for actually calculating a dual Fourier series approximation, one for the first working current and the other for the second working current; 2. The electrosurgical generator of claim 1, further comprising an automatic coefficient determination device configured to calculate coefficients of the Fourier series approximation based on the measurement of the sum of output first and second currents.

3. a further current, preferably a cross current, and a voltage, preferably a cross voltage, are determined taking into account said first and second working currents; and / or Electrosurgical generator according to the preceding claim, characterized in that root mean square (RMS) values ​​of the respective currents, voltages and powers are measured and calculated.

4. Electrosurgical generator according to any one of the preceding claims, characterized in that the observer unit (6) further comprises a phase angle determination module (65) configured to determine a phase angle between a voltage of the first and second outputs (16, 16') and the first and / or second current, respectively.

5. Electrosurgical generator according to any one of the preceding claims, characterized in that the observer unit (6) further comprises a sliding window device (7) for data processing of the measured values, the sliding window preferably having a variable length.

6. 7. An electrosurgical generator according to any one of the preceding claims, wherein the variable length is determined as a function of the first frequency, the second frequency, and / or a frequency difference between the first and second frequencies.

7. Electrosurgical generator according to any one of the preceding claims, characterized in that the sliding window device (7) comprises a common denominator calculation device (70), preferably configured to use the reciprocal of the common denominator, in particular the reciprocal of the greatest common denominator, for the length of the sliding window.

8. Electrosurgical generator according to any one of the preceding claims, characterized in that a cross current detector (80) is provided, said detector configured to determine a cross current between the first and second outputs (16, 16') in the activated state.

9. Electrosurgical generator according to any one of the preceding claims, characterized in that the cross current detector (80) is operatively connected to a cross current regulator (8) configured to adjust the electrical properties, in particular the voltage, current and / or frequency, of the second HF generating unit (4') so as to control the cross current.

10. the outputs of said first and second HF generation units (4, 4') are independently controlled by respective first and second HF generation controllers (41, 41'), preferably using said first and second working currents, respectively, as input variables; An electrosurgical generator according to any one of the preceding claims, further preferably characterized in that a decoupling controller (9) is provided configured for independent control of the first and second HF generating units (4, 4'), said decoupling controller interacting with the observer unit (6).

11. Electrosurgical generator according to any one of the preceding claims, characterized in that the first and second HF generation controllers (41, 41') are capable of applying different control laws, preferably current control, voltage control and / or power control.

12. Electrosurgical generator according to any one of the preceding claims, characterized in that the various control laws are selectively used depending in particular on the load and / or the power of the respective electrosurgical instrument (19, 19').

13. 10. An electrosurgical generator according to any one of the preceding claims, wherein the first frequency, the second frequency, and the frequency difference between the first and second frequencies are selected such that their respective values ​​are composite, i.e. non-prime, numbers.

14. The first and second HF generating units (4, 4') are combined into a composite unit (4) capable of outputting the first and second high frequency AC voltages at the first and second outputs, respectively. ＊ Electrosurgical generator according to any one of the preceding claims, characterized in that it is formed as a

15. The composite unit (4 ＊ 13. An electrosurgical generator according to any one of the preceding claims, characterized in that the inverter (4-1, 4-2, 4-3, 4-4) is a multilevel inverter having a plurality of inverter cells (4-1, 4-2), a first portion (4-1, 4-2) of the plurality of inverter cells configured to generate the first high frequency AC voltage and a second portion (4-3, 4-4) of the plurality of inverter cells configured to generate the second high frequency AC voltage.

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