system

Abstract

To provide a generator with improved control of the output voltage.SOLUTION: A push-pull generator 12 provided for supplying to a medical instrument 10 includes at least one capacitive branch connected to ground, preferably in a switchable configuration, in parallel to at least one of its two transistors. Such a capacitive switchable branch consists of a series connection of one capacitor and one switch. Thereby one of the two half waves of the output voltage of generator can be specifically influenced and the other one of the two half waves can be left largely uninfluenced. If switchable branches comprising capacitors are connected in parallel to the transistors, both half waves of the output voltage of the generator can be influenced independently from one another. This arrangement allows for the specific influence of half oscillations of the push-pull generator that is symmetric except the part, thereby the application spectrum for supplying medical instruments with treatment current is enlarged.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a generator for supplying an electrosurgical instrument, particularly a generator in which the control of the output voltage provided by the generator is improved.

Background Art

[0002] Many electrosurgical instruments, such as an electric scalpel, an electrosurgical forceps or a coagulation device, are usually supplied with high-frequency alternating current. To avoid nerve muscle stimulation, the frequency of this alternating voltage usually exceeds 100 kHz. The power of such a generator usually considerably exceeds 1 W and can reach several hundred watts.

[0003] A generator for generating such a voltage is apparent from Patent Document 1. This generator includes at least one oscillation circuit, which is excited to oscillate by an active transistor circuit, and from this oscillation circuit, energy is decoupled in a converter type manner for supply to a connected instrument.

[0004] A generator for simultaneous supply to a plurality of instruments is apparent from, for example, Patent Document 2. This generator includes a plurality of oscillation circuits connected to a full-bridge circuit.

[0005] Patent Document 3 discloses a push-pull oscillator having two transistors operating in a push-pull manner, and a parallel oscillation circuit is arranged between their collectors. By coupling the oscillation circuit coil to the coil in a transformer type manner, the voltage and current of the surgical instrument are decoupled.

[0006] It has been found that the waveform of the current supplied from the generator to the instrument significantly affects the physiological effect achieved. For this reason, it is desired to be able to affect the waveforms of the output voltage and output current of the generator for supply to the instrument.

Prior Art Documents

Patent Documents

[0007] [Patent Document 1] German Patent Application Publication No. 102008039884 [Patent Document 2] German Patent Application Publication No. 602004009293 Specification [Patent Document 3] German Patent Application Publication No. 2910196 [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] From there, the object of the present invention is to provide a generator having extended potential for influencing current and voltage modes. [Means for solving the problem]

[0009] This objective is achieved by the generator described in claim 1.

[0010] The generator according to the present invention is based on the concept of having two amplifiers with inductors of a resonant circuit positioned between their outputs. Assigned to the inductors are at least one first capacitor, which thereby forms an oscillating circuit, and a second capacitor for further influence of the resonant frequency of the oscillating circuit. Preferably, thereby at least the second capacitor is connected to ground inseparably or via a switch, preferably an electronic switch. If the amplifier is realized by an electronic amplification component such as a bipolar transistor or a field-effect transistor, one electrode of this capacitor is connected to the output electrode (collector or drain) of the respective transistor, and the other electrode of the capacitor is connected to ground. Previously, each frequency-influencing capacitor was switched in parallel with the amplification component on the output side. In particular, if the amplification component operates during switching operation, it creates a temporary short circuit of each capacitor and is therefore temporarily disabled. The capacitors affect only half of the oscillation initiated in the oscillating circuit while the amplification component connected in parallel is non-conductive (highly ohmic).

[0011] The generator is configured as a push-pull oscillator. The two amplifiers are connected to a control circuit configured to control the amplifiers in push-pull mode. Preferably, the control circuit is configured to control the amplifiers in switching operation. This means that each amplification component (transistor) is either conductive to current, i.e., low-ohmic conductivity, or blocked.

[0012] The circuit concept according to the present invention has a specific effect on the amplitude and duration of individual half-waves of such a generator. Specifically, in doing so, for example, the positive (or negative) half-waves of the generator oscillation may have their amplitudes increased or decreased, as well as their durations extended or shortened. If multiple such additional capacitors are connected to the oscillation circuit and associated amplifier output by their respective switches, the resulting generator oscillation may also produce, and could not otherwise produce, an output waveform of the voltage or current supplied by the generator. For example, the oscillation supplied to the appliance may be produced particularly asymmetrically, for example, to support or hinder spark formation at the appliance electrodes.

[0013] As described above, the two amplifiers can be realized by electronic switches, which are preferably controlled in push-pull mode by a control circuit. The inductor may have a center tap through which the operating current is supplied to the generator, and therefore to the amplifier. According to this concept, the generator is a symmetric push-pull oscillator that can be made asymmetric by connecting and disconnecting a capacitor. Asymmetric supply, especially high-frequency high-ohmic asymmetric supply, is also possible.

[0014] Details of the circuit modifications according to the present invention are the subject of the dependent claims, drawings, and their respective descriptions. [Brief explanation of the drawing]

[0015] [Figure 1]This is a schematic diagram of the generator and connected equipment. [Figure 2] This is a schematic circuit diagram of a generator for supplying power to the equipment. [Figure 3] Figure 2 is a schematic diagram of the generator's output voltage. [Figure 4] This figure shows a modified embodiment of the generator in the principle circuit diagram. [Figure 5] This is another diagram showing a modified embodiment of the generator in the principle circuit diagram. [Figure 6] This is another diagram showing a modified embodiment of the generator in the principle circuit diagram. [Figure 7] This is another diagram showing a modified embodiment of the generator in the principle circuit diagram. [Modes for carrying out the invention]

[0016] Figure 1 shows an instrument 10 for treating biological tissue 11 and a generator 12 for supplying power to the instrument 10. In this example, a unipolar instrument 10 is shown having a single electrode 13 that affects the biological tissue 11 by a spark 14. A neutral electrode 15 is provided, which is attached to a human or animal patient from whom the tissue 11 is part, to guide the current generated from the instrument 10 or electrode 13 back to the generator 12. Lines 16, 17 connect the instrument 10 and preferably a large-sized neutral electrode 15 to the generator 12. This arrangement is just one example. The generator 12 is also suitable for supplying power to bipolar instruments, for example, to coagulation tools having two or more electrodes. This is especially true because the generator 12 is particularly well-suited to supplying output voltage Ua with waveforms that can be adapted to different physiological conditions as well as surgical requirements and tasks.

[0017] Figure 2 shows the principle circuit of the generator 12. The generator includes a first amplifier V1 and a second amplifier V2 that can be realized by transistors T1 and T2. The transistors T1 and T2 are preferably field effect transistors such as enhancement type or depletion type n-MOS transistors. Other transistors, especially bipolar transistors, IGBTs (bipolar transistors with insulated gates), etc. can also be used. When the transistors T1 and T2 are field effect transistors, they each have a gate G1, G2, a source electrode S1, S2, and a drain electrode D1, D2. The two transistors T1 and T2 operate in a common source circuit such that the gates G1 and G2 become the input electrodes of the amplifiers V1 and V2. Therefore, the drain electrodes D1 and D2 become the output electrodes of the amplifiers V1 and V2.

[0018] The gates G1 and G2 are connected to a control circuit 18 configured to open and close the transistors T1 and T2 in a reverse manner, that is, to make them conductive and non-conductive, according to a clock having the frequency of the generated AC voltage. Therefore, the transistors T1 and T2 are controlled in a push-pull mode and operate in a switching operation. In all embodiments of the generator 12, the control circuit 18 can be realized by two coupling capacitors in which one gate of one transistor is connected to the drain of the other transistor, as exemplarily shown in FIG. 4. This type of coupling has the effect that one of the transistors T1 and T2 is always conductive and the other of the two transistors T1 and T2 is blocked therebetween. The blocking phase and the transmission phase change at a frequency predefined by the oscillation circuit. The two coupling capacitors are preferably dimensioned equally.

[0019] The source electrodes S1, S2 of the two amplifiers V1, V2 (transistors T1, T2) are connected to ground, either directly or at least with respect to alternating current. The output electrodes of the two amplifiers V1, V2, that is, the drains D1, D2 of the transistors T1, T2 are connected to each other by an inductor 19 which preferably has a center tap 20. Through the center tap, the inductor 19, and thus the amplifiers V1, V2, are supplied with an operating voltage Ub, and thus also with their respective operating currents. In the supply line to the center tap 20, a choke 21 and, optionally, additional filter means can be provided. The choke 21 blocks the flow of high-frequency currents to the operating voltage source and thus avoids undesirable attenuation of the oscillation of the inductor.

[0020] The generator 12 further comprises a first capacitor C1 connected in parallel with the inductor in order to form a parallel oscillating circuit with the inductor 19. Thus, the first capacitor C1 connects the output electrodes of the amplifiers V1 and V2, that is, the drains D1 and D2 to each other.

[0021] The generator 12 described so far can generally oscillate and is operable with the configuration described so far. However, the generator comprises additional means for influencing its operation. A second capacitor C2 is part of this, with one end connected to the parallel oscillating circuit formed by the inductor 16 and the capacitor C1, and the other end 23 connected to ground inseparably or via a first switch SW1 as shown in FIG.

[0022] The first switch SW1 can be configured, for example, as a field effect transistor, that is, as an electronic switch in the form of a transistior T3. This can be of the same type as the transistors T1, T2 or of a different type. Its gate electrode G3 is specifically connected to a control circuit 24 which opens and closes the switch SW1 over at least one oscillation period or over a longer time interval.

[0023] The generator 12 described above operates as follows:

[0024] Lines 16 and 17 are connected to the voltage Ua generated by the generator 12, in that lines 16 and 17 lead to a coupling coil K inductively connected to the inductor 19. The parallel oscillator circuit formed by the inductor 19 and capacitor C1 is excited to oscillate so that the two amplifiers V1 and V2 operate in push-pull mode. For this purpose, transistors T1 and T2 alternately become conductive and non-conductive. This is controlled by the control circuit 18. The frequencies and control of transistors T1 and T2 preferably correspond to the resonant frequencies of the parallel oscillator circuit (inductor 19 and capacitor C1).

[0025] First, we assume that switch SW1 is non-conductive, meaning transistor T3 is blocked. This results in the effective portion of the generator 12 circuit being symmetrically configured, and capacitor C2 being ineffective. Symmetric oscillation is produced during time period A, as shown in Figure 3.

[0026] The generated symmetric output voltage Ua is initially provided as an unmodulated output voltage. If necessary, amplitude modulation can be performed, for example, by modulating the operating voltage Ub. However, for the purposes of subsequent discussion, we assume that the operating voltage Ub is constant.

[0027] The output voltage Ua, when supplied by the instrument 10, affects the tissue 11, produces a specific physiological effect, such as a coagulation effect, during period A. Here, it is assumed that a different physiological effect is desired, and therefore the generator 12 generates an output voltage Ua having a different waveform. In particular, for example, it is assumed that there are different oscillation progressions between the positive and negative half-waves. For example, the half-waves can be distinguished by their duration and height (amplitude). For this purpose, the control circuit 24 closes the switch SW1, i.e., makes the transistor T3 conductive between its source electrode S3 and its drain electrode D3. In this way, the end 23 of the capacitor C2 is connected to ground. This electrical connection is maintained throughout the entire period B shown in Figure 3.

[0028] The second capacitor C2 is inactive during the half-wave when transistor T2 is conductive. However, during the half-wave when T1 is conductive and transistor T2 is non-conductive, capacitor C2 is active, and the connection point between the first capacitor C1 and inductor 19 is connected to ground. This makes it possible to create half-waves with altered amplitude and frequency, for example, smaller but longer half-waves. Thus, this oscillation of the generator 12 can have the form shown in Figure 3, for example, during time period B. When a positive half-wave is connected to electrode 13 via line 16, spark generation between electrode 13 and biological tissue 11 is thereby facilitated, and a different physiological effect is obtained compared to the case of period A.

[0029] Figure 4 shows a modified embodiment of the generator 12, which distinguishes it from the above-described embodiment only in that amplifiers V1 and V2 are realized by a cascode circuit from transistors T1, T2, T4, and T5. Transistors T1 and T2 correspond to transistors T1 and T2 in Figure 2. Transistors T4 and T5 are connected to a common gate circuit, thus forming a power amplifier with their source electrodes S4 and S5 as input electrodes, while their gate electrodes G4 and G5 are connected to a suitable non-varying potential that is connected to ground via a capacitor Cp with respect to AC.

[0030] Capacitor C1 is here divided into two separate capacitors C1a and C1b, each with one end connected to ground. The other ends of capacitors C1a and C1b are connected to both ends of inductor 19. Here again, capacitors C1a and C1b form a parallel oscillation circuit together with inductor 19. Switch SW1 is useful for modifying the operation of generator 12 by the circuit described in relation to Figure 2. In particular, the oscillation of generator 12 can be made asymmetric, thereby allowing the generator to switch between time period A and time period B of the oscillation mode shown in Figure 3 as needed.

[0031] Regardless of whether the generator 12 is a simple push-pull generator according to the concept in Figure 2, or a push-pull generator with amplifiers V1, V2 in a cascode circuit according to Figure 4, in addition to switch SW1, there may be additional switches SW2, SW3 with capacitors C3, C4. Such an example is shown in Figure 5. The circuit branch is connected in parallel to both transistors T1, T2, and thus both amplifiers V1, V2, which the circuit branches capacitors C2, C3, C4, are connected in series to ground respectively by one switch SW1, SW2, SW3. The control circuit 24 controls SW1, SW2, SW3 to enable capacitors C2, C3, C4 when connecting one or more of the capacitors or more of the capacitors C2, C3, C4 to ground.

[0032] Similarly, the control circuit 24 can open (make non-conductive) one or more of the switches SW1, SW2, SW3 to disable one or more of the capacitors C2, C3, and C4. When all capacitors C2, C3, and C4 are disabled, the generator 12 oscillates according to the sample of time period A in Figure 3. When one or more of the capacitors C2, C3, and C4 are activated in such a way that their respective associated switches SW1, SW2, and SW3 are closed (made conductive), the form of the output voltage Ua is characteristically deformed in such a way that, for example, a positive or negative half-wave is amplified or reduced in amplitude and shortened or lengthened in time.

[0033] In all embodiments described, there may be a single switch SW1 having a capacitor C2 (Figures 2 and 6), two switches SW1 and SW2 having two capacitors C2 and C3, three switches SW1, SW2 and SW3 having three capacitors C2, C3 and C4 (Figures 5 and 7), or multiple such branches.

[0034] In the circuit concepts shown in Figures 2 to 5 above, the inductor 19 is provided with a center tap 20 through which the operating current is supplied via a choke 21 that is highly ohmic to RF. In this way, a symmetric current supply is provided. However, in all the circuits described above, it is also possible to supply the operating current asymmetrically through the choke 21 at one end of the inductor 19, as is particularly evident from Figures 6 and 7. Preferably, the inductance of the choke 21 is higher than the inductance of the inductor 19. For the purpose of describing the structure and function of these circuits shown in Figures 6 and 7, refer to the circuit descriptions in Figures 4 and 5, based on the reference numerals already introduced. Furthermore, the asymmetric supply of operating current to the generator 12 shown in Figures 6 and 7 provides an initiation asymmetry that can result in oscillations that are not entirely symmetric, even when the additional capacitors C2, C3, and C4 are disabled, i.e., when the associated switches SW1, SW2, and SW3 are closed. The current initiation asymmetry of the oscillation of the generator 12 can be amplified or attenuated by specifically opening or closing one or more of the switches SW1, SW2, and SW3.

[0035] A push-pull generator 12, provided for supplying power to the medical device 10, preferably in a switchable configuration, includes at least one capacitive branch connected to ground in parallel with at least one of its two transistors T1, T2. Such a capacitive switchable branch may consist of a series connection of one capacitor C2 and one switch SW1. This allows one of the two half-waves of the output voltage of the generator 12 to be particularly affected, while the other half-wave remains largely unaffected. When switchable branches with capacitors C2, C4 are connected in parallel with both transistors T1, T2, both half-waves of the output voltage Ua of the generator 12 can be affected independently of each other.

[0036] Therefore, the concept according to the present invention enables a specific effect of half-oscillation in the push-pull generator 12, which is otherwise symmetrical, thereby expanding the application spectrum for supplying therapeutic current to the medical device 10. [Explanation of Symbols]

[0037] 10 devices 11. Living tissue 12 RF Generators 13 electrodes 14 Spark 15 Neutral electrode 16. Line of 10 fixtures 17 Neutral electrode 15 line Ua Voltage output from generator 12 to device 10 V1, V2 Amplifiers T1~T5 Transistors G1~G5 Gridgate S1~S5 Source electrodes D1~D5 Drain electrodes 18 Control circuits 19 Inductors 20 Center tap C1 First capacitor C2 Second capacitor Cp buffer capacitor 21 Chalk 22 First end of capacitor C2 23 Second end of capacitor C2 SW1 First switch 24 Control circuit for switch SW1 (SW2, SW3) K coupling coil A, B Time period shown in Figure 3 C4, C5 Additional capacitors

Claims

1. A system comprising a surgical instrument (10) for treating biological tissue (11) and a generator (12) for supplying electric current to the surgical instrument (10), The system includes a first amplifier (V1) comprising a first input electrode (G1) and a first output electrode (D1), The system includes a second amplifier (V2) comprising a second input electrode (G2) and a second output electrode (D2), The device has an inductor (19) positioned between the first and second output electrodes (D1, D2), It has a first capacitor (C1) that is connected to the inductor (19) to form an oscillation circuit, A system having a second capacitor (C2) having an end (22) connected to the inductor (19) and an end (23) connected to a switch (SW1).

2. The system according to claim 1, characterized in that the first amplifier (V1) is a first field-effect transistor (T1) whose drain electrode is the first output electrode (D1), and the second amplifier (V2) is a second field-effect transistor (T2) whose drain electrode is the second output electrode (D2).

3. The system according to claim 2, characterized in that the first input electrode (G1) is the gate electrode of the field-effect transistor (T1), and the second input electrode (G2) is the gate electrode of the second field-effect transistor (T2).

4. The system according to claim 2, characterized in that the first amplifier (V1) is a first field-effect transistor (T4) whose drain electrode is the first output electrode (D4), the second amplifier (V2) is a second field-effect transistor (T5) whose drain electrode is the second output electrode (D5), the first input electrode (S4) is the source electrode of the first field-effect transistor (T4), and the second input electrode (S5) is the source electrode of the second field-effect transistor (T5).

5. The system according to any one of claims 1 to 4, characterized in that the two amplifiers (V1, V2) are connected to a push-pull control circuit (18).

6. The system according to any one of claims 1 to 4, characterized in that the inductor (19) is provided with a center tap (20) connected to an operating voltage source (Ub).

7. The system according to any one of claims 1 to 4, characterized in that an operating voltage source (Ub) is connected to one of the two ends of the inductor (19).

8. The system according to any one of claims 1 to 4, characterized in that the switch (SW1) is configured to selectively terminate the end (23) of the second capacitor (C2) in a high-ohmic manner or to connect it to ground.

9. The system according to any one of claims 1 to 4, wherein at least one additional capacitor (C3) is provided, having one end connected to the inductor (19) and one end connected to a switch (SW2), and the switch (SW2) is configured to selectively terminate the end of the additional capacitor (C3) connected thereto in a high-ohmic manner or to connect it to ground.

10. The first capacitor (C1) is connected in parallel with the inductor (19). A system characterized by any one of claims 1 to 4.

11. The system according to any one of claims 1 to 4, characterized in that the first capacitor comprises two subcapacitors (C1a, C1b), each having one end connected to the inductor (19) and the other end connected to ground.

12. The system according to claim 11, characterized in that the ends of the sub-capacitors (C1a, C1b) connected to ground are each inseparably connected to ground.

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