Generator with characteristic curve switching

Abstract

We provide a generator for powering the load resistance of various devices, which provides a desired output characteristic curve without the need for a control loop. [Solution] The generator 11 can use different branching points of a reactive network that themselves (i.e., essentially) have a desired characteristic curve. This objective is achieved by providing a variety of selectable, discrete complex internal resistances 18 at the output branching points of the generator 11, which provide different relationships between output power and load resistance 10.

Description

[Technical Field]

[0001] The present invention relates to a generator for supplying electric current to electrosurgical instruments to induce tissue changes, particularly deactivating tissue changes. The present invention also relates to a system comprising the generator and a plurality of instruments connectable to the generator, which perform different tasks and for this purpose require different current / time curves, voltage / time curves, current / voltage characteristic curves, or different relationships between tissue resistance and the power introduced into the tissue in a portion of the generator (tissue resistance / power characteristic curves). [Background technology]

[0002] Electrosurgical instruments such as electrosurgical units and cauterizing forceps are known. Various generator concepts for powering such instruments are also known.

[0003] U.S. Patent Application Publication No. 2022 / 0313345 discloses a generator having a resonant circuit excited by two transistor amplifiers operating in push-pull mode in a cascode circuit. The generator can be fully or partially housed within an appliance. To supply power to the electrodes of the appliance, the resonant circuit is provided with a decoupling coil which may have two or three connections, depending on the number of electrodes.

[0004] European Patent Application Publication No. 2499982 discloses a generator equipped with a sensor circuit that includes several sensors for detecting tissue and energy characteristics such as tissue impedance, tissue temperature, current, and / or voltage output. This sensor circuit provides a feedback signal to a generator controller. This feedback forms a control loop that adjusts the current output of the generator to power the equipment as needed.

[0005] A similar generator is known from European Patent Application Publication No. 1862137. This generator also uses a sensor circuit that detects the voltage and current at the generator output and controls the generator accordingly. This also applies to the generator described in European Patent Application Publication No. 1051948.

[0006] European Patent No. 2520241 also provides a control loop for controlling the operation of a generator, where the control loop functions to establish a desired relationship between the current flowing through the system and the applied voltage, and these characteristic curves can be defined as linear or nonlinear.

[0007] European Patent No. 2405842 also discloses a generator having an output transformer, with a series resonant circuit connected downstream to suit the connected load. In one of the illustrated embodiments, the resonant circuit can be connected via a switch to various taps of the generator's output transformer.

[0008] This type of generator often needs to be able to supply surgical current to different types of instruments. For example, cauterizing instruments require fundamentally different voltage and current values ​​and time curves than, for example, electrosurgical units, and electrosurgical units require different voltage and current curves than, for example, ablation instruments or plasma probes. For this reason, such generators typically have a mode selector switch for selecting different modes (coagulation, cutting, cauterization, etc.), which gives the generator controller different values ​​and time curves for current, voltage, or other electrical parameters (frequency, modulation, crest factor, power, or limit value for one or more of these parameters).

[0009] Control loops are used to achieve the desired output behavior of a generator, but these are subject to design constraints. For example, control oscillations can occur during rapid load changes, leading to significant temporary deviations between the desired current and the actual current flowing. However, if the voltage or current deviates significantly from the setpoint, even for a short time as part of a control oscillation, undesirable therapeutic effects may occur. For example, adhesion effects can occur during coagulation. If the electrode adheres to the tissue, tearing can lead to undesirable lesions that may impair the surgical outcome. During cutting, excessive or insufficient coagulation of the cutting edge can also cause bleeding or adhesion effects, which is undesirable. [Prior art documents] [Patent Documents]

[0010] [Patent Document 1] U.S. Patent Application Publication No. 2022 / 0313345 [Patent Document 2] European Patent Application Publication No. 2499982 [Patent Document 3] European Patent Application Publication No. 1862137 [Patent Document 4] European Patent Application Publication No. 1051948 [Patent Document 5] European Patent No. 2520241 [Patent Document 6] European Patent No. 2405842 [Overview of the Initiative] [Problems that the invention aims to solve]

[0011] Based on this, the objective of the present invention is to specify an improved generator. [Means for solving the problem]

[0012] This objective is achieved by the generator described in claim 1.

[0013] On the output side, the generator according to the present invention has a reactive network comprising a plurality of inductors and a plurality of capacitors that can or are connected to the generator output in any selected pairing. Each pairing forms an output branch, formed by a series connection of at least one of the plurality of inductors and a capacitor selected from a group of the plurality of capacitors. Depending on which output branch of the output network is used, the output network of the generator determines a different internal resistance of the generator, which results in a different output characteristic curve. This determination is preferably made without feeding back current and voltage measurements to a controlled switch for energizing a clock generator or resonant circuit. The relationship between the tissue resistance required for the operation of a particular instrument and the power applied to the tissue is then caused solely by the tissue resistance, which changes over time during the course of treatment. In other words, the internal impedance, i.e., the complex internal resistance of the generator, and therefore the output characteristic curve, is determined according to the mode so that the desired surgical effect is achieved on the connected instrument without control intervention. Changing the tissue resistance results in a shift in the operating point on the output characteristic curve of the generator, and therefore the desired adjustment of current and voltage. Various output branching sections can provide different outputs for the generator, or can be connected to the generator's two-pole or multi-pole outputs via optionally provided switch units.

[0014] Different output branching points enable quick and easy selection of different modes (cutting, coagulation, etc.), and load changes or load currents during use do not result in controlled oscillations and, in some cases, undesirable surgical effects. The therapeutic current output by the generator is due to the direct interaction between the generator's internal resistance and tissue resistance. For example, in one generator setting, coagulation and cutting instruments, such as those used for vascular sealing and vascular separation, can be supplied with current and voltage via the generator according to the present invention without requiring any control intervention to determine the voltage or current. Changes in the resistance of the treated tissue result in changes in the voltage applied to the electrodes during the course of treatment, where the voltage changes correspond to the course of treatment by corresponding characteristic curves corresponding to the surgical process. In another generator setting, another instrument, such as an electrosurgical unit, can also be powered without control intervention.

[0015] Hereinafter, the primary inductor will be referred to as the primary inductor. Hereinafter, the primary capacitor will be referred to as the primary capacitor. The primary inductor and primary capacitor constitute a parallel resonant circuit. This parallel resonant circuit is connected to one or more electronic switches used to excite and oscillate the parallel resonant circuit. The (at least one) electronic switch is alternately opened and closed by a clock generator, where the switching signal output by the clock generator for this purpose can have a predetermined frequency. Alternatively, the resonant circuit can be part of a free-running oscillator circuit. The frequency is time-invariant and therefore can be a fixed frequency. However, it is possible to design the clock generator so that the clock signal is modulated, for example, pulse-width modulation or frequency modulation. The clock generator can also be amplitude-modulated at different frequencies, for example, with on / off sampling, where this modulation frequency can also be pulse-width modulated. The modulation of the clock generator can be set according to a selected operating mode. Here again, various modes of modulation can be fixed.

[0016] Hereinafter, the secondary inductor of the generator is referred to as the secondary inductor. The secondary inductor is closely coupled to the primary inductor. The coupling coefficient is preferably greater than 0.9, preferably greater than 0.95, and most preferably 0.97 or more. The number of turns of the inductor winding is based on the desired open circuit voltage when the generator is idling. The number of turns of the secondary inductor winding is preferably less than the number of turns of the primary inductor winding. At least preferably, the total number of turns of all secondary inductor windings is also at most the same as the number of turns of the primary inductor winding.

[0017] The secondary capacitor is hereinafter referred to as the secondary capacitor. One or more secondary inductors are connected to the output pole of the generator via a circuit branch. The circuit branch can include a secondary capacitor and a switching path of a selector switch (i.e., a switch unit) connected in series with the secondary capacitor. These series circuits can have the same or different resonance frequencies. Due to the strong coupling between the primary inductor and the secondary inductor, the secondary capacitor is converted into the primary circuit, thus reducing its resonance frequency. Preferably, the switching frequency of at least one switch used to excite the primary resonance circuit is higher than the resonance frequency of the resonance unit formed by the primary resonance circuit and the secondary capacitor. This applies to at least one or more modes, preferably all of them.

[0018] In the generator according to the present invention, the resonance frequency of the oscillation unit mentioned above can vary according to the impedance of the energized tissue. This effect can be used to establish the desired relationship between tissue resistance and the power introduced into the tissue.

[0019] By activating one of the series circuits mentioned (i.e., switching each switching path to on) and switching the other series circuit to off (turning each switching path off), the output characteristics of the generator are greatly affected. It is possible to provide various series circuit characteristic curves for enabling different treatment modes. For example, the generator can be used for coagulation instruments, dissection instruments, and other instruments without the need to generate the required output characteristics via a control loop. Instead, each output characteristic curve is provided only by a reactive network consisting of a primary resonance circuit and a series circuit activated respectively on the output side.

[0020] The selector switch can also be connected to the clock generator. Alternatively, a signal for controlling the mode selector switch can be sent to the clock generator. In either case, the clock generator can be configured to supply a clock signal that conforms to the requirements of the selected mode.

[0021] Further details of advantageous embodiments of the present invention are the subject of the drawings, the related description, or the claims.

Brief Description of the Drawings

[0022] [Figure 1] It is a schematic diagram of the symbolic representation of a generator according to the present invention having connected instruments. [Figure 2] It is a further symbolic representation diagram of the generator according to FIG. 1. [Figure 3] It is a schematic circuit diagram of the generator according to FIGS. 1 and 2, connected to the first instrument. [Figure 3a] It is a schematic circuit diagram within the push-pull circuit of the generator shown in FIGS. 1 and 2, connected to the instrument. [Figure 3b] It is a diagram showing an embodiment of free rotation of the embodiment of the generator shown in FIG. 3a. [Figure 4] It is a diagram of the generator of FIG. 3, connected to another instrument. [Figure 4a] It is a modified generator for connecting the instrument shown in FIG. 4. [Figure 4b] This diagram shows the equipment shown in Figure 4, connected to two generators as shown in Figure 3, Figure 3a, or Figure 3b. [Figure 4c] The device shown in Figure 4 is connected to a generator having two different output circuits for two different electrode pairs of the device shown in Figure 4. [Figure 5] Figures 3 and 4 show various output characteristic curves of the generator under the settings shown. [Figure 6] Figures 3 and 4 are equivalent circuit diagrams illustrating the function of the generator. [Figure 7] This diagram shows the resonant frequencies of generator resonant circuits under different settings. [Figure 8] This diagram shows the switching signal sequence of the generator's clock generator. [Modes for carrying out the invention]

[0023] Figure 1 shows the load resistance 10 formed by the patient and the equipment, and the generator 11 that supplies power to the load resistance 10, indicated by symbols. The load resistance 10 has a load impedance Z that depends on the type of tissue and the type of treatment, as well as the progress of the treatment, i.e., the elapsed time and the intensity of the current supply. L The type of treatment involves the shape and size of the electrode, the strength of the contact between the electrode and the tissue, and the state of the tissue (wet, dry, coagulated, etc.), to the extent that the load impedance Z plays a role. L This affects the load impedance Z. L This is shown as a variable complex resistor in Figure 1.

[0024] The load resistor 10 is connected to the two poles 14 and 15 of the generator output 16 via two lines 12 and 13. The generator 11 includes a high-frequency voltage source 17, and its complex internal resistance 18 is shown as a separate circuit symbol in Figure 1. The complex internal resistance 18 has an impedance Z which can have a linear or nonlinear current / voltage characteristic curve. i It has.

[0025] The internal resistance 18 can be steppedly varied so that it can take discrete different impedances Z1, Z2, and Z3, as shown in Figure 2. The impedances Z1, Z2, and Z3 of the internal resistance 18 can be formed by different branching points of the reactive network 19 shown in Figure 3. A selector switch 20 having different switching paths 21, 22, and 23 is used to activate or deactivate the different branching points. The selector switch 20 can be a manual switch or a switch controlled by a control signal S. A control module CC can be used to generate the control signal.

[0026] The number of switching paths 21 to 23 depends on the number of different impedances Z1 to Z3 of the internal resistance 18 to be realized, and therefore the number of output characteristic curves of the generator 11 to be realized and the corresponding modes. The selector switch 20 is designed so that only one of its switching paths 21 to 23 can be conductive (permeable), and all other switching paths are impermeable (blocked). The switch can be a non-contact electronic switch, a mechanical switch with switching contacts, or a socket configuration that provides a selection of several poles for one of lines 12, 13. The selector switch 20 can be controlled using a control signal S, and the selector switch is provided by a manually operated switch or even a generator controller (not shown).

[0027] As shown in Figure 3, for example, the generator 11 includes a primary side resonant circuit 24 comprising a primary capacitor 25 and a primary inductor 26 electrically connected in parallel with each other. The resonant circuit 24 is tuned to a resonant frequency of several hundred kHz, for example, 480 kHz. For this purpose, the primary capacitor 25 can have a value of 2.2 nF and the primary inductor 26 can have a value of 50 μH. However, other values ​​for the resonant frequency, primary capacitor 25, and primary inductor 26 are also possible.

[0028] The primary inductor 26 is preferably formed by the primary winding of the high-frequency transformer 27. The high-frequency transformer 27 has a plurality of secondary windings that form secondary inductors 28, 29, 30 and inductively couple to the primary inductor 26. The secondary inductors 28, 29, 30 may have the same or different number of windings, and therefore the same or different inductance values. These inductors may be wound as individual coils, or they may be formed by a single coil having several taps, and therefore dividing the coil into individual secondary inductors 28, 29, 30. The number of secondary inductors 28, 29, 30 corresponds to the number of switching paths 21 to 23 and may vary depending on the number of desired output characteristic curves of the generator 11 to be realized. Each of the secondary inductors 28, 29, 30 preferably has fewer windings than the number of windings of the primary inductor 26. More preferably, the total number of windings of the secondary inductors 28, 29, 30 is not significantly more, and preferably at most the same as the number of windings of the primary inductor 26.

[0029] The first inductor 28 is connected to pole 14 of the generator output 16. A coupling capacitor 31 may be placed between the secondary inductor 28 and the generator output 16. This is optional in all embodiments of the generator 11 described herein and below. The other end of the secondary inductor 28 is connected to the other pole 15 of the generator output 16 via a switching path 21 of a secondary capacitor 32 and a selector switch 20. The secondary inductor 28, together with the secondary capacitor 32, forms a first output branch 28 / 32. The secondary inductor 28 and the secondary capacitor 21 form a first inductive power supply series circuit for selectively supplying power to the output 16. The order of the secondary capacitor 32 and the switching path 21 can be as shown in Figure 3, or vice versa.

[0030] The winding ends of secondary inductors 28, 29, and 30 are each marked with dots in Figure 3. This is important in the following description of the interconnection of secondary inductors 28 to 30.

[0031] The starting point of the secondary inductor 29 is connected to the winding end of the secondary inductor 28. Similarly, the starting point of the secondary inductor 30 is connected to the winding end of the secondary inductor 29. A circuit branch extends from the winding end of the secondary inductor 29, where a further secondary capacitor 33 is located, forming a series connection with the secondary inductors 29 and 28. This series circuit forms a second output branch 29 / 33. This series circuit can be connected to pole 15 of the generator output 16 via a switching path 22. The order of the secondary capacitor 33 and the switching path 22 can be as shown in Figure 3, or vice versa.

[0032] The winding end of the secondary inductor 30 forms a series connection with a third secondary capacitor 34, which can be optionally connected to pole 15 of the generator output 16 via the switching path 23 of the selector switch 20. This series connection forms a second output branch section 30 / 34. The order of the secondary capacitor 34 and the switching path 23 can be as shown in Figure 3, or vice versa. Further secondary inductors, secondary capacitors, and switching paths can be provided in the same manner.

[0033] The secondary inductors 28, 29, and 30 have the same or different values ​​and can be inductively coupled to the primary inductor 26. The coupling coefficient is preferably greater than 0.95, and more preferably greater than 0.97. The secondary capacitors 32, 33, and 34 have decreasing and shifted values. Secondary capacitor 32 is greater than secondary capacitor 33, and secondary capacitor 33 is further greater than secondary capacitor 34. The coupling capacitor 31, if present, is preferably greater than all the secondary capacitors. In particular, it can be greater than the sum of the capacitances of all secondary capacitors 32 to 34. This is also true when there are not only three different circuit branch sections with three switching paths 21 to 23, contrary to what is shown in the figures, but also when there are several secondary inductors and several secondary capacitors. The number of windings of the secondary inductors 28, 29, and 30 is matched with the number of windings of the primary inductor 26 such that the voltage of the secondary inductors 28-30 is at most the same height as the voltage of the primary (parallel) resonant circuit 24. Therefore, inductors 26, 28, 29, and 30 transform the resonant circuit voltage by coefficients of ratios such as 1.5:1, 2:1, 3:1 or other ratios, or form transformers that decouple at a maximum of 1:1. Conversely, this increases the tissue impedance (if the maximum transmission rate of at least 1:1 is not used), which is converted into the resonant circuit 24, thus reducing the attenuation of the resonant circuit 24 due to the tissue impedance.

[0034] A surgical instrument 35 having an electrode 36 is connected to a generator output 16 and is designed as a unipolar instrument, used, for example, to act on biological tissue 37 to make an incision. The biological tissue 37 (e.g., the morphology of a living patient) is connected to the generator output 16 via a neutral electrode 38. The instrument 35, having the electrode 36 and an optional spark gap 39, together with the contact resistance to the biological tissue 37 and the neutral electrode 38, forms a load resistance 10. Generally, the instrument 35 can be a tool portion that can be connected to an open surgery instrument, a laparoscopy instrument, an endoscopic instrument, or an arm of a surgical robot.

[0035] An electronic circuit having at least one electronic switch 39 is used to excite the reactive network 19, in particular to excite the resonant circuit 24. This electronic circuit has a control path 40 and a control input 41 connected to a clock generator 42 to receive a control signal 43 from the clock generator. The clock generator 42 is preferably configured to emit a switching signal 43 as a square wave signal having a fixed frequency. This frequency is preferably above 200 kHz and can be, for example, 350 kHz or even 480 kHz. Preferably, the clock frequency is less than 5 MHz, more preferably less than 1 MHz.

[0036] In the simplest embodiment, the switching signal 43 generated by the clock generator 42 is constant for all selected operating modes, i.e., regardless of the switching position of the selector switch 20. However, preferably, a connection is provided not only between the control module CC and the selector switch 20, but also between the control module CC and the clock generator. This enables the clock generator 42 to output an appropriate clock signal 43 for each selected operating mode (each mode). The clock signals 43 for the various modes may have different modulations. Preferably, these clock signals are square waves with a fixed frequency between 100 kHz and 5 MHz, for example, fixed 350 kHz or fixed 480 kHz. However, the frequency may also be fixed for some modes. However, preferably, the frequency is fixed within at least one mode.

[0037] The clock signal 43 in different modes can be, for example, unmodulated ("CW" square wave continuous wave) with different pulse / pause ratios t1 / t0. See Figure 8. The clock signal 43 can be defined according to pattern A or B. The clock signal 43 can also be pulsed in groups with different group pulse / pause ratios T1 / T0. See the clock signal 43 in Figure 8 according to patterns C, D, or F.

[0038] Therefore, the control signal 43 can be an uninterrupted pulse sequence (A, B) or a pulsed pulse sequence (C, D, F). In this case, the clock signal 43 is on / off sampled, i.e., multiplied by a square wave signal having a frequency lower than the frequency of the control signal 43. This modulation frequency can be pulse-width modulated to accommodate different instrument requirements. In addition, the control signal 43 can also be pulse-width modulated to meet, for example, power limits or power specifications.

[0039] Figure 3a shows a modified embodiment of the generator 11 to which the device 35 is connected. The generator 11 is designed as a symmetrical push-pull oscillator having switches 39a, 39b that are opened and closed by a clock generator 42 in push-pull mode. The clock generator 42 can be designed to provide a fixed clock. Alternatively, the clock generator 42 can generate control signals 43a, 43b using the resonance of a parallel resonant circuit 24. Such a clock generator and free-oscillating oscillator are shown in Figure 3b.

[0040] The oscillator 11 shown in Figure 3b has two transistors, preferably field-effect transistors or bipolar transistors, as switches 39a and 39b, which are coupled to each other in an astable multivibrator manner. The base or gate of each transistor is connected to the collector or drain of the other transistor via a capacitor. Further transistors are connected to these bipolar or field-effect transistors Ta, Tb in their base or gate circuits, and their collectors or drains are connected to the resonant circuit 24. The transistors 39a, Ta, 39b, and Tb each constitute a cascode circuit. A cascode circuit is an arrangement of two transistors in a signal path, of which the first transistor operates in the emitter or source circuit and the subsequent transistor in the signal path operates in the base or gate circuit.

[0041] As shown in Figure 3b, the base or gate of transistors Ta, Tb is connected to a bias voltage UV, which can be derived from the operating voltage UB via, for example, a resistor RV and a Z diode DZ. When the bias voltage UV is constant, transistors Ta, Tb operate with constant amplification, and the generator 11 oscillates continuously. However, it is also possible to modulate the high-frequency oscillations generated by the generator in the resonant circuit 24. For this purpose, an electronic switch SW can be provided in the circuit branch connected in parallel with the Z diode DZ and controlled by a control signal S, for example, a clock on / off. This clocking can be performed at frequencies from a few kilohertz to several tens of kHz. The control signal S can also be used to pulse-width modulate the high-frequency output voltage of the generator 11.

[0042] The generator 11 shown in Figure 3 is shown in Figure 4, where another instrument 44 is connected to this generator 11, which is designed, for example, as a fusion and cutting instrument. Such instruments are commonly used as bipolar instruments for sealing and separating blood vessels, such as blood vessels. Instrument 44 can be an instrument for open surgery, an instrument for laparoscopy, an instrument for endoscopy, or a tool part that can be connected to the arm of a surgical robot.

[0043] The instrument 44 includes two bifurcations 45, 46 that can grasp biological tissue 47 in the form of, for example, blood vessels or other tubes. Each bifurcation 45, 46 has two laterally spaced partial electrodes 45a, 45b, 46a, 46b, which function as coagulation and fusion electrodes and are connected to lines 12, 13 for this purpose. Between the partial electrodes 45a, 45b, a cutting electrode 48 can be placed which can be electrically connected to the bifurcation 45. Alternatively, the instrument 44 may include a voltage conversion device, such as a transformer, which is powered via lines 12, 13 and supplies current to the cutting electrode 48.

[0044] Between the partial electrodes 46a and 46b, a preferably elastically formed contact portion 49 can be positioned to press the tissue 47 against the cutting electrode 48.

[0045] The device 44 shown in Figure 4 can also be connected to the generator 11 shown in Figure 3a or Figure 3b and powered by that generator.

[0046] The generator 11 described in this regard operates in conjunction with various devices 35 and 44 as follows.

[0047] When device 35 is operating, control module CC sends a switching signal S to selector switch 20, resulting in switching path 23 being enabled and switching paths 21 and 22 being disabled. Thus, secondary inductors 28, 29, and 30 are connected in series with secondary capacitor 34 from the perspective of output 16. Coupling capacitor 31 completes the circuit. On the primary side, electronic switch 39 is alternately opened and closed at a predetermined clock frequency f. Clock generator 42 outputs a switching signal 43 appropriate for the selected mode. This switching signal is, for example, the switching signal of pattern A in Figure 8.

[0048] The frequency f of the switching signal 43 is preferably close to the resonant frequency of the resonant circuit 24. Secondary inductors 28, 29, 30 and secondary capacitor 34 and load impedance Z* L This is converted to the primary side using the transformation ratio of transformer 27.

[0049] The equivalent circuit diagram is shown in Figure 6. The overall result is a reactive conversion network 19*, and its characteristic curve I is shown in Figure 5. The horizontal axis represents the load impedance Z*. L The value R is shown, and the vertical axis P shows the power converted by tissue resistance (apparent power). When the tissue is still wet, the tissue resistance is low. Therefore, the power converted by the tissue is still low, but it increases sharply as the tissue dries, reaching a maximum value at moderate tissue resistance. This means that a spark of 36 can be maintained at the electrode, resulting in tissue cutting.

[0050] On the other hand, when connecting a bipolar coagulation and cutting instrument to the generator output 16, the corresponding mode must be selected. For this purpose, the control module CC outputs a control signal S, which causes the selector switch 20 to block switching path 23 and instead open switching path 21 or switching path 22 as shown in Figure 4. At this time, the lower inductance of the two secondary inductors 28 and 29, combined with the higher capacitance of the secondary capacitor 33, results in a modified output characteristic curve II, as shown in Figure 5. In addition, the signal S transmitted simultaneously to the clock generator 42 can cause the clock generator to emit different control signals 43, for example, a control signal according to pattern C in Figure 8.

[0051] The maximum power introduced into the tissue here has already reached a lower tissue resistance, thereby causing tissue coagulation between the partial electrodes 45a, 46a or 45b, 46b. In this state, the small-area cutting electrode 48 transmits only a small amount of current. As the tissue dries, the power introduced into the tissue decreases. On the other hand, because there is a current concentration in the cutting electrode 48, cutting can be performed despite the low power.

[0052] As shown in the schematic diagram in Figure 7, activating the various switching paths 21, 22, and 23 can result in a shift in the resonant frequency f of the reactive network 19 or the converted reactive network 19*. The three resonant frequencies f21, f22, and f23 assigned to the switching paths 21, 22, and 23 can all be below the frequency f43 of the switching signal 43. However, in principle, it is also possible to set one or more of the frequencies F21, F22, and F23 above the switching signal 43.

[0053] In all embodiments described above, it was assumed that the switch 40 was opened and closed at a fixed predetermined frequency in order to excite the resonant circuit 24 and cause it to oscillate. However, in all embodiments, it is also possible to cause the resonant circuit to oscillate at its natural resonance by deriving the control signal 43 of the switch 40 from the oscillation frequency of the resonant circuit 24. The resonant circuit 24 is the frequency determining element of the oscillator circuit thus formed. This is particularly applicable to the generator 11 shown in Figure 3b. In the first modification, in the generator according to Figure 3a, the control signal S can be used to specify the switching frequencies of switches 39a and 39b, and therefore the oscillation frequency of the resonant circuit 24. In the second modification, the oscillator 11 in Figure 3a can operate according to the principle of Figure 3b and therefore can be free-running (self-controlled).

[0054] Figure 4a shows the operation of an instrument 44 on a generator 11 with separate supplies for electrodes 45, 46, and 48. The selector switch 20 can have two, three, or several switching paths 21, 22, 23, etc., as shown. The electrode pair 46 / 45 can then be connected to one of the multiple available switching paths. Similarly, the electrode pair 46 / 48 can then be connected to one of the single available switching path or one of the multiple available switching paths. This makes it possible to open and close the switching paths for supplying electrodes 56, 45, and 48 simultaneously or sequentially, with or without temporal overlap. Thus, the electrode pairs 46 / 45 and 46 / 48 can operate sequentially or simultaneously as needed, where the electrode pairs 46 / 45 and 46 / 48 are connected to different reactive networks. Consequently, the generator 11 has different characteristic curves for the electrode pairs 46 / 45 and 46 / 48.

[0055] The oscillator circuit connected to the resonant circuit 24 can be designed within the generator according to Figure 4a, according to the model in Figure 3, and according to Figure 3a or Figure 3b.

[0056] Figure 4b shows a further modification of the generator 11. In this example, electrode pairs 46 / 45 of the apparatus 44 are connected to the first generator 11a, and electrode pairs 46 / 48 are connected to the second generator 11b. Wires 12a, 13a; 12b, 13b can be used for this purpose. Generators 11a and 11b may be designed as shown in Figure 3, Figure 3a, or Figure 3b, respectively. The generators may also be connected to a common control module CC that controls generators 11a and 11b according to one of the principles described in relation to the generators in Figure 3, Figure 3a, Figure 3b, Figure 4, or Figure 4a.

[0057] Figure 4c shows a further modification of the generator 11 according to the present invention. Therefore, the above description of the generator shown in Figure 4b applies to this generator. In addition, generators 11a and 11b are combined to form a common generator circuit. With respect to the primary side transformer 27, the generator 11 follows the model of the generator 11 shown in Figures 3, 3a, 3b, 4, or 4a. With respect to the secondary side transformer 27, the generator follows the model of the generator shown in Figure 4a or 4b. A special feature of the generator 11 shown in Figure 4c is the complete absence of a switch unit 20. It is also possible to provide a switch unit having switching paths 21, 22 (not shown), where these switching paths are permanently closed simultaneously (i.e., conductive) while at least electrode pairs 46 / 45 and 46 / 48 are energized.

[0058] In all embodiments, the generator can be located entirely or partially within fixtures 35, 44. In particular, the clock generator 42, the resonant circuit 24, the transformer 27, and the coupling capacitors 31 and 32, 33, 34, as well as the selector switch 20, can be part of fixtures 35, 44. A power supply device for providing the operating voltage UB can be located in an external device, further not shown, connected to the generator via wires. The control module CC can be part of a separate device. Alternatively, the control module can be incorporated into the generator 11 and located together with the generator within fixtures 35, 44. Alternatively, any type of generator 11 described herein can be located entirely within a separate device. Furthermore, in all embodiments of the generator 11, it is applicable that instead of the switch unit 20, different sockets connected to individual output branching sections 28 / 32, 29 / 33, 30 / 34 for connecting different fixtures may be provided.

[0059] The concept according to the present invention proposes a generator 11 for powering various devices 35, 44, which provides a desired output characteristic curve without the help of a control loop. For this purpose, the generator 11 uses a reactive network 19 which itself (i.e., essentially) has a desired characteristic curve. This objective is achieved by providing a complex resistor within the output branch of the generator 11, which can be turned on as needed and provides different relationships between power output and load resistance. [Explanation of symbols]

[0060] 10 Load Resistance 11 Generators Z L Load impedance R Load impedance Z L quantity Lines 12 and 13 14,15 poles 16 Generator output 17. High-frequency voltage source 18. Complex internal resistance Zi Impedance of internal resistance 18 Z1, Z2, Z3 Impedance of internal resistance 18 19 Reactive network 19* Converted reactive network 20 Selector switch 21 - 23 Switching paths of selector switch S Control signal 24 Resonance circuit 25 Primary capacitor 26 Primary inductor 27 High - frequency transformer 28, 30 Secondary inductors 31 Coupling capacitor 32, 34 Secondary capacitors 35 Appliance 36 Electrode 37 Biological tissue 38 Neutral electrode 39 Switch 40 Control section 41 Control input 42 Clock generator 43 Control signal 44 Appliance 45, 46 Branch 45a, 45b Partial electrodes of branch 45 46a, 46b Partial electrodes of branch 46 47 Tissue 48 Cutting electrode 49 Contact part Z* L Converted load impedance L* S Converted secondary inductance C* S Converted secondary capacitance

Claims

1. A generator (11) for supplying an electric current to electrosurgical instruments (35, 44) that causes tissue changes, particularly inactivating tissue changes, A resonant circuit (24) having a resonant frequency (fR) and comprising a primary inductor (26) and a primary capacitor (25) connected in parallel to the primary inductor (26), An electronic switch (39) having a control path (40) connected to the resonant circuit (24) and a control input (41) that can alternately switch the control path (40) between a conductive state and a non-conductive state, A clock generator (42) configured to generate a switching signal (43) and connected to the control input (41) to switch the control path (40) on and off, The first and second secondary inductors (28, 29) are inductively coupled to the primary inductor (26), A first secondary capacitor (32) connected in series with the first secondary inductor (28), and a second secondary capacitor (33) connected in series with the second secondary inductor (29), A generator comprising: a selector switch (20) having two switching paths (21, 22), wherein one of the switching paths (21, 22) is connected in series with the first secondary inductor (28) and the first secondary capacitor (32), and the other of the switching paths (21, 22) is connected in series with the second secondary inductor (29) and the second secondary capacitor (33).

2. The series connection of the first secondary inductor (28) and the first secondary capacitor (32) is connected to the electrode (38 or 36) of the patient-side electrode pair (36 / 38, 46 / 45, 46 / 48) via the switching path (21) of the selector switch (20). The generator according to claim 1, characterized in that the first secondary inductor (28) is connected to the electrode (36 or 38) of the patient-side electrode pair (36 / 38, 46 / 45, 46 / 48) at the end opposite to the secondary capacitor (32).

3. The generator (11) has further secondary inductors (29, 30) inductively coupled to the primary inductor (28), and the secondary inductors (29, 30) are each connected in series with further secondary capacitors (34, 35). The generator according to claim 1, characterized in that a selector switch (20) may be provided which, at any given time, is configured to connect only one series connection (28, 33) consisting of a secondary inductor (28) and a secondary capacitor (33) to the electrodes of a patient-side electrode pair (36 / 38, 46 / 45, 46 / 48).

4. The generator according to claim 1, characterized in that the clock generator (42) is configured to generate the control signal (41) at a predetermined frequency.

5. The generator according to claim 1, characterized in that the clock generator (42) is configured to generate the control signal (41) according to the resonant frequency of the resonant circuit (24).

6. The generator according to claim 1, characterized in that the generator (11) has different internal resistances (Z1, Z2, Z3) for different settings of the selector switch (20).

7. The generator according to claim 1, characterized in that the secondary capacitors (32, 33, 34) and secondary inductors (28, 29, 30) are sized such that the resonant frequency of the parallel resonant circuit is greater than 200 kHz.

8. The generator according to claim 1, characterized in that the clock generator (42) is configured to output the switching signal (43) at a switching frequency (f) that is greater than the resonant frequency (fR) of the resonant circuit (24).

9. The generator according to claim 1, characterized in that all secondary inductors (28, 29, 30) are connected in series with each other.

10. The generator according to claim 1, characterized in that the secondary capacitors (32, 33, 34) have different capacitance values.

11. The generator according to claim 1, characterized in that the capacitance value of the secondary capacitors (32, 33, 34) decreases as more secondary inductors (28, 29, 30) are connected in series with the secondary capacitors (32, 33, 34).

12. The generator according to claim 1, characterized in that the generator (11) is a push-pull oscillator.

13. The generator according to claim 1, characterized in that the device (11) is configured to be coupled with an operating robot.

14. A system comprising a generator (11) according to any one of claims 1 to 13, and a device (35, 44) having at least one pair of electrodes (36, 38) supplied by the generator (11).

15. The system according to claim 14, characterized in that the generator (11) is at least partially incorporated into the devices (35, 44).

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