Generator with plasma length display

Abstract

To provide a possibility of displaying the length of generated plasma to a treatment person even when the field of view to a treatment site and the generated plasma is restricted.SOLUTION: A generator 10 comprises a converter module having a transformer. A secondary winding of the transformer is electrically connected to an electrode 17 and a counter electrode 14 of an instrument 12. A primary winding of the transformer has one side connected to an operating voltage Ub and the other side connected to the ground via an electronic switch. The switch is periodically cut off, and voltage impulses for supplying plasma are generated in the secondary winding. A voltage detector that detects a voltage Up generated in the primary winding and displays it through an indicator device 24 functions to display the plasma length. The invention is based on a concept that the voltage Up generated in the primary winding, particularly the peak voltage, characterizes the length of plasma 16. Affecting parameters other than the plasma length have less significance with respect to the voltage Up measured at the primary winding.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an electrosurgical generator for performing HF surgical applications.

Background Art

[0002] Electrosurgical generators are basically known from the prior art. For example, Patent Document 1 discloses a generator composed of individual impulse generators, and those impulse generators are connected in parallel on the output side. Using this generator, specifically, voltage impulses for electrosurgically treating a patient can be generated.

[0003] Furthermore, Patent Document 2 discloses an electrosurgical generator for generating a DC voltage for treatment. For this purpose, the generator includes a flyback converter, and the flyback converter can apply a load to an output capacitor in which a DC current accumulates. Furthermore, the generator can include a plurality of such blocks for supplying current to a plurality of loads.

[0004] Patent Document 3 discloses a generator including a plurality of generator modules connected in series on the output side and operating according to the flyback converter principle. Each generator module includes an externally controlled switch and a transformer, and the primary winding of the transformer is connected in series to the switch. The secondary windings of different generator modules are connected in series to each other. The switch is specifically controlled externally in a control circuit so that the current in the primary winding of the transformer can be increased or the switch can be suddenly turned off. By induction, a high peak voltage is generated in the secondary winding of the transformer, and a smaller peak voltage is generated in the primary winding corresponding to the turns ratio. In order to avoid destruction of the switch due to the primary peak voltage being too high, a protection capacitor is connected in parallel to the switch.

[0005] Further prior art is formed by Patent Document 4, Patent Document 5, and Patent Document 6.

[0006] At least one of the above-described electrosurgical generators is suitable for supplying a voltage to an instrument provided with an electrode for treating biological tissue. For treatment, an electric spark or plasma can be maintained between the tissue and the electrode, and the length of the electric spark or plasma affects the physiological effect. The electrode can be disposed within a gas stream, particularly within an inert gas stream, such as an argon stream, and the gas stream is directed onto the biological tissue and thereby flows along the electrode. Such an instrument is referred to as an argon plasma probe or an argon plasma instrument.

[0007] An example of such an argon plasma instrument is known, for example, from Patent Document 7. This instrument comprises a tube or hose-shaped substrate including a channel for guiding gas and plasma that opens at the distal end. Inside the channel, an electrode for ionizing the gas jet is disposed, and as a result, the instrument generates a plasma jet that flows distally from the instrument.

[0008] Further instruments are known from Patent Document 8 or Patent Document 9.

Prior Art Documents

Patent Documents

[0009]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

[0010] During the treatment of biological tissue, the operator may have a restricted view of the treatment site. Therefore, it may be difficult for the operator to estimate the length of the generated plasma. However, the length of the generated plasma can significantly affect the treatment result obtained.

[0011] The object underlying the present invention is derived from the above and is to provide the possibility of displaying the length of the generated plasma to the operator even when the view of the treatment site and the generated plasma is restricted. [Means for Solving the Problems]

[0012] This object is achieved by the generator according to claim 1.

[0013] The electrosurgical generator according to the present invention is for providing an HF surgical instrument, in particular an instrument for generating a plasma jet. For this purpose, the generator comprises at least one converter module connected to a DC voltage at the input side so as to be supplied with power. The converter module includes an output section that outputs a sequence of high voltage impulses. Thereby, since the pulse sequence frequency can exceed a minimum frequency of 100 kHz, the impulse sequence generates a high frequency high voltage. In particular, it is possible to generate a non-sinusoidally generated high voltage.

[0014] The converter module includes a transformer having a primary winding and a secondary winding. The secondary winding forms the output of the converter module, and the primary winding is connected to an externally controlled electronic switch. The externally controlled electronic switch includes a control circuit and a control electrode connected to a controlled path that connects one connection of the primary winding to ground in a controlled manner. The other connection of the primary winding is connected to an operating voltage.

[0015] A connection point to which a voltage detector is connected is formed between the controlled path and the end of the primary winding connected to the controlled path. This voltage detector detects the voltage generated at this connection point. The voltage detector further includes an indicator device that generates a signal corresponding to the voltage detected by the voltage detector. The signal is a signal perceptible by the operator, for example, optically, or auditorily, or even tactilely perceptible. Combinations of such signals are also possible.

[0016] The voltage detected by the voltage detector depends on the length of the generated plasma. This plasma can occur between the electrode of the instrument connected to the generator and the biological tissue, and the biological tissue is also connected to the output of the generator via a neutral electrode. This applies to monopolar instruments. However, bipolar instruments having two electrodes connected to the generator are also possible, and plasma is generated between the two electrodes.

[0017] Based on the signal presented to the operator, the operator can draw conclusions about the length of the plasma present in the instrument and adjust their actions accordingly. For example, in this way, the operator can avoid generating a plasma length that is too long, or even a plasma length that is too short such that the electrode of the instrument and the tissue are in direct contact. The present invention helps the operator to control the appropriate distance between the instrument or electrode and the tissue and maintain the appropriate distance during the treatment.

[0018] The voltage detector can be a peak voltage detector that displays the maximum voltage occurring at the connection point. Furthermore, the peak voltage detector can be configured as a sample and hold circuit in which the voltage measurement performed by the voltage detector is synchronized with the switching of the externally controlled switch. For this purpose, the control circuit for controlling the switch can be connected to the voltage detector. In this way, the voltage detector can receive control impulses from the control circuit.

[0019] When the voltage detector is a peak voltage detector, the voltage detector usually includes a storage capacitor connected to the connection point via a current path in order to load the peak voltage applied to the connection point. When the voltage detector is a sample and hold circuit, a discharge current path can be connected in parallel to the storage capacitor. In order to always discharge the storage capacitor immediately before the controlled switch of the converter module is interrupted, thereby reaching a new peak voltage, the discharge current path can be provided with a controllable controlled discharge switch controlled by the control circuit.

[0020] The generator can include a plurality of converter modules of the described configuration. It is preferable that energy or power is supplied to these converter modules in parallel by a DC voltage. On the output side, the converter modules are preferably connected in series. Each converter module can "fire" individually, i.e., output a high voltage impulse at the output when its controlled switch is interrupted for a short period. In this case, the "firing sequence" is a sequence of high voltage impulses in which each converter module involved in the firing sequence has fired one or more times. The firing sequence is generated by the control circuit and corresponds to a sequence of control signals supplied to the switches of the converter modules. The control circuit can repeatedly repeat the sequence of control signals periodically in order to generate an HF output voltage. Therefore, the HF output voltage is generated by continuous repetition of the firing sequence.

[0021] During the ignition sequence, the control circuit preferably shuts off the control switches of the converter modules individually or together, whereby the other switches of the other converter modules are preferably maintained in the conducting state. At that time, the high-voltage output part of the converter module that is not currently igniting can pass the high-voltage impulse of the igniting converter module. The converter module ignites when its control type switch is shut off (preferably for a short period), and the high-voltage output impulse is thus generated.

[0022] Each of these converter modules can include a voltage detector according to the described configuration. However, this indicates that it may be sufficient to connect only a single converter module or only a part of the converter module to the voltage detector.

[0023] Further details of the embodiments of the present invention are derived from the dependent claims, as well as the specification and the related drawings.

Brief Description of the Drawings

[0024]

Figure 1

Figure 1a

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

[0025] FIG. 1 shows an apparatus G having a generator 10 according to the present invention. A device 12 for treating a biological tissue 13 is connected to the generator 10 via a line 11. The biological tissue 13 is connected to the generator 10 via a neutral electrode 14 and a line 15. Thus, FIG. 1 shows a monopolar device in which current flows from the device 12 toward the tissue 13. However, basically, the present invention can also be applied to a bipolar device or a multipolar device that acts on a biological tissue by a plasma 16. In FIG. 1, the plasma 16 is indicated by jagged arrows.

[0026] The device 12 includes an electrode 17 for generating a plasma. The electrode 17 is electrically connected to the generator 10 via a line 11. In FIG. 1, the device 12 is shown as a handle with the electrode 17 protruding. Such a device is suitable for laparotomy applications. Thereby, the electrode 17 can extend away from the handle 18 and can be configured in the type of a needle or a scalpel. However, the electrode 17 can also extend through the device 12 and be disposed inside a channel 19 that is connected to the supply device G at the proximal end 20. In this case, the supply device G includes respective gas supply parts in addition to the generator 10.

[0027] At the distal end 21 (Fig. 1a), the gas supplied into the channel 19 by the device G can flow out. Here too, the gas can be ionized by the electrode 17 so that an outflowing plasma stream 16 as indicated by the jagged arrow is formed. Thereby, the instrument 12 can be a probe that penetrates the working channels of instruments for laparotomy, laparoscopic instruments, and endoscopes and is guided, for example, towards the surgical site as shown in Fig. 1. However, what is common to all these applications is that the operator does not necessarily have unrestricted free view of the plasma stream 16 and its length.

[0028] As shown in Fig. 1, the device G includes a display device 22 and an operating element 23 such as a push button or a knob. Further, the device G includes an indicator device 24 that functions to display the length of the plasma stream 16. The indicator device 24 is shown in Fig. 1 as an optical indicator device that shows a light bar representing the length of the plasma stream 16. Further, the light bar can have a colored field at at least one of its ends, and the field can indicate an overly long and / or overly short plasma stream 16.

[0029] The indicator device 24 can be configured as an optical indicator device and can also be incorporated into the display device 22 if necessary. Further, additionally or alternatively, it is possible to provide the indicator device 22 with auditory indicator means. Additionally or alternatively, the indicator device 24 can generate a tactilely perceptible signal, such as a prominent vibration at the handle 18 or another location.

[0030] Fig. 2 shows a schematic diagram of a part of the electrical circuit in the generator 10. The reference signs already introduced are used with the same meaning hereinafter.

[0031] The electrosurgical generator 10 comprises a converter module 25, and a part of the converter module 25 is an electric circuit configured in the type of a flyback converter. The flyback converter is formed by an externally controlled electronic switch 26 in the form of, for example, a field effect transistor or a bipolar transistor or a bipolar transistor having an insulated gate, or another electronic switch, and the electronic switch is connected in series to the primary winding 27 of the transformer 28. Thereby, the first end of the primary winding 27 is connected to the positive operating voltage U b and the other end of the primary winding 27 is connected to the connection point 29. At this connection point 29, the externally controlled electronic switch is connected to one end (drain or collector), and the other end (source or emitter) of its controlled path is connected to the ground potential M.

[0032] The externally controlled switch 26 further includes a control electrode 30 connected to the control circuit 31 for unblocking or blocking the controlled path of the electronic switch 26 in a controlled manner.

[0033] The transformer 28 further includes a secondary winding 32, one end of which is connected to the electrode 17 of the instrument 12 via a coupling capacitor 33 if necessary. The other end of the secondary winding is connected to the neutral electrode 14 via an additional coupling capacitor 34 if necessary, whereby the neutral electrode 14 is attached to the patient and thus to the biological tissue 13. The secondary winding 32, or the electrode facing away from the secondary winding in the coupling capacitors 33, 34 if any, forms the output of the converter module 25 and thus of the generator 10.

[0034] A protection capacitor 35 or yet another protection circuit can be connected in parallel to the electronic switch 26. The protection capacitor 35 has one connection connected to the connection point 29 and the other connection connected to the ground. The protection capacitor 35 serves to limit the voltage of the switch 26.

[0035] A voltage detector is connected to connection point 29, and the voltage detector detects the voltage U that occurs at connection point 29, and thus at switch 26 (and similarly at protection capacitor 35). p Indicator device 24 is part of voltage detector 36 and serves to generate a signal corresponding to the detected voltage U p (FIG. 6) and characterizes its magnitude. For example, indicator device 24 can be arranged in device G or generator 10, or further in appliance 12, or at another location.

[0036] Voltage detector 36 is preferably configured as an integrating detector or further as a peak voltage detector. Voltage detector 36 includes a storage capacitor C connected to connection point 29 via a load circuit 37. In the simplest case, load circuit 37 is a diode polarized in the direction of flow with respect to the voltage U p occurring at connection point 29. It is preferable to use a diode with a very low capacitance. In order to reduce the parasitic capacitance of load circuit 37, a plurality of diodes can be connected in series with each other.

[0037] On the one hand, indicator device 24 indicates the voltage of capacitor C, and on the other hand, an evaluation circuit 38 that periodically discharges storage capacitor C is connected in parallel with storage capacitor C.

[0038] The generator described so far operates as follows.

[0039] To treat tissue 13, electrode 17 is brought close to tissue 13. Here, control circuit 31 continuously opens and closes switch 26, thus igniting converter module 25. When switch 26 is conducting, current flows at the (e.g., positive) operating voltage U bFrom this, it flows through the primary winding 27 from the start end of the winding characterized by the dot to the end of the winding, and then to the ground potential M via the connection point 29 and the conducting switch 26. Each time the control circuit 31 supplies a cut-off impulse to the control electrode 30, the switch 26 is cut off so that no more current flows to the ground. Here, the direction of the current flow is converted to the secondary winding 32, and the current continuously flows from the start end of the winding characterized by the dot to the end of the winding (and thus to the coupling capacitor 33), and then to the electrode 17 via the coupling capacitor 33.

[0040] Due to the spark discharge from the generated high-voltage impulse to the tissue 13, a combustible plasma 16 is generated in the air, in the vapor, or more specifically in any of the supplied gases, such as argon. Thereby, the increasing voltage between the electrode 17 and the tissue 13 or the neutral electrode 14 serves as a measure of the length of the plasma 16. The voltage applied between the electrode 17 and the neutral electrode 14 also exists in the secondary winding 32. Corresponding to the turns ratio of the transformer 28, each voltage U p exists in the primary winding 27, and thus also at the connection point 29, in the form of each voltage impulse. For the sake of explanation, refer to the figures according to FIGS. 5 and 6.

[0041] In FIG. 5, the switch 26 is conducting during the period t1. The conducting state is characterized by the capital letter L on the vertical coordinate. At the end of the period t1, the switch 26 is cut off. The cut-off period characterized by the period t2 in FIG. 5 begins. The non-conducting state is characterized by the letter N on the vertical coordinate. At the start of the cut-off period t2, the voltage impulse U p generated in the primary winding 27 and also increases in the secondary winding 32. This voltage impulse U p is shown in FIG. 6 as three different quantities U p1 , U p2 , U p3 , which correspond to three different plasma lengths of the plasma 16. Therefore, this shows that the voltage impulse U p becomes higher as the plasma 16 becomes longer.

[0042] FIG. 7 shows the voltage U of the storage capacitor C for this purpose. The voltage impulse U p During, the current flows through the storage capacitor C via the load circuit 37, applying a load to the storage capacitor C up to the respective voltages U1, U2 or U3. The voltage impulse U p The higher the voltage U is, the higher the voltage U of the storage capacitor C becomes.

[0043] If necessary, the storage capacitor C can be discharged from time to time. For example, the storage capacitor C can be discharged during or after the switch 26 is switched on again during the conduction period t3, as shown in FIG. 5. FIG. 8 shows such a discharge impulse D1.

[0044] The indicator device 24 generates a signal corresponding to, for example, the voltages U1, U2 or U3, since the light bar represented by the indicator device 24 changes its length stepwise or continuously according to the voltage U of the storage capacitor C.

[0045] FIG. 3 shows a further developed type of the generator according to FIG. 2, so the above description applies, taking the following description further into account while maintaining the reference signs already introduced.

[0046] The generator according to FIG. 3 comprises a plurality of converter modules 25, 25a, 25b, 25c, and preferably the converter modules 25a, 25b, 25c have the same structure as the converter module 25, and the above description applies with the addition of the respective letter subscripts.

[0047] The load circuit 37 is at least connected to the connection point 29 and is connected to the circuit point E via a series connection of diodes polarized in the flow direction. The current path preferably leads from this circuit point E to the storage capacitor C via the resistors 38 and the capacitor 39 connected in parallel. The indicator device 24 is connected to this storage capacitor C.

[0048] A discharge circuit 42 having a discharge current path 43 in which a discharge switch 40 is arranged is provided to discharge the storage capacitor C sometimes, periodically, or as needed. The discharge switch 40 includes a controlled path connected in parallel with the storage capacitor C. Its control electrode 41 is connected to a control circuit 31 that controls not only all the switches 26, 26a, 26b, 26c but also the discharge switch 40. In this case, the impulse D1 shown in FIG. 8 represents the period during which the discharge switch 40 is released from blocking, that is, conducting. Thereby, the discharge of the charge of the storage capacitor C becomes possible, whereby the voltages U1, U2, or U3 decay, that is, decrease to near zero.

[0049] In many cases, it is sufficient for the load circuit 37 to simply connect the connection point 29 to the circuit point E. However, it may also be useful to connect one or more of the converter modules 25a, 25b, 25c each having a respective load circuit 27a, 27b, 27c to the circuit point E.

[0050] The control circuit 31 can operate and stop the converter modules 25, 25a, 25b, 25c in cooperation, that is, open and close the respective switches 26, 26a, 26b, 26c. For this purpose, the individual switches 26, 26a, 26b, 26c can individually transition from the conducting state to the non-conducting state during a short period of the blocking period t2 according to FIG. 5 to generate, that is, ignite, voltage impulses in the respective secondary windings 32, 32a, 32b, or 32c. The switches of the converter modules 25, 25a, 25b, 25c that do not ignite are preferably conducting. At this time, the high-voltage impulses respectively output from the igniting converter modules 25, 25a, 25b, 25c can pass through the secondary windings with low ohmic resistance of the converter modules that do not ignite, and as a result, can flow through the secondary windings 32, 32a, 32b, 32c connected in series with each other.

[0051] In connection therewith, FIG. 10 shows a firing sequence F based on the voltage U17 of the electrode 17. The converter modules 25 and 25a fire simultaneously, and then the converter modules 25b, 25c fire. The voltage detector 36 connected to the converter module 25 detects the voltage U p and, accordingly, loads the capacitor C. Since the control circuit 31 activates the discharge switch 40, the charge is maintained until the load on the capacitor C is removed again. If only the voltage U p of one of the converter modules is monitored, the control circuit 31 can activate the discharge switch 40 at the end of the firing sequence F. If a plurality or all of the converter modules 25, 25a, 25b, 25c are connected to the voltage detector 36, the capacitor can also be discharged each time before the next converter module fires.

[0052] Normally, the control circuit 31 fires the converter modules 25, 25a, 25b, 25c individually or together according to a preset scheme. Thereby, as shown in FIG. 10, equal or different amounts of high-voltage impulses can be generated. If the discharge of the storage capacitor C occurs only after the end of the firing sequence, the storage capacitor C accumulates a voltage characterized by the highest of the generated high-voltage impulses present in the firing sequence F. This voltage characterizes the optical arc length or plasma length indicated by the indicator device 24.

[0053] FIG. 9 shows the correlation between the voltage U c of the storage capacitor C and the optical arc length l. Different voltages U1, U2 occur at different arc lengths l1, l2, whereby the relationship is approximately linear in a relatively wide range, although at least limited. Irrespective of its linearity, the voltage U c is a measure of the optical arc length l.

[0054] Another modified embodiment of the generator according to the present invention is shown in FIG. 4. The reference numerals already introduced are also applicable to this embodiment since the explanations related thereto are applied as appropriate. The difference between the embodiment according to FIG. 4 and the embodiment according to FIG. 3 is only the polarity of the secondary windings 32, 32a, 32b, 32c. In the embodiment according to FIG. 3, all of the secondary windings 32, 32a, 32b, 32c are identically polarized since the starting ends of the windings characterized by a dot are directed towards the neutral electrode 14, whereas in the embodiment according to FIG. 4, different polarities exist. The secondary windings 32, 32a have their starting ends facing the neutral electrode 14, and the secondary windings 32b, 32c have their starting ends facing the electrode 17. However, it should be noted that other groupings and polarities can also be provided.

[0055] In the embodiment according to FIG. 4, when the converter modules 25, 25a are firing, they generate a positive voltage impulse at the electrode 17, and the converter modules 25b, 25c generate a negative voltage impulse at the electrode 17. (This applies in the case of a positive operating voltage U b and in the case of a negative operating voltage U b the situation is reversed.) By combining converter modules 25, 25a, 25b, 25c with different polarities, symmetric and asymmetric HF output voltage sequences can be generated. Also, in the case of a symmetric HF impulse sequence including positive and negative peak voltages, the plasma length can be successfully displayed as described above by detecting the voltage U p at appropriate connection points 29 and / or 29a, 29b, 29c.

[0056] The generator 10 according to the present invention comprises at least one converter module having a transformer 28, and the secondary winding 32 of the transformer 28 is electrically connected to the electrode 17 and the opposing electrode 14 of the instrument 12. One side of the primary winding 27 of the transformer 28 is the operating voltage U bis connected on one side, and on the other side is connected to the ground M via the electronic switch 26. The switch 26 is periodically interrupted, thereby generating a voltage impulse in the secondary winding 32 that supplies a spark or another plasma for the medical treatment of the patient. The voltage U p generated in the primary winding 27 is detected, and a voltage detector 36 that displays it by the indicator device 24 serves to display the plasma length. The present invention is based on the concept that the voltage U p generated in the primary winding 27, particularly the peak voltage, characterizes the length of the generated plasma 16. The inventor has discovered that parameters that affect factors other than the plasma length are less significant with respect to the voltage U p measured in the primary winding 27.

Explanation of Reference Numerals

[0057] 10 Generator G Device 11 Line 12 Instrument 13 Living Tissue 14 Neutral Electrode 15 Line 16 Plasma, Plasma Flow 17 Electrode 18 Handle 19 Channel 20 Proximal End 21 Distal End 22 Display Device 23 Operating Element 24 Indicator Device 25 Converter Module 26 Externally Controlled Electronic Switch 27 Primary Winding of Transformer 28 28 Transformer U b Operating Voltage 29 Connection Point M Ground Potential F Ignition Sequence 30 Control Electrode 31 Control Circuit 32 Secondary Winding 33, 34 Coupling Capacitor 35 Protection capacitor 36 Voltage detector C Storage capacitor U c Voltage of storage capacitor C 37 Load circuit t1, t3 Conduction period of switch 26 t2 Cut-off period of switch 26 U p , U p1 ~U p3 Voltage impulse U, U1~U3 Voltages of storage capacitors l, l1, l2 Optical arc lengths E Circuit point 38 Resistor 39 Capacitor 40 Discharge switch 41 Control electrode D, D1 Discharge impulses 42 Discharge circuit 43 Discharge current path

Claims

1. An electrosurgical generator (10) particularly for HF surgical applications, a converter module (25) including an externally controlled switch (26) connected to a control circuit (31) and a transformer (28), wherein a primary winding (27) of the transformer (28) is connected in series with the switch (26), and a secondary winding (32) of the transformer (28) is connected to an electrode (17) and a counter electrode (14), and the converter module (25) is such that a patient to be treated can be arranged between the electrode (17) and the counter electrode (14); A voltage detector (36) connected to the switch (26) and detecting a generated voltage (U ｐ ), the voltage detector (36) including an indicator device (24) that generates a signal corresponding to the detected voltage (U ｐ ) a generator.

2. The externally controlled switch (26) has one end connected to a reference potential (M) and the other end connected to a connection point (29), the connection point (29) being connected to an end of the primary winding (27), and the voltage detector (36) being connected to the connection point (29). The generator according to claim 1.

3. The voltage detector (36) is a peak voltage detector. The generator according to claim 1 or 2.

4. The voltage detector (36) is a sample and hold circuit. The generator according to claim 1 or 2.

5. The voltage detector (36) includes a storage capacitor (C) connected to the switch (26) via a load circuit (37). The generator according to claim 1.

6. The load circuit (37) is formed by at least one diode, preferably a plurality of diodes connected in series with each other. The generator according to claim 5.

7. A discharge circuit (42) is assigned to the storage capacitor (C), the discharge circuit (42) including a controllable discharge current path (43) connected in parallel with the storage capacitor (C). The generator according to claim 5 or 6.

8. The discharge circuit (42) is connected to the control circuit (31) such that the control circuit (31) can alternately switch the discharge current path (43) between a non-conductive state and a conductive state. The generator according to claim 7.

9. The control circuit (31) alternately opens and closes the externally controlled switch (26), and the control circuit (31) further cuts off the discharge current path (43) when the switch (26) is interrupted. The generator according to claim 8.

10. Before interrupting the switch (26), the control circuit (31) temporarily opens the discharge current path (42). The generator according to claim 9.

11. In addition to the converter module (25), at least one additional converter module (25a) is provided, and the secondary windings (32, 32a) of the converter modules (25, 25a) are connected in series. The generator according to claim 1.

12. The converter modules (25, 25a) have the same structure. The generator according to claim 11.

13. At least some of the secondary windings (32, 32a) of the converter modules (25, 25a) are connected in series in the same direction. The generator according to claim 11.

14. At least some of the secondary windings (32a, 32b) of the converter modules (25a, 25b) are connected in series in opposite directions. The generator according to any one of claims 11 to 13.

15. The voltage detector (36) is connected to only one of the converter modules (25, 25a, 25b, 25c). The generator according to any one of claims 11 to 13.

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