Generator with regenerative device

Abstract

To provide a high frequency voltage for the operation of an appliance.SOLUTION: An electrosurgical generator (10) includes an oscillating circuit (17) excited by an excitation circuit having a frequency close to a resonant frequency, the oscillation being periodically interrupted. A regeneration circuit (25) realized by a voltage multiplier circuit is provided in order to stop the oscillation in the oscillator circuit of the generator as abruptly as possible without losing the energy stored in the oscillator circuit. Compared with a step-up conversion coupled inductor, the voltage multiplier circuit is provided in the oscillator circuit (17) because it is effectively electrically connected to the oscillator circuit (17) through a switch, especially only during the regeneration phase, thus providing the advantage of low capacitive loading. This concept allows efficient energy recovery and enables precise amplitude modulation of high frequency voltages, especially square wave modulation (on-off switching).SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an electrosurgical generator having a regeneration device.

Background Art

[0002] An electrosurgical generator typically provides a high-frequency voltage for the operation of an electrical instrument. Such a generator often includes an oscillation circuit that supplies a high-frequency voltage and a high-frequency current for the supply of an electrosurgical instrument. In many cases, the high-frequency voltage must be modulated to achieve a specific surgical purpose.

[0003] Such a generator is known from German Patent Application Publication No. 10046592, in which the high-frequency voltage is amplitude-modulated by a square wave. At the end of the oscillation cycle of the oscillation circuit, the oscillation must be stopped as quickly as possible. German Patent Application Publication No. 10046592 proposes an attenuation circuit for this purpose. The attenuation circuit includes an inductor, which is transformer-coupled to the oscillation circuit inductor of the generator, and supplies the energy removed from the oscillation circuit to an attenuation resistor that transfers the energy to heat. By doing so, the attenuation of the oscillation of the generator oscillation circuit is accelerated, and the oscillation is quickly stopped.

[0004] Although good modulation of the surgical voltage can actually be achieved by this method, high energy consumption is correlated with it.

[0005] As a solution, European Patent No. 2424458 proposes using a regenerative circuit instead of a resistor to eliminate the energy contained in the oscillator circuit. This regenerative circuit sends the energy back to a storage capacitor at the end of the RF impulse, and converts only the remaining energy that cannot be sent back to the storage capacitor into heat in an ohm resistor. In this way, the process of stopping the oscillation of the oscillator circuit is carried out in two stages. In the first stage, the energy of the oscillator circuit is regenerated onto the storage capacitor, and in the second stage, the remaining energy still contained in the oscillator circuit is converted into heat. This concept can achieve higher energy efficiency. However, the energy portion still needs to be eliminated. In addition, more efficient and faster decay of the oscillator circuit is desired.

[0006] Further prior art includes German Patent Application Publication No. 4009819, U.S. Patent No. 4429694, Japanese Patent Publication No. 08-299356, International Publication No. 98 / 07378, International Publication No. 03 / 090635, U.S. Patent No. 4281373, International Publication No. 98 / 27880, German Patent Application Publication No. 10046592, and U.S. Patent No. 6261286. [Overview of the project] [Problems that the invention aims to solve]

[0007] Based on the above, the object of the present invention is to provide a generator having an improved regenerative circuit. [Means for solving the problem]

[0008] This objective is achieved by the generator described in claim 1.

[0009] The generator according to the present invention comprises a regenerative circuit that can be operated and stopped in a controlled manner. For example, each switching element contributes to the controlled operation and stopping. When operated, the regenerative circuit connects the oscillator circuit of an electrosurgical generator to a buffer capacitor in order to send energy back from the oscillator circuit to the supply circuit, in particular onto a buffer capacitor provided thereon. According to the present invention, the regenerative circuit comprises a voltage multiplier circuit, in particular a voltage multiplier circuit realized by a capacitor-diode combination. When operated, the voltage multiplier circuit removes electrical energy from the oscillator circuit, thereby building up a voltage that increases with each oscillation, which is a multiple of the voltage removed from the oscillator circuit. The voltage multiplier is obtained from the number of stages of the voltage multiplier circuit. By voltage multiplication, the energy present in the oscillator circuit is recovered very quickly and efficiently onto the buffer capacitor, thereby maintaining the attenuation of the oscillator circuit when the voltage in the oscillator circuit is less than the supply voltage. In addition, the voltage of the buffer capacitor can be increased during regeneration without interfering with the regeneration process.

[0010] The concept of the present invention, in particular, eliminates the need for attenuation resistors to reduce voltage residue in the oscillation circuit. In doing so, the generator according to the present invention enables operation in which the high-frequency voltage of the oscillation circuit can be in the range of 100 kHz to several MHz with high modulation frequencies in the range of several tens of kHz, e.g., 20 kHz, 40 kHz, 60 kHz, 80 kHz or higher. In addition, the energy efficiency is improved in particular in modes where the switch-on duration of the RF impulse is very short, for example, in cut-off modes where the pulse pause ratio of the modulated RF voltage is particularly low.

[0011] Typically, an oscillator circuit is a parallel oscillator circuit consisting of at least one oscillator circuit inductor and at least one oscillator circuit capacitor. The oscillator circuit is assigned an excitation circuit configured to excite the oscillator circuit at its resonant frequency. In the simplest case, the excitation circuit comprises a single controlled switch that supplies energy to the parallel oscillator circuit in an impulse. However, the excitation circuit can also comprise multiple controlled switches, for example, within a half-bridge or bridge circuit.

[0012] The supply circuit is preferably a DC voltage source with a storage capacitor located at its output. The DC voltage source can be a voltage conversion circuit such as a Power Factor Correction (PFC) circuit. A flyback converter can serve this purpose. The PFC circuit supplies a substantially constant DC voltage from a pulsed, rectified grid AC voltage. Other converter circuits may also be used.

[0013] The storage capacitor located at the output of the power supply circuit forms a buffer that absorbs the energy supplied by the regenerative circuit. Therefore, the storage capacitor can be used again to supply power to the oscillation circuit.

[0014] The regenerative circuit can be directly connected to the oscillator circuit inductor. Alternatively, the regenerative circuit can be connected to a regenerative inductor that is transformer-coupled to the oscillator circuit inductor. In either case, the voltage multiplier circuit results in an increase in the voltage obtained from the oscillator circuit, and therefore efficient energy regeneration.

[0015] Preferably, the voltage multiplier circuit is a so-called capacitor cascade, particularly a multi-stage cascade. Such a circuit comprises two series circuits of multiple capacitors, thereby connecting the capacitor connection points of each series circuit to the connection points of each other series circuit of capacitors via a zigzag-arranged diode chain. Preferably, a switch is provided for operating or stopping the voltage multiplier circuit. The switch is preferably placed between the regenerative inductor or oscillator circuit capacitor and the voltage multiplier circuit. This concept minimizes capacitive coupling between the regenerative circuit and the oscillator circuit when the regenerative circuit is not operating, and thus allows for uninterrupted operation of the generator outside of the regenerative phase. Preferably, the switch is configured and controlled so that the regenerative circuit is connected to the oscillator circuit only during the regenerative phase.

[0016] The generator according to the present invention preferably includes a control circuit configured to alternately operate an excitation circuit on the one hand and a regenerative circuit on the other. This allows the oscillation of the oscillator circuit to be switched on and off so that nearly perfect square wave modulation of the generator's RF output voltage is possible. Other types of modulation, such as sawtooth modulation, are also possible. The present invention always offers advantages when the desired modulation requires a steep back flank, i.e., when a rapid stopping of RF oscillation is required.

[0017] Further details of advantageous embodiments are provided for in the dependent claims, specification and related drawings. [Brief explanation of the drawing]

[0018] [Figure 1] This is a schematic diagram of a generator according to the present invention having connected equipment. [Figure 2] Figure 1 is a simplified circuit diagram of the generator. [Figure 3] Figure 1 shows the modified circuit diagram of the generator. [Figure 4] Figure 1 is a schematic circuit diagram of another part of the generator. [Figure 5]It is a diagram showing the oscillation behavior of the generator according to FIGS. 1 to 4.

Embodiments for Carrying Out the Invention

[0019] FIG. 1 shows a generator 10 for supplying a surgical voltage to an output unit 11. A bipolar surgical instrument, or a monopolar surgical instrument as shown in FIG. 1 and a neutral electrode 13 can be connected to the generator. The instrument 12 and the neutral electrode 13 can be connected to the output unit 11 via their respective lines 14, 15.

[0020] The instrument 12 includes at least one electrode 16 that affects the patient's biological tissue. In contrast, the neutral electrode 13 is configured over a wide area to allow a current to flow between the patient and the neutral electrode 13 without a physiological effect.

[0021] In FIG. 1, the instrument 12 is shown schematically. The instrument can be a cutting instrument, a coagulation instrument, and any other monopolar or bipolar electro-surgical instrument. In the case of a bipolar electro-surgical instrument, this instrument includes two electrodes that are each connected via the output unit 11 and their respective lines or cables.

[0022] The generator 10 is particularly suitable for supplying appliances that must be supplied with a pulsed electrical high-frequency voltage. The pulsed electrical high-frequency voltage (RF voltage) means, in particular, a voltage having a fundamental frequency between 100 kHz and 5 MHz, preferably between 300 kHz and 500 kHz, and amplitude-modulated by a square-wave impulse sequence. This means that the amplitude of the RF voltage generated by the generator 10 alternates at the frequency of the square-wave pulse sequence between a first value and a second value, for example, between several hundred volts and 0 volts, or between several hundred volts and just a few tens of volts. Thus, the RF voltage is, for example, an "on / off switching" voltage. However, the present invention is also suitable for the generation of RF voltages having other modulation shapes, such as an RF voltage having sawtooth modulation, and all other modulation shapes, particularly those for which it is important that the RF oscillation at the end of the RF voltage impulse stops rapidly.

[0023] The structure of the generator 10 is shown as in the overview of FIG. 1. To generate the desired high-frequency alternating voltage, an oscillation circuit 17 is useful, which comprises at least one oscillation circuit capacitor 18 and at least one oscillation circuit inductor 19 connected in parallel with each other.

[0024] To supply the appliance 12 with electrical high-frequency energy, the oscillation circuit 17 is connected to a decoupling circuit 20, which is realized in this embodiment by at least one decoupling inductor 21 magnetically (transformer-wise) coupled to the oscillation circuit inductor 19. Other decoupling circuits are possible. The decoupling inductor 21 can be composed of a plurality of sub-inductors connected in series with each other. Thus, preferably, the oscillation circuit inductor 19 and the decoupling inductor 21 form a transformer having a transmission ratio greater than 1. The transmission ratio is the ratio of the number of turns of the decoupling inductor 21 to the number of turns of the oscillation circuit inductor 19.

[0025] An excitation circuit 22 is provided to supply excitation energy to the oscillator circuit 17 for the excitation and sustainment of oscillation in the oscillator circuit 17. The excitation circuit 22 includes a DC voltage source 23 for supplying DC voltage power. Each line supplying the DC voltage V is connected to a buffer capacitor 24. The buffer capacitor serves to store energy and also absorbs energy regenerated from the oscillator circuit 17 when the RF oscillation of the oscillator circuit 17 is stopped.

[0026] A regenerative circuit 25 is provided to regenerate energy from the oscillator circuit 17 when the RF oscillation is stopped. The regenerative circuit connects the oscillator circuit 17 to the buffer capacitor 24 to regenerate energy onto the buffer capacitor 24 whenever the oscillation of the oscillator circuit 17 should be stopped as quickly as possible.

[0027] Figure 2 shows a more detailed circuit diagram of the generator 10, particularly the regenerative circuit 25. As is clear, the excitation circuit 22 can be implemented in its simplest form by an electronically controlled switch 26 and its associated control circuit 27. The switch 26 is placed between the oscillator circuit 17 or regenerative inductor 29 (Figure 3) and the input of the regenerative circuit 25. When conducting, the regenerative circuit 25 is active and returns energy from the oscillator circuit 17, which is under attenuation, to the buffer capacitor 24. When disconnected, the regenerative circuit is inactive and does not attenuate the oscillator circuit 17.

[0028] The regenerative circuit 25 can be directly connected to the oscillator circuit 17. This allows its two input lines a and b to be directly connected to the input section of the regenerative circuit. As a result, lines a and c form the output of the regenerative circuit 25.

[0029] The regenerative circuit 25 is preferably a voltage multiplier circuit. The regenerative circuit comprises two branch sections, each having a series connection of multiple capacitors, for example, two, three, or four or more capacitors. In one branch section, capacitors C11, C12, and C13 are connected in series with each other. In the other branch section, which extends parallel to this, the same number of capacitors C21, C22, and C23 are connected in series with each other. The connection points between the capacitors in each of the two branch sections are connected to each other by diodes, thereby forming a common voltage multiplier circuit. Diodes D1 to D7 are arranged in a staggered pattern between the branch sections formed by capacitors C11 to C13 and C21 to C23. Diodes D1 to D7 are connected in series with the same polarity, that is, at each connection point, the anode of one diode and the cathode of the other diode are connected to each other.

[0030] The actuation switch 28 located within line b is part of the regenerative circuit 25. Line b forms a connection between the oscillation circuit 17 and the regenerative circuit 25. The actuation switch is configured to open and close the current path within line b.

[0031] The actuarial switch 28 and the electronic switch 26 are controlled in coordination. For control, a control device B29 can be provided to control switches 26 and 28 directly or through the intervention of a control circuit such as the control circuit 27. The control circuit opens and closes switch 26 in synchronization with the oscillation of the oscillation circuit 17 as long as the oscillation circuit is excited. When the oscillation should be stopped, switch 26 remains in a non-conductive state and switch 28 transitions to a conductive state. When the oscillation circuit resumes oscillation, switch 28 transitions to a non-conductive state and switch 26 is switched on and off again at a switching frequency corresponding to the resonant frequency of the oscillation circuit 17.

[0032] A modified embodiment of the generator 10 is shown in Figure 3. The above description applies as appropriate to the basic description, based on the reference numerals already introduced.

[0033] In the embodiment shown in Figure 2, lines a and b of the regenerative circuit 25 are directly connected to the oscillator circuit, whereas in the embodiment shown in Figure 3, lines a and b are connected to a regenerative inductor 29 that is coupled to the oscillator circuit inductor 19 in a transformer type. Therefore, the regenerative inductor 29 and the oscillator circuit inductor 19 form a transformer with a transfer rate preferably between 1 and 2. Other transfer rates are also possible. The transfer rate is defined as the ratio between the number of turns of the regenerative inductor 29 and the number of turns of the oscillator circuit inductor 19.

[0034] Figure 4 shows a further modification of the generator 10. In this modification, the excitation circuit comprises a plurality of switches 26a, 26b, 26c, and 26d that form a bridge circuit to excite the oscillator circuit 17. Figure 4 shows a full-bridge circuit with four switches 26a to 26d. However, a half-bridge circuit in which two switches, such as switches 26a and 26b, are replaced with capacitors can also be used to excite the oscillator circuit 17.

[0035] The generator 10 shown in Figure 2, as described above, operates as follows.

[0036] To illustrate the function, let us assume, as an example, that the oscillator circuit 17 includes resonant frequencies between 200 kHz and 1 MHz, for example, 350 kHz, 500 kHz, etc. Therefore, the control device B29 is provided to open and close the switch 26 at the above frequencies, thereby exciting the oscillator circuit 17 at its resonant frequencies. For example, a DC voltage source 23 supplied from a typical power grid 30 supplies a DC voltage of, for example, several hundred volts, for example, 300V, between ground and the operating voltage line V, so that the operating voltage (e.g., 300V) is loaded onto the buffer capacitor 24.

[0037] Here, assuming that the oscillation present in the oscillator circuit 17 is pulsed with a square wave function R, as shown in Figure 5, it is necessary to create oscillation pauses PA between each pulse PU. RF voltage U HFThe pulse PU can have a length of, for example, a few microseconds, or 5 μs. The duration of the pause PA between individual impulse PUs of the RF voltage depends on the modulation frequency and the so-called duty cycle. In particular, in the cut-off mode, where the RF can be very high (about 1000 V), the impulse PUs of the RF voltage are very short (1 to several RF oscillations per impulse PU of the RF voltage), but the pulse pause ratio is small, and therefore the duration of the RF pause PA can be relatively long (e.g., 100 μs).

[0038] In the generator 10, it is important that the RF oscillation at the end of each RF voltage impulse PU is stopped quickly and efficiently, thereby ensuring that there is little to no oscillation in the oscillator circuit 17 after the pulse. Figure 5 shows the attenuation curve 31 that can occur in the generator without attenuation by the regenerative circuit 25, shown as a dashed line. However, since the control device B29 at the end of the RF voltage impulse PU closes switch 28 and thus activates the regenerative circuit 25, the attenuation process shown as a solid line in Figure 5 is significantly shortened. This assumes that the regenerative circuit 25 is equipped with capacitors C11 to C23 loaded by the previous regenerative operation. Thus, the energy contained within the oscillator circuit 17 is transferred to the buffer capacitor 24 with the slight oscillation of the oscillator circuit 17. Furthermore, the regenerative circuit 25 also acts as a voltage multiplier circuit, and therefore increases the voltage that decreases during the attenuation of the RF oscillation by multiplying again to a value sufficient to supply the buffer capacitor 24, so the regenerative process continues with the attenuated oscillation amplitude of the oscillator circuit 17.

[0039] The electrosurgical generator 10 according to the present invention comprises an oscillator circuit, which is preferably excited by an excitation circuit at a frequency close to its resonant frequency, and this oscillation is periodically interrupted. This is, for example, the high-frequency voltage U that must be generated. HFThis can be done in a pulse-pause modulation situation, and its fundamental frequency, for example, 350 kHz or 500 kHz, can be modulated with a modulation frequency of, for example, 50 kHz. Other modulation frequencies are also possible. Typically, these modulation frequencies are less than 100 kHz. A regenerative circuit 25, implemented by a voltage multiplier circuit, is provided to stop the oscillation in the generator's oscillator circuit as abruptly as possible without losing the energy stored in the oscillator circuit 17. Compared with a boost conversion coupling inductor, the voltage multiplier circuit has the advantage of providing a lower capacitive load to the oscillator circuit 17, as it is electrically and effectively connected to the oscillator circuit 17 via a switch 28 only, especially during the regenerative stage. This concept enables efficient energy regeneration, and therefore the high-frequency voltage U HF This enables precise amplitude modulation, particularly square wave modulation (on-off switching). [Explanation of Symbols]

[0040] 10 RF Generators 11 Output section 12 devices 13 Neutral electrode Lines 14 and 15 16 electrodes 17 Oscillator Circuit 18 Oscillator circuit capacitor 19 Oscillator circuit inductor 20 Decoupling Circuits 21 Decoupling Inductors 22 Supply Circuit / Excitation Circuit 23 DC voltage source 24 buffer capacitors 25 Regeneration circuit 26 Electronic switches 27 Control circuits a, b, c lines C11~C13 Capacitors at the first branch C21~C23 Capacitors at the second branch D1~D7 Diodes 28. Operating switch 29 Inductors B29 Control Device 30 Power grid PU RF Voltage Impulse PA RF Pause 31 Damping Curve U HF High-frequency voltage

Claims

1. Electrosurgical generator (10), The oscillator circuit (17) comprises at least one oscillator circuit inductor (19) and at least one oscillator circuit capacitor (18), and the oscillator circuit (17) is connected to an excitation circuit (22) configured to generate electrical oscillations within the oscillator circuit (17). The oscillator circuit (17) is configured to supply a supply voltage (V), and has a DC voltage source (23) connected to a buffer capacitor (24). It has a decoupling circuit (20) that is connected to the oscillation circuit (17) on one end and to a connection device (11) for surgical instruments (12) on the other end, The regenerative circuit (25) is capable of transferring the energy stored in the oscillation circuit (17) back to the buffer capacitor (24). The excitation circuit (22) comprises the buffer capacitor (24) and the DC voltage source (23), The regenerative circuit (25) includes a voltage multiplier circuit (C11 to C23, D1 to D7), An electrosurgical generator characterized in that the voltage multiplication circuit (C11-C23, D1-D7) is a capacitor cascade.

2. The generator according to claim 1, characterized in that the oscillation circuit is a parallel oscillation circuit.

3. The generator according to claim 1, characterized in that the excitation circuit (22) comprises at least one controllable switch (26).

4. The generator according to claim 1, characterized in that the buffer capacitor (24) is connected to the output section of the DC voltage source (23).

5. The generator according to claim 1, characterized in that the decoupling circuit (20) is realized by a decoupling inductor (21) coupled in a transformer type to the oscillation circuit inductor (19).

6. The regenerative circuit (25) includes a regenerative inductor (29), The regenerative inductor (29) and the oscillation circuit inductor (19) form a transformer. The generator according to claim 1, characterized in that it does so.

7. The generator according to claim 1, characterized in that the regenerative circuit (25) is connected to the oscillation circuit inductor (19).

8. The generator according to claim 1, characterized in that the capacitor cascade is a multi-stage cascade.

9. The generator according to claim 1, characterized in that the capacitor cascade each comprises two series connections (C11-C13; C21-C23) of a plurality of capacitors (C11-C23), each connection point between two capacitors (C11 / C12, C12 / C13) of one series connection (C11-C13) is connected to two diodes (D3-D6) arranged in antiparallel, and the two diodes (D3-D6) are each connected to different connection points (C21 / C22, C22 / C23) of another series connection (C21-C23).

10. The generator according to claim 6, characterized in that the switch (28) is arranged between the regenerative inductor (29) and the voltage multiplier circuit.

11. The generator according to claim 6 or 10, characterized in that the ratio of the number of windings of the regenerative inductor (29) to the number of windings of the oscillation circuit inductor (19) is between 2 and 1.

12. The generator according to claim 1, further comprising a control device (B29) configured to alternately operate the excitation circuit (22) and the regeneration circuit.

13. The generator according to claim 10, characterized in that the switch (28) is a semiconductor switch.

14. The generator according to claim 13, characterized in that one end of the regenerative inductor (29) is connected to ground and the other end is connected to the switch (28).

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