Electrosurgical generator with improved inverter control and corresponding method

Description

[0001] The invention relates to an electrosurgical generator for delivering a high-frequency alternating voltage to an electrosurgical instrument and a corresponding method. The electrosurgical generator comprises a control unit and a high-voltage inverter that generates a high-frequency alternating voltage with variable frequency and amplitude, which is fed to an output socket for connecting the electrosurgical instrument.

[0002] Electrosurgical generators typically have a fairly complex functionality, encompassing a large number of functions. This enables the surgical generators to handle a variety of applications. These functions differ in the way they supply power to the electrosurgical instrument. The different ways of supplying power to the electrosurgical instrument are commonly referred to as "modes." If only tissue is to be cut, a cutting mode is selected, which continuously supplies the electrosurgical instrument with a medium voltage. If coagulation is more important, a different mode is chosen, such as a spray or coagulation mode, which uses a relatively high voltage with a low duty cycle. There are many other different modes for other types of applications.

[0003] Currently, electrosurgical generators use high-voltage generators, usually generated using resonant converters. This is a reliable and proven technology. However, it has disadvantages in that the frequency cannot be controlled, and the amplitude can only be adjusted by changing the voltage of the DC power supply to the resonant converter. Any changes to the frequency and / or amplitude are quite cumbersome.

[0004] To improve controllability, it is known to equip an electrosurgical generator with an H-bridge inverter (EP 3 248 560 A1). However, special control methods must be used to avoid the formation of excessive harmonics.

[0005] In addition, the applicant has developed electrosurgical generators consisting of multilevel inverters in a cascaded topology. This has significantly improved the adjustability of the output signal. Rapid changes in amplitude and frequency are possible. Furthermore, any waveform of the output voltage is, in principle, possible. However, this requires a special high-performance controller, e.g., an FPGA, capable of driving the inverter's current valves at a significantly higher frequency than the output frequency of the generated high voltage. Typical drive frequencies are 200 MHz for an output voltage with a frequency of 400 kHz. This is feasible, but providing the reference signal for such a high drive frequency requires many data points in rapid succession, which in turn requires high-speed controllers, which are expensive.

[0006] It is an object of the invention to provide an electrosurgical generator and an improved inverter control that reduces this disadvantage.

[0007] The inventive solution lies in the features of the independent claims. Advantageous embodiments are the subject of the dependent claims.

[0008] In an electrosurgical generator for outputting a high-frequency alternating voltage to an electrosurgical instrument, comprising a control unit and a high-voltage inverter which generates a high-frequency alternating voltage with variable frequency and amplitude, which is fed to an output socket for connecting the electrosurgical instrument, the invention provides that the inverter is a multilevel inverter which is controlled by a reference signal which defines the shape of the generated high-frequency alternating voltage, wherein the reference signal is defined by a datagram, wherein the datagram comprises a finite series of consecutive amplitude and frequency data vectors for a defined number of periods.

[0009] First, let's explain a few terms: A multilevel inverter is an inverter capable of delivering an output voltage at different levels, as opposed to a purely on / off output with positive and / or negative polarity. Typical topologies include cascaded H-bridges, neutral clamped capacitors, and flying capacitors.

[0010] A datagram is a data packet of finite length. It is typically small, up to a maximum of 256 bytes, especially 50 bytes or less. It may optionally contain source and destination identification, but this is not required.

[0011] The term "period" is used here to describe the time required to complete one full oscillation of a waveform. Typically, this refers to the high-frequency AC voltage waveform generated by the inverter.

[0012] Controlling the inverter and providing its reference signal according to the present invention eliminates the need for an expensive high-speed controller, such as an FPGA. The invention offers a different approach to generating the reference signal, specifically datagram-based generation, which provides a flexible and precise description of the reference signal to be generated. For this purpose, a special data format was developed that comprises a finite series of consecutive amplitude and frequency data vectors for a specific number of periods. The datagram describes the reference signal to be generated with a minimum of information.

[0013] Electrosurgical generators deliver their high-frequency alternating voltage in various modes. A simple mode is provided as a continuously oscillating voltage, e.g., for a "PureCut" mode. In addition, there are several more complex modes configured so that the output voltage varies over time in terms of frequency, amplitude, duty cycle, and / or crest factor. One example is a "SprayCoag" mode, in which a very high voltage is applied as a peak for a very short time, e.g., one or two oscillations, followed by a much longer pause with very low or no voltage. The duration of the pause is at least one dimension (10 times) longer than the peak, e.g., 20 times longer.

[0014] In order to generate the output voltage according to fairly complex modes, providing a reference signal for a multilevel inverter can be quite data-intensive. A multilevel inverter generating a high-frequency AC output voltage of up to 500 kHz is typically driven at a much higher frequency, typically around 200 MHz. Depending on the number of stages, each data point may require half a byte, one byte, or even two bytes. This results in quite high bandwidth requirements, which are demanding and costly.

[0015] Within the scope of the invention, it was recognized that the amount of data and thus the required bandwidth can be drastically reduced by providing a datagram containing descriptive data for the desired high-frequency sinusoidal curve of the output voltage instead of an extensive stream of data points. This becomes quite clear when the desired output voltage is a continuous voltage, for which the datagram requires only a tens of bits. But surprisingly, even more complex modes require only a small amount of data when using the datagram according to the invention, namely a finite series of consecutive amplitude and frequency data vectors for a certain number of periods. In this way, a multitude of modes can be described with a minimum of data, which need only be a few dozen bytes long. This obviously represents a drastic reduction in bandwidth requirements.

[0016] Preferably, the reference signal is formed by a reference signal forming unit. It is configured to form the reference signal according to the datagram. Further preferably, the reference signal forming unit comprises a receiver configured to receive a data set describing the reference signal. The reduced bandwidth requirements of the datagrams according to the invention allow for increased freedom regarding the positioning of the reference signal forming unit within the electrosurgical generator, without being restricted to proximity to the source of the datagram.

[0017] The invention preferably enables efficient generation of the reference signal by using a synthesizer. For this purpose, the reference signal forming unit preferably comprises a decoder configured to decode the data set received by the receiver and extract the data vectors for each of the periods, a sequencer configured to output amplitude and frequency signals from the extracted data vector for each period in a sequence defined by the data fields and to repeat this sequence; and a synthesizer configured to form, for each of the data vectors, an oscillation wave with the amplitude and frequency according to the respective data vector, wherein a series of the oscillation waves forms the reference signal supplied to the inverter.In conjunction with the control according to the invention by means of the datagrams, both continuous and non-continuous reference signals for the output voltage can be formed in a simple manner.

[0018] Preferably, the datagram comprises a plurality of data fields, one data field for each period, each data field comprising one of the data vectors with values ​​indicative of the amplitude and frequency of a respective one of the defined number of periods. Providing a separate data field containing the data vector for each of the periods allows a high degree of flexibility in defining a complex sequence, thereby enabling the reference signal generation unit to generate reference signals even for complex modes of the electrosurgical generator, such as modes with voltage pulses separated by pauses.

[0019] Advantageously, the datagram further contains a first additional data field indicative of a polarity, in particular the polarity of a first half-wave of a first period. This allows selection of whether the reference signal begins with a positive half-wave or a negative half-wave, and thus allows the surgeon to select the polarity (positive or negative first half-wave) of the high-voltage output voltage using the RF generator.

[0020] Advantageously, the datagram also contains a second additional data field indicative of the number of periods. This enables the receiver, and in particular the decoder and sequencer, to check the datagram for completeness. This allows for easily detecting and rejecting erroneous datagrams or datagrams missing data vectors for some periods, thus increasing operational reliability.

[0021] Additionally or alternatively, the datagram may preferably contain additional data fields indicative of start and stop information, in particular start and stop bytes. This uniquely identifies the beginning and end of the datagram. This further improves the data quality of the datagram. By using start and stop information, it is also possible to have datagrams with an indefinite number of periods, thus facilitating the inclusion of additional periods with additional data vectors for more complex codes. This improves the capability for future updates. Furthermore, the start and / or stop information may optionally determine the direction of data flow, thereby reading the data of the datagram, and / or it may include data integrity data fields, e.g., a checksum such as a CRC (cyclic redundancy checksum).

[0022] Preferably, the datagram contains at least data fields for two periods. This allows for a relatively free selection of the duty cycle, which is a great advantage when defining complex modes of the electrosurgical generator. In a preferred embodiment, the synthesizer is designed to generate half-wave oscillations, and the periods in the datagram refer to the duration of the half-wave oscillation. An individual frequency and amplitude could be assigned to each half-wave. This enables even greater granularity in defining the voltage curves of the modes. Furthermore, it permits asymmetric shaping of the reference signal, further increasing the freedom in designing even more complex modes. It is worth noting that due to the data vector concept, the frequency and / or amplitude of the second half-wave may differ from the frequency and / or amplitude of the first half-wave.This is an important aspect of the invention, and in particular, the ability to have different frequencies for the first and second half-waves is a major advantage. Accordingly, the half-wave capability offers greater flexibility in designing a wide variety of different reference signals for different modes.

[0023] In addition, the synthesizer can be configured to generate only unipolar half-waves, especially positive half-waves. A synthesizer that can only generate half-waves can be simplified compared to a bipolar synthesizer. Furthermore, with the same number of bits, higher quantization and thus better resolution in terms of voltage amplitude can be achieved, allowing for a finer reproduction of sinusoidal voltage waveforms. Another advantage is that the proportion of unwanted harmonics can be reduced due to the improved quantization.

[0024] Preferably, the synthesizer is coupled to an inversion circuit configured to invert every second half-wave output by the synthesizer. By inverting every second half-wave, a fully bipolar oscillation can be generated with the simplified half-wave synthesizer.

[0025] Preferably, the inversion circuit is a switchable inversion circuit in which, depending on a selection signal, it is possible to switch whether even or odd half-waves are to be inverted. The selection signal can be used to easily determine whether the reference signal, and thus the oscillation to be generated, begins with a positive or negative half-wave. Preferably, the selection signal of the inversion circuit is automatically adjusted according to a first additional data field that specifies the polarity.

[0026] Particularly when the electrosurgical generator, which supplies the output voltage to the electrosurgical instrument, is operating for an extended period of time, or during complex operating modes such as those involving switching between different operating modes (e.g., switching between CUT and COAG operation), it may be necessary from time to time to update the data vectors of some, but not all, periods of the reference signal. Of course, a new, complete datagram could be created and sent to be received and processed by the reference signal formation unit. However, it is even more efficient to send only a reduced set (fragment) rather than the entire datagram.Advantageously, the receiver is further configured to receive a datagram fragment, the datagram fragment comprising a limited number of data fields with modified amplitude and frequency data vectors and an identifier for the respective period, the limited number being one or more, but less than the defined number of periods. This enables the reference signal forming unit to selectively replace amplitude and frequency data vectors for one (or several) specific periods without requiring the complete transmission of the entire datagram. This further reduces the amount of data to be transmitted. It also enables faster updates, which is very important for quickly switching between operating modes, e.g., between CUT and COAG mode.

[0027] For this purpose, the decoder is preferably configured to extract the data vectors and identifiers, and the sequencer is configured to selectively replace the amplitude and frequency output signals for the relevant period with those received in the decoded datagram fragment. Only the actually modified data vectors need to be replaced, which simplifies and accelerates the process.

[0028] Advantageously, the datagram is compressed so that the bit length of the amplitude and / or frequency value in the data vector is limited to the number of levels of the multilevel inverter or the frequency range. This avoids the transmission of unnecessarily long data, resulting in even more compact datagrams that enable faster transmission and processing.

[0029] Preferably, the datagram is less than 256 bytes, preferably less than 50 bytes.

[0030] In most cases, the receiver is coupled to the control unit for receiving the datagram, with the control unit being located locally on the electrosurgical generator. However, in an advantageous embodiment, it is also possible for the receiver to be configured to receive the datagram from a remote control unit. The compact datagram and the resulting reduced bandwidth requirements thus facilitate operation via a remote control connection, particularly a wireless connection.

[0031] The invention further relates to a corresponding method for outputting a high-frequency alternating voltage from the electrosurgical generator. For further explanation of the generation of the high-frequency alternating voltage by means of the electrosurgical generator and its inverter, reference is made to the above description of the electrosurgical generator, which applies mutatis mutandis, to avoid unnecessary repetition.

[0032] The invention is explained in more detail below using an advantageous embodiment. In the figures: Fig. 1 shows a block diagram of a surgical generator according to an exemplary embodiment with a connected electrosurgical instrument; Fig. 2 shows a block diagram of a cascaded multilevel inverter; Fig. 3a, b shows a schematic representation of two examples of datagrams; Fig. 4 shows a block diagram of an exemplary embodiment of a reference signal formation unit; Fig. 5a, b shows a first example of a reference signal and data of the corresponding datagram; Fig. 6a, b shows a second example of a reference signal and data of the corresponding datagram; and Fig. 7: an exemplary flowchart of a method for forming the reference signal.

[0033] An electrosurgical generator according to an exemplary embodiment is shown in a block diagram in Fig. 1The electrosurgical generator, designated overall by reference numeral 1, comprises a housing 11 provided with an output socket 14 for an electrosurgical instrument 16. This is connected to the output socket 14 of the electrosurgical generator 1 via a high-voltage connection cable. A power cable 12 is provided for the power supply of the electrosurgical generator 1, which can be connected to a public power grid or another suitable power supply device.

[0034] The electrosurgical generator 1 comprises a power supply unit 2 in the housing 11, which is supplied with electrical energy via the power cable 12 (see Fig. 1). The power supply unit 2 comprises a rectifier and supplies a DC link 20 with DC voltage, which supplies an inverter. The inverter 3 generates high-frequency alternating current in the high-voltage range of several kilovolts. The output RF high voltage is fed via an output line 23, a low-pass filter 25, and an isolation transformer 26, which steps up the high voltage, to the output socket 14, which contains a series capacitor 27 to block any DC current to the output socket 14. The electrosurgical instrument 16 can be plugged into the output socket 14. The output voltage and current at the output socket 14 are measured by a voltage and current sensor 28, and corresponding measurement signals are delivered to the control unit 10 via a feedback circuit 19. This is well known in the art and will not be explained further for the sake of brevity.The operation of the electrosurgical generator 1 is controlled by a control unit 10, which is connected to the power supply unit 2 and the inverter via signal lines. The control unit 10 operates the RF generator 1 based on functions stored in a memory of the control unit 10. The functions define operating characteristics and modes of the RF generator 1. The functions can be selected by a user using input devices, which can be conventional buttons and knobs and / or a touchscreen interface (not shown). For example, the power to be output can be selected with a power selector switch 13, and the mode to be used can be selected with a mode selector switch 14.

[0035] The inverter generates a high-frequency alternating voltage in the range between 200 kHz and 4 MHz. The inverter is designed as a multilevel inverter 3. The shape, frequency, duty cycle, and amplitude of the voltage generated by the multilevel inverter are determined by an inverter controller 31 based on a reference signal generated by a reference signal generation unit 30, which in turn is controlled by the control unit 10 depending on the selected power and operating mode.

[0036] The multilevel inverter 3 comprises a plurality of cells arranged in a cascaded formation as shown in Fig. 2shown. There are two different types of cells, arranged in two groups, each supplied with a different DC voltage. The first group comprises the low-voltage cells 3-1, 3-2, and 3-3. They are supplied with a lower DC voltage, 12 V in the illustrated embodiment. The second group comprises the high-voltage cells 3-4 and 3-5, which are supplied with a higher DC voltage, 48 V in the illustrated embodiment. Both groups are connected in series so that the voltages output by each of the cells 3-1 to 3-5 are added to a common output voltage Vout. The configuration shown can provide an output voltage in the range -132 V to +132 V, which corresponds to 23 levels in 12 V steps.

[0037] In Fig. 3a ) and b) show examples of datagrams. In the first example of the Fig. 3a) the datagram 100 comprises data fields 101 and 102 for two periods. Each data field 101 and 102 comprises a data vector 121, 122, each containing two values, one value "A", which indicates an amplitude, and another value "f" which indicates a frequency of the respective period. These values ​​thus describe the properties of the respective period in terms of amplitude and frequency. Furthermore, the datagram 100 contains a first additional data field 111 which indicates the polarity of the first period, i.e., whether the oscillation begins with a positive or a negative wave. Furthermore, the datagram 100 includes a second additional data field 112 which specifies a number "n" of periods for which data vectors are contained in the data fields 101, 102; in this case, "n" is 2. Optionally, the datagram 100 can also include additional data fields 113, 114 for a start byte and a stop byte, respectively.

[0038] The available data fields are shown in Table 1 below for a datagram with data fields for up to 15 periods: Table 1 parameter Area Bits Description polarity 0 or 1 1 0 - pos. / 1 - negative nPeriods 1 ... 15 4 Number of periods Amplitude0 0 ... 127 7 Rel. Ampl. 1st period ... ... ... ... Amplitude14 0 ... 127 7 Rel. Ampl. 15th period Frequency0 0 ... 511 9 Frequency of the 1st period ... ... ... ... Frequency14 0 ... 511 9 Frequency of the 15th period

[0039] The italicized rows of the table refer to additional data fields. The other rows contain the data vector with an amplitude value and a frequency value for each of the up to 15 periods. The amplitude value is a relative amplitude value, not an absolute value.

[0040] In Fig. 3b) a more complex datagram 200 is shown. It comprises four data fields 201, 202, 203 and 204 for two periods and separately for each half-wave of one of the two periods. Each of these fields comprises one of the data vectors 221, 222, 223, 224. For the same period, its positive half-wave can have a different amplitude and / or frequency than its negative half-wave. Furthermore, similar to datagram 100, datagram 200 contains an additional data field 211 for the polarity and an additional data field 212 for the number of periods. The value in additional data field 211 is an indicator of the polarity of the first half-wave of each period. In addition, datagram 200 can also contain optional additional data fields 213, 214 for a start byte and a stop byte, respectively.

[0041] The data fields for datagram 200 with data fields separated for each half-wave are shown in the following Table 2: Table 2 parameter Area Bits Description polarity 0 or 1 1 0 - pos. / 1 - negative nPeriods 1 ... 15 4 Number of periods AmplitudeA0 0 ... 127 7 Rel. Ampl. 1st period 1st half-wave ... ... ... ... AmplitudeA14 0 ... 127 7 Rel. Ampl. 15th period 1st half-wave AmplitudeB0 0 ... 127 7 Rel. Ampl. 1st period 2nd half-wave ... ... ... ... AmplitudeB14 0 ... 127 7 Rel. Ampl. 15th period 2nd half-wave FrequencyA0 0 ... 511 9 Frequency of the 1st period 1st half-wave ... ... ... ... FrequencyA14 0 ... 511 9 Freq. of the 15th period 1st half-wave FrequencyB0 0 ... 511 9 Frequency of the 1st period of the 2nd half-wave ... ... ... FrequencyB14 0 ... 511 9 Frequency of the 15th period, 2nd half-wave

[0042] Similar to Table 1, the italicized rows of Table 2 refer to additional data fields. The other rows contain the data vector, which includes an amplitude value and a frequency value for each half-wave of each of up to 15 periods. The amplitude value is a relative amplitude value, not an absolute value. It is worth noting that, due to these datagrams 200, the frequency of the second half-wave may differ from the frequency of the first half-wave. This is an important feature of the invention and provides greater flexibility in designing a variety of different reference signals for different modes.

[0043] In Fig. 4Shown is a block diagram of an exemplary embodiment of a reference signal generation unit 30, which receives these datagrams 100, 200 to form the reference signal for the inverter 3. It comprises a receiver 4 connected to the control unit 10. It is configured to receive the datagram 100, 200, which describes the reference signal to be formed, from the local control unit 10 of the electrosurgical generator 1.

[0044] Optionally, it is also possible for such a datagram 100, 200 to be sent from a remote device 92 via a preferably secure wireless connection 99, thereby enabling remote control of the reference signal generation unit 30. The low bandwidth requirements of the datagrams 100, 200 are advantageous for remote control, which is typically bandwidth-limited.

[0045] The receiver 4 forwards the received datagram 100, 200 to a decoder 5. The decoder 5 is configured to decode the datagram and extract the data vectors 121, 122, 221, 222, 223, 224 from the various data fields, as well as the data from the additional data fields 111, 112, 113, 114, 211, 212, 213, 214. The decoder 5 delivers the extracted data to a sequencer 6, which is configured to arrange the data extracted from the data vectors for each period in the correct order defined by the data fields and to start over when the end of the sequence is reached to repeat this sequence over and over again. This continues until a new datagram with new data or a data fragment with an update to some of the data vectors is received, and then these updated data vectors replace the respective earlier ones without interrupting the sequence.The amplitude and frequency data "A" extracted from the data vectors are fed to a digitally controlled synthesizer 7, which forms a continuous oscillation comprising a sequence of waves, the amplitude and frequency of each of the waves in this sequence being determined by the data extracted from the data vectors of the datagram. It should be noted that in the example shown in . Fig. 4 In the embodiment shown, the digitally controlled synthesizer 7 is optionally configured to deliver a current of only unipolar, in this case positive, half-waves. This allows double the resolution with the same number of bits.

[0046] To create the missing negative half-waves, a switchable inversion circuit 8 is provided. It is configured to invert every other half-wave, thereby forming the missing negative half-waves. To control the inversion circuit 8, a signal relating to the polarity is extracted from an additional data field 111, 211. If the extracted polarity data requires positive polarity, the first and each subsequent odd half-wave are not inverted, and the inversion is performed on the second and each subsequent even half-wave, thereby creating full waves with a positive first half-wave. Conversely, if the extracted polarity data requires negative polarity, the inversion is performed on the first and each subsequent odd half-wave, thereby creating full waves with a negative first half-wave.This completes the formation of the full-wave reference signal 38, which is output by the reference signal formation unit 30 and fed to the inverter controller 31 for processing by the multilevel inverter 3.

[0047] An example of a reference signal formed in this way by the reference signal forming unit 30 is shown in Fig. 5a The reference signal is a non-complex signal. In this example, it is a sinusoidal wave suitable for a "Pure Cut" mode of electrosurgical generator 1. The data values ​​and parameters used for the various data fields of the datagram are shown in Fig. 5bshown. The bit length for each of the data fields is also specified. The total amount of data required to control the multilevel inverter 3 by defining the reference signal with the datagram is only 37 bits. This datagram only needs to be transmitted once, and the reference signal forming unit 30 generates a continuous reference signal with the shape, amplitude, and frequency defined by the datagram. This is in stark contrast to the large amounts of data required for conventional control of the multilevel inverter 3.

[0048] An example of a more complex reference signal is shown in Fig. 6a This reference signal is more complex and comprises two periods defined as half-waves. It therefore uses a datagram like the one shown in Fig. 3bDatagram 200 is shown. The frequency of the first period is quite high (350 Hz), and the frequency of the second period is much lower (19 Hz). Combined with a high amplitude for the first period and a low, more precisely zero, amplitude for the second period, a needle-like reference signal with a duty cycle of approximately 5.5% is generated, which is well suited for a "spray and coagulation" mode of the electrosurgical generator 1. As this example demonstrates, even complex reference signals with high duty cycles can be formed with a minimum of data, in this example only 69 bits. This, in turn, is in stark contrast to the large amounts of data required for conventional control of the multilevel inverter 3.

[0049] In Fig. 7An exemplary flowchart for a method for forming the reference signal for controlling the multilevel inverter 3 is shown. After receiving a datagram 100 in step 81, a reference signal is formed in step 83, as described above. In many cases, the reference signal defined by the datagram 100 is used directly (via branch "n") to control the inverter 3 in step 89 to define the shape, frequency, and amplitude of the high-frequency alternating voltage generated by the multilevel inverter 3. However, if a check of the reception of a data fragment in step 85 reveals that such a data fragment has been received, the workflow branches (via branch "p") to perform an extraction of data vectors contained in the data fields contained in said data fragment in step 86.Subsequently, the data vectors thus extracted replace the corresponding previous data vectors, and an updated reference signal is formed in step 88. Finally, in step 89, the multilevel inverter 3 is controlled based on the reference signal, including any updates by the data fragments, if applicable, to generate the high-frequency alternating voltage whose shape, frequency, and amplitude are defined by the datagrams 100 used to form the reference signal.

Claims

1. Electrosurgical generator for outputting a radiofrequency AC voltage to an electrosurgical instrument (16), comprising a control unit (10) and a high-voltage inverter (3) that creates a radiofrequency AC voltage of variable frequency and amplitude that is supplied to an output socket (14) for connecting the electrosurgical instrument (16), wherein the inverter is a multilevel inverter (3) that is controlled by a reference signal which defines the shape of the created radiofrequency AC voltage, characterized in that the reference signal is defined by a datagram (100, 200), wherein the datagram (100, 200) comprises a finite series of consecutive amplitude and frequency data vectors for a defined number of periods.

2. Electrosurgical generator according to Claim 1, wherein the reference signal is provided by a reference signal forming unit (30).

3. Electrosurgical generator according to Claim 2, wherein the reference signal forming unit (30) comprises: - a receiver (4) that is designed to receive a data set with the datagram (100, 200), - a decoder (5) that is designed to decode the data set received by the receiver (4) and extract the data vectors for each of the periods, - a sequencer (6) that is designed to output signals for the amplitude and frequency from the extracted data vector for each period in a sequence which is defined by the data fields and repeat this sequence, and - a synthesizer (7) that is configured to form for each of the data vectors an oscillation wave with the amplitude and frequency according to the respective data vector, wherein a series of oscillation waves form the reference signal that is supplied to the inverter (3).

4. Electrosurgical generator according to any of the preceding claims, wherein the datagram (100, 200) comprises a multiplicity of data fields (101, 102; 201, 202, 203, 204), one data field for each period, wherein each data field comprises one of the data vectors with values that are indicative of the amplitude and the frequency of a respective one of the defined number of periods.

5. Electrosurgical generator according to any of the preceding claims, wherein the datagram (100, 200) further comprises a first additional data field (111, 211) that is indicative of a polarity, in particular the polarity of a first half wave of a first period.

6. Electrosurgical generator according to any of the preceding claims, wherein the datagram (100, 200) further comprises a second additional data field (112, 113) that is indicative of the number of periods.

7. Electrosurgical generator according to any of the preceding claims, wherein the datagram (100, 200) comprises additional data fields (113, 114; 213, 214) that are indicative of start and stop information, in particular start and stop bytes.

8. Electrosurgical generator according to any of Claims 3 to 7, wherein the synthesizer (7) is designed to form half-wave vibrations, and the periods in the datagram (100, 200) refer to the duration of the half-wave vibration.

9. Electrosurgical generator according to the preceding claim, wherein the synthesizer (7) is configured such that it forms only unipolar half waves, in particular positive half waves.

10. Electrosurgical generator according to the preceding claim, wherein an inversion circuit (8) is coupled to the synthesizer (7) and configured such that it inverts every second half wave emitted by the synthesizer (7).

11. Electrosurgical generator according to the preceding claim, wherein the inversion circuit (8) is a switchable inversion circuit that is switchable depending on a selection signal in relation to whether even or odd half waves should be inverted.

12. Electrosurgical generator according to the preceding claim, wherein the selection signal is automatically set in accordance with a first additional data field (111, 211) that is indicative of the polarity.

13. Electrosurgical generator according to any of Claims 3 to 12, wherein the receiver (4) is further designed to receive a datagram fragment, wherein the datagram fragment comprises a limited number of data fields (101, 102; 201, 202, 203, 204) with modified amplitude and frequency data vectors and an identifier for the period in question, wherein the limited number is one or more periods, but less than the defined number of periods.

14. Electrosurgical generator according to the preceding claim, wherein the decoder is designed to extract the data vectors and identifiers, and the sequencer is designed to selectively replace the output signals for amplitude and frequency for the period in question with those received in the decoded datagram fragment.

15. Electrosurgical generator according to any of the preceding claims, wherein the datagram (100, 200) is compressed such that the bit length of the amplitude and / or frequency value in the data vector is limited to the number of levels in the multilevel inverter or to the frequency range.

16. Electrosurgical generator according to any of Claims 3 to 15, wherein the receiver (4) is coupled to the control unit (10) for receiving the datagram (100, 200) and / or configured to receive the datagram (100, 200) from a remote control unit (92).

17. Method for outputting a radiofrequency AC voltage by means of an electrosurgical generator, which is intended for output to an electrosurgical instrument (16), wherein the electrosurgical generator comprises a control unit (10) and a high-voltage inverter (3) that creates a radiofrequency AC voltage of variable frequency and amplitude that is supplied to an output socket (14) for connecting the electrosurgical instrument (16), wherein the inverter is a multilevel inverter (3); the method comprises: controlling (89) the multilevel inverter (3) by means of a reference signal which defines the shape of the created radiofrequency AC voltage; and is characterized by: forming (83) the reference signal according to a datagram (100, 200), wherein the datagram (100, 200) that defines the reference signal comprises a finite series of sequenced amplitude and frequency data vectors for a defined number of periods.

18. Method according to Claim 17, wherein the reference signal is formed according to any of Claims 2 to 16.