阅读说明：本技术 X射线发射器的电压供给装置、x射线装置和测试方法 (Voltage supply device for X-ray emitter, X-ray device and test method ) 是由 弗洛里安·鲍尔 安德烈亚斯·伯梅 彼得·克林格尔 于 2020-09-15 设计创作，主要内容包括：本发明涉及一种用于X射线发射器的电压供给装置,电压供给装置包括控制装置,其设立用于,在第二运行模式中检测第一与第二内部接触点之间的电压和/或经由第一和/或第二内部接触点的电流,根据检测到的电压和/或检测到的电流,操控用于发提示的提示装置和/或传输提示信号,其开关装置设立用于,在第一运行模式中将第一内部接触点与第一高压连接端连接而在第二运行模式中将其分开,和/或在第一运行模式中,将第二内部接触点与第二高压连接端连接而在第二运行模式中将其分开,和/或在第二运行模式中将第一内部接触点与第二内部接触点连接而在第一运行模式中将其分开。(The invention relates to a voltage supply device for an X-ray emitter, comprising a control device, which is designed to detect a voltage between the first and second internal contact points and/or a current flowing through the first and/or second internal contact point in the second operating mode, according to the detected voltage and/or the detected current, a prompting device for prompting is controlled and/or a prompting signal is transmitted, the switching device is designed to connect the first internal contact to the first high-voltage connection in the first operating mode and to disconnect it in the second operating mode, and/or in the first operating mode, the second internal contact is connected to the second high-voltage connection and in the second operating mode is disconnected, and/or to connect the first internal contact point with the second internal contact point in the second operating mode and to separate it in the first operating mode.)

1. A voltage supply device for an X-ray emitter (2) having a first high-voltage connection (11) and a second high-voltage connection (12) for connecting the X-ray emitter (2), wherein a voltage source (35) of the voltage supply device (3) is set up to provide an acceleration voltage or a heating voltage between a first internal contact (18) and a second internal contact (19) of the voltage supply device (3) in order to energize the X-ray emitter (2) in a first operating mode of the voltage supply device (3), characterized in that the voltage supply device (3) comprises a control device (16) which is set up to detect a voltage between the first internal contact (18) and the second internal contact (19) and/or via the first internal contact (18) and/or the second internal contact (19) in a second operating mode -the current of the internal contact (19), and, depending on the detected voltage and/or the detected current, actuating a prompting device (34) for prompting a user and/or transmitting a prompting signal to an external device (5), wherein the switching device (17) of the voltage supply device (3) is designed to connect the first internal contact (18) to the first high-voltage connection (11) in the first operating mode and to disconnect the first internal contact from the first high-voltage connection in the second operating mode; and/or the switching device is designed to connect the second internal contact (19) to the second high-voltage connection (12) in the first operating mode and to disconnect the second internal contact from the second high-voltage connection in the second operating mode; and/or the switching device is designed to connect the first internal contact (18) to the second internal contact (19) in the second operating mode and to disconnect the first internal contact from the second internal contact in the first operating mode.

2. Voltage supply device according to claim 1, characterized in that the voltage source (35) has a further internal contact (21) and is designed to apply an acceleration voltage between the further internal contact (21) and the first internal contact (18) and/or the second internal contact (19), wherein the switching device (17) is designed to connect the further internal contact (21) to a further high-voltage connection (14) in the first operating mode and to disconnect the further internal contact from the further high-voltage connection in the second operating mode.

3. Voltage supply device according to claim 2, characterized in that the control device (16) is designed to detect a voltage between the further inner contact (21) and the first inner contact (18) or the second inner contact (19) in the second operating mode, wherein the actuation of the prompting device (34) and/or the transmission of the prompting signal is additionally dependent on the voltage.

4. Voltage supply device according to one of the preceding claims, characterized in that the control device (16) is set up for, in the first operating mode, detecting a current via the first internal contact point (18) and/or the second internal contact point (19) and/or detecting a voltage between the first internal contact point (18) and the second internal contact point (19) and/or detecting a voltage between the further internal contact point (21) and the first internal contact point (18) and/or the second internal contact point (19) as a respective measurement variable and switching the voltage supply device (3) into the second operating mode when a changeover condition relating to one or more of the measurement variables is fulfilled.

5. Voltage supply arrangement according to any one of the preceding claims, characterized in that the switching device (17) comprises: a first oil switch (30) which, in the first operating mode, connects the first internal contact point (18) to the first high-voltage connection (11), and which, in the second operating mode, separates the first internal contact point from the first high-voltage connection; and/or a second oil switch (31) which, in the first operating mode, connects the second internal contact point (19) to the second high-voltage connection (12) and, in the second operating mode, separates the second internal contact point from the second high-voltage connection.

6. An X-ray device, in particular for medical imaging, having an X-ray emitter (2) for generating X-ray radiation (6), characterized in that the X-ray device (1) comprises a voltage supply device (3) according to one of the preceding claims.

7. A method for testing an X-ray device (1), wherein, in a first operating mode of a voltage supply device (3), an X-ray emitter (2) for generating X-ray radiation (6) is energized via a first high-voltage connection (11) and a second high-voltage connection (12) of the voltage supply device (3) in the following manner: providing an acceleration or heating voltage between a first internal contact (18) and a second internal contact (19) of the voltage supply device (3), wherein the first internal contact (18) is connected to the first high-voltage connection (11) and the second internal contact (19) is connected to the second high-voltage connection (12) by means of a switching device (17), wherein the voltage supply device (3) is switched into a second operating mode when a changeover condition is fulfilled, in which second operating mode the switching device (17) separates the first internal contact (18) from the first high-voltage connection (11) and/or separates the second internal contact (19) from the second high-voltage connection (12) and/or conductively connects the first internal contact (18) and the second internal contact (19) to one another, in this way, a current flowing via the first internal contact (18) and/or the second internal contact (19) and/or a voltage between the first internal contact (18) and the second internal contact (19) is detected by a control device (16), and a prompting device (34) for prompting a user is actuated and/or a prompting signal is transmitted to an external device (5) as a function of the detected voltage and/or the detected current.

Technical Field

The invention relates to a voltage supply device for an X-ray emitter, comprising a first high-voltage connection and a second high-voltage connection for connecting the X-ray emitter, wherein a voltage source of the voltage supply device is designed to provide an acceleration voltage or a heating voltage between a first internal contact and a second internal contact of the voltage supply device in order to energize the X-ray emitter in a first operating mode of the voltage supply device. In addition, the invention relates to an X-ray device and a method for testing an X-ray device.

Background

In an X-ray device, an X-ray emitter, such as an X-ray tube, is a lossy component. It is therefore entirely to be expected that during normal operation disturbances occur at certain time intervals, which disturbances may lead to a malfunction of the X-ray device. By monitoring the voltage supply, corresponding problems can generally be identified. Thus, emitter failure is often attributable to a damaged filament, which can be identified from disturbances in the heating current. Other damage, for example a short circuit, can be identified by evaluating the voltage dip.

Since most of the problems mentioned can be eliminated by replacing the X-ray emitter, the X-ray emitter is usually replaced first when there is a problem in the heating circuit or when there is a high voltage problem. However, this results in damage to the voltage supply, for example a defective heating transformer or high-voltage transformer, typically not being detected until after the X-ray emitter has been replaced, and the problem persists. Since the service technician typically does not carry the corresponding replacement component with him, a second service typically has to be scheduled, which results in a longer non-operational time of the X-ray device. Furthermore, unnecessary costs may arise, since the X-ray emitter may be unnecessarily replaced.

Alternatively, it is possible to first only perform measurements to determine the source of the fault. For example, an external device can be connected in order to be able to carry out a measurement of the high voltage or a measurement of the heating voltage without a connected X-ray emitter. However, the corresponding service is not always available.

It may also be possible to directly replace the power supply device or to replace a component of the power supply device in order to test the functional capability of the X-ray emitter. The method is also very costly and requires large and heavy additional components.

Disclosure of Invention

The object on which the invention is based is therefore to specify a possibility for achieving better maintainability of an X-ray apparatus with little technical effort and to limit the possible sources of malfunctions, in particular in the event of malfunctions.

According to the invention, this object is achieved by a voltage supply device of the type mentioned above, wherein the voltage supply device comprises a control device which is set up to detect a voltage between the first internal contact and the second internal contact and/or a current flowing through the first internal contact and/or the second internal contact in a second operating mode and to activate a prompting device for prompting a user and/or to transmit a prompting signal to an external device as a function of the detected voltage and/or the detected current, wherein the switching device of the voltage supply device is set up to connect the first internal contact to the first high-voltage connection in the first operating mode and to disconnect the first internal contact from the first high-voltage connection in the second operating mode; and/or the switching device is designed to connect the second internal contact to the second high-voltage connection in the first operating mode and to disconnect the second internal contact from the second high-voltage connection in the second operating mode; and/or the switching device is designed to connect the first internal contact point to the second internal contact point in the second operating mode and to disconnect the first internal contact point from the second internal contact point in the first operating mode.

According to the invention, in a second operating mode, at least part of the high-voltage connection is separated from the associated internal contact points and/or the internal contact points are connected to one another. The separation of the internal contact from the high-voltage connection can be achieved, and the X-ray emitter is also decoupled from the high-voltage cable which connects the high-voltage connection with the X-ray emitter. Thereby, the influence of external components on the current or voltage at the internal contact point can be excluded.

If, for example, a voltage dip between the first contact point and the second contact point is detected in the first operating mode, all external disturbances can be excluded by separating at least one, preferably all, of the high-voltage terminals from the respective internal contact point. Thus, if a voltage dip is also detected in the second operating mode, this indicates an internal fault, for example an internal short circuit or a damaged transformer. If, on the other hand, a voltage dip no longer occurs in the second operating mode, it can be concluded that the voltage dip is caused by an external component, namely the X-ray emitter or a high-voltage cable connecting the X-ray emitter to a high-voltage connection. By using the second operating mode, it is therefore possible to distinguish between an internal breakdown of the voltage supply device and an external fault, for example a leak or a short circuit, which leads to a voltage dip.

As already explained above, a further general problem is to detect disturbances of the heating current, in particular of a heating current which is too low. This may be caused by damage to the heating wire of the X-ray emitter, but also by damage to the power supply, for example a low-voltage transformer which should supply a heating current. A normally operable heating device, in particular a normally operable heating wire, of an X-ray emitter can be simulated by an electrically conductive connection of the first internal contact point to the second internal contact point, either directly or via a defined resistance or a defined impedance. Therefore, if too low heating currents or other disturbances of the heating currents are also measured in the second operating mode, this is a strong indication of the following: the voltage supply device or its components are damaged. If, on the other hand, the switching to the second operating mode eliminates disturbances of the heating current, problems outside the voltage supply device, in particular damaged heating wires, can result.

The first high voltage connection and the second high voltage connection may be used for energizing different electrodes of the X-ray emitter, i.e. for energizing the cathode and the anode. In this case, a high voltage, in particular a high dc voltage, is applied between the first internal contact point and the second internal contact point. In this case, damage to the voltage supply, the X-ray emitter and the high-voltage cable can lead in particular to voltage dips, so that in this case voltage measurements are preferably carried out. In order to exclude external influences on the voltage supply device, the two internal contact points should preferably be separated from the respective high-voltage connection. In this case, the connection of the first internal contact point and the second internal contact point to one another is rather unfavorable.

It is also possible for the first high-voltage connection and the second high-voltage connection to be used for applying a heating voltage to the cathode of the X-ray emitter. In this case, it can be particularly advantageous to check whether sufficient current flows through the first or second internal contact point. In this case, it is therefore particularly preferred to measure the current flowing through the first contact point and/or the second contact point. As explained above, in the second operating mode, the first internal contact point and the second internal contact point can be conductively connected in order to simulate an active heating wire and thus to detect whether there is an internal damage to the voltage supply.

In particular, an alarm signal can be emitted or transmitted if an alarm condition is fulfilled, for example if the detected voltage or the detected current is less than a respective limit value. Alternatively, the content of the issued indication or cue signal may also be related to the satisfaction of the cue condition.

Relatively high acceleration voltages are used for X-ray emitters, in particular in the medical field. The potential difference between the first internal contact and the second internal contact, or in particular in the first operating mode, the potential difference between the first high-voltage connection and the second high-voltage connection, may thus be several 10kV or more than 100 kV. Typically, the acceleration voltage is for example between 10kV and 150 kV. For example, 125kV may be used, but 260kV or more may also be used as the acceleration voltage. The acceleration voltage can be controlled, for example, in the following manner: the input voltage of the high voltage transformer is changed. For robust detection of a leakage, it can be advantageous to set a maximum output voltage before the voltage measurement for detection of a fault, or to measure the voltage dropped between the first internal contact point and the second internal contact point for a plurality of desired output voltages.

The voltage source may have a further internal contact and may be designed to apply an accelerating voltage between the further internal contact and the first internal contact and/or the second internal contact, wherein the switching device is designed to connect the further internal contact to the further high-voltage connection in the first operating mode and to disconnect the further internal contact from the further high-voltage connection in the second operating mode. In this case, in particular, a heating voltage can be applied between the first internal contact point and the second internal contact point. The high-voltage connection for supplying the heating voltage is therefore at the same time the opposite potential for the acceleration voltage in the first operating mode. This is known per se in the prior art and therefore should not be elaborated upon. With the proposed feasibility: the further internal contact is also separated from the associated high-voltage connection and thus from the X-ray emitter, in particular the voltage supply device can be completely decoupled from the X-ray emitter or the high-voltage cable connecting the X-ray emitter with the voltage supply device, whereby a robust distinction can be made between internal faults of the voltage supply device and external faults, for example of the cable or the X-ray emitter.

The number of high voltage connection terminals or internal contact points is not limiting. For example, three high-voltage connections or also more high-voltage connections can be routed to the cathode of the X-ray emitter in order to fill a plurality of heating wires. In a particularly advantageous embodiment, all high-voltage connections of the voltage supply device, which couple the voltage supply device to the X-ray emitter, can be separated from the associated internal contact points, and/or in the second operating mode all internal contact points for supplying the heating voltage or the heating current can be connected to one another.

The voltage supply means may be used to energize the plurality of X-ray emitters simultaneously or alternately. In a first operating mode, the high-voltage connection for a selected one of the X-ray emitters or for both X-ray emitters can be connected to the respectively associated internal contact point by means of a switching device. In a second operating mode, the high-voltage connections for all X-ray emitters can be separated from the internal contact points.

In particular, an alternating voltage can be used as the heating voltage. The heating voltage or the amplitude of the heating voltage can be significantly smaller, in particular at least by a factor of 10 or 100 smaller, than the acceleration voltage provided by the voltage supply.

The control device can be set up to detect a voltage between the further internal contact and the first internal contact or the second internal contact in the second operating mode, wherein the actuation of the prompting device and/or the transmission of the prompting signal is additionally related to said voltage. In particular, it can thus be checked that the acceleration voltage is correctly supplied by the voltage supply device, wherein, as explained above, the correct supply of the heating voltage or the heating current can be checked simultaneously or also at another point in time.

The control device can be set up to detect, in the first operating mode, a current via the first and/or second internal contact point and/or a voltage between the first and second internal contact point and/or a voltage between the further internal contact point and the first and/or second internal contact point as a respective measured variable, and to switch the voltage supply device into the second operating mode when a changeover condition relating to one or more measured variables is fulfilled. In particular, switching into the second operating mode can take place if the detected voltage or the detected current is below a respective limit value or is otherwise detected as being faulty, for example as a result of a sudden change.

The satisfaction of the changeover condition can indicate that the supply of the acceleration voltage or the heating current is disturbed. As explained at the outset, this may be the case for external reasons, i.e. in particular damage to the X-ray emitter or the high-voltage cable, or for internal reasons, e.g. damage to the heating transformer or the acceleration transformer. When a possible fault is detected, a change can be made to the second operating mode by the described method in order to check whether an internal fault of the voltage supply device is present. Subsequently, the user may be given a corresponding indication or a prompt signal may be transmitted to the external device, which indication or prompt signal may comprise corresponding information. Therefore, for example, information for presuming the presence of an internal failure or an external failure can be directly provided. Depending on this information, it is possible to provide alternative components which are supposed to be correct directly, or to avoid costly measures for service technicians. Overall, therefore, in the event of a malfunction, shorter maintenance intervals of the X-ray device can be achieved and costs can be saved in part.

In addition or alternatively to the above-described automatic change into the second operating mode, it is also possible in the second operating mode to trigger the operation manually at the voltage supply device or at a control computer of a device communicating with the voltage supply device, for example an X-ray device. For example, during installation or maintenance, it may be expedient to test the function of the voltage supply device independently of the faults which have been identified above.

The switching device may include: a first oil switch which connects the first internal contact point to the first high-voltage connection terminal in the first operating mode and separates the first internal contact point from the first high-voltage connection terminal in the second operating mode; and/or a second oil switch, which connects the second internal contact to the second high-voltage connection in the first operating mode and separates the second internal contact from the second high-voltage connection in the second operating mode. In particular, all the switching processes described, i.e. in particular the connection of the internal contacts of the voltage supply device, can also be realized by means of an oil switch. The oil switch is a circuit breaker in which the switch is located in a container filled with oil. The oil serves here to dissipate switching arcs that occur during the switching process. Oil switches per se are known in the art and are not described in detail.

In the voltage supply device according to the invention, the high-voltage connection can be at a floating potential as long as it is separated from the respective associated internal contact. However, it is also possible to pull the high-voltage connection to a defined potential, for example, ground potential.

In addition to the voltage supply device according to the invention, the invention relates to an X-ray device, in particular for medical imaging, having an X-ray emitter for generating X-ray radiation, wherein the X-ray device comprises the voltage supply device according to the invention.

The invention further relates to a method for testing an X-ray device, wherein, in a first operating mode of the voltage supply device, an X-ray emitter for generating X-ray radiation is energized via a first high-voltage connection and a second high-voltage connection of the voltage supply device by: providing an acceleration voltage or a heating voltage between a first internal contact and a second internal contact of the voltage supply device, wherein the first internal contact is connected to the first high-voltage connection and the second internal contact is connected to the second high-voltage connection by means of a switching device, wherein the voltage supply device is switched into a second operating mode in which the switching device separates the first internal contact from the first high-voltage connection and/or separates the second internal contact from the second high-voltage connection and/or conductively connects the first internal contact and the second internal contact to one another if a changeover condition is met, whereby a current via the first internal contact and/or the second internal contact and/or a voltage between the first internal contact and the second internal contact is detected by means of the control device, and operating a prompting device for prompting a user and/or transmitting a prompting signal to an external device according to the detected voltage and/or the detected current.

As already explained with regard to the voltage supply device according to the invention, the satisfaction of the changeover condition can depend on the detected current or the detected voltage. In addition or alternatively, the satisfaction of the changeover condition can be dependent on the voltage between the further internal contact point and the first internal contact point or the second internal contact point, as has likewise already been explained with regard to the voltage supply device according to the invention. However, the changeover condition can also be fulfilled if a manual changeover into the second operating mode has been triggered, for example by an operating element at the voltage supply device or other component of the measuring device, or by a signal from an external device, for example by remote polling by a service technician or the like.

The different features described with respect to the voltage supply device can be transferred to the method according to the invention with the advantages mentioned there. In particular, the signaling or transmission of the signaling signal can be correlated, in particular, with a further voltage drop between the first or second internal contact point and the further internal contact point. In a first operating mode, the further internal contact can be connected first to the further high-voltage connection of the voltage supply device, while in a second operating mode the further internal contact can be separated from the high-voltage connection by a switching device.

Drawings

Further advantages and details of the invention are explained below on the basis of exemplary embodiments and the associated drawings. In this case, the figure shows an embodiment of the X-ray device according to the invention, which comprises an embodiment of the voltage supply device according to the invention and by means of which an embodiment of the method according to the invention can be carried out.

Detailed Description

Fig. 1 shows an X-ray device 1 which can be used, for example, for medical imaging. X-ray radiation 6 is generated by the X-ray emitter 2, which, after it has passed through an examination object 7, for example a patient, impinges on the X-ray detector 4. The measurement data of the X-ray detector 4 can be detected by the device 5, for example a control and/or evaluation computer of the X-ray device 1, and used, for example, for imaging. Furthermore, the device 5 controls the voltage supply 3 of the X-ray device 1 in order to energize the X-ray emitter 2.

On the one hand, the X-ray emitter 2 is energized via a first high-voltage connection 11, a second high-voltage connection 12 and a third high-voltage connection 13 of the voltage supply device 3, via which the filament 10 of the cathode 9 of the X-ray emitter is energized in order to heat the cathode 9. On the other hand, the anode 8 is charged with a voltage via a further high-voltage connection 14, so that a high acceleration voltage of, for example, 125kV is applied between the cathode 9 and the anode 8. By means of the acceleration voltage, electrons emerging from the hot cathode are accelerated towards the anode 8 and impinge on the anode at a high velocity, thereby generating X-ray radiation 6. For clarity, a stationary anode is shown in fig. 1, wherein typically a rotating anode is used. The method for generating X-ray radiation is known in principle and therefore not described in detail.

In the case of such an X-ray device 1, a certain loss of the X-ray emitter 2 is expected. The filament 10 may in particular be damaged and sufficient heating of the cathode 9 is no longer possible, or leakage may occur due to the high voltages used, whereby voltage dips are accelerated. In both cases, it is no longer possible to generate X-ray radiation 6 robustly, so that damaged components should be replaced during service. Damage to the filament 10 can be identified in particular by: the heating current is detected by the control device 16 of the voltage supply device 3 via the ammeters 26, 27 and 28. Too low a heating current indicates a damage of the filament 10. The problem here is that damage to the lamp filament 10 and thus external faults cannot be easily distinguished in this case from damage to the voltage supply 3, for example damage to the transformer 24 for the heating current.

Instead, a short circuit or a leakage in the X-ray emitter 2 or in the high voltage cable 15 can be detected by the voltmeter 25 by monitoring the acceleration voltage. In this case, however, external leaks and short circuits cannot be distinguished from internal leaks or short circuits of the voltage supply 3 or, for example, from damage to the transformer 22 for high voltages.

In order to be able to distinguish between internal and external damage and thus in particular to be able to service the X-ray apparatus 1 more quickly or cost-effectively, the voltage supply device 3 can be operated in two different operating modes. In the first operating mode, the X-ray emitter 3 is supplied with a heating voltage and an acceleration voltage as usual. In order to provide the acceleration voltage, an ac voltage is initially provided by a prestage 38, which is of conventional design and therefore not described in detail, said ac voltage being converted via the transformer 22 into a high voltage, said high voltage being rectified by the rectifiers 36, 37 and being provided at the first internal contact 18 and the further internal contact 21 of the voltage source 35. In the first operating mode, the switching device 17 connects the first internal contact 18 to the first high-voltage connection 11 and the further internal contact 21 to the further high-voltage connection 14.

In order to provide the heating voltage, an ac voltage is again provided via a known input stage 23, which is not explained in detail, said ac voltage being converted by a transformer 24 in such a way that a heating voltage is generated between the first internal contact 18 and the second internal contact 19 and the third internal contact 20. The second internal contact is connected to the second high-voltage connection 12 via a switching device 17, and the third internal contact 20 is connected to the third high-voltage connection 13 via the switching device 17. Thus, in the first operating mode, energizing the X-ray emitter 2 corresponds to energizing the X-ray emitter normally.

If during operation in the first operating mode it is detected that the heating current or the acceleration voltage is disturbed, for example because the voltage detected via the voltmeter 25 between the inner contacts 18 and 21 or the current detected via the ammeters 26, 27, 28 via the inner contacts 18, 19, 20 falls below a limit value or fluctuates in a sudden manner, this indicates that: either one of the external components, i.e. in particular one of the X-ray emitter 2 or the high-voltage cable 15, is damaged or one of the voltage supply device 3 or its components is damaged.

To identify: whether an internal fault or an external fault is present, in which case the control device 16 can switch the voltage supply device 3 into the second operating mode. In the second operating mode, the switching device 17 separates all internal contact points 18, 19, 20, 21 from the respectively associated high-voltage connection 11, 12, 13, 14. This results in: in the second operating mode, the voltage detected via the voltmeter 25 between the inner contact points 18 and 21 is independent of the state of the external components, i.e. the X-ray emitter 2 and the high-voltage cable 15. If a disturbance of the voltage, i.e. for example an excessively low value or a sudden change, is also detected, this indicates: the voltage supply means 3 and in particular the transformer 22 may be damaged. Conversely, if the disturbance of the acceleration voltage is eliminated after the transition into the second operating mode, this indicates that: the disturbance is caused by external components, i.e. in particular by the X-ray emitter 2 or the high-voltage cable 15.

In the second operating mode, the first internal contact 18 is additionally short-circuited to the second internal contact 19 and the third internal contact 20 via a short-circuiting bridge 29 of the switching device 17. Thus, if the X-ray emitter 2 is connected to a properly functioning filament 10, a current flow through the internal contact points 18, 19, 20 and thus through the current meters 26, 27, 28 is approximately achieved, as it does. In the second operating mode, if the current measurement values detected via the current meters 26, 27, 28 continue to indicate a disturbance of the heating current, this indicates a damage of the voltage supply, in particular of the transformer 24. In contrast, if the disturbance of the heating current is no longer present in the second operating mode, it is assumed that it is caused by damaged external components, in particular by damaged lamp filaments 10.

Therefore, from the voltage and current detected in the second operating mode, it can be determined that: it is presumed whether there is an internal failure or an external failure. In order to communicate this to the user, for example, the display device 34 of the voltage supply device 3 can be actuated or a display signal can be transmitted to the external device 5 in order to indicate this to the user. In the example shown, only local signaling is carried out, but it is also possible, for example, to send the message directly to a service technician. This is possible, for example, by transmitting a text message, by sending an email, etc.

The switching device 17 can be formed by a plurality of switches, in particular oil switches 30, 31, 32, 33. The use of the oil switches 30, 31, 32, 33 enables robust switching of the occurring high voltages. The oil switches 30, 31, 32 can be selector switches which switch between the connection of the respective internal contact 18, 19, 20 to the respective high-voltage connection 11, 12, 13 and the connection of the respective internal contact 18, 19, 20 to the short-circuit bridge 29. The oil switch 33 can only be used to separate the internal contact point 21 from the high-voltage connection 14.

Although the invention has been illustrated and described in detail by means of preferred embodiments, the invention is not limited by the disclosed examples and other variants can be derived therefrom by the person skilled in the art without departing from the scope of protection of the invention.