Power supply device for an X-ray imaging device, X-ray imaging device and associated method

Abstract

Power supply device (2, 2a, 2b) for a, in particular medical, X-ray imaging device (1), wherein the power supply device (2, 2a, 2b) comprises: - a mains connection means (3) for connection to a power network (4) providing an input AC voltage, which has at least one fuse arrangement (5) which does not trip below a safety current, - an actively controllable converter arrangement (12), in particular comprising a rectifier (22) and a step-up converter (23), for converting the input AC voltage into an output DC voltage as a supply voltage for the X-ray imaging device (1), - an electrical energy storage device (16), and - a control device (17) for controlling the converter arrangement (12) to limit the power consumption from the power grid (4) as a function of the safety current and to provide missing required power for the X-ray imaging device (1) from the energy store (16), characterized in that the control device (17) is designed to control the converter arrangement (12) for the time-dependent limitation of the power consumption from the power grid (4) according to a current-time profile (20, 21), in particular related to a mains current flow from the power grid (4), wherein the current-time profile (20, 21) is derived from a temporal triggering profile (8) of the safety arrangement (5).

Description

The invention relates to a power supply device for an in particular medical X-ray imaging device, wherein the power supply device has:a grid connection means for connection to a power grid which provides an input alternating voltage and which has at least one safety arrangement which does not trigger below a safety current,an actively controllable converter arrangement, in particular comprising a rectifier and a step-up converter, for converting the input alternating voltage into an output direct voltage as a supply voltage for the X-ray imaging device,an electrical energy store, anda control device for controlling the converter arrangement to limit the power consumption from the power grid as a function of the safety current and to provide missing required power for the X-ray imaging device from the energy store.In addition, the invention relates to an X-ray imaging device and to a method for operating a power supply device.X-ray imaging has been a modality that has been established for a long time, in particular in medical technology. X-ray imaging devices (X-ray apparatuses) have the particular feature that there are severe load fluctuations in the electrical power consumption. For example, an X-ray imaging device in standby mode receives only a relatively small and largely constant basic load from the power grid. However, if an X-ray image is performed, a very high peak load occurs for a very short period of time, which must likewise be supplied by the power supply system. This peak load occurs in order to generate an x-ray pulse for image recording, in particular with the aid of an x-ray tube or another x-ray emitter component of the x-ray imaging device.These requirements are fulfilled in the prior art by providing a suitable supply connection of the power network. For this purpose, however, an adaptation of the power network must often take place at the site of the planned installation of the X-ray imaging device, for example with regard to increased safety measures and increased line cross sections. This requires additional effort. This results in an interruption of the operating procedures and thus additional costs. Thus, it can represent an inhibition threshold if a medical facility, for example a hospital or a doctor's practice, wishes to transfer to an X-ray device of higher performance.This is because even in the case of X-ray sources which manage with low peak powers, for example in the case of mammography apparatuses, a conventional, conventional protective contact socket is not sufficient for the operation of the X-ray imaging device and changes have to be made in the installation on the power supply system side.To counteract these problems, it has been proposed in the prior art, for example, to use X-ray imaging devices with an energy storage function that buffers the peak energy required. In this case, an additional electrical energy store is provided in the X-ray device, wherein a required power demanded by the remaining components of the X-ray imaging device is covered, by means of a control device, partially from the energy store and partially from the power grid whenever said required power exceeds a power grid that can be provided from the power grid. In this case, the maximum network power that can be drawn from the power network is usually limited by the control device in such a way that safety measures provided on the network side, for example a safety arrangement comprising at least one safety device, do not trigger. With respect to such fuse arrangements, it is known to specify an associated safety current, which is also referred to as rated current or guaranteed minimum holding current, in which it is ensured that the fuse arrangement does not trip and the power supply breaks. In order to realize such a limitation of the power consumption from the power grid to a specific grid power, it is known, for example, to actuate an actively actuatable converter arrangement of a corresponding power supply device for the X-ray imaging device in such a way that the current in the power grid does not exceed the safety current. This intervention can be implemented, for example, as part of a regulation of the converter arrangement, which also serves for power factor correction (PFC). As such converter arrangements, for example, a sequence of a bridge rectifier and a step-up converter or else a flyback converter can be used. It is relevant here that a controllable converter topology exists. In other approaches, it has also been proposed in the prior art to provide an additional, external uninterrupted power supply between the X-ray imaging device and the power grid.DE 10 2010 042 565 A1 discloses, by way of example, a device for supplying an imaging medical device with electrical energy, wherein the device is designed such that the imaging medical device can be operated solely with the operating DC voltage provided by a charger, with the operating DC voltage provided by the charger and an energy store or solely with the grid-independent operating DC voltage provided by the energy store. Lithium-ion batteries are used as energy stores, wherein the device in this case allows an X-ray apparatus to be operated at a conventional supply connection of a power grid without having to load the power grid unduly. In particular, the X-ray apparatus can be operated on a normal three-phase 16 ampere domestic connection, wherein 16A represents an exemplary safety current.DE 103 55 424 A1 describes an X-ray apparatus having means for storing energy which comprise an ultra capacity in order to compensate for deficits in the energy which can be drawn from an energy supply network.DE 10 2009 010 219 A1 relates to an imaging tomography device which uses an energy store in order to enable the operation of the tomography device without special measures using the normal house connection at the customer. The power network at the customer therefore no longer has to be adapted to the maximum required power in high-power operation by laying higher-safety lines.Especially in the field of X-ray imaging devices, in which peak powers need to be called up only briefly, capacitors, in particular supercapacitors (supercapacitors), are suitable as energy stores, since these can be charged and discharged quickly. However, it is desirable to dimension them small for cost, installation space and cost reasons. Other rapidly chargeable and dischargeable storage technologies, for example accumulators, are also expensive and complex to realize.US 2017 / 0027537 A1 discloses medical high frequency diagnostic x-ray machines and power supplies therefor. An alternating current or current of a battery is increased by means of a boost circuit and provided via a capacitor.US 2018 / 0263591 A1 describes a CT system with built-in uninterrupted power supply and a stabilizer designed for peak sharing. For this purpose, an energy storage component and an associated energy storage management system are provided.The object of the invention is therefore to make possible an improved utilization of the power network in X-ray imaging devices and / or to allow cost-effective energy stores realized.To achieve this object, according to the invention, a power supply device, an X-ray imaging device and a method for operating a power supply device according to the independent claims are provided. Advantageous embodiments are evident from the dependent claims.In a power supply device of the type mentioned at the beginning, it is provided according to the invention that the control device for controlling the converter arrangement for time-dependent limiting of the power consumption from the power grid is designed according to a current-time profile, in particular related to a grid current flow from the power grid, wherein the current-time profile is derived from a temporal triggering profile of the fuse arrangement, which in particular takes into account a thermal fuse triggering in the event of continuous overloading.The starting point is a classic power supply device whose actively controllable converter arrangement serves in particular not only for the at least intermediate rectification of the AC input voltage from the power grid in order to provide an DC output voltage as the supply voltage, but can also serve for power factor correction (PFC). Accordingly, the control device is particularly advantageously designed for controlling the converter arrangement for power factor correction and / or for regulating the converter arrangement with respect to a predefined voltage for the DC output voltage. Superimposed on such a basic control is now a current-time profile, which can be stored in the control device or implemented by components, which ultimately describes a limit current that can be drawn from the power grid in a time-dependent manner. This means that a safety current, and therefore a guaranteed minimum holding current, which can be drawn from the power grid for any time without the safety arrangement triggering is no longer used, but instead a time-variable limit current is used, which results according to a triggering profile of the safety arrangement. In the context of the present invention, two findings are ultimately combined. On the one hand, current fuse arrangements, which can have circuit breakers as fuses, for example, have different mechanisms which, when considered together, define a temporal triggering profile for the average current (in particular RMS current) in the power grid by the fuse arrangement. A first such mechanism can be a magnetic safety mechanism which triggers when a specific, fixed triggering current, which is usually significantly higher than the safety current, is exceeded. The second mechanism can be a thermal mechanism which is intended to protect against overheating and the current required for triggering thereof through the safety arrangement decreases over time and approaches in particular the safety current, optionally taking into account a safety distance. It should be noted here that, of course, these triggering characteristics of the different mechanisms are generally determined by tolerance ranges, wherein, for safety purposes, the lower limit of the tolerance range, i.e. the lowest possible triggering current, can be considered here as a triggering profile. Viewed in time, the triggering profile for the fuse arrangement thus gives the possibility of drawing a significantly higher grid current from the power grid for a specific period of time, for example a few seconds, than would be possible as rated current according to the safety current. For conventional known safety arrangements in Germany, the safety current is usually 16 A in single-phase networks, as also already indicated in the cited prior art. However, the analysis of the safety arrangement reveals that it is entirely possible, for example in the first five seconds of the heavy load on the power network, in particular exceeding a threshold value, to draw a multiple, for example up to five times, of the safety current from the power network without triggering the safety arrangement. This is contrasted with the second finding of the present invention that peak powers are usually only required for quite short periods of time in x-ray imaging devices, in particular when x-ray pulses are to be output.Thus, if one considers the actual temporal triggering profile of the safety arrangement in conjunction with the short peak power time scales in x-ray imaging devices, the described time window, in which higher grid currents can be drawn from the power grid without the safety arrangement triggering, can be used to increase the energy that can be drawn overall from the power grid. In other words, the current-time profile can describe a limit current that exceeds the safety current, in particular by at least twice, for low time values and / or can at least approach a limit current described by the safety current for higher time values. It is of course conceivable to utilize the triggering profile as completely as possible, depending on how it is considered, but it is also conceivable for the current-time profile for each time and / or each time interval to describe a grid current, which is lower in particular by a percentage safety distance, than a triggering current of the triggering profile at this time. In general terms, the current-time profile therefore essentially provides limit current values for different points in time / time intervals, which allow temporary exceeding of the safety current by the safety arrangement and thus allows greater power extraction and thus energy extraction from the power grid for shorter periods of time. The limit-value utilization of the triggering characteristic of the fuse arrangement therefore provides an energy excess value which influences the dimensioning of the energy store in a cost-effective, weight-effective and construction-space-effective manner, in particular as regards the use of capacitor energy stores (electrolytic capacitors or supercapacitors). This means that, within the scope of the present invention, it is particularly advantageous if the energy store is a capacitor, since here the short-term gains of energy from the power grid are particularly sufficient and become noticeable in the design, in particular can lead to great savings in terms of the dimensioning (capacitance, size,... ). In this case, an output-side capacitor of the converter arrangement is particularly advantageously used as the energy store.In other words, the present invention provides a regulation of a converter device according to a predefinable current-time characteristic (the current-time profile) for limiting avoidance of triggering of a safety arrangement on the power supply system side, which permits minimal dimensioning of capacitor energy stores. In particular, it is possible in a particular advantage to use only the capacitor on the output side of the converter arrangement as an energy store.It should be noted here that the power supply device according to the invention can also be used in other applications, and therefore consumer devices, in which brief peak powers rather than required powers occur in comparison with a relatively low basic power as required power. Welding devices may be mentioned as an example of this.For X-ray imaging devices, the present invention can be understood as a development of configurations which allow operation of X-ray imaging devices also at normal home connections. This is naturally possible without problems within the scope of the present invention, as well, after the electricity consumed or the power consumed from the power grid is throttled by the special control method such that the safety arrangement installed in the house installation remains below the triggering characteristic. This means that the mains connection used by the mains connection means of the power supply device is not electrically overloaded and the mains connection on the mains side does not have to be adapted. It should be emphasized here that, in a particularly advantageous embodiment of the present invention, the current-time profile can be adaptable to different trigger profiles on the user side, so that it can ultimately be suitably selected for the X-ray imaging device according to the planned installation location. In other words, any desired current-time profile can be expediently set.In general, in the present invention, the power or energy required for an x-ray recording is only partially recorded from the power network during the recording process. The difference is provided from the energy store, wherein the present invention allows the installed energy store with its energy store properties to be dimensioned smaller on account of the better utilization of the power grid. With regard to the energy store, it should also be noted that the dependence of the X-ray imaging device on the internal network resistance and on the network quality also decreases, since the required energy can be obtained from the internal energy store during an X-ray recording.With regard to the converter arrangement, it is preferred according to the invention to use a rectifier, in particular a bridge rectifier, with a downstream step-up converter (step-up converter), but it is essential that a topology is present in the power supply device in which the current consumption and thus power consumption can be actively limited or influenced by active switching elements.It should also be noted here that at least one further converter device can also be connected downstream of the converter arrangement according to the present invention, which device converts, for example, the DC output voltage, which can be in the range from 380 to 750 V, into an AC operating voltage of an X-ray radiator and, if appropriate, further components of the X-ray imaging device, for example in the range from 40 to 140 kW.In a specific embodiment of the present invention, it can be provided that the control device has a regulating unit for providing a control variable, in particular a duty cycle of a pulse width modulation for actuating a switching element, to the converter arrangement as a function of at least one first measured variable, in particular comprising the output DC voltage of the voltage converter, and an adaptation unit for pre-adaptation of at least one of the at least one first measured variables for implementation of the current-time profile. Such an adaptation unit can also be understood as a shaper unit, since it ultimately suitably adapts the profile of the or a first measured variable such that the desired current limitation for the mains current by the regulation occurs in the regulating unit. It is therefore proposed to adapt a first measured variable which represents an input value of the control, so that the other control strategy and also the specific configuration of the control unit can remain completely unchanged. This is of particular advantage in the case of an analogous configuration of the regulating unit, since the regulating unit can then remain completely unchanged and the control device overall nevertheless enables the desired limitation of the power consumption from the power grid. However, even in the case of digital control, which is implemented, for example, via a control algorithm, the previous components of the control algorithm can ultimately remain unchanged if only an algorithm section, which implements the adaptation unit and predicts the value of the first measurement variable in accordance with the current-time profile, is added. The adaptation unit can be connected, for example, between a measuring device, for example a tap point, of the first measured variable and the regulating unit.A development in this context provides that the power supply device has a measuring device for recording at least one second measured variable describing the current power consumption from the power grid, in particular the grid current flowing in the converter arrangement and / or a measuring current describing it, wherein the adaptation unit is designed for evaluating the second measured variable for adapting at least one of the at least one first measured variable for converting the current-time profile. For example, it is thus conceivable to measure the mains current or a measurement current describing it in the converter arrangement, to analogally and / or digitally compare it with the current-time profile and to undertake a corresponding modification of the first measurement variable in order to specifically implement the current-time profile in the adaptation unit. A current is particularly suitable as one of the at least one second measured variable, wherein, in addition to in particular the mains current and / or the measurement current as a further second measured variable, a voltage, for example an input DC voltage to the step-up converter, which is associated with the mains current or measurement current can also be measured with particular advantage. If, in a concrete exemplary embodiment, a step-up converter is used, it usually has an inductance, in particular a coil, wherein the grid current flowing therein mainly describes the power extraction from the grid, in particular together with the corresponding input DC voltage for the step-up converter, that is to say the rectified input AC voltage. However, it is preferred here to carry out a current measurement downstream of an actuatable switching element of the boost converter, wherein the switching element is usually actuated at a high frequency on the basis of pulse width modulation, such that there is a sufficiently close relationship between the measurement current there and the grid current in the inductance, in particular as regards its profile, from which a RMS value of the grid current comparable to the limit current of the current-time profile can be derived. Naturally, however, other measurement points are also conceivable. In exemplary embodiments, it may also be possible to measure a power directly as a second measured variable.Expediently, at least one second measurement variable can be used, which is also included in the control system as a further of the first measurement variables in any case. In other words, it can be provided that the control unit is likewise designed to take account of the second measured variable as a further first measured variable which is not adapted by the adaptation unit when ascertaining the control variable. This applies in particular to the input DC voltage of a step-up converter and the measurement current downstream of the actively driven switching element, since, for power factor correction and regulation to a predefined voltage as the output DC voltage, the input DC voltage for the step-up converter arising downstream of the rectifier is usually multiplied by a deviation from the predefined voltage in order to derive a duty cycle for pulse width modulation as the control variable, it being possible for instantaneous current regulation to be carried out preferably on the basis of the measurement current by the switching element. In such cases, the second measured variable therefore also serves as a further first measured variable and is likewise incorporated into the control.In a somewhat generalized manner, it can be said to be particularly advantageous for the first measured variable which can be adapted by the adaptation unit to be the DC output voltage and for the at least one second measured variable which is taken into account for the adaptation to describe the mains current and / or the AC input voltage (and therefore optionally also the DC input voltage downstream of a rectifier). If the DC output voltage as the first measurement variable is modified such that it appears lower, the power consumption from the power grid would be increased by the control, and conversely it would be the case if the DC output voltage is increased as the first measurement variable, so that this makes it possible to influence the power consumption from the power grid in a particularly simple manner, in particular by carrying out an addition and / or subtraction process. Expediently, the at least one second measured variable describes the power drawn from the power grid and thus also the current flowing there, in particular in the fuse arrangement, which can be compared, for example, with the limit current from the current-time profile. In particular with regard to an analog conversion, a "shaping" of the output DC voltage as the first measurement variable can be implemented particularly straightforwardly, since the addition or subtraction operation is to be implemented with little complexity. Although it is also conceivable in principle to modify other first measured variables, for example the input AC voltage or the input DC voltage, this has proven to be more complex, since multiplication operations, as would then be necessary, are more difficult to implement and additionally represent non-linear interventions.As already indicated, it is particularly advantageous if, in the case of an analog configuration of the control unit, the adaptation unit, in particular an analog adaptation unit realized external to the control unit, is connected upstream of the control unit, in particular with respect to the first measured variable which can be adapted by it. In this way, the control unit does not have to be changed and can be taken over directly, as is known from the prior art. It is precisely in single-phase power grids that the use of analog regulating units is still common because of their simple and favorable implementation, so that a further clear advantage is produced here by the present invention. The adaptation unit itself can be implemented in an analog manner, for example using logic elements and / or comparators and / or operational amplifiers and / or resistors and / or capacitances. If, for example, a current-time profile is to be implemented which is intended to allow a first limit current, for example two to five times the safety current, for a first time interval up to four seconds, and is intended to define the safety current as the limit current for the remaining time interval after four seconds, it is conceivable to use two comparators having different time constants / time elements. In the second comparator, a time delay can then be provided, which ensures that it only becomes effective after the first time interval, in particular after four seconds. These two comparators can both be separately adjustable in order to allow adaptation to the corresponding trip profile of a fuse arrangement to be used, and thus to derive the current-time profile actually used from the trip profile. In addition to such a simple exemplary embodiment, a multistage, analogous realization of more complex current-time profiles is of course also possible.However, it is also conceivable within the scope of the present invention that both the control unit and the adaptation unit are digitally implemented, for example in the form of at least one chip or IC. In this case, a control algorithm is ultimately implemented by the control unit and also the adaptation unit. Such digital control topologies are frequently used in the prior art for larger powers and / or three-phase power grids, but are also generally useful.In addition to the power supply device, the present invention also relates to an X-ray imaging device, having a power supply device according to the present invention. All embodiments with respect to the power supply device according to the invention can be transferred analogously to the X-ray imaging device according to the invention, so that the already mentioned advantages can also be obtained therewith.In particular, as already mentioned, it can be provided that the X-ray imaging device has a further converter device operated by the output DC voltage, in particular an inverter for generating an operating voltage of an X-ray tube of the X-ray imaging device. In this case, it is conceivable both to ultimately generate an operating voltage for all components of the X-ray device and to provide different operating voltages for different components.Finally, the present invention also relates to a method for operating a power supply device for an in particular medical X-ray imaging device, wherein the power supply device has:a grid connection means for connection to a power grid which provides an input alternating voltage and which has at least one safety arrangement which does not trigger below the safety current,an actively controllable converter arrangement, in particular comprising a rectifier and a step-up converter, for converting the input alternating voltage into an output direct voltage as a supply voltage for the X-ray imaging device,an electrical energy store, anda control device for controlling the converter arrangement to limit the power consumption from the power grid as a function of the safety current and to provide missing required power for the X-ray imaging device from the energy store,which method is characterized in that the control device controls the converter arrangement for time-dependent limiting of the power consumption from the power grid according to a current-time profile, in particular related to a grid current flow from the power grid, wherein the current-time profile is derived from a temporal triggering profile of the fuse arrangement, which in particular takes into account a thermal fuse triggering in the event of continuous overloading.All explanations regarding the power supply device according to the invention and regarding the X-ray imaging device according to the invention also apply accordingly to the method according to the invention.Further advantages and details of the present invention are evident from the exemplary embodiments described below and on the basis of the drawings. The following are shown: FIG. 1 shows functional components of an X-ray imaging device according to the invention, FIG. 2 shows a triggering characteristic of a safety arrangement together with current-time profiles that can be derived therefrom, FIG. 3 shows a first specific embodiment of a power supply device according to the invention, and FIG. 4 shows a second specific embodiment of a power supply device according to the invention.FIG. 1 shows a schematic schematic diagram of functional components of an X-ray imaging device 1 according to the invention, which has a power supply device 2 according to the invention, via the network connection means 3 of which the X-ray imaging device 1 can be connected to a network connection of a power network 4 only indicated here. The grid-side grid connection is assigned a safety arrangement 5. For this, a guaranteed minimum holding current is known as safety current / rated current, for which the safety arrangement 5 does not trigger even if this safety current is held for a longer time. Furthermore, a triggering characteristic in the form of a triggering profile is known with respect to the fuse arrangement 5, which triggering characteristic indicates at which triggering currents are occurring after which time a triggering takes place.Such a triggering characteristic is illustrated by way of example in FIG. 2. Plotted downwards is the multiple of the safety current I N, in the horizontal is the time in seconds / min, and, with respect to the shown triggering characteristic, is therefore the triggering time after which the safety arrangement 5 is triggered at a specific multiple of the safety current.In the present case, the at least one securing of the securing arrangement 5 is based on two triggering mechanisms, namely a magnetic triggering mechanism, the triggering characteristic of which is indicated by the tolerance range 6, and a thermal triggering mechanism, the triggering characteristic of which is indicated by the tolerance range 7. The lower limit of the tolerance ranges 6, 7 with respect to the current, i.e. the upper limit shown in FIG. 2, forms the triggering profile 8, which denotes the minimum possible triggering current.Returning to FIG. 1, the X-ray device 1 comprises, in addition to the power supply device 2, further components, of which a recording arrangement 9 with an X-ray radiator 10 and an X-ray detector 11 is shown by way of example. In order for the X-ray radiator 10 to be able to illuminate an object for X-ray recording, it must generate X-ray radiation at very high required powers for a short time. This is done, for example, by means of an X-ray tube. In order to be able to provide the operating voltage for the X-ray radiator 10, the power supply device 2 first has a converter arrangement 12 which provides an output DC voltage, for example in the range from 380 to 750 V, which is passed on to a further converter device 13 which provides the operating AC voltage, for example in the range from 40 kW to 140 kW, for the X-ray radiator 10 (and optionally further components of the X-ray imaging device 1).The converter arrangement 12 has an active converter topology 14, only indicated here, with at least one switch element that can be controlled for regulating the converter arrangement 12. Furthermore, the converter arrangement 12 in the present case comprises a capacitor 15, for example an electrolytic capacitor or a supercapacitor, which, as will be explained below, also serves as an energy store 16 of the power supply device 2.The operation of the power supply device 2 is controlled by means of a control device 17 which in the present case first comprises a regulating unit 18. The control unit 18 controls the converter arrangement 12 to a preset voltage for power factor correction and with respect to the DC output voltage. However, the control device 17 also has an adaptation unit 19. The adaptation unit 19 ensures a temporal limitation of the power that can be drawn from the power grid 4 according to a current-time profile, which ensures that the safety arrangement 5 does not trigger, but nevertheless allows the safety current to be exceeded at least temporarily and thus allows the power to be drawn from the power grid 4 that is at least temporarily greater and thus energy to be drawn from the power grid 4.If, for example during an x-ray recording, the required power of the x-ray imaging device 1 is greater than the grid power currently removable from the power grid 4, the remaining difference is provided from the energy store 16.The current-time profile is derived from the triggering profile 8, as is likewise shown in FIG. 2. Two current-time profiles 20, 21 are schematically shown there by way of example. The current-time profile 20 is a simple, analogously uncomplicated triggering profile, as will be explained below, which allows about 2.8 times the safety current for a first time interval up to about four seconds, but only the safety current in the time interval after four seconds. However, the current-time profile 21 follows the triggering profile 8 more precisely at a safety margin.In any case, higher currents than the safety current can be drawn temporarily from the power grid 4, so that there more grid power and thus also more energy can be achieved temporarily, which is why the capacitor 15 can be dimensioned smaller. It should be noted here that times in which such a peak power is required as required power are frequently also rather small in the case of X-ray imaging devices 1, for example lie within the time interval shown up to four seconds, so that an actually relevant energy excess value is obtained.The control device 17 according to the general description in FIG. 1 thus permits analog or digital PFC and predefined voltage regulation taking into account a predefinable current-time characteristic for limiting avoidance of triggering of the fuse arrangement 5, which permits minimal dimensioning of capacitors 15 / generally energy stores 16 used.FIGS. 3 and 4 show specific exemplary embodiments of power supply devices 2 a, 2 bin accordance with the invention. In the case of FIG. 3, an analogous realization of both the control unit 18 and the adaptation unit 19 is provided.Starting from the power grid 4, the equivalent circuit diagram of which, in addition to the fuse arrangement 5, also exhibits impedances there, the converter arrangement 12 comprises a rectifier 22 and a boost converter 23 (boost converter). In addition to an inductance 24, as is known in principle, the step-up converter 23 comprises an actuatable switching element 25, a freewheeling diode 26 and the capacitor 15.The analog circuit of the control unit 18 is unchanged compared to known devices. The first measured variables used according to which regulation is carried out are the DC output voltage (U SENSE,DC), the DC input voltage (U IN,DC) and a measurement current (I SENSE) measured via a measuring device 27, the control variable forms a duty cycle (PWM) to the switching element 25, and the measurement current is recorded via the measuring device 27 downstream of the switching element 25 on the ground side. From this, however, the RMS value of the mains current can be derived with sufficient accuracy by the inductance 24.It is understood that the control unit 18 now described is purely exemplary. Of course, any fundamentally known control topology of the prior art can be used here.In the depicted, purely schematically shown control topology, the deviation of the DC output voltage from the preset voltage (U REF) is first determined by an error amplifier 28 and can be prefiltered in an optional filter 29 before multiplication with the DC input voltage takes place in a multiplier 30. In a block 31, the pulse width modulation is carried out, specifically in the present case as instantaneous current control taking into account the measurement current.In order to implement the limitation of the power draw in accordance with the current-time profile 20 or 21, the adaptation unit 19 is connected upstream of the regulating unit 18 as a first measured variable in the supply path of the DC output voltage, wherein a circuit 32 converting the current-time profile 20, 21 is used, which circuit can expediently also be designed analogously. This circuit 32 pre-adjusts the value of the DC output voltage, wherein in particular an increase will lead to a lowering of the power extraction from the power grid 4 within the scope of the control of the control unit 18. As input variables, referred to here as second measured variables, the measurement current and the input DC voltage are used as describing the power extraction from the grid. For analog conversion of the current-time profile 20, for example, two comparators can be used which have different delay elements, so that the second comparator only becomes active after four seconds (end of the time interval) and the different limit currents can accordingly be realized in a simple manner in the two time intervals used. Of course, more complex configurations are also conceivable, for example if the current-time profile 21 is to be approached closer.The adaptation unit 19 can therefore also be understood as a shaper unit after the first measured variable of the DC output voltage is pre-adapted using second measured variables in such a way that the control of the control unit 18 without changing it inevitably limits the power consumption in such a way that the (temporal) triggering characteristic 6, 7 of the fuse arrangement 5 is taken into account.FIG. 3 shows another embodiment with digital control device 17, wherein for the sake of simplicity the active converter topology 14 is again only shown schematically, also as a clarification that different embodiments of the converter arrangement 12 can be used. The regulation is implemented here as a regulation algorithm, which is supplemented by a step 33 implementing the adaptation unit. Without being restricted to this specific exemplary embodiment, the remaining control algorithm, which remains unchanged, once again shows the determination of the deviations of the output DC voltage from the predefined voltage in an error calculation step 34, a voltage regulator 35, a current regulator 36 and a pulse width modulation step 37.Although the invention has been illustrated and described in more detail by the preferred exemplary embodiment, the invention is not restricted by the disclosed examples and other variations can be derived therefrom by the person skilled in the art without departing from the scope of protection of the invention.

Claims

Power supply device (2, 2a, 2b) for an, in particular medical, X-ray imaging device (1), wherein the power supply device (2, 2a, 2b) has: - a grid connection means (3) for connection to a power grid (4) which provides an input alternating voltage and has at least one safety arrangement (5) which does not trigger below a safety current, - an actively drivable converter arrangement (12), in particular comprising a rectifier (22) and an upconverter (23), for converting the input alternating voltage into an output direct voltage as supply voltage for the X-ray imaging device (1), - an electrical energy store (16), and - a control device (17) for controlling the converter arrangement (12) for limiting the power consumption from the power grid (4) as a function of the safety current and for providing a lack of required power for the X-ray imaging device (1) from the energy store (16), characterized in that the control device (17) for controlling the converter arrangement (12) is designed for time-dependent limiting the power consumption from the power grid (4) according to a current-time profile (20, 21), in particular related to a grid current flow from the power grid (4), wherein the current-time profile (20, 21) is derived from a temporal triggering profile (8) of the safety arrangement (5).Power supply device according to Claim 1, characterized in that the current-time profile (20, 21) describes a grid current, in particular lower by a percentage safety distance, for each point in time and / or each time interval than a triggering current of the triggering profile (8) at this point in time, and / or describes a limit current exceeding the safety current, in particular by at least twice, for low time values, and / or at least approximates a limit current described by the safety current for higher time values.Power supply device according to Claim 1 or 2, characterized in that the energy store (16) is a capacitor (15), in particular an output-side capacitor (15) of the converter arrangement (12).Power supply device according to one of the preceding claims, characterized in that the control device (17) has a regulating unit (18) for providing a control variable, in particular a duty cycle of a pulse width modulation for actuating a switching element (25), to the converter arrangement (12) as a function of at least one first measurement variable, in particular comprising the DC output voltage of the boost converter (23), and an adaptation unit (19) for pre-adaptation of at least one of the at least one first measurement variables for implementation of the current-time profile (20, 21).Power supply device according to Claim 4, characterized in that it has a measuring device (27) for recording at least one second measurement variable describing the current power consumption from the power grid (4), in particular the grid current flowing in the converter arrangement (12) and / or a measurement current describing it, wherein the adaptation unit (19) is designed for evaluating the second measurement variable for adapting at least one of the first measurement variables for converting the current-time profile (20, 21).Power supply device according to Claim 5, characterized in that the regulating unit (18) is likewise designed to take account of the second measurement variable as a further first measurement variable which is not matched by the matching unit (19) when ascertaining the control variable.Power supply device according to Claim 5 or 6, characterized in that the first measurement variable which can be adapted by the adaptation unit (19) is the DC output voltage, and the at least one second measurement variable which is taken into account for the adaptation describes the mains current and / or the AC input voltage.Power supply device according to one of the preceding claims, characterized in that the control device (17) is designed to actuate the converter arrangement (12) for power factor correction and / or to regulate the converter arrangement (12) with respect to a predefined voltage for the DC output voltage.X-ray imaging device (1) comprising a power supply device (2, 2a, 2b) according to one of the preceding claims.X-ray imaging device according to claim 9, characterised in that it has a further converter device (13) operated by the output DC voltage, in particular an inverter for generating an operating voltage of an X-ray tube of the X-ray imaging device (1).Method for operating a power supply device (2, 2a, 2b) for an, in particular medical, X-ray imaging device (1), wherein the power supply device (2, 2a, 2b) has: - a grid connection means (3) for connection to a power grid (4) which provides an input alternating voltage and has at least one safety arrangement (5) which does not trigger below a safety current, - an actively drivable converter arrangement (12), in particular comprising a rectifier (22) and an upconverter (23), for converting the input alternating voltage into an output direct voltage as a supply voltage for the X-ray imaging device (1), - an electrical energy store (16), and - a control device (17) for controlling the converter arrangement (12) for limiting the power consumption from the power grid (4) as a function of the safety current and for providing a lack of required power for the X-ray imaging device (1) from the energy store (16), characterized in that the control device (17) controls the converter arrangement (12) for time-dependent limiting the power consumption from the power grid (4) according to a current-time profile (20, 21), in particular related to a grid current flow from the power grid (4), wherein the current-time profile (20, 21) is derived from a temporal triggering profile (8) of the safety arrangement (5).

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