Electrosurgical generator

Abstract

The invention relates to an electrosurgical generator. The invention relates to an electrosurgical generator configured to output a high-frequency alternating voltage to an electrosurgical instrument, comprising a first high-frequency generating unit (4) / a second high-frequency generating unit (4 '), a first high frequency AC voltage / second high frequency AC voltage having a first frequency / second frequency is supplied to a first output (16) / second output (16 ') configured to be connected to a first electrosurgical instrument (19) / second electrosurgical instrument (19'). Upon activation, a first current flows through the first electrosurgical instrument while a second current flows through the second electrosurgical instrument. The operating current actually delivered from the electrosurgical instrument to the tissue to be treated is important for correct and safe operation, but cannot be measured directly. The invention provides an observer unit (6) configured to indirectly determine a first and a second operating current (Iw1, Iw2) based on measured values.

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 generating unit which generates a high-frequency (HF) alternating voltage to be supplied to at least two output sockets which are configured to simultaneously connect and activate electrosurgical instruments. Background Art

[0002] In electrosurgery or high frequency surgery, an electrosurgical instrument such as an electrosurgical knife is used to apply high frequency alternating current to tissue in the human body. Typically, high frequencies in the radiofrequency range of about 200kHz up to 4000kHz are used. This results in local heating of the tissue. Thus, the tissue is cut or severed by heating, and the tissue is removed by thermal resection. A major advantage of this is that by closing the affected blood vessels, bleeding can be stopped while cutting, and the electrosurgical instrument can be used for other applications, such as coagulation. Different types of applications require different electrosurgical instruments.

[0003] For certain applications, it may be necessary to use more than one, in particular two, electrosurgical instruments simultaneously (dual activation) to perform a surgical task. To do this, separate electrosurgical generators can be used, one for each electrosurgical instrument. A typical problem encountered is that interference may occur between the outputs of the high voltages generated by the generators. If the two frequencies are close to each other but do not exactly match, this interference may include unwanted low-frequency beats, similar to the phenomena encountered in the field of acoustics. In addition, cross currents may be generated in the human body, which flow from one of the electrosurgical instruments to the other. Such cross currents hinder the proper control of the current / power delivered to the electrosurgical instrument and are therefore detrimental to operational safety. In addition to this, another costly difficulty is that two electrosurgical generators must be provided.

[0004] A similar situation may be encountered if a single electrosurgical generator with dual inverters and output stages is used, allowing dual activation of electrosurgical instruments. However, avoiding unwanted interference remains difficult. This can be alleviated by using a single inverter that supplies both outputs in an alternating manner. However, this limits the use to modulation modes with a duty cycle of less than 50%, which is a significant limitation.

[0005] It is also envisaged to perform power measurements on both outputs. However, this also has the disadvantage that it is only possible for outputs with the same settings and mode. In addition, the true power distribution between each of these dual outputs remains unknown.

[0006] Another method is to supply a voltage with two different fundamental frequencies to the dual output terminals and use a Goertzel type filter to perform a discrete Fourier transform (DFT) on the measured values ​​of the two output terminals (EP 3 912 580 A1). If the fundamental frequencies are not completely orthogonal, they will overlap, and the overlap will produce discontinuities in the Goertzel array diagram. This is used to detect whether significant cross conduction occurs. If a certain threshold is exceeded, the HF generation and output will be shut down as a safety measure. As another variant, based on this method, the beat amplitude can be measured to determine the size of the resistance. However, this can only estimate the transverse current at best, and cannot accurately determine the working current actually injected into the working tissue by the corresponding electrosurgical instrument connected to either output terminal. As a result, although this may be a feasible safety device, the control of the energy delivered by the corresponding electrosurgical instrument still needs to be improved. Summary of the invention

[0007] It is therefore an object of the present invention to provide an improved electrosurgical generator with dual outputs in order to alleviate this disadvantage.

[0008] An electrosurgical generator configured to output a high-frequency alternating voltage to an electrosurgical instrument, the electrosurgical generator comprising: a first HF generating unit, the first HF generating unit supplying a first high-frequency alternating voltage having a first frequency to a first output terminal; a second HF generating unit, the second HF generating unit supplying a second high-frequency alternating voltage having a second frequency different from the first frequency to a second output terminal, the first output terminal and the second output terminal being configured to be connected to a first electrosurgical instrument and a second electrosurgical instrument, so that in an activated state, a first current flows through the first electrosurgical instrument, and at the same time, a second current flows through the second electrosurgical instrument; and a central control unit, the central control unit The central control unit is configured to control the operation of the electrosurgical generator, the central control unit includes an inverter controller for simultaneously operating the first HF generating unit and the second HF generating unit, wherein, according to the present invention, the inverter controller is configured to receive a calculated working current as an input signal, wherein the working current is obtained by a working current calculation device communicatively connected to the inverter controller, the working current calculation device includes an observer unit, and the observer unit is configured to indirectly determine the first working current and the second working current based on measurement values ​​obtained by double measurement of actual current output at the first output terminal and the second output terminal.

[0009] In the following, some expressions used in the context of the present invention are explained.

[0010] In the field of electrosurgical generators, "high frequency" refers to frequencies typically in the range between 200 kHz and 4000 kHz, which are also known as radio frequencies (RF).

[0011] "High voltage" generally refers to a voltage up to 10 kV, preferably up to 4000 V, more preferably at least 10 V.

[0012] 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 at its output. It is configured to determine variables or states that are not accessible or at least not directly accessible by using parameters and other measured variables output by the system. Various such observers are known to those skilled in the art of control systems.

[0013] The inverter controller is a device that provides the actual high frequency AC voltage output for the surgical instrument connected to the output socket. The term is quite broad and includes inverter technology as well as converters and amplifiers.

[0014] In the activated state of the electrosurgical generator, the crossover current is the part of the total current emitted by the output terminal, which flows to the other output terminal. The working current is the other part of the total current, which actually flows from the output terminal via the electrosurgical instrument to the tissue to be treated (and returns to the same output terminal in the case of a bipolar configuration, or returns to a separate neutral patch electrode in the case of a monopolar configuration). The working current and the crossover current form the (total) current of the corresponding output terminal. This (total) current is measured by a sensor arranged at the output terminal and / or the output line.

[0015] The fundamental problem is that it is not possible to directly measure the operating current actually delivered from the electrosurgical instrument to the tissue being treated. This is largely due to the presence of crossover currents between the dual output terminals.

[0016] The present invention has recognised that by using the operating current (or the power produced) as a control signal, improved control of the output and the electrosurgical instrument powered thereby can be achieved, even though the operating current cannot be directly measured. Although this may appear contradictory at first glance, the present invention has recognised that the difficulties experienced by known concepts can thereby be overcome.

[0017] The core of the invention is to use calculated rather than measured operating currents, since direct measurement is not possible, and to create an observer unit configured to determine said operating currents indirectly based on measured values, in particular the (total) current output of either output (which can be measured directly). These operating currents of the two outputs thus determined are then used as input signals for the central control unit.

[0018] The present invention makes use of the fact that, due to the first HF generating unit and the second HF generating unit, a voltage with a first frequency is applied at the first output terminal, and a voltage with a different second frequency is applied at the second output terminal, thereby generating a beat frequency and a crossover current. However, once a crossover current occurs, the current measured at either output terminal will be a combination of the currents of the two frequencies. The present invention has recognized that this can not only be used to detect the presence of a crossover current, but that this dual frequency characteristic can also be used to determine the portion of the current delivered by the output terminals that is the actual operating current.

[0019] Thus, the present invention allows to directly determine the individual working currents for the two outputs. This allows to significantly improve the control of the energy delivered by the corresponding electrosurgical instrument. In addition, the uncertainties encountered in the prior art by estimation alone can be effectively avoided. The control quality and the operational safety of the electrosurgical generator can be improved, and the risk to the patient due to undetected or wrongly estimated overcurrents and / or cross-currents 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 the approximation by means of a double Fourier series, one of the devices being used 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 double Fourier series approximation based on the measured values ​​of the double current output, and transmitting the coefficients to the Fourier series approximation device. As known to those skilled in the art, by selecting the order of the Fourier series, the quality of the approximation can be determined. A high order can provide more accurate results, however, this is not necessary. In a preferred embodiment, an approximation to first order (ie relative to the fundamental frequency) will provide the best value between sufficiently accurate results and required computational effort / processing power.

[0020] First, the automatic coefficient determination means will be explained using a simplified Fourier series as an approximation of the first order (fundamental frequency). It uses K measurement samples of the measurable (total) current output I1 at the first output terminal to determine the offset coefficients of the Fourier series around the first frequency f1:

[0021]

[0022] and two first-order coefficients:

[0023]

[0024] Use △ as the sampling time.

[0025] Likewise, based on the measurable (total) current output I2 at the second output terminal, the offset factor is determined:

[0026]

[0027] And the two first-order coefficients:

[0028]

[0029] The same operation is performed for a second Fourier series around the second frequency f2, thereby generating a set of another six coefficients. These coefficients as determined by the automatic coefficient determination means are supplied to the Fourier series approximation means of the observer unit.

[0030] In a system with two monopolar electrosurgical instruments, an actual operating current (first operating current I w1 ) and the actual working current (second working current I w2 ) is determined as follows, where I(k) represents a single measurement value:

[0031]

[0032] According to Kirchhoff's current law, by w1 (or the second working current I w2 ) by subtracting the corresponding measured total current I1 (or I2), the crossover current I cross The corresponding voltage is V cross .

[0033] The corresponding resistance R of this impedance Z is calculated according to the following equation, where, Abbreviated as It represents the phase shift between voltage and current Determined power factor:

[0034]

[0035] Based on the current, the power signal delivered by either output terminal can be determined according to the following equation:

[0036]

[0037] As input and output signals of the control, the root mean square (RMS) value of each parameter is measured with the 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. Next, the average power can be calculated according to the following equation:

[0038]

[0039] For a system with two bipolar electrosurgical instruments, the determination of the actual operating current is similar to that in the monopolar system. According to Kirchhoff's current law, the following applies to the crossover current

[0040] I cross1 =-I cross2 =I w1 -I1

[0041] Use the following equation to calculate the crossover resistance R cross1 and R cross2 sum:

[0042]

[0043] Assume that R cross1 Equal to R cross2 , then assume that the corresponding voltage V cross1 and V cross2 are related according to the following equation:

[0044]

[0045] The average power for each instrument was determined using the following equation:

[0046]

[0047] The power of each instrument is compared with the corresponding reference power and can be controlled in the power control.

[0048] For current control, the RMS value of the output currents I1 and I2 of each instrument can be controlled by manipulating the output voltage.

[0049] For voltage control, the output voltage is compared to the voltage drop across the cross impedance, and the maximum value is used as the controlled variable that is manipulated by the output voltage itself.

[0050] An important advantage of the present invention is that this is done at two different frequencies f1 and f2. Thus, the number of available coefficients is doubled, allowing the observer unit to calculate not only the measurable total current output, but also the unmeasurable operating current flowing through the electrosurgical instrument and into the tissue to be treated. Thus, previously unachievable accuracy and granularity of the current determination can be achieved.

[0051] As can be easily understood, taking into account the first operating current and the second operating current, other electrical parameters such as voltage (including crossover voltage) and / or other currents (preferably crossover current) can be determined. The root mean square value (RMS) of the corresponding current, voltage and power can also be determined.

[0052] Advantageously, the observer unit further comprises a phase angle determination module, which is configured to determine the phase angle between the voltage at the first and second output terminals and the first and / or second current, respectively. This allows a proper account to be taken of the phase shift between the voltage and the current at either output terminal. This is very important for assessing the effective power and energy delivered to the tissue by the electrosurgical instrument. Furthermore, the phase angle determination module helps to determine the RMS value.

[0053] In order to efficiently calculate the Fourier transform, the observer unit advantageously comprises a sliding window arrangement for data processing of the measured values. Advantageously, the sliding window has a variable length, which is preferably determined as a function of the first frequency, the second frequency and the frequency difference between the first frequency and the second frequency. This enables the length of the sliding window to be appropriately matched to the frequencies used. For computational efficiency, preferably a fast (FFT) or discrete (DFT) Fourier transform may be used, however, this is not essential.

[0054] Preferably, the sliding window device comprises a common denominator calculation unit and is preferably configured to use the reciprocal of the common denominator for the length of the sliding window. Thus, the sliding window can adapt to the frequency, thereby reducing unnecessary spectrum leakage. It is particularly advantageous to use the reciprocal of the largest (or second largest) common denominator for the length of the sliding window. This results in that a short window provides the best results with respect to frequency resolution and avoiding spectrum leakage.

[0055] Although the actual current flowing through the electrosurgical instrument is a more important parameter, it may also be beneficial to address the crossover current. To this end, a crossover current detector is advantageously provided, which is configured to determine the crossover current between the first output terminal and the second output terminal in an activated state. This allows for a more accurate calculation of the total power output of the electrosurgical generator at its dual output terminals. In addition, this enables the crossover current to be correctly taken into account. The crossover current detector is also preferably cooperatively connected to a crossover current regulator, which is configured to adjust the electrical characteristics (particularly voltage, current and / or frequency) of the second HF generating unit in order to control the crossover current.

[0056] Preferably, the outputs of the first HF generating unit and the second HF generating unit are independently controlled by the corresponding first HF generating controller and the second HF generating controller, respectively, preferably using the first working current and the second working current, and optionally, also using the cross current as input variables (and / or corresponding impedance). The use of independent controllers allows for the most specific response to the changing impedance at the electrosurgical instrument, in particular due to the different characteristics of the tissue to which the corresponding electrosurgical instrument is applied. The load impedance of the tissue to be treated 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 generating controller and the second generating controller can apply various control laws, preferably "current control" and / or "power control", optionally, also "voltage control". It is particularly preferred if various control laws are to be selectively adopted, in particular according to the load and / or power of the corresponding electrosurgical instrument. It is particularly preferred if more than one control law is processed and the output of each control law is compared and one is selected. For example, for each control law, the error between the actual value and the reference value is determined, and the control law with the minimum error used by the selection device determines the set point for further control ("current control") in order to maintain the current and thus maintain the tissue effect achieved by the electrosurgical instrument. This is particularly useful for relatively low load impedances. "Power control" enables precise control of the energy delivered to the electrosurgical instrument each time. As shown in the power equations of P1 and P2 above, calculated values ​​for the working current and the crossover current are taken into account. This is particularly useful for medium load impedances at the electrosurgical instrument. For relatively high load impedances at the electrosurgical instrument, "voltage control" is provided, for example, so as to ensure that the output and applied voltage are within the safety limits of the electrosurgical instrument and the patient. Various control laws can be used separately or in parallel, such as current control performed using basic voltage control. Further preferably, a decoupling controller is provided, which is configured to independently control the first HF generating unit and the second HF generating unit, and the decoupling controller interacts with the observer unit. Therefore, with the aid of the observer unit and in particular the calculated working current, a control decoupling of the electrosurgical instrument at the two output terminals can be achieved. Thus, even taking into account that the first HF generating unit and the second HF generating unit are electrically connected by the cross current, adverse interference between them can be minimized or avoided. This is a major advantage of applying appropriate control. It is important to note that the first HF generating controller and the second HF generating controller can be operated independently of each other, including that they are configured to apply different control laws.

[0057] However, it is also possible to form these first HF generating unit and the second HF generating unit as a combined unit, which enables the output of the first high-frequency AC voltage and the second high-frequency AC voltage that are independent of each other. Therefore, the first frequency and the second frequency with different voltages and frequencies can be generated by a single combined unit. To this end, the combined unit is preferably a multi-level inverter with a plurality of inverter units, wherein a first part of the plurality of inverter units is configured to generate the first high-frequency AC voltage, and a second part of the plurality of inverter units is configured to generate the second high-frequency AC voltage. Therefore, the first frequency and the second frequency for dual output can be generated in a very efficient manner, and if only one output terminal is supplied, the same inverter can be used alternatively with all inverter units in a group. This achieves higher versatility with minimal effort.

[0058] A multilevel inverter is an inverter unit that is able to generate output voltages at different levels, rather than just providing an on / off output terminal with positive and / or negative polarity. Typical topologies include, but are not limited to, cascaded H-bridges, neutral clamps, and flying capacitors.

[0059] For practical purposes, it is beneficial if the first frequency, the second frequency and the frequency difference between the first frequency and the second frequency are selected so that their respective values ​​are composite numbers, i.e. non-prime numbers. Due to the non-prime numbers, a relatively large common denominator can be established for the first frequency, the second frequency and the different frequencies, thereby allowing the length of the sliding window to be relatively short for achieving good spectral resolution and minimizing spectral leakage. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] The invention is explained in more detail below with reference to advantageous exemplary embodiments. In the drawing:

[0061] Figure 1 Shown is a front view of an electrosurgical generator with two attached electrosurgical instruments.

[0062] Figure 2 A schematic diagram showing multiple electrosurgical instruments at a surgical site;

[0063] Figure 3 shows a schematic functional diagram of an electrosurgical generator including two monopolar output sockets;

[0064] Figure 4 shows a detailed view of the observer unit;

[0065] Figure 5 An equivalent circuit diagram and currents for supplying two outputs of two monopolar electrosurgical instruments are shown;

[0066] Figure 6 The currents for two different frequency outputs and the resulting beat frequencies are shown;

[0067] Figure 7 shows a power diagram with different control regions;

[0068] Figure 8 A schematic functional diagram showing another embodiment of an electrosurgical generator including a combined high frequency generating unit; and

[0069] Fig. 9 The equivalent circuit diagram and current flow for supplying two outputs of two bipolar electrosurgical instruments are shown. DETAILED DESCRIPTION

[0070] Figure 1 An exemplary embodiment of an electrosurgical generator according to a first embodiment of the present invention is illustrated in . The electrosurgical generator (indicated as a whole 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 patch electrode) for connecting electrosurgical instruments 19, 19'. A power cable 12 is provided with a plug for connection to a power source (not shown), which may be a grid such as an AC power source in a building, or an off-grid power source such as a 12 volt or 24 volt battery in a vehicle or mobile hospital. In addition, a user interface 14 is provided, which includes a display 15, which may be a touch screen, or a knob 13 may be provided for user input.

[0071] The electrosurgical instrument 19 comprises a cable 18 which is to be plugged into the outlet socket 16 in order to supply a high frequency alternating voltage for operating the electrosurgical instrument 19. The same applies to another electrosurgical instrument 19' connected to the outlet socket 16' by its cable 18'.

[0072] Figure 2 Two electrosurgical instruments 19, 19' are shown in the figure, which are powered by an electrosurgical generator 1 at a surgical site. An operating table 98 is provided, which is configured to accommodate a patient 99 to be treated. In the depicted embodiment, the electrosurgical instruments 19, 19' will both be used on the same patient 99 at different locations. In the depicted embodiment, the electrosurgical instruments 19, 19' are both monopolar. This requires a neutral patch electrode 10, which is attached to the operating table 98, or preferably, to the patient 99, thereby creating a considerable contact area. The neutral patch electrode 10 is connected to an additional socket 17 of the electrosurgical generator 1 via a cable 10', thereby providing a return path for the HF energy provided by the electrosurgical generator 1 to the electrosurgical instruments 19, 19', and closing the circuit.

[0073] Figure 3A schematic functional diagram of an electrosurgical generator is shown in . Electric power is delivered by a power cable 12 to a power supply unit 20 of the electrosurgical generator 1. The power supply unit supplies power (in the depicted embodiment, direct current) to various devices, units and modules of the electrosurgical generator 1. In particular, it supplies power via a DC bus 22 to a first HF generating unit 4, which is configured to generate a first high-frequency alternating voltage, which is supplied to a first output socket 16 (also referred to as the output end 16 for simplicity) for powering an insertable electrosurgical instrument 19 via a first output line 23 and a first sensor assembly 26 for voltage and current measurement. The output line 24 includes an active electrode (AE) line 24 and a neutral electrode (NE) line 25. The high voltage is typically in the range of several kilovolts, but may have an amplitude in the range of tens of volts to up to 4000 volts. Furthermore, a second HF generating unit 4' is provided, which is also powered from the power supply 20 via the DC bus 22 and is provided with a second output line 23' for outputting a voltage in a similar manner, said second output line 23' comprising an active electrode line 24' and a neutral electrode line 25' and a second sensor assembly 26' for measuring voltage and current at the second output socket 16'. In the depicted embodiment, a monopolar configuration is shown, wherein the output sockets 16, 16' are configured as monopolar output terminals for connecting monopolar instruments 19, 19' and also have a neutral electrode (NE) line 25, 25' connected to an additional neutral output socket 17 connected to the neutral patch electrode 10. As shown Figure 8 and Fig. 9 As shown in , for a bipolar output terminal, a second implementation is provided.

[0074] The operation of the first HF generating unit 4 and the second HF generating unit 4' is controlled by a central control unit 2, which is in turn connected to a user interface 14 so that a user can issue instructions and commands for operating the electrosurgical generator 1. The central control unit 2 generates corresponding control signals and controls the relevant devices, units and modules of the electrosurgical generator 1 according to these instructions and commands. In particular, the central control unit 2 includes a common inverter controller 3, which provides instruction signals to the first HF generating controller 41 and the second HF generating controller 41', wherein each controls its corresponding first HF generating unit 4 and the second HF generating unit 4' in turn. The first high frequency voltage generated by the first HF generating unit 4 is transmitted to the output socket 16 via the corresponding output line 23 and the sensor assembly 26. Similarly, the second high frequency voltage generated by the second HF generating unit 4' is transmitted to the output socket 16' via the corresponding output line 23' and the sensor assembly 26'.

[0075] The first HF generating unit 4 and the second HF generating unit 4' generate a first HF voltage and a second HF voltage, respectively, with a voltage and a frequency as specified by the corresponding first HF generating controller 41 and the second HF generating controller 41'. The voltage and the frequency of the first HF generating unit 4 and the second HF generating unit 4' can be controlled and generated independently of each other. However, the final current delivered from the first HF generating unit 4 and the second HF generating unit 4' via their respective output sockets 16, 16' is determined by the impedance of the corresponding electrosurgical instrument 19, 19' and the impedance of the tissue contacted by either instrument. The total current I1 flowing through the first output socket 16 is determined by the first sensor assembly 26, which also determines the corresponding actual voltage; similarly, the total current I2 flowing through the second output socket 16' is determined by the second sensor assembly 26', which also determines the corresponding actual voltage. The resulting measurement signal is applied to the signal conditioning unit 9, which may include an analog-to-digital converter (ADC) and also provides feedback to the central control unit 2 via the working current quantization device 5.

[0076] However, the total current I1 determined by the respective sensor assembly 26, 26' is different from the current flowing through the tissue (the "working current") to which the electrosurgical instrument is applied.

[0077] like Figure 2 As can be seen in Figure 1, electrosurgical instruments 19, 19' are usually applied at different parts of the patient's body. These different parts may be very close to each other, especially in the case of auxiliary surgery, or may be far away from each other, especially in the case of combined surgery. In either case, the current delivered by the output terminal 16 of the electrosurgical instrument 19 will not only take the desired path through the tissue to be treated toward the neutral patch electrode 10, but will also flow to the other electrosurgical instrument 19' as a so-called cross current. The same applies to the current delivered by the output terminal 16' of the electrosurgical instrument 19' relative to the cross current toward the electrosurgical instrument 19.

[0078] Figure 5 1 shows an equivalent circuit diagram for the case of two monopolar electrosurgical instruments 19, 19' with a shared neutral patch electrode 10. In the equivalent circuit diagram, two voltage sources are shown at the far left and far right, representing a first high-frequency generating unit 4 that emits and alternates a voltage V1 having a first frequency f1 and a second high-frequency generating unit 4' that emits and alternates a voltage V2 having a second frequency f2. Since the high-frequency generating units 4, 4' emit different frequencies, a beat frequency is generated.

[0079] This is also Figure 6, wherein 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 V2 at a second frequency f2. These voltages are represented by waves with large amplitudes (the two frequencies are very similar, and they are difficult to distinguish in the figure because they have the same amplitude). The resulting beat frequency is depicted by a wave with a smaller amplitude. As will be illustrated below, the beat frequency is generated due to the cross-coupling caused by the cross-impedance of the patient's body.

[0080] In the upper left corner of the sub-diagram, the total current I1 supplied by the output terminal 16 and flowing to the electrosurgical instrument 19 via the cable 18 is shown, and likewise, in the upper right sub-diagram, the total current I2 supplied by the output terminal 16' and flowing to another electrosurgical instrument 19' via the cable 18' is shown. As can be easily understood, the current flow is affected by the beat frequency.

[0081] Any current supplied by any high frequency generating unit 4, 4' is divided into a part Icross and another part, namely the first working current I w1 Or the second working current I w2 , wherein part Icross flows toward the corresponding other high-frequency generating unit 4, 4' through the cross impedance formed by the patient's body, and the other part flows through the corresponding body impedance Z w1 , Z w2 Flows toward the shared neutral patch electrode 10 (and eventually returns to the high frequency generating unit 4, 4'). For effective treatment, it is necessary to properly control the first working current I flowing through the tissue impedance w1 and the second operating current I w2 However, due to the crossover current I cross The only currents that can be directly measured are the total currents I1 and I2 supplied by the corresponding high frequency generating units 4, 4'.

[0082] In order to correctly control the power and energy delivered to the tissue to be treated by the corresponding electrosurgical instrument 19, 19', it is necessary to know the corresponding first working current I w1 Or the second working current I w2 However, as mentioned above, they cannot be measured directly. In order to enable appropriate control, the present invention provides an operating current quantization device 5, which is configured to indirectly determine the first operating current I through an observer unit 6. w1 Or the second working current I w2 , the observer unit receives as input a quantity that can be measured. For the same reason, the crossover current I cross , and can subsequently be used for current and power control.

[0083] like Figure 2and Figure 4 As shown in , the measured quantities of the total currents I1 and I2 of the respective output terminals 16, 16' and the measured voltages are sensed by the respective sensor assemblies 26, 26' and the measured values ​​are provided to a signal conditioning unit 9, in particular comprising an analog-to-digital converter (ADC), and subsequently to an 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 different frequency f2 (i.e. the frequency of the voltage generated by the second high-frequency generating unit 4') and the frequency difference Af between the first frequency and the second frequency. Based on these values, their common denominator is calculated by a common denominator device 70. Using the common denominator thus determined, the length of the sliding window is defined by the reciprocal of the common denominator, preferably the greatest common denominator. An illustrative example (with exaggerated figures for better illustration) has a first frequency f1 of 300kHz, a second frequency of 400kHz, resulting in a Δf of 100kHz. The highest common denominator of these numbers is 100k, which results in a window length of 10μs (10 - 5 s). Assuming a sampling frequency of 150M / s, 150M / s*10μs=1500 samples are generated for the window length. Therefore, a relatively short window length can be achieved, thereby achieving high spectral resolution with minimal spectral leakage. The resulting window data is provided to the Fourier series approximation device 61 and the automatic coefficient determination device 62, which is configured to calculate the coefficients for the Fourier series approximation device 61.

[0084] The automatic determination of Fourier series coefficients and the Fourier transform will be implemented by the Fourier series approximation device 61 and the automatic coefficient determination device 62 as shown below.

[0085] Based on the measured total current I supplied by the output 16 to the first electrosurgical instrument 19 i , the Fourier coefficients of the first-order Fourier series with offset are determined to obtain the first operating current I w1 :

[0086]

[0087] This is performed by the automatic coefficient determination device 62. Similarly, with the second operating current I w2 The coefficients of the associated corresponding Fourier series are determined by the automatic coefficient determination means 62:

[0088]

[0089] These coefficients are supplied from the automatic coefficient determination means 62 to the Fourier series approximation means 61 which in turn uses a first order Fourier series to calculate the operating current:

[0090]

[0091] Therefore, the first operating current I which cannot be directly measured can be obtained by the Fourier series approximation device 61. w1 and the second operating current I w2 They are transmitted to the central control unit 2, in particular its common inverter controller 3, by means of a multi-parameter signal 69, which preferably also includes a measurement signal for the voltage measured at either output 16, 16'. This allows the power to be calculated.

[0092] Furthermore, the observer unit 6 is provided with a phase angle determination module 65. It is configured to determine the phase angle between the voltage at the first output terminal 16 and the second output terminal 16' and the first current I1 and / or the second current I2, respectively. This allows the actual phase angle at either output 16, 16' to be determined. The phase shift between the voltage and the current supplied to the electrosurgical instrument 19, 19' at the respective first output 16 and second output 16' can thereby be correctly taken into account. This is essential for assessing the effective power and therefore the energy delivered to the tissue by the electrosurgical instrument. In addition, the RMS value can be obtained using the phase angle provided by the phase angle determination module 65 to be sure.

[0093] The common inverter controller 3 is also provided with a cross current regulator 8. It is communicatively connected to a cross current detector 80, to which the data of the observer unit 6, in particular the data of its Fourier series approximation device 61, are supplied. Thus, the cross current I cross , and a corresponding signal can be supplied to the cross current regulator 8. The cross current regulator 8 cooperates with the common inverter controller 3 to modify the drive of the high frequency generating units 4, 4', in particular their respective HF generating controllers 41, 41', so as to control their outputs taking into account the cross current. For example, this can be achieved by current control, since the effect on the tissue is determined by the total current, which is the sum of the working current and the cross current. Similarly, power control can make use of the cross current, because the total power acting on the tissue is the sum of the power delivered to the body impedances Zw1 and Zw2, respectively, and to the cross body impedance Zcross. In addition, with regard to voltage control, the tissue is affected by the maximum of the body impedance Zw1 or Zw2 and the voltage drop across Zcross, respectively.

[0094] Using the first operating current I determined in this way w1 and the second operating current I w2 , various control laws are implemented in the common inverter controller 3 and the first HF generation controller 41 and the second HF generation controller 41 '. Due to the operating current determined by the observer unit 6, the first operating current I determined by extracting the corresponding voltage for the electrosurgical instrument 16 as the measured value V1 and dividing it w1 (In the case of the second electrosurgical instrument 19', the voltage V2 is divided by the second operating current I w2 ), the actual load impedance of any electrosurgical instrument can be easily determined. Figure 7 . Three embodiments are depicted, in which up to three control laws are implemented. Preferably, the various control laws should be used in sequence, in particular depending on the load and / or power of the respective electrosurgical instrument 19, 19'. It should be noted that due to the independent first HF generation controller 41 and the second HF generation controller 41', the two high frequency generation units 4, 4' can be operated with different control strategies and control laws.

[0095] In a first embodiment, shown by the upper solid line, for relatively low load impedances (e.g., less than about 200Ω in the described embodiment), "current control" may be beneficial, as it strives to achieve a defined operating current. For medium load impedances (e.g., in the range between about 200Ω and about 500Ω in the described embodiment), "power control" may be beneficial in order to maintain a defined power delivered by the operating current. For higher load impedances, greater than about 500Ω (up to about 2000Ω at the end of the control law), "voltage control" is preferably used to avoid overvoltage. If the electrosurgical generator is allowed to run at full power, this sequence of control laws may be applied. If power is limited (e.g., "half power"), the lower solid line applies, with "power control" for any load impedance below about 1000Ω, and switching to "voltage control" above this value.

[0096] In a second embodiment, illustrated by long dashed lines, for example for different generator modes for different surgical applications, "current control" is performed for load resistances below about 200Ω, while above this threshold it switches to "voltage control".

[0097] In a third embodiment shown by dashed lines, a generator mode for a different surgical application, for example, "current control" is performed for load impedances below about 200Ω, then for increasing load impedances, temporarily switches to "power control" with linear power, and thereafter switches to "voltage control" at about 300Ω for higher load impedances.

[0098] exist Figure 8 A schematic functional diagram of another embodiment of an electrosurgical generator is shown in . This embodiment features a bipolar configuration for a bipolar electrosurgical instrument, wherein the output sockets 16, 16' are configured as bipolar outputs for connecting bipolar instruments 19, 19', each output socket 16, 16' being powered by an output line 23, 23' having its own pair of active electrode (AE) and neutral electrode (NE) lines.

[0099] As Figure 3 Another difference in the implementation of Figure 8 An embodiment of the invention is characterized by a combined high-frequency generating unit 4*, which replaces the two separate high-frequency generating units 4, 4'. It is implemented as a multi-level inverter having a plurality of inverter units 4-1, 4-2, 4-3, 4-4. The inverter units 4-1, 4-2, 4-3, 4-4 are connected in a cascade manner in a first state and are divided into two groups (for example, each group has two inverter units, but other allocations between the groups are also possible), each group being connected to one of the output terminals 16, 16'. Therefore, the inverter units of either group generate a high-frequency AC voltage for their respective output terminals 16, 16'. The HF generation of the two groups is controlled by a combined HF generation controller 4*, which therefore performs the functions of a first HF generation controller 41 and a second HF generation controller 41'. However, the provision of a combined high-frequency generating unit 4* is independent of a bipolar configuration. As Figure 3 As shown in FIG, the combined high frequency generating unit 4* can also be configured for a single-pole configuration of an output socket, and as Figure 3 As shown in , and this bipolar configuration can also be applied to two separate high frequency generating units 4, 4'. In addition, a mixed arrangement of one monopolar and one bipolar output socket and the corresponding electrosurgical instrument is also possible.

[0100] As an additional benefit, the combined high frequency generating unit 4* also allows (in its first state) the removal of grouping and allows all of the inverter units 4-1, 4-2, 4-3, 4-4 to be configured in one cascade, thereby supplying double the voltage range and power to only one output terminal 16. This switching between the first state and the second state is controlled by a unit configuration regulator 45 controlled by the central control unit 2.

[0101] The present invention can be summarized as follows:

[0102] An electrosurgical generator, which is configured to output a high-frequency alternating voltage to an electrosurgical instrument, comprises a first high-frequency generating unit 4 / a second high-frequency generating unit 4', and provides a first high-frequency alternating voltage / a second high-frequency alternating voltage having a first frequency / a second frequency to a first output terminal 16 / a second output terminal 16', wherein the first output terminal 16 / a second output terminal 16' is configured to connect a first electrosurgical instrument 19 / a second electrosurgical instrument 19'. When started, a first current flows through the first electrosurgical instrument, while a second current flows through the second electrosurgical instrument. The first working current Iw1 and the second working current Iw2 actually delivered from the electrosurgical instrument to the tissue to be treated are very important for correct and safe operation, but cannot be directly measured. The present invention provides an observer unit 6, which is configured to indirectly determine the first working current Iw1 and the second working current Iw2 based on the measured values. By configuring the observer unit for indirectly determining the working currents, these currents can be used as input signals for an inverter controller 3, which is configured to receive the calculated working currents, thereby achieving improved control of the electrosurgical generator.

Claims

1. An electrosurgical generator configured to output a high-frequency alternating voltage to an electrosurgical instrument, the electrosurgical generator comprising: A first high-frequency generating unit (4) which supplies a first high-frequency alternating voltage having a first frequency to a first output terminal (16); a second high-frequency generating unit (4') which supplies a second high-frequency alternating voltage having a second frequency different from the first frequency to a second output terminal (16'), The first output and the second output are configured to be connected to a first electrosurgical instrument (19) and a second electrosurgical instrument (19'), so that in an activated state, a first current flows through the first electrosurgical instrument and, at the same time, a second current flows through the second electrosurgical instrument; as well as A central control unit (2) configured to control the operation of the electrosurgical generator (1), the central control unit (2) comprising an inverter controller (3) for operating the first high-frequency generating unit (4) and the second high-frequency generating unit (4'), characterized in that: The inverter controller (3) is configured to receive a calculated operating current as an input signal, wherein the operating current is obtained by an operating current calculation device (5) communicatively connected to the inverter controller (3), and the operating current calculation device (5) includes an observer unit (6), and the observer unit (6) is configured to indirectly determine a first operating current and a second operating current based on measurement values ​​obtained by double measurement of actual current output at the first output terminal (16) and the second output terminal (16′).

2. The electrosurgical generator according to claim 1, characterized in that The observer unit (6) is provided with Fourier series approximation means (61) for actually calculating double Fourier series approximations, one of which is for the first operating current and the other is for the second operating current, and The observer unit (6) further comprises automatic coefficient determination means (62) configured to calculate coefficients of the Fourier series approximation based on the measured values ​​of the first output terminal (16) and the second output terminal (16').

3. The electrosurgical generator according to claim 2, characterized in that taking into account the first operating current and the second operating current, determining a further current, preferably a crossover current, and a voltage, preferably a crossover voltage, and / or The RMS values ​​of the corresponding current, voltage and power are measured and calculated.

4. An 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 the phase angles between the voltages at the first output terminal (16) and the second output terminal (16') and the first current and / or the second current, respectively.

5. An 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 of the sliding window device preferably having a variable length.

6. The electrosurgical generator according to claim 5, characterized in that The variable length is determined according to the first frequency, the second frequency and / or a frequency difference between the first frequency and the second frequency.

7. The electrosurgical generator according to claim 5, characterized in that The sliding window device (7) comprises a common denominator calculation device (70), and the sliding window device (7) is preferably configured to use the common denominator of the length of the sliding window, in particular the reciprocal of the greatest common denominator.

8. An electrosurgical generator according to any one of the preceding claims, characterized in that A crossover current detector (80) is provided, which is configured to determine a crossover current between the first output terminal (16) and the second output terminal (16') in an activated state.

9. The electrosurgical generator according to claim 8, characterized in that The crossover current detector (80) is cooperatively connected to a crossover current regulator (8), which is configured to adjust the electrical characteristics of the second high-frequency generating unit (4'), in particular the voltage, current and / or frequency, so as to control the crossover current.

10. An electrosurgical generator according to any one of the preceding claims, characterized in that The outputs of the first high frequency generating unit (4) and the second high frequency generating unit (4') are independently controlled by corresponding first generating controllers (41) and second generating controllers (41'), preferably using the first working current and the second working current as input variables, wherein: It is further preferred that a decoupling controller (9) is provided, which is configured to independently control the first high-frequency generating unit (4) and the second high-frequency generating unit (4'), and the decoupling controller (9) interacts with the observer unit (6).

11. The electrosurgical generator according to claim 10, characterized in that The first generation controller (41) and the second generation controller (41') can apply various control laws, preferably current control, voltage control and / or power control.

12. The electrosurgical generator according to claim 11, characterized in that The various control laws are selectively applied, in particular depending on the load and / or power of the first electrosurgical instrument (19) and the second electrosurgical instrument (19').

13. An electrosurgical generator according to any one of the preceding claims, characterized in that The first frequency, the second frequency, and the frequency difference between the first frequency and the second frequency are selected such that their respective values ​​are composite numbers, ie, non-prime numbers.

14. An electrosurgical generator according to any one of the preceding claims, characterized in that The first high-frequency generating unit (4) and the second high-frequency generating unit (4') are formed into a combined unit (4*), and the combined unit (4*) can output the first high-frequency alternating voltage and the second high-frequency alternating voltage at the first output end (16) and the second output end (16'), respectively.

15. An electrosurgical generator according to claim 14, wherein: The combined unit (4*) is a multi-level inverter having a plurality of inverter units (4-1, 4-2, 4-3, 4-4), wherein a first portion (4-1, 4-2) of the plurality of inverter units is configured to generate the first high-frequency AC power source, and a second portion (4-3, 4-4) of the plurality of inverter units is configured to generate the second high-frequency AC power source.

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