Method of validating electrosurgical RF generator power record and corresponding RF generator

Abstract

The invention relates to a method of validating an electrosurgical RF generator power record and a corresponding RF generator. A method for verifying a power record of an RF generator for controlling at least one electrosurgical instrument, in which the RF generator has an inverter for generating an RF signal, and the inverter is supplied with a current via an inverter input and emits an RF signal having a voltage value and a current value via an inverter output for driving the electrosurgical instrument, the method comprises the steps of: recording an output power delivered via an RF signal as a directly recorded output power by directly measuring the RF signal by means of an RF power acquisition device; recording a comparison power based on the power measured on the input side of the inverter; and verifying the functionality of the RF power harvesting device by comparing the recorded comparison power with the directly recorded output power.

Description

Technical Field

[0001] The present invention relates to a method for verifying the power record of an RF generator for controlling at least one electrosurgical instrument. The invention also relates to an RF generator using such a method. Background Art

[0002] To control an electrosurgical instrument, an RF generator is used that supplies an RF signal with a specific power to the electrosurgical instrument. The power depends on the specific task that the electrosurgical instrument is currently performing.

[0003] Because such electrosurgical instruments are used on the human body, safety issues are extremely important. One safety issue is ensuring that the correct power (i.e., the correct amount of power) is supplied by the RF generator. To ensure this, a redundant system for evaluating the supplied power is required. The supplied power can be used for feedback control, and thus control also depends on the power determined by the RF generator.

[0004] To record (i.e., estimate or measure) the output power of an RF generator supplied to an electrosurgical instrument, the voltage and current of the output signal can be measured, and the corresponding output power can be calculated. Due to the high frequency and high voltage of the signal, determining the power in this way is not straightforward. For this calculation, the phase angle between the voltage and current is important, and therefore good accuracy of the phase angle for such high-frequency signals is required. However, this can be accomplished using a well-known FPGA (field programmable gate array).

[0005] In order to have a redundant record of the output power, two similar systems can be implemented. That is, two FPGAs can be used to determine the output power, and the determined values ​​of the two systems can be compared to verify whether the determined output power is correct. If there is a significant difference between the two output powers determined in this way, there is definitely an error. Problems may arise due to the same or similar methods or systems used to measure the output parameters. The hardware, FPGA code, and software may have design errors, which may be in the path of both and may cause the same erroneous behavior. Therefore, comparing two signals with the same error may result in the inability to identify this error. It is also important to note that this way of measuring RF current and RF voltage can be complex and expensive.

[0006] It has also been found that any additional sensors (ie, redundant sensors) may result in increased leakage current, whereas leakage current should be reduced rather than increased.

[0007] Therefore, the redundant system described above has the following disadvantages: It can be prone to errors due to design and system errors. Due to the redundant system, it is expensive. Furthermore, higher leakage currents occur due to the bypassed paths. Summary of the Invention

[0008] One object of the present invention is therefore to propose at least one solution that addresses at least one of the above-identified drawbacks. In particular, a solution for verifying the recording of the output power of an RF generator supplying an electrosurgical instrument should be proposed, which avoids system errors, reduces costs, and avoids an increase in leakage currents. At least an alternative to the solutions known to date should be proposed.

[0009] According to the present invention, a method according to claim 1 is provided. This method therefore involves verifying a power record of an RF generator for controlling at least one electrosurgical instrument. The RF generator has an inverter for generating an RF signal. The inverter is supplied with a current via an inverter input. A power supply may be present for supplying the current to the inverter. The power supply may be part of the RF generator or may be an external device.

[0010] The inverter outputs an RF signal having voltage and current values ​​for driving the electrosurgical instrument. The inverter converts an input signal (which may be a DC input current) into this RF signal. The RF signal thus drives the electrosurgical instrument, and the voltage and / or current values ​​can be set based on the actual needs of the electrosurgical instrument. This also ensures that a specific power value (i.e., the recorded power) is met.

[0011] The output power is thus delivered via the RF signal, and this output power is recorded as directly recorded output power by directly measuring the RF signal using an RF power acquisition device. This power acquisition device can be an FPGA as described above. The RF signal emitted by the inverter output can also be understood as the RF output signal. Therefore, as described, this RF output signal is measured. The power acquisition device therefore performs measurements at the inverter output and is designed to measure the RF signal and, based on this, estimate the power provided by this RF signal.

[0012] A comparative power based on the power measured on the input side of the inverter (i.e., at the inverter input) is also recorded. In particular, the power supplied by the power supply connected to the inverter input can be measured. As explained, the power supply at the inverter input can use DC current, and in addition to measuring the corresponding voltage, this DC current will also be measured in order to record the power at the input side of the inverter. Even if the power on the input side is not supplied by DC current, it can be supplied by a low-frequency signal of 50 Hz or 60 Hz. For such DC signals or signals with such low frequencies, inexpensive devices for measuring power are known and available. Such devices can be used and therefore the comparative power can be measured in a fairly inexpensive manner.

[0013] Based on this, it is proposed to verify the function of the RF power acquisition device by comparing the recorded comparative power with the directly recorded output power.

[0014] In this way, a solution is proposed that avoids the need for an expensive and potentially complex additional redundant measurement system. This solution also avoids systematic errors, since the recording of the comparative power is systematically different from the direct recording of the output power at the inverter output. Additional leakage currents are also avoided, since the proposed solution measures the comparative power at the inverter input, thus avoiding such leakage currents at the inverter output.

[0015] According to one aspect, it is proposed to record the input power at the inverter input and to determine the comparative power based on the recorded input power minus the power dissipation. It is thus recognized that the output power must generally correspond to the input power minus any dissipated power. Therefore, it is proposed to determine the comparative power based not only on the power measurement at the inverter input, but also on the power dissipation. It has been found that this power dissipation can be calculated with good accuracy and can be done without expensive measurement equipment. The specific values ​​that influence the dissipated power are known or can be assessed offline. The corresponding parameters are described below with respect to possible aspects of the invention.

[0016] Therefore, if the dissipated power is also taken into account, the comparative power can be determined with high accuracy without expensive measurement equipment. In this way, good redundancy can be achieved. Therefore, a good and reliable solution can be proposed.

[0017] According to one aspect, the functionality of the RF power acquisition device is verified if the absolute value of the difference between the recorded comparative power and the directly recorded output power is below a predetermined verification threshold. Thus, the difference is determined by comparing the recorded comparative power with the directly recorded output power. In particular, the verification threshold is in the range of between 5% and 30% of the directly recorded output power, and more particularly, in the range of between 10% and 20%.

[0018] In this way there is a clear criterion for deciding whether a correct function of the RF power harvesting device can be assumed. In particular, it is proposed to use this verification threshold as a relative threshold (ie relative to the amplitude of the directly recorded output power).

[0019] In particular, it was found that a value of 5% of the directly recorded output power would not indicate a fault, since, in particular, the determination of the power dissipation could differ within this range simply due to any inaccuracies. Therefore, if this verification threshold is chosen to be too small (i.e., below 5%), the problem of false alarms will arise. On the other hand, the upper limit value of the verification threshold of 30% seems rather vague. However, it should be remembered that in the event of a fault, very large differences will occur between the directly recorded output power and the comparison output power. Based on these findings, the lower limit value of the verification threshold can be chosen to be 10%, since this is still an acceptable accuracy, and the upper limit value can be chosen to be 20% or 25% of the directly recorded output power, since this will enable faults that do not differ too much to be identified. In other words, faults that only have a difference of slightly more than 20% or slightly more than 25% can still be identified.

[0020] According to one aspect, the power dissipation is determined based on at least one loss parameter. Possible loss parameters are described below. In particular, it has been found that such loss parameters are known or can be determined and can be used to estimate the power dissipation and thus facilitate the calculation of the comparative power.

[0021] According to one aspect, the loss parameter can be the modulation degree of the inverter. The modulation degree of the inverter can be defined as the ratio of the amplitude of the modulated signal to the amplitude of the DC / C voltage of the inverter (i.e., the intermediate circuit). The inverter can control a modulated current signal, but this current signal also has a voltage amplitude. Therefore, this voltage amplitude, in particular the peak value of the voltage signal, is considered. The ratio of this peak value to the amplitude of the DC / C voltage of the intermediate circuit can therefore be regarded as the degree of modulation, which can also be referred to as the modulation degree.

[0022] Therefore, this modulation degree ranges from 0 to 1. In particular, a high modulation degree indicates an efficient operating point. The less efficient the operating point, the higher the relative power dissipation. However, the most efficient operating point is not a modulation degree of 1. It is more likely to be in the range between 0.8 and 0.9.

[0023] Therefore, the degree of modulation is always known, as the exact operation of the inverter is known.Hence, any power dissipation due to modulation can be estimated with good accuracy.

[0024] According to one aspect, the selected RF mode may be used as a loss parameter.The RF mode (ie, high frequency mode) may indicate characteristics of the selected mode of the inverter.

[0025] RF mode refers to the setting or purpose of the planned or selected operation, such as cutting mode, coagulation mode or other modes. It is found that there are continuous modes or continuous sinusoidal oscillations and modulated oscillations. Modulated oscillations can be interrupted oscillations, such as 2 oscillations at 350 kHz, followed by a pause and then 2 oscillations again. Forced coagulation mode is an example. This is then repeated at about 18 kHz to give an example. Here, modulation also always refers to amplitude modulation (i.e., modulating the voltage in the intermediate circuit or using PWM).

[0026] It has been found that also depending on the selected RF mode the power dissipation may vary and since the selected RF mode is known the corresponding power dissipation may also be calculated with high accuracy if the selected RF mode is therefore taken into account.

[0027] The ambient temperature of the inverter can also be used as a loss parameter. Due to the ambient temperature of the inverter, it can be measured using a temperature sensor placed on the inverter housing or at a distance of less than 10 m, or particularly less than 1 m, from the inverter. If the inverter is operated in a room, the room temperature can be used as the ambient temperature. It has been found that this ambient temperature affects the temperature in the inverter and, therefore, higher temperatures can lead to higher power dissipation. It has also been found that high ambient temperatures can lead to higher activity of the cooling vents, which will result in higher power consumption by these cooling vents. Therefore, by taking the ambient temperature into account, the power required by these cooling vents can be indirectly taken into account.

[0028] According to one aspect, the component temperature of a component of the inverter can be used as a loss parameter. This component temperature can specifically be the temperature of a semiconductor and / or a circuit carrying several semiconductors, in particular the temperature of a circuit including a semiconductor switch used to generate a pulsed signal to generate an RF signal. Such semiconductors perform the most work in converting power and dissipate power primarily in the form of heat. Therefore, the temperature of such a component of the inverter (in particular, such a semiconductor or circuit) provides an indication of the dissipated power. Therefore, based on this, the power dissipation can be calculated with high accuracy.

[0029] According to one aspect, the switching frequency of the inverter can be used as a loss parameter. It has been found that such switching frequency can affect the losses, and it is therefore recommended to take it into account. In particular, the switching frequency of the inverter may affect the losses of the converter, and the losses of the converter can therefore be evaluated based on the switching frequency. In particular, the losses of the converter can be evaluated as described in the following paragraphs. According to one aspect, the losses of the converter can be used as a loss parameter. Such a converter can be used to convert the RF signal generated by the inverter to the higher voltage level required by the connected electrosurgical instrument. Such losses of the converter can be significant, and therefore if the converter losses are taken into account, the accuracy of the calculated power dissipation can be improved.

[0030] The primary current is measured at the converter in order to compare the current with the target current and, if necessary, actively counteract it, in particular with state feedback, for example in the case of distortion due to resonance, which occurs in particular with no load or with very high load.

[0031] In addition to the switching frequency, or as an alternative, measured currents and / or measured voltages or other parameters may be used to determine the losses of the converter.It is also possible to use models, in particular theoretical models.

[0032] According to one aspect, at least one loss parameter is recorded in advance (in particular before the inverter is put into operation) and assigned to the power dissipation and / or at least one loss parameter is recorded during operation of the inverter and assigned to the power dissipation.

[0033] Thus, at least for the first feature described in this regard, it is found that at least some of the above-mentioned loss parameters can be taken into account and used to calculate the power dissipation. Some loss parameters do not change rapidly, so that these can be taken into account before the inverter is started. Pre-recording, in particular before the inverter is put into operation, can in particular mean just before the operation. For example, the selection may include a specific operating step of the surgical instrument used, and loss parameters such as the degree of modulation may be selected separately or depending on the electrosurgical instrument used, or the selected RF mode is also known. Such parameters can be recorded just before starting the operation (i.e. just before starting the inverter to modulate a specific signal).

[0034] On the other hand, the ambient temperature of the inverter can also be measured before it changes over the next few minutes. This ensures that this loss parameter is specifically taken into account even at the start of operation. This ensures a redundant determination of the output current right from the start.

[0035] Additionally or alternatively, at least one loss parameter can be recorded during operation, and this is particularly true for loss parameters that may change during operation. In particular, it is proposed to take into account the component temperatures during operation of the inverter. It has been found that the temperature of the semiconductor components, in particular, and even further the temperature of the circuit components mentioned, may change rapidly and change their magnitude during operation (i.e. during a single operating task). Even an operating task that may only take a few seconds (e.g. 5 to 20 seconds) is long enough for the component temperature to change significantly. Therefore, as found, it is proposed to record the corresponding loss parameter during operation of the inverter and assign it to the power dissipation, so that it is taken into account when determining the comparative power.

[0036] According to one aspect, the inverter has a DC voltage input, and in order to record the comparative power, the input power is detected based on the DC voltage and / or DC current measurement at the inverter input. For this reason, the relevant structure includes an inverter with a DC input and an AC output. Therefore, the inverter receives a DC input power, and it is found that this input power can be used to calculate the comparative power. This DC power can be easily measured by measuring the DC voltage and DC current at the same time and calculating the power (in particular by multiplying the measured voltage and current) according to an example. If the relevant signals are each DC signals, this multiplication can be easily performed. In this way, a good basis for the input power can be achieved with simple measurement equipment and still with good accuracy. After further considering the dissipated power, the comparative power with good accuracy can be determined.

[0037] According to one aspect, the RF power acquisition device includes an FPGA (field programmable gate array) connected to the inverter output via an isolation converter to measure the RF signal. In conjunction with this, a DC measurement device is used to measure the power at the inverter input. If the FPGA is not used to measure the RF signal at the inverter output, a DC measurement device can also be used.

[0038] However, the combination of an FPGA with an isolation converter at the inverter output and a DC measurement device at the inverter input has particular advantages.

[0039] An FPGA connected to the inverter output via an isolation converter can measure the output power quickly and with high accuracy, and usually also in a reliable manner.

[0040] Therefore, it was found that a DC measurement device could be a less expensive, yet still very reliable, measurement solution just to be able to identify a fault in this measurement using an FPGA. This solution might not be as accurate as the FPGA used with respect to the output power, but it was found to be accurate enough to verify whether the FPGA is functioning properly or whether it has a fault.

[0041] The combination of an FPGA using an isolating converter on the output side and a DC measuring device on the input side therefore produces the described synergistic advantages.

[0042] It's also important to note that using an FPGA connected to the inverter output via an isolation converter is quite complex and, in particular, quite expensive. It has been found that, to ensure the required redundancy, a solution using a DC measurement device on the input side can avoid the need for two measurement solutions, each with an FPGA connected to the inverter output via an isolation converter. This combination therefore provides a good and reliable (yet inexpensive) solution.

[0043] Furthermore, the FPGA connected to the inverter via the isolation converter on the one hand and the DC measuring device on the other hand are based on different measurement principles, thus preventing systematic errors. For example, if an FPGA has a logic fault, this fault may also be present in the other FPGA, resulting in two erroneous measurements, which may provide similar but erroneous measurement values. In this case, comparing these two erroneous measurement values ​​may not be sufficient to identify the fault.

[0044] According to one aspect, a model is used to determine the comparative power and / or for determining the power dissipation. It has been found that by using a model, all significant elements and effects leading to power loss can be taken into account without much effort.

[0045] Such a model may specifically obtain all loss parameters as input and based on this the model may simply output a specific power dissipation.

[0046] Such a model may be or include a transfer model of the inverter that determines losses depending on certain modes of the inverter.

[0047] The model can be designed using known information such as the power dissipation of the inverter depending on the degree of modulation and / or the selected high-frequency mode. The power dissipation of the components of the inverter (particularly the semiconductors) is usually known, or at least the model of such semiconductors is known, as semiconductors are usually designed using simulations based on very accurate models of the semiconductors. Such models or simplified models based thereon can be used.

[0048] Additionally or alternatively, the power dissipation can be measured while recording the described loss parameters. This can be done offline before operating the RF generator. Complex simulations can also be used to test the entire RF generator, including the attached electrosurgical instrument, and based on such complex simulations, the behavior of power dissipation as a function of the power loss parameters can also be simulated. Based on this, a specific model for modeling power dissipation can be designed.

[0049] The power dissipation can also be continuously measured and based on this, a model can be designed or at least validated by online learning.

[0050] Based on the power dissipation determined using this model, a comparative power can be calculated. However, the calculation of the comparative power can also be performed by the model itself. In other words, the calculation of the comparative power can also be integrated into the functionality of the model. In this case, the model can directly output the comparative power. However, the power dissipation can also be output by the model as an additional value that can be used to verify the correct operation of the model.

[0051] According to one aspect, the comparative power is estimated using an adaptive and / or self-learning estimation method and / or estimation model with estimation parameters. It has been found that the method for estimating the comparative power can be provided as an adaptive and / or self-learning estimation method, thereby leading to increasingly improved, in particular increasingly accurate, results. This method can be implemented in a model, and the model can therefore be correspondingly adaptive and / or self-learning.

[0052] This method or model has estimated parameters that are used in particular to estimate the power dissipation and to estimate or calculate the comparative power based on this. This is also based on the power measured at the input side of the inverter. To give a simple example, one estimated parameter can be a factor by which the portion of the dissipated power is calculated by multiplying the recorded input power. The factor can have a starting value of 0.1 (i.e., 10%) and can be adapted during operation. The power dissipation can be calculated by adding the power dissipation of this portion to the power dissipation of the other portions.

[0053] It has also been found that the comparative power estimate, and in particular the power dissipation estimate required for it, is part of providing a redundant power measurement or redundant recording of power. That is, the comparative power is redundant for a fairly accurate power measurement, in particular the power measurement using an FPGA as described above. It has therefore been found that this measurement (i.e., the directly recorded output power measurement or estimate) can also be used for adaptation and / or self-learning of the comparative power recording or estimate.

[0054] The estimated parameter may specifically be any parameter that describes the relationship between any of the aforementioned loss parameters. Thus, the estimated parameter may be the relationship between the inverter's modulation level and the resulting power dissipation. It may also be the relationship between the selected RF mode and the resulting power dissipation. It may also be the relationship between the inverter's ambient temperature and the resulting power dissipation. It may also be the relationship between component temperature and the resulting power dissipation.

[0055] It should be noted that the power dissipation taken into account for calculating the comparative power based on the power measured on the input side can be the sum of the resulting power dissipations described for each of the loss parameters described. Of course, additional power dissipation components can also be added. In particular, there may be a residual power dissipation that covers all power dissipations that are not mentioned and / or not considered. The losses of the converter can also be added to the power dissipation. Therefore, the power dissipation used to calculate the comparative power based on the power measured on the input side can also be referred to as the total power dissipation. In other words, the comparative power is determined based on the recorded input power minus this total power dissipation.

[0056] One estimated parameter can be the relationship between any explicitly considered power dissipation components and the residual power dissipation. For example, if the explicitly considered power dissipation components sum to 100W, but it is found that the total power dissipation is actually 110W. For this example, the estimated parameter describing the relationship between the summed explicitly considered power dissipation and the residual power dissipation would be 0.1 according to this illustrative example. Alternatively, the estimated parameter could be the relationship between the explicitly considered power dissipation components (which sum to 100W) and the total power dissipation (110W in this example), and thus according to this example, the estimated parameter would be 1.1.

[0057] In particular, it is proposed to estimate the comparative power based on the initial settings or previously adapted values ​​of the estimated parameters. Thus, when the device, model, or method is first started, the estimated parameters are initially set to default values. Thereafter, the estimated values ​​can be further adapted, and the actual values ​​of these estimated parameters thus form the basis for further adaptation and / or self-learning.

[0058] Furthermore, the estimated comparative power is compared with the directly recorded output power. If, based on the comparison, the functionality of the RF generator is verified (i.e., if no fault is found), the directly recorded output power is identified as the verified output power. The relevant concept and finding here is that the value of the directly recorded output power is assumed to be quite accurate unless a fault is present. Therefore, if no fault is found, the value of the directly recorded output power is assumed to be very accurate.

[0059] Therefore, it is further proposed that the estimation parameters are adapted to align the estimated comparison power with the verified output power.

[0060] For the purpose of illustration with the above example and therefore only as an illustrative illustration with respect to only one estimated parameter, the estimated parameter used to take into account the residual power dissipation is 1.1. This calculates the 100W that is explicitly taken into account to a total power dissipation of 110W. However, if, by comparing the directly recorded output powers, it is discovered that the total power dissipation is actually 120W, the estimated parameter just mentioned can be changed from 1.1 to 1.2. However, it is proposed not to completely change the parameter, but to let it move towards the new value in an asymptotic manner. Based on the above example, the value of 1.1 can be modified by only 10% of the total difference. Therefore, the value will change from 1.1 to 1.11. If the same difference will be present again next time, it can be further modified from 1.11 to 1.12. This has a filtering effect from the identified difference to the resulting adjustment of the estimated parameter.

[0061] According to the present invention, an RF generator is also provided. This RF generator is designed to control at least one electrosurgical instrument connected to the RF generator. The electrosurgical instrument may be part of the generator or a separate component. However, specific functions are specific to the situation when the electrosurgical instrument is connected. Different electrosurgical instruments can also be connected in parallel or one after another to the same or different output plugs of the RF generator.

[0062] The RF generator is adapted to verify a power record of the RF generator. The recorded power is the power supplied to the electrosurgical instrument connected to the RF generator during operation.

[0063] The RF generator has an inverter for generating an RF signal. This RF signal can be fed to the electrosurgical instrument to supply energy and specific signals to the electrosurgical instrument to operate the electrosurgical instrument.

[0064] When operating, the inverter is supplied with current via the inverter input and transmits, via the inverter output, an RF signal with voltage and current values ​​for driving the electrosurgical instrument.The RF generator is further adapted to perform the following steps.

[0065] According to one procedure, the RF generator records the output power delivered via the RF signal by directly measuring the RF signal with the aid of an RF power acquisition device. This output power is referred to as the directly recorded output power. Another procedure involves recording a comparative power, which is based on the power measured at the input side of the inverter. A further procedure involves verifying the functionality of the RF power acquisition device by comparing the recorded comparative power with the directly recorded output power.

[0066] The RF generator may be adapted to do so by having an RF controller adapted to perform and / or control the steps for verifying the power record. These steps, in particular the steps according to any of the aforementioned aspects, may be performed using a computer program implemented by the RF controller, which may of course also perform other functions, in particular controlling the RF generator to provide an RF signal for operating a connected electrosurgical instrument.

[0067] According to one aspect, the RF generator and in particular its RF controller is adapted to perform at least one method according to any one of the aspects described above with respect to the method for verifying a power log. BRIEF DESCRIPTION OF THE DRAWINGS

[0068] The present invention will now be described by way of example based on embodiments with reference to the accompanying drawings.

[0069] Figure 1 A schematic diagram shows an RF generator for controlling at least one electrosurgical instrument.

[0070] Figure 2 A graph illustrating input power and output power relative to dissipated power is illustrated.

[0071] Figure 3 A simplified flow chart of a method according to at least one aspect is shown. DETAILED DESCRIPTION

[0072] Figure 1 A schematic diagram shows an RF generator 100 having an electrosurgical instrument 102 connected for operation on tissue 104, which is shown only symbolically. RF generators for controlling at least one electrosurgical instrument are typically very complex and include many components. However, in the illustrated RF generator 100, only some essential components are illustrated that are useful for understanding the present invention.

[0073] The RF generator 100 comprises a DC power supply 106 for supplying DC power to the RF generator 100. The DC power supply 106 may be connected at its power input 108 to a conventional power grid supplying a voltage of 110V or 230V.

[0074] The DC power supply 106 essentially rectifies the input voltage received at its power input 108 into a DC signal that is output at its power output 110. The DC power supply 106 may also include a device for varying the voltage amplitude at its power output 110. The power output 110 is connected to a DC input 112 of an inverter circuit 114. The inverter circuit 114 includes a DC intermediate circuit 116 with an intermediate capacitor 118. The inverter circuit 114 includes four semiconductor switches 121-124 connected to the intermediate circuit 116 for generating an AC output signal at an AC output 126 of the inverter circuit 114. This generation of the AC output signal is based on the DC voltage in the DC intermediate circuit 116. The semiconductor switches 121-124 may be IGBTs. The semiconductor switches 121-124 generate the RF output signal through pulse modulation, such as PWM. However, different circuits and modulation methods may be used.

[0075] To control the modulation, the four semiconductor switches 121-124 are controlled by an inverter controller 128. The inverter controller 128 is thus connected to each of these semiconductor switches 121-124 and, by controlling the semiconductor switches, also has any information related to the modulation, such as the modulation frequency and the degree of modulation. The inverter controller 128 can also know the temperature of the inverter circuit, or even the temperature of each of the four semiconductor switches 121-124 in detail. For this purpose, a circuit diagram may be provided, which is omitted in order to keep the schematic structure simple. Figure 1 A temperature sensor is not shown.

[0076] The RF converter 130 is connected to the AC output 126 of the inverter circuit. The RF converter 130 converts the AC signal of the AC output 126 to a higher voltage to provide this higher voltage RF signal at the generator output 132. Connected to this generator output 132 is the electrosurgical instrument 102, which receives this RF signal at a high voltage in order to operate using this signal.

[0077] When in operation, the inverter circuit 114 is controlled so that it provides an RF signal that will have a voltage amplitude as high as required at the generator output 132. One value for controlling the signal at the generator output 132 is the output power P supplied to the electrosurgical instrument 102 at the generator output 231. OUT .

[0078] Importantly, the output power P OUT This corresponds to a corresponding set value for the output power. This output power is delivered to the electrosurgical instrument and thus to the tissue 104 shown as part of the human body. Providing too much power can be dangerous, so it is important that the output power provided is correct.

[0079] To ensure this, there are current sensors 140 and voltage sensors 142. Based on these measured current and voltage signals, a power calculation unit 144 calculates the corresponding output power P OUT , the current sensor 140, the voltage sensor 142 and the power calculation unit 144 can be understood to form an RF power acquisition device 146. However, it is also possible to use the measured current and voltage signals in a part of the inverter controller 128 or in a part that is part of another controller of the RF generator and calculate the output power based on these signals.

[0080] In any case, such RF power harvesting means 146 are quite complex and expensive. One reason for this is that the current sensor 140 and the voltage sensor 142 measure at high voltage levels, so it is important to insulate these sensors from the power computing unit 144 or any other computing unit portion to which they are connected (whether a separate computing unit or part of another controller).

[0081] Since it is important to ensure that the correct power is supplied, there is usually a need for redundancy. As an alternative to directly measuring the output power with a second device similar to the RF power acquisition device 146, it is proposed to measure the power at the input of the RF generator 100. This is illustrated by a DC sensor 150, which is also only illustrated schematically. Such a DC sensor 150 can be a current sensor that measures the DC current. It is also possible to measure the DC voltage at the power supply output 110. Based on this, the input power P IN can be calculated as the input power of the RF generator. However, it can also be assumed that the voltage amplitude at the intermediate circuit is constant or known by the inverter controller 128.

[0082] In any case, the specific output power P can be measured more easily (ie, more accurately than with the RF power acquisition device 146). OUT This input power P is measured at the input of the inverter using a cheaper sensor than IN .

[0083] However, due to the power dissipation of several components, the input power P is found to be IN Higher than the output power P OUT Therefore, it is proposed to determine this power dissipation and this Figure 1 This is explained by way of example in FIG. The inverter controller 128 knows the control scheme of the four semiconductor switches 121 - 124 and also knows the modulation level of the inverter. As described above, the inverter controller may also have information about the temperature of the semiconductor switches 121 - 124 and thus can calculate the power dissipation of these semiconductor switches.

[0084] However, the power dissipation of the semiconductor switches may also be determined based on a known control scheme for the inverter and, therefore, the semiconductor switches, and based on the ambient temperature. In any case, the inverter controller 128 may calculate the dissipated power P of the inverter. DI . It is also expected that there will be significant power dissipation in the RF converter 130. Considering that this power is also Figure 1 As shown in FIG, the power dissipation of the RF converter 130 output converter P DT The value of all power dissipation collected in this way (according to Figure 1 In the example, the power dissipation P of the inverter DI and the converter's power dissipation P DT ) can be added to get the total dissipated power P D This is done in the summing element 152. This is for illustration purposes only and other power dissipation components may be considered, or one of the mentioned power dissipation components may be so small that it may be neglected, or may be a fairly constant value that it may therefore be considered a constant value.

[0085] However, in the subtraction element 154, the input power P IN Subtract the total dissipated power P from D , and the result is the comparative power P C Therefore, in logic block 156 the power P is compared. C With output power P OUT This logic block 156 may be a single separate block, or it may also be implemented in one of the controllers shown or other controllers.

[0086] In particular, it can be implemented in the general controller of the RF generator or in the inverter controller 128. In this logic block 156, the comparison power P is checked. C Is it equal to the output power P OUT However, there is an acceptable uncertainty, so in the logic block, a comparison checks whether the two power values ​​are approximately the same. One way to do this can be by subtracting one power value from the other and checking whether the magnitude of the difference is below a predetermined tolerance value. This predetermined tolerance value can be in the range of 5% to 20% of the output power or set power.

[0087] Therefore, in the logic block, the result of the comparison is "no" or "yes", so if the comparison result is "no", the generator can be stopped. Otherwise, if the comparison result is "yes", the generator can keep operating.

[0088] Figure 2 The relevant ideas of the present invention are briefly illustrated. Figure 2 , the RF inverter 200 receives input power PIN As input signal 202. The result is an output power P OUT The RC output signal 204. However, the output power P OUT Less than input power P IN , since there is dissipation and this is determined by the total dissipated power P D This is illustrated by a single dissipation signal 206. However, there may be multiple elements or parts or locations in the inverter that consume a portion of the dissipated power.

[0089] According to one aspect of the method Figure 3 As illustrated in the flowchart in FIG. 3 , a method flowchart 300 is shown. At the beginning of the method shown, the output power P is recorded according to the output power recording step 302. OUT In addition, the input power P at the input of the RF generator is recorded according to the input power recording step 304. IN , and there is also the dissipated power P recorded according to the dissipated power recording step 306 D .

[0090] The dissipated power or power dissipation is usually not a single power, but the sum of various dissipated power parts, such as Figure 1 By way of example, it illustrates the power dissipation P of the inverter. DI and the converter's power dissipation P DT .

[0091] In the subtraction step 308, the input power P IN Subtract the total dissipated power P from D , and the result is the comparative power P C .

[0092] In the comparison step 310, the output power P OUT and comparison power P C Comparison is performed. This can be done by subtracting two values ​​from each other and checking whether the result is less than a predefinable threshold value based on its absolute value. In this case, since there is only a small difference (i.e., less than the mentioned threshold value), the comparison result will be true or "yes".

[0093] If, according to the comparison at the comparison step 310 , the two values ​​are not identical (ie the difference is above the threshold just mentioned), the power generator will be stopped immediately according to a first stopping step 312 .

[0094] If the comparison is positive (i.e., the output power P OUT and comparison power P C Similar), the result is "yes", and the output power can be further checked according to the value check step 314 to see whether it is also the same as the set power P SETThe comparison can be performed similarly to that described with respect to the comparison step 310. Thus, not only the evaluated power value (ie the output power P OUT and comparison power P C ) are similar, and it is checked whether these values ​​are at the expected amounts (i.e. as set by the actual control of the electrosurgical instrument). Therefore, if the result of the value checking step is "yes", then according to the confirmation step 316, everything is OK, and the RF generator and therefore the electrosurgical instrument can remain in operation.

[0095] On the other hand, if the result of the value checking step is negative, the generator will be stopped according to a second stopping step 318 .

[0096] According to the present invention, the following problem is identified: To ensure the correct / regulated output of RF power, current and voltage, the monitoring of RF voltage and RF current is redundant. Therefore, the output parameters are determined and compared in almost the same process.

[0097] In the event that there is a discrepancy between the primary RF monitor and the redundant RF monitor in measured RF current and / or RF voltage, a fault condition exists.

[0098] By implementing the measurement method and / or using the same system to determine the output parameters (if an FPGA is used, this refers to hardware, FPGA code, and software), design errors in both paths can lead to the same undesirable behavior. Furthermore, performing RF current and voltage measurements is complex and expensive. Furthermore, the additional sensor in the application circuit results in higher leakage currents, which must be minimized.

[0099] Therefore, the known system may have the following disadvantages.

[0100] Known systems can be prone to design errors and system errors.

[0101] According to the known solution, there are also high costs since the measuring system has to be implemented twice.

[0102] Because of the additional bridging of the insulation distance by the sensor, higher leakage currents may occur.

[0103] Based on this, the following ideas and solutions are proposed.

[0104] Verification of the output parameters should be performed indirectly via the inverter input parameters and known losses. Taking into account the losses of the RF inverter (e.g., thermal losses, electrical losses), the input DC power (current, voltage) is determined and set relative to the RF output power. This is illustrated by the following equation:

[0105] P HF–Output =PDC–Input +P Loss

[0106] The power dissipation depends on various factors such as the modulation level of the RF, the RF mode, the ambient temperature, etc. These factors are determined during development and included in the calculations.

[0107] If there is a deviation between the calculated output power (which may be referred to as PHF output) and the actual output power (calculated from the RF output parameters), an error condition exists (eg, a defective voltage sensor) and the system can react to it.

[0108] The proposed solution has the following advantages.

[0109] The expensive design of an RF current-voltage sensor (a faster analog-to-digital conversion or converter (ADC) and a field programmable gate array (FPGA) and an additional microcontroller unit (MCU)) can be avoided.

[0110] Because fewer sensors are needed to bridge the application circuit and the secondary circuit, lower leakage current can be achieved.

Claims

1. A method for verifying a power record of an RF generator for controlling at least one electrosurgical instrument, wherein: The RF generator has an inverter for generating an RF signal, and The inverter is supplied with current via the inverter input, and transmitting an RF signal having a voltage value and a current value via an inverter output for driving an electrosurgical instrument, The method comprises the following steps: recording the output power delivered via the RF signal as directly recorded output power by directly measuring the RF signal with the aid of an RF power acquisition device, recording a comparative power based on the power measured on the input side of the inverter, and The functionality of the RF power acquisition device is verified by comparing the recorded comparative power with the directly recorded output power.

2. The method according to claim 1, characterized in that recording the input power at the inverter input, and The comparative power is determined by subtracting the power dissipation from the recorded input power.

3. The method according to claim 1 or 2, characterized in that The functionality of the RF power acquisition device is verified if the absolute value of the difference between the recorded comparison power and the directly recorded output power is below a predetermined verification threshold, wherein, in particular, The verification threshold is in the range between 5% and 30%, in particular, in the range between 10% and 20%, of the directly recorded output power.

4. The method according to any one of claims 1 to 3, characterized in that The power dissipation is determined based on at least one loss parameter from the list consisting of: The modulation degree of the inverter, The selected RF mode, The ambient temperature of the inverter, component temperatures of components of the inverter, The switching frequency of the inverter, and Converter losses.

5. The method according to any one of claims 1 to 4, characterized in that At least one loss parameter is recorded in advance, in particular before the inverter is put into operation, and allocated to the power dissipation, and / or is recorded during operation of the inverter and assigned to power dissipation.

6. The method according to any one of claims 1 to 5, characterized in that The inverter has a DC voltage input, and In order to record the comparative power, the input power is detected from DC voltage and / or DC current measurements at the inverter input.

7. The method according to any one of claims 1 to 6, characterized in that The RF power acquisition device includes an FPGA connected to the inverter output via an isolation converter to measure the RF signal, and / or To measure the power on the input side of the inverter, a DC measuring device is used.

8. The method according to any one of claims 1 to 7, characterized in that A model is used to determine the comparative power and / or determine the power dissipation.

9. The method according to any one of claims 1 to 8, characterized in that Adaptive and / or self-learning estimation methods and / or estimation models with estimation parameters are used to estimate the comparative power, wherein, in particular, estimating the comparison power based on an initial setting or a previously adapted value of the estimation parameter, comparing the estimated comparative power with the directly recorded output power, If, according to a result of said comparison, said functionality of said RF generator is verified, The directly recorded output power is then identified as the verified output power, and The estimation parameters are adapted to align the estimated comparison power with the verified output power.

10. An RF generator controlling at least one electrosurgical instrument, the RF generator being adapted to verify a power record of the RF generator, The RF generator has an inverter for generating an RF signal, and When the inverter is in operation, is supplied with current via the inverter input, and transmitting, via an inverter output, an RF signal having a voltage value and a current value for driving the electrosurgical instrument, And the RF generator is adapted to perform the following steps: recording the output power delivered via the RF signal as directly recorded output power by directly measuring the RF signal with the aid of an RF power acquisition device, recording a comparative power based on the power measured on the input side of the inverter, and The functionality of the RF power acquisition device is verified by comparing the recorded comparative power with the directly recorded output power.

11. The RF generator according to claim 10, wherein: The RF generator comprises an RF controller for performing and / or controlling the steps for verifying the power record, and wherein, The RF generator, in particular the RF controller, is adapted to perform the method according to any one of claims 1 to 9.

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