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EP0716561B1 - X-ray apparatus with a power supply unit for an x-ray tube - Google Patents

X-ray apparatus with a power supply unit for an x-ray tube Download PDF

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Publication number
EP0716561B1
EP0716561B1 EP95203284A EP95203284A EP0716561B1 EP 0716561 B1 EP0716561 B1 EP 0716561B1 EP 95203284 A EP95203284 A EP 95203284A EP 95203284 A EP95203284 A EP 95203284A EP 0716561 B1 EP0716561 B1 EP 0716561B1
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EP
European Patent Office
Prior art keywords
inverters
voltage
ray apparatus
windings
primary
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP95203284A
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German (de)
French (fr)
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EP0716561A1 (en
Inventor
Heinz Dr. Ing. Van Der Broeck
Christoph Loef
Hans Negle
Bernhard Wagner
Martin Wimmer
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Philips Intellectual Property and Standards GmbH
Koninklijke Philips NV
Original Assignee
Philips Intellectual Property and Standards GmbH
Koninklijke Philips Electronics NV
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    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05G—X-RAY TECHNIQUE
    • H05G1/00—X-ray apparatus involving X-ray tubes; Circuits therefor
    • H05G1/08—Electrical details
    • H05G1/10—Power supply arrangements for feeding the X-ray tube
    • H05G1/20—Power supply arrangements for feeding the X-ray tube with high-frequency AC; with pulse trains

Definitions

  • the invention relates to an X-ray device according to the preamble of claim 1
  • Such an X-ray device is known from DE-OS 32 18 535.
  • the known X-ray equipment could also use symmetrical x-ray tubes with a metal piston be fed, in which the cathode current is greater than the anode current. This sets an asymmetrical power distribution between the two inverters ahead, which is disruptive Compensating currents in the transformer would result if not would prevent the transformer from windings from different groups are weakly coupled compared to windings from the same group.
  • the well-known X-ray device whose inverter as equipped with thyristors Series resonance inverters are designed, allows the unbalanced Power distribution through delayed switching on of the switching elements from the two Inverters.
  • the power is changed by changing the frequency, with which the two inverters are operated.
  • the supplied power With an X-ray generator, the supplied power but can be changed by several powers of ten, which is a requires a correspondingly large frequency change. But it is not possible avoid that the X-ray device is operated in the hearing frequency range, which leads to audible and annoying operating noise leads and also an undesirably high Ripple of the output voltage.
  • Another disadvantage is that at Setting different voltages the inverters through different Switching currents are loaded, which results in this mode of operation Performance restriction results.
  • the object of the present invention is an arrangement of the type mentioned continue to improve. This object is achieved by the in claim 1 specified measures solved.
  • the duty cycle is the ratio of the pulse duration of the voltage pulses supplied by the inverters to the primary windings Period of the fixed frequency with which the inverters are switched designated.
  • the operation with a fixed frequency has the advantage that this frequency is chosen can be that it lies above the hearing frequency range, so that no disturbing Operating noises occur.
  • the power setting by changing the duty cycle has the Advantage that in a working point with a constant current of the consumer largely linear relationship between the output voltage (at the Secondary windings) and the duty cycle, what a higher-level control is cheap.
  • the duty cycle of the two inverters is indeed can still be controlled independently of one another, however the voltage pulses are in kind of synchronized. Basically, it would then be possible, for example, to The leading edges of the two voltage pulses or the trailing edges coincide to let. However, equalizing currents can also occur here, which can lead to this would that the inverter generating the shorter pulse by a higher switching current would be charged than the other inverter, and there would be between exchanged a large reactive power for the inverters.
  • the invention according to claim 3 in contrast, run by the two Inverters generated voltage pulses symmetrically in time with each other. unequal long voltage pulses only result in a small exchange of reactive power between the two inverters, the switching currents in the two Inverters have approximately the same maximum value.
  • Fig. 1 shows an X-ray tube 4, the transformer 3 of two AC voltage sources 1, 2 is fed as a series resonance inverter are trained.
  • the two inverters are each connected to a DC voltage source 5a and 5b connected.
  • Each inverter comprises four to one in a manner known per se Full bridge interconnected switches 11 ... 14 or 21 ... 24 of the IGBT type or other power semiconductors that can be switched off.
  • the connection point of the switches 11, 12 comprising a bridge branch is via the series connection a capacitor 15 and one to one first winding group belonging primary winding 16 of Transformer 3 with the connection point of the switches 13, 14 of the other bridge branch connected.
  • connection point of the switches 21 and 22 via the series connection a capacitor 25 and one to one second winding group belonging primary winding 26 des Transformer 3 with the connection point of the switch 23 and 24 connected.
  • the secondary side of the transformer 3 is by two identically constructed secondary wedges 31st and 32 formed to the first and second winding groups, respectively belong.
  • the series resonance frequency of the circles 15, 16 and 25, 26 is determined by the capacitance of the capacitor 15 or 25 and the leakage inductance of the identically constructed primary windings 16, 26 and the secondary windings 31, 32 of Transformer determined; is an additional inductance in principle not necessary.
  • the winding capacities 91, 92 of the secondary windings can be part of the series resonant circuit be used.
  • the switches 11 ... 14 or 21 ... 24 of inverters 1 and 2 are connected with the same, constant switching frequency operated, that of the series resonance frequency equivalent.
  • a rectifier is connected to each of the secondary windings 31 and 32 6 or 7 connected, its output voltage is smoothed by a capacitor 61 or 71. frequently are the two secondary windings for insulation reasons subdivided even further, with each partial winding receives its own rectifier.
  • the rectifiers 6 and 7 are connected in series and the smoothed output voltage becomes the cathode or the anode of the X-ray tube 4 fed. Due to the series connection the secondary windings 31 and 32, the rectifiers 6 and 7 and the capacitors 61 and 71 only for half of the Maximum value of the high voltage designed on the X-ray tube his.
  • the x-ray tube 4 can have a grounded metal piston, as indicated schematically in the drawing. In in this case part of the cathode current flows to the anode and another part about the metal piston to earth, so that the cathode current is greater than the anode current. Because of these different currents, one would High voltage generator, in which the inverter voltage pulses generate with an identical course over time would, the cathode voltage be lower than the anode voltage. This would be especially low Voltage between anode and cathode cause the Cathode current due to space charge effects in the X-ray tube would be limited so that their thermal resilience for low anode voltages can no longer be fully utilized could.
  • the prerequisite for these control options is that the voltage pulses of the inverter 1 another (greater) duration than that of the inverter 2. Then disturbing equalizing currents can occur between the windings result.
  • the effect of the equalizing currents can be explained on the basis of the simplified equivalent circuit diagram according to FIG. 2, the transformer being replaced by the inductors L 12 , L 1s , L 2s and L h .
  • the inductors L 1s and L 2s represent the leakage inductance of the primary windings 16 and 26 with respect to the secondary side, and the inductance L 12 represents the leakage inductance between the two primary windings, by means of which the outputs of the inverters 1, 2 are coupled to one another.
  • L h is the main inductance, which is large compared to the inductors mentioned above.
  • the inductance L 12 would be small compared to the inductances L 1s , L 2s . If the voltages supplied by the inverters 1, 2 then differ in time due to different switching times for the switches 11 ... 14 on the one hand and 21 ... 24 on the other hand, the output voltage of the inverter 1 would initially be completely at the inductance L 12 apply and cause a differential current, the rate of change would correspond to the quotient of this voltage and the inductance L 12 .
  • the coupling of the two primary windings 16, 26 to one another is made smaller than the coupling between each of these primary windings and the secondary winding as a whole (i.e. the series connection between the windings 31 and 32) or between the relevant primary winding 16 or 26 and belonging to the same winding group Partial winding 31 or 32.
  • FIG. 3 schematically shown construction of the transformer achieved.
  • the primary windings 16 and 26 are side by side and spaced apart on a transformer core 30 arranged, e.g. a cutting tape core.
  • the Primary windings 16 and 26 are from the secondary winding 31 or 32 enclosed.
  • This construction is magnetic or inductive Coupling between the primary windings 16 and 26, however also clearly between the secondary windings 31 and 32 weaker than the coupling between one of the primary windings (e.g. 16) and the secondary winding surrounding it (31).
  • the leakage inductance between the two windings is proportional to the factor (1 - k 2 ).
  • L 12 is greater than L 1s or L 2s . If the coupling factor between the primary windings is 0.973, for example, and between a primary winding and the secondary winding is 0.993, then L 12 is approximately four times as large as L 1s and L 2s . Then only a reduced equalizing current flows, the frequency of which is generally not increased.
  • the leading edges of the two voltage pulses could or the trailing edges collapse. Also however, equalizing currents can still occur, which would cause the shorter pulse generating inverters due to a higher switching current would be loaded than the other inverter and it would a large reactive power between the inverters replaced. This can be done by a temporally symmetrical Avoid course of the output voltages.
  • a suitable circuit results from Fig. 4. Die Voltage between anode and earth is thereby high-voltage measuring divider consisting of resistors 201 and 202 measured while the voltage between Cathode and earth through one of the resistors 101 and 102 existing high-voltage measuring divider is measured.
  • the Measuring voltages at the taps of the high-voltage measuring divider are fed to a control arrangement 50, the two Measuring voltages, if necessary also their sum, with Compares setpoints from the given setpoint the voltage at the X-ray tube, but also from the control strategy depend.
  • the control circuit 50 delivers at a first output first control signal for controlling a pulse width modulator 103 and a second control signal at a second output to control a pulse width modulator 203.
  • Die Pulse width modulators 103 and 203 also provide pulses a fixed frequency and a duty cycle or a pulse duration, of the control signal at the input of the depends pulse width modulator.
  • the pulse width modulators 103 and 203 are supplied with a symmetrical triangular voltage U d generated by a function generator 53.
  • the frequency of the delta voltage U d is twice as large as the series resonance frequency of the circuits 15, 16 and 25, 26 of the inverters 1 and 2.
  • the function generator 53 delivers this clock signals for the blocks 104 and 204, as indicated in FIG. 4 by dashed lines.
  • the triangular voltage U d is compared with the control signals S 1 and S 2 , indicated by dashed lines in FIG. 5, and pulses PWM 1 and PWM 2 are generated at the output of the pulse width modulators, the leading edge of which is exceeded and whose trailing edge coincides with the falling below the control signals S 1 or S 2 by the delta voltage U d .
  • inverter voltages U 1 and U 2 with the pulse-shaped shown in FIG. 5 result temporal course (U 1 and U 2 each represent the voltage at the series circuit 15, 16 and 25, 26).
  • U 1 and U 2 differ from PWM 1 and PWM 2 in that the polarity of every second pulse is inverted, so that the fundamental wave contained in the output voltages U 1 and U 2 has a frequency that is half as large as that Frequency of the triangular wave U d . Since the frequency of the triangular oscillation is twice as high as the series resonance frequency of the inverters 1, 2, the frequency of this fundamental oscillation corresponds to the series resonance frequency. It can be seen from FIG. 5 that the voltage pulses U 1 and U 2 are symmetrical in time with respect to one another, ie the time centers of these pulses coincide. The voltage pulses from U 1 and U 2 each have the same polarity - if the primary windings 16 and 26 have the same winding sense. If the winding directions of the primary windings 16 and 26 are opposite, the pulses must each have the opposite polarity.
  • the compensation currents are minimal and only a small reactive power is exchanged between the windings.
  • the currents I 1 and I 2 flowing in the primary windings 16 and 26 have almost the same maximum value, ie the current load in the switches 11 ... 14 is approximately the same as in FIG the switches 21 ... 24, although the duty cycle of U 1 is approximately twice as high as the duty cycle of U 2 , so that the cathode voltage derived from U 1 is also approximately twice as large as the anode voltage derived from U 2 .
  • the cathode voltage or the anode voltage depend largely linearly on the duty cycle or the pulse duration of the pulse-width-modulated signals PWM 1 and PWM 2 .
  • the cathode voltage depend largely linearly on the duty cycle or the pulse duration of the pulse-width-modulated signals PWM 1 and PWM 2 .
  • there is only a weak dependency of the cathode voltage on the duty cycle of the pulse duration modulated signal PWM 2 the same applies to the dependence of the anode voltage on the duty cycle of the PWM 1 signal.
  • the linear dependence of the high voltage on the duty cycle is favorable for the control behavior.
  • the pulse width modulators 103 are shown in FIGS. 4 and 5 and 203 as analog circuits. It is however, pulse width modulation is also possible - and if necessary also the switching pulse generation by the blocks 104 and 204 - with the help of programmable controller modules perform.

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  • X-Ray Techniques (AREA)
  • Dc-Dc Converters (AREA)
  • Inverter Devices (AREA)

Description

Die Erfindung betrifft ein Röntgen-Gerät nach dem Oberbegriff des Anspruchs 1The invention relates to an X-ray device according to the preamble of claim 1

Ein solches Röntgen-Gerät ist aus der DE-OS 32 18 535 bekannt. Mit dem bekannten Röntgen-Gerät könnten auch Röntgenröhren mit einem Metallkolben symmetrisch gespeist werden, bei denen der Kathodenstrom größer ist als der Anodenstrom. Dies setzt eine unsymmetrische Leistungsverteilung auf die beiden Wechselrichter voraus, was zu störenden Ausgleichsströmen im Transformator führen würde, wenn dies nicht dadurch verhindert würde, daß bei dem Transformator Wicklungen aus verschiedenen Gruppen schwach gekoppelt sind im Vergleich zu Wicklungen aus der gleichen Gruppe.Such an X-ray device is known from DE-OS 32 18 535. With the known X-ray equipment could also use symmetrical x-ray tubes with a metal piston be fed, in which the cathode current is greater than the anode current. This sets an asymmetrical power distribution between the two inverters ahead, which is disruptive Compensating currents in the transformer would result if not would prevent the transformer from windings from different groups are weakly coupled compared to windings from the same group.

Das bekannte Röntgen-Gerät, dessen Wechselrichter als mit Thyristoren bestückte Serienresonanz-Wechselrichter ausgebildet sind, erlaubt die unsymmetrische Leistungsverteilung durch verzögertes Einschalten der Schaltelemente aus den beiden Wechselrichtern. Die Leistung wird dabei durch eine Änderung der Frequenz geändert, mit der die beiden Wechselrichter betrieben werden. Bei einem Röntgengenerator muß die zugeführte Leistung aber um mehrere Zehnerpotenzen veränderbar sein, was eine entsprechend große Frequenzänderung voraussetzt. Dabei läßt es sich aber nicht vermeiden, daß das Röntgen-Gerät im Hörfrequenzbereich betrieben wird, was zu hörbaren und störenden Betriebsgeräuschen führt und außerdem eine unerwünscht hohe Welligkeit der Ausgangsspannung zur Folge hat. Von Nachteil ist weiterhin, daß bei Einstellung unterschiedlicher Spannungen die Wechselrichter durch unterschiedliche Schaltströme belastet werden, woraus sich für diese Betriebsweise eine Leistungsbeschränkung ergibt.The well-known X-ray device, whose inverter as equipped with thyristors Series resonance inverters are designed, allows the unbalanced Power distribution through delayed switching on of the switching elements from the two Inverters. The power is changed by changing the frequency, with which the two inverters are operated. With an X-ray generator, the supplied power but can be changed by several powers of ten, which is a requires a correspondingly large frequency change. But it is not possible avoid that the X-ray device is operated in the hearing frequency range, which leads to audible and annoying operating noise leads and also an undesirably high Ripple of the output voltage. Another disadvantage is that at Setting different voltages the inverters through different Switching currents are loaded, which results in this mode of operation Performance restriction results.

Aus dem Dokument EP 0315335A ist ein Leistungsteil zur Speisung einer Röntgenröhre bekannt, bei dem die Primärwicklungen eines Hochspannungstransformators an einen Wechselrichter angeschlossen sind, dessen Tastgrad in Abhängigkeit zweier wählbarer Betriebsmodi der Röntgenröhre steuerbar ist. From document EP 0315335A there is a power section for feeding an X-ray tube in which the primary windings of a high-voltage transformer are connected to an inverter whose Duty cycle depending on two selectable operating modes of the X-ray tube is controllable.

Aufgabe der vorliegenden Erfindung ist es, eine Anordnung der eingangs genannten Art weiter zu verbessern. Diese Aufgabe wird erfindungsgemäß durch die im Anspruch 1 angegebenen Maßnahmen gelöst. Dabei wird als Tastgrad das Verhältnis der Impulsdauer der von den Wechselrichtern an die Primärwicklungen gelieferten Spannungsimpulse zur Periodendauer der festen Frequenz, mit der die Wechselrichter geschaltet werden, bezeichnet. Der Betrieb mit fester Frequenz hat den Vorteil, daß diese Frequenz so gewählt sein kann, daß sie oberhalb des Hörfrequenzbereiches liegt, so daß keine störenden Betriebsgeräusche auftreten. Die Leistungsstellung durch Änderung des Tastgrades hat den Vorteil, daß sich in in einem Arbeitspunkt mit konstantem Strom des Verbrauchers ein weitgehend linearer Zusammenhang zwischen der Ausgangsspannung (an den Sekundärwicklungen) und dem Tastgrad ergibt, was für eine übergeordnete Regelung günstig ist.The object of the present invention is an arrangement of the type mentioned continue to improve. This object is achieved by the in claim 1 specified measures solved. The duty cycle is the ratio of the pulse duration of the voltage pulses supplied by the inverters to the primary windings Period of the fixed frequency with which the inverters are switched designated. The operation with a fixed frequency has the advantage that this frequency is chosen can be that it lies above the hearing frequency range, so that no disturbing Operating noises occur. The power setting by changing the duty cycle has the Advantage that in a working point with a constant current of the consumer largely linear relationship between the output voltage (at the Secondary windings) and the duty cycle, what a higher-level control is cheap.

Wie bereits erwähnt, können durch die im Anspruch 1 angegebene Gestaltung der Kopplungsverhältnisse zwischen den zur gleichen Gruppe und den zu unterschiedlichen Gruppen gehörenden Wicklungen die Ausgleichsströme reduziert werden. Bei ungünstigem Verlauf der Spannungsimpulse können jedoch immer noch beträchtliche Ausgleichsströme entstehen. Diese Ausgleichsströme lassen sich durch die Ausgestaltung der Erfindung nach Anspruch 2 vermindern. Wenn die Primärwicklungen der beiden Gruppen den gleichen Wicklungssinn aufweisen, wird eine gleichsinnige zeitliche Änderung des magnetischen Flusses durch Spannungsimpulse mit der gleichen Polarität erreicht; bei Wicklungen mit entgegengesetztem Wicklungssinn ist dies bei entgegengesetzter Polarität der zugeführten Spannungsimpulse der Fall.As already mentioned, by the design specified in claim 1 Coupling relationships between the same group and the different Group-owned windings, the compensating currents are reduced. at However, the unfavorable course of the voltage pulses can still be considerable Equalizing currents arise. These equalizing currents can be designed reduce the invention of claim 2. If the primary windings of the two Groups with the same sense of winding will have the same sense of time Change in magnetic flux due to voltage pulses with the same polarity reached; this is the case for windings with opposite winding direction opposite polarity of the supplied voltage pulses.

Bei dieser Ausgestaltung der Erfindung ist der Tastgrad der beiden Wechselrichter zwar weiterhin voneinander unabhängig steuerbar, jedoch sind die Spannungsimpulse in gewisser Weise synchronisiert. Grundsätzlich wäre es danach beispielsweise möglich, die Vorderflanken der beiden Spannungsimpulse oder die Rückflanken zusammenfallen zu lassen. Auch hierbei können jedoch noch Ausgleichsströme auftreten, was dazu führen würde, daß der den jeweils kürzeren Impuls erzeugende Wechselrichter durch einen höheren Schaltstrom belastet würde als der andere Wechselrichter, und es würde zwischen den Wechselrichtern eine große Blindleistung ausgetauscht. Bei der bevorzugten Weiterbildung der Erfindung nach Anspruch 3 verlaufen demgegenüber die von den beiden Wechselrichtern erzeugten Spannungsimpulse zeitlich symmetrisch zueinander. Ungleich lange Spannungsimpulse führen lediglich zu einem geringen Austausch von Blindleistung zwischen den beiden Wechselrichtern, wobei die Schaltströme in den beiden Wechselrichtern etwa den gleichen Maximalwert haben.In this embodiment of the invention, the duty cycle of the two inverters is indeed can still be controlled independently of one another, however the voltage pulses are in kind of synchronized. Basically, it would then be possible, for example, to The leading edges of the two voltage pulses or the trailing edges coincide to let. However, equalizing currents can also occur here, which can lead to this would that the inverter generating the shorter pulse by a higher switching current would be charged than the other inverter, and there would be between exchanged a large reactive power for the inverters. In the preferred further training the invention according to claim 3, in contrast, run by the two Inverters generated voltage pulses symmetrically in time with each other. unequal long voltage pulses only result in a small exchange of reactive power between the two inverters, the switching currents in the two Inverters have approximately the same maximum value.

Die Erfindung soll nachstehend anhand der Zeichnungen näher erläutert werden. Es zeigen:

Fig. 1
einen Teil eines Schaltbildes eines Röntgen-Gerätes,
Fig. 2
ein Ersatzschaltbild eines Teils dieses Röntgen-Gerätes
Fig. 3
die Anordnung der Primär- und Sekundärwicklungen auf dem Transformatorkern,
Fig. 4
einen weiteren Teil der Anordnung und
Fig. 5
den zeitlichen Verlauf verschiedener Signale bei dieser Anordnung.
The invention will be explained below with reference to the drawings. Show it:
Fig. 1
part of a circuit diagram of an X-ray device,
Fig. 2
an equivalent circuit diagram of a part of this X-ray device
Fig. 3
the arrangement of the primary and secondary windings on the transformer core,
Fig. 4
another part of the arrangement and
Fig. 5
the time course of various signals with this arrangement.

Fig. 1 zeigt eine Röntgenröhre 4, die über einen Transformator 3 von zwei Wechselspannungsquellen 1, 2 gespeist wird, die als Serienresonanz-Wechselrichter ausgebildet sind. Die beiden Wechselrichter sind an je eine Gleichspannungsquelle 5a und 5b angeschlossen. Jeder Wechselrichter umfaßt in an sich bekannter Weise vier zu einer Vollbrücke zusammengeschaltete Schalter 11 ... 14 bzw. 21 ... 24 vom IGBT-Typ bzw. andere abschaltbare Leistungshalbleiter. Der Verbindungspunkt des die Schalter 11, 12 umfassenden einen Brückenzweiges ist über die Serienschaltung eines Kondensators 15 und einer zu einer ersten Wicklungsgruppe gehörenden Primärwicklung 16 des Transformators 3 mit dem Verbindungspunkt der Schalter 13, 14 des anderen Brückenzweiges verbunden. Analog dazu ist der Verbindungspunkt der Schalter 21 und 22 über die Serienschaltung eines Kondensators 25 und einer zu einer zweiten Wicklungsgruppe gehörenden Primärwicklung 26 des Transformators 3 mit dem Verbindungspunkt der Schalter 23 und 24 verbunden. Die Sekundärseite des Transformators 3 wird durch zwei identisch aufgebaute Sekundärwichungen 31 und 32 gebildet, die zu der ersten bzw. der zweiten Wicklungsgruppe gehören.Fig. 1 shows an X-ray tube 4, the transformer 3 of two AC voltage sources 1, 2 is fed as a series resonance inverter are trained. The two inverters are each connected to a DC voltage source 5a and 5b connected. Each inverter comprises four to one in a manner known per se Full bridge interconnected switches 11 ... 14 or 21 ... 24 of the IGBT type or other power semiconductors that can be switched off. The connection point of the switches 11, 12 comprising a bridge branch is via the series connection a capacitor 15 and one to one first winding group belonging primary winding 16 of Transformer 3 with the connection point of the switches 13, 14 of the other bridge branch connected. The same is true the connection point of the switches 21 and 22 via the series connection a capacitor 25 and one to one second winding group belonging primary winding 26 des Transformer 3 with the connection point of the switch 23 and 24 connected. The secondary side of the transformer 3 is by two identically constructed secondary wedges 31st and 32 formed to the first and second winding groups, respectively belong.

Die Serienresonanzfrequenz der Kreise 15, 16 bzw. 25, 26 wird dabei durch die Kapazität des Kondensators 15 bzw. 25 und die Streuinduktivität der identisch aufgebauten Primärwicklungen 16, 26 und der Sekundärwicklungen 31, 32 des Transformators bestimmt; eine zusätzliche Induktivität ist prinzipiell nicht erforderlich. Die Wicklungskapazitäten 91, 92 der Sekundärwicklungen können als Teil des Serienresonanzkreises genutzt werden. Die Schalter 11...14 bzw 21...24 der Wechselrichter 1 und 2 werden mit der selben, konstanten Schaltfrequenz betrieben, die der Serienresonanzfrequenz entspricht.The series resonance frequency of the circles 15, 16 and 25, 26 is determined by the capacitance of the capacitor 15 or 25 and the leakage inductance of the identically constructed primary windings 16, 26 and the secondary windings 31, 32 of Transformer determined; is an additional inductance in principle not necessary. The winding capacities 91, 92 of the secondary windings can be part of the series resonant circuit be used. The switches 11 ... 14 or 21 ... 24 of inverters 1 and 2 are connected with the same, constant switching frequency operated, that of the series resonance frequency equivalent.

An die Sekundärwicklungen 31 bzw 32 ist je ein Gleichrichter 6 bzw. 7 angeschlossen, dessen Ausgangsspannung durch einen Kondensator 61 bzw. 71 geglättet wird. Vielfach werden die beiden Sekundärwicklungen aus Isolationsgründen noch weiter unterteilt, wobei jede Teilwicklung einen eigenen Gleichrichter erhält. Die Gleichrichter 6 und 7 sind in Serie geschaltet und die geglättete Ausgangsspannung wird der Kathode bzw. der Anode der Röntgenröhre 4 zugeführt. Aufgrund der Serienschaltung müssen die Sekundärwicklungen 31 und 32, die Gleichrichter 6 und 7 sowie die Kondensatoren 61 und 71 nur für die Hälfte des Maximalwerts der Hochspannung an der Röntgenröhre ausgelegt sein.A rectifier is connected to each of the secondary windings 31 and 32 6 or 7 connected, its output voltage is smoothed by a capacitor 61 or 71. frequently are the two secondary windings for insulation reasons subdivided even further, with each partial winding receives its own rectifier. The rectifiers 6 and 7 are connected in series and the smoothed output voltage becomes the cathode or the anode of the X-ray tube 4 fed. Due to the series connection the secondary windings 31 and 32, the rectifiers 6 and 7 and the capacitors 61 and 71 only for half of the Maximum value of the high voltage designed on the X-ray tube his.

Die Röntgenröhre 4 kann einen geerdeten Metallkolben aufweisen, wie in der Zeichnung schematisch angedeutet. In diesem Fall fließt ein Teil des Kathodenstroms zur Anode und ein anderer Teil über den Metallkolben nach Erde, so daß der Kathodenstrom größer ist als der Anodenstrom. Aufgrund dieser unterschiedlichen Ströme würde bei einem Hochspannungserzeuger, bei dem die Wechselrichter Spannungsimpulse mit identischem zeitlichem Verlauf erzeugen würden, die Kathodenspannung niedriger sein als die Anodenspannung. Dies würde insbesondere bei einer niedrigen Spannung zwischen Anode und Kathode dazu führen, daß der Kathodenstrom durch Raumladungseffekte in der Röntgenröhre begrenzt würde, so daß deren thermische Belastbarkeit für niedrige Anodenspannungen nicht mehr voll ausgenutzt werden könnte. Wünschenswert ist ein Betrieb, bei dem zumindest bei hohen Röhrenspannungen die Spannung zwischen Anode und Erde dem Betrage nach genauso groß ist wie die Spannung zwischen Kathode und Erde. Bei einer niedrigen Röhrenspannung könnte es sogar zweckmäßig sein, die Kathodenspannung größer zu machen als die Anodenspannung, so daß die erwähnten Raumladungseffekte vermieden und die thermische Belastbarkeit der Röntgenröhre besser ausgenutzt werden könnte.The x-ray tube 4 can have a grounded metal piston, as indicated schematically in the drawing. In in this case part of the cathode current flows to the anode and another part about the metal piston to earth, so that the cathode current is greater than the anode current. Because of these different currents, one would High voltage generator, in which the inverter voltage pulses generate with an identical course over time would, the cathode voltage be lower than the anode voltage. This would be especially low Voltage between anode and cathode cause the Cathode current due to space charge effects in the X-ray tube would be limited so that their thermal resilience for low anode voltages can no longer be fully utilized could. Operation in which at least at high tube voltages the voltage between Anode and earth are the same in amount as that Voltage between cathode and earth. At a low Tube voltage could even be useful, the cathode voltage to make greater than the anode voltage, so that the space charge effects mentioned are avoided and the better utilized thermal capacity of the x-ray tube could be.

Für diese Steuerungsmöglichkeiten ist aber Voraussetzung, daß die Spannungsimpulse des Wechselrichters 1 eine andere (größere) Dauer haben als die des Wechselrichters 2. Dann können sich jedoch zwischen den Wicklungen störende Ausgleichsströme ergeben. However, the prerequisite for these control options is that the voltage pulses of the inverter 1 another (greater) duration than that of the inverter 2. Then disturbing equalizing currents can occur between the windings result.

Die Wirkung der Ausgleichsströme läßt sich anhand des vereinfachten Ersatzschaltbildes nach Fig. 2 erläutern, wobei der Transformator durch die Induktivitäten L12, L1s, L2s und Lh ersetzt wurde. Die Induktivitäten L1s bzw. L2s repräsentieren die Streuinduktivität der Primärwicklungen 16 bzw. 26 gegenüber der Sekundärseite, und die Induktivität L12 stellt die Streuinduktivität zwischen den beiden Primärwicklungen dar, durch die die Ausgänge der Wechselrichter 1, 2 miteinander gekoppelt werden. Lh ist die Hauptinduktivität, die groß ist im Vergleich zu den zuvor genannten Induktivitäten.The effect of the equalizing currents can be explained on the basis of the simplified equivalent circuit diagram according to FIG. 2, the transformer being replaced by the inductors L 12 , L 1s , L 2s and L h . The inductors L 1s and L 2s represent the leakage inductance of the primary windings 16 and 26 with respect to the secondary side, and the inductance L 12 represents the leakage inductance between the two primary windings, by means of which the outputs of the inverters 1, 2 are coupled to one another. L h is the main inductance, which is large compared to the inductors mentioned above.

Wenn die Primärwicklungen 16, 26 stark miteinander gekoppelt wären, wie es normalerweise bei derartigen Transformatoren angestrebt wird, dann wäre die Induktivität L12 klein im Vergleich zu den Induktivitäten L1s, L2s. Wenn die von den Wechselrichtern 1, 2 gelieferten Spannungen dann aufgrund unterschiedlich langer Schaltzeiten für die Schalter 11...14 einerseits und 21...24 andererseits zeitlich voneinander abweichen würden, dann würde die Ausgangsspannung des Wechselrichters 1 zunächst vollständig an der Induktivität L12 anliegen und einen Differenzstrom hervorrufen, dessen Änderungsgeschwindigkeit dem Quotienten aus dieser Spannung und der Induktivität L12 entsprechen würde. Wenn anschließend beide Spannungen wieder gleich wären, würde der in L12 fließende Strom in dem durch die Kondensatoren 15, 16 und die Induktivität L12 gebildeten Schaltkreis oszillieren, wobei die Resonanzfrequenz wesentlich höher wäre als die Serienresonanzfrequenz des Wechselrichters, weil L12 klein ist im Vergleich zu L1s bzw. L2s. Es würden somit Ausgleichsströme mit hoher Frequenz und hoher Amplitude fließen.If the primary windings 16, 26 were strongly coupled to one another, as is normally sought in such transformers, the inductance L 12 would be small compared to the inductances L 1s , L 2s . If the voltages supplied by the inverters 1, 2 then differ in time due to different switching times for the switches 11 ... 14 on the one hand and 21 ... 24 on the other hand, the output voltage of the inverter 1 would initially be completely at the inductance L 12 apply and cause a differential current, the rate of change would correspond to the quotient of this voltage and the inductance L 12 . If both voltages were subsequently the same again, the current flowing in L 12 would oscillate in the circuit formed by the capacitors 15, 16 and the inductor L 12 , the resonance frequency being significantly higher than the series resonance frequency of the inverter, because L 12 is small in Compared to L 1s or L 2s . Compensating currents with a high frequency and high amplitude would thus flow.

Amplitude und Frequenz der Ausgleichsströme lassen sich durch zwei Maßnahmen auf ein nicht mehr störendes Maß reduzieren:

  • a) Verringerung der Kopplung zwischen Transormatorwicklungen, die zu unterschiedlichen Wicklungsgruppen gehören.
  • b) Synchronisierung der Schaltimpulse für die beiden Wechselrichter.
    • Diese beiden Maßnahmen werden im folgenden näher erläutert.The amplitude and frequency of the equalizing currents can be reduced to a level that is no longer disturbing by two measures:
  • a) Reducing the coupling between transformer windings belonging to different winding groups.
  • b) synchronization of the switching pulses for the two inverters.
    • These two measures are explained in more detail below.

    Die Kopplung der beiden Primärwicklungen 16, 26 untereinander wird kleiner gemacht als die Kopplung zwischen jeder dieser Primärwicklungen und der Sekundärwicklung insgesamt (d.h. der Serienschaltung zwischen den Wicklungen 31 und 32) oder zwischen der betreffenden Primärwicklung 16 bzw. 26 und der zu der selben Wicklungsgruppe gehörenden Teilwicklung 31 bzw. 32. Dies wird durch den in Fig. 3 schematisch dargestellten Aufbau des Transformators erreicht. Die Primärwicklungen 16 und 26 sind dabei nebeneinander und im Abstand voneinander auf einem Transformatorkern 30 angeordnet, z.B. einem Schnittbandkern. Die Primärwicklungen 16 bzw. 26 werden von der Sekundärwicklung 31 bzw. 32 umschlossen.The coupling of the two primary windings 16, 26 to one another is made smaller than the coupling between each of these primary windings and the secondary winding as a whole (i.e. the series connection between the windings 31 and 32) or between the relevant primary winding 16 or 26 and belonging to the same winding group Partial winding 31 or 32. This is shown in FIG. 3 schematically shown construction of the transformer achieved. The primary windings 16 and 26 are side by side and spaced apart on a transformer core 30 arranged, e.g. a cutting tape core. The Primary windings 16 and 26 are from the secondary winding 31 or 32 enclosed.

    Durch diese Bauweise ist die magnetische bzw. induktive Kopplung zwischen den Primärwicklungen 16 und 26, aber auch zwischen den Sekundärwicklungen 31 und 32 deutlich schwächer als die Kopplung zwischen einer der Primärwicklungen (z.B. 16) und der sie umschließenden Sekundärwicklung (31).This construction is magnetic or inductive Coupling between the primary windings 16 and 26, however also clearly between the secondary windings 31 and 32 weaker than the coupling between one of the primary windings (e.g. 16) and the secondary winding surrounding it (31).

    Die magnetische bzw. induktive Kopplung zwischen zwei Wicklungen L1, L2 läßt sich bekanntlich durch den Kopplungsfaktor k=M/(L1·L2) definieren, wobei M die Gegeninduktivität zwischen den beiden Wicklungen L1, L2 ist. Die Streuinduktivität zwischen den beiden Wicklungen ist dem Faktor (1 - k2) proportional.As is known, the magnetic or inductive coupling between two windings L 1 , L 2 can be determined by the coupling factor k = M / (L 1 · L 2 ) define, where M is the mutual inductance between the two windings L 1 , L 2 . The leakage inductance between the two windings is proportional to the factor (1 - k 2 ).

    Dadurch, daß die Kopplung zwischen den Primärwicklungen schwächer ist als die Kopplung zwischen einer Primärwicklung und der Sekundärwicklung 31, 32 wird erreicht, daß L12 größer ist als L1s bzw. L2s. Beträgt der Kopplungsfaktor zwischen den Primärwicklungen beispielsweise 0,973 und zwischen einer Primärwicklung und der Sekundärwicklung 0,993, dann ist L12 rund viermal so groß wie L1s und L2s. Es fließt dann nur noch ein verringerter Ausgleichsstrom, dessen Frequenz in der Regel nicht erhöht ist.Because the coupling between the primary windings is weaker than the coupling between a primary winding and the secondary winding 31, 32, it is achieved that L 12 is greater than L 1s or L 2s . If the coupling factor between the primary windings is 0.973, for example, and between a primary winding and the secondary winding is 0.993, then L 12 is approximately four times as large as L 1s and L 2s . Then only a reduced equalizing current flows, the frequency of which is generally not increased.

    Man kann die Kopplung der Primärwicklungen untereinander und der Sekundärwicklungen untereinander noch dadurch verringern, daß man die Primärwicklungen mit den sie umschließenden Sekundärwicklungen nicht auf dem gleichen Schenkel anordnet, sondern auf gegenüberliegenden Schenkeln. Allerdings resultieren daraus andere Abmessungen des Transformatorkerns.One can couple the primary windings with each other and the secondary windings with each other reduce that the primary windings with the enclosing them Secondary windings are not on the same Arranges thighs, but on opposite thighs. However, this results in different dimensions of the Transformer core.

    Auch bei dem angegeben Transformaroraufbau können bei ungünstiger zeitlicher Lage der Schaltimpulse für die Schalter der beiden Wechselrichter 1,2 noch erhebliche Ausgleichsströme auftreten. Diese werden weitgehend dadurch reduziert, daß die von den beiden Wechselrichtern erzeugten Spannungsimpulse sich zeitlich so überlappen, daß der kürzere der beiden Spannungsimpulse jeweils während der Dauer des längeren Spannungsimpulses auftritt, und daß die beiden Spannungsimpulse in dem Transformatorkern gleichsinnige zeitliche Änderungen des magnetischen Flusses im Transformatorkern hervorrufen. Even with the specified transformer construction, unfavorable timing of the switching pulses for the Switches of the two inverters 1, 2 still considerable Equalization currents occur. These are largely due to this reduced that of the two inverters generated voltage pulses overlap in time so that the shorter of the two voltage pulses each during the duration of the longer voltage pulse occurs, and that the two voltage pulses in the transformer core same-time temporal changes in the magnetic Cause flux in the transformer core.

    Grundsätzlich könnten die Vorderflanken der beiden Spannungsimpulse oder die Rückflanken zusammenfallen. Auch hierbei können jedoch noch Ausgleichsströme auftreten, was dazu führen würde, daß der den jeweils kürzeren Impuls erzeugende Wechselrichter durch einen höheren Schaltstrom belastet würde als der andere Wechselrichter, und es würde zwischen den Wechselrichtern eine große Blindleistung ausgetauscht. Dies läßt sich durch einen zeitlich symmetrischen Verlauf der Ausgangsspannungen vermeiden.Basically, the leading edges of the two voltage pulses could or the trailing edges collapse. Also however, equalizing currents can still occur, which would cause the shorter pulse generating inverters due to a higher switching current would be loaded than the other inverter and it would a large reactive power between the inverters replaced. This can be done by a temporally symmetrical Avoid course of the output voltages.

    Eine dazu geeignete Schaltung ergibt sich aus Fig. 4. Die Spannung zwischen Anode und Erde wird dabei durch einen aus den Widerständen 201 und 202 bestehenden Hochspannungsmeßteiler gemessen, während die Spannung zwischen Kathode und Erde durch einen aus den Widerständen 101 und 102 bestehenden Hochspannungsmeßteiler gemessen wird. Die Meßspannungen an den Abgriffen der Hochspannungsmeßteiler werden einer Regelanordnung 50 zugeführt, die die beiden Meßspannungen, erforderlichenfalls auch deren Summe, mit Sollwerten vergleicht, die von dem vorgegebenen Sollwert der Spannung an der Röntgenröhre, aber auch von der Regelstrategie abhängen.A suitable circuit results from Fig. 4. Die Voltage between anode and earth is thereby high-voltage measuring divider consisting of resistors 201 and 202 measured while the voltage between Cathode and earth through one of the resistors 101 and 102 existing high-voltage measuring divider is measured. The Measuring voltages at the taps of the high-voltage measuring divider are fed to a control arrangement 50, the two Measuring voltages, if necessary also their sum, with Compares setpoints from the given setpoint the voltage at the X-ray tube, but also from the control strategy depend.

    Wenn lediglich angestrebt wäre, daß Anoden- und Kathodenspannungen stets gleich groß sind, könnten zwei voneinander unabhängige einfache Regler verwendet werden, die die Spannung an der.Anode und an der Kathode jeweils auf einen vorgebbaren Sollwert bringen. Wenn dagegen die Aufteilung der Spannung zwischen Anode und Kathode auch von der Höhe dieser Spannung abhängen soll, muß die Regelschaltung 50 die beiden Meßsignale zusammen verarbeiten. Die Regelschaltung 50 liefert an einem ersten Ausgang ein erstes Regelsignal zur Steuerung eines Pulsbreitenmodulators 103 und an einem zweiten Ausgang ein zweites Regelsignal zur Steuerung eines Pulsbreitenmodulators 203. Die Pulsbreitenmodulatoren 103 und 203 liefern Impulse mit einer festen Frequenz und einem Tastgrad bzw. einer Impulsdauer, der bzw. die von dem Regelsignal am Eingang des betreffenden Pulsbreitenmodulators abhängt. Diese Impulse, die zeitlich symmetrisch zueinander verlaufen, werden mittels eines PLD-Bausteines (Programmable Logic Device) 104 bzw. 204 in ein Schaltimpulsmuster für die vier Schalter 11 ... 14 bzw. 21 ... 24 des zugehörigen Wechselrichters 1 bzw. 2 umgesetzt, derart, daß die von den Wechselrichtern 1 und 2 gelieferten Spannungsimpulse jeweils die durch den zugehörigen Pulsbreitenmodulator 103 bzw. 203 vorgegebene Impulsdauer haben.If only the aim was that anode and cathode voltages are always the same size, two of them could be independent simple controls are used that the voltage on the anode and on the cathode bring a predefinable setpoint. If, on the other hand, the division the voltage between anode and cathode also from the control circuit must depend on the level of this voltage 50 process the two measurement signals together. The control circuit 50 delivers at a first output first control signal for controlling a pulse width modulator 103 and a second control signal at a second output to control a pulse width modulator 203. Die Pulse width modulators 103 and 203 also provide pulses a fixed frequency and a duty cycle or a pulse duration, of the control signal at the input of the depends pulse width modulator. These impulses that are symmetrical in time to each other by means of a PLD component (Programmable Logic Device) 104 or 204 in a switching pulse pattern for the four switches 11 ... 14 or 21 ... 24 of the associated inverter 1 or 2 implemented, such that the inverters 1 and 2 delivered voltage pulses each by the associated pulse width modulator 103 or 203 have a predetermined pulse duration.

    Außer den Regelsignalen wird den Pulsbreitenmodulatoren 103 und 203 eine von einem Funktionsgenerator 53 erzeugte symmetrische Dreieckspannung Ud zugeführt. Die Frequenz der Dreieckspannung Ud, deren zeitlicher Verlauf in Fig. 5 (erste Zeile) dargestellt ist, ist doppelt so groß wie die Serienresonanzfrequenz der Kreise 15, 16 bzw. 25, 26 der Wechselrichter 1 bzw. 2. Der Funktionsgenerator 53 liefert darüber hinaus Taktsignale für die Bausteine 104 und 204, wie in Fig. 4 durch gestrichelte Linien angedeutet.In addition to the control signals, the pulse width modulators 103 and 203 are supplied with a symmetrical triangular voltage U d generated by a function generator 53. The frequency of the delta voltage U d , the time profile of which is shown in FIG. 5 (first line), is twice as large as the series resonance frequency of the circuits 15, 16 and 25, 26 of the inverters 1 and 2. The function generator 53 delivers this clock signals for the blocks 104 and 204, as indicated in FIG. 4 by dashed lines.

    In den Pulsbreitenmodulatoren 103 und 203 wird die Dreieckspannung Ud mit den - in Fig. 5 gestrichelt angedeuteten - Regelsignalen S1 bzw. S2 verglichen, und am Ausgang der Pulsbreitenmodulatoren werden Impulse PWM1 bzw. PWM2 erzeugt, deren Vorderflanke mit dem Überschreiten und deren Rückflanke mit dem Unterschreiten der Regelsignale S1 bzw. S2 durch die Dreieckspannung Ud zusammenfällt.In the pulse width modulators 103 and 203, the triangular voltage U d is compared with the control signals S 1 and S 2 , indicated by dashed lines in FIG. 5, and pulses PWM 1 and PWM 2 are generated at the output of the pulse width modulators, the leading edge of which is exceeded and whose trailing edge coincides with the falling below the control signals S 1 or S 2 by the delta voltage U d .

    Nach dem Umsetzen der pulsbreitenmodulierten Impulse PWM1 und PWM2 in Schaltimpulse für die Schalter 11 ... 14 bzw. 21 ... 24 der Wechselrichter 1 bzw. 2 ergeben sich Wechselrichterspannungen U1 und U2 mit dem in Fig. 5 dargestellten impulsförmigen zeitlichen Verlauf (U1 bzw. U2 stellen jeweils die Spannung an der Serienschaltung 15, 16 bzw. 25, 26 dar).After converting the pulse width modulated pulses PWM 1 and PWM 2 into switching pulses for the switches 11 ... 14 and 21 ... 24 of the inverters 1 and 2, respectively, inverter voltages U 1 and U 2 with the pulse-shaped shown in FIG. 5 result temporal course (U 1 and U 2 each represent the voltage at the series circuit 15, 16 and 25, 26).

    U1 bzw. U2 unterscheiden sich von PWM1 bzw. PWM2 dadurch, daß die Polarität jedes zweiten Impulses invertiert ist, so daß die in den Ausgangsspannungen U1 und U2 enthaltene Grundschwingung eine Frequenz hat, die halb so groß ist wie die Frequenz der Dreieckschwingung Ud. Da die Frequenz der Dreieckschwingung doppelt so groß ist wie die Serienresonanzfrequenz der Wechselrichter 1, 2, entspricht die Frequenz dieser Grundschwingung der Serienresonanzfrequenz. Man erkennt aus Fig. 5, daß die Spannungsimpulse U1 und U2 zeitlich symmetrisch zueinander verlaufen, d.h. die zeitlichen Mitten dieser Impulse fallen zusammen. Die Spannungsimpulse von U1 bzw. U2 haben jeweils die gleiche Polarität - falls die Primärwicklungen 16 bzw. 26 den gleichen Wicklungssinn haben. Bei entgegengesetztem Wicklungssinn der Primärwicklungen 16 und 26 müssen die Impulse jeweils die entgegengesetzte Polarität haben.U 1 and U 2 differ from PWM 1 and PWM 2 in that the polarity of every second pulse is inverted, so that the fundamental wave contained in the output voltages U 1 and U 2 has a frequency that is half as large as that Frequency of the triangular wave U d . Since the frequency of the triangular oscillation is twice as high as the series resonance frequency of the inverters 1, 2, the frequency of this fundamental oscillation corresponds to the series resonance frequency. It can be seen from FIG. 5 that the voltage pulses U 1 and U 2 are symmetrical in time with respect to one another, ie the time centers of these pulses coincide. The voltage pulses from U 1 and U 2 each have the same polarity - if the primary windings 16 and 26 have the same winding sense. If the winding directions of the primary windings 16 and 26 are opposite, the pulses must each have the opposite polarity.

    Unter dieser Bedingung sind die Ausgleichsströme minimal und es wird lediglich eine geringe Blindleistung zwischen den Wicklungen ausgetauscht. Wie man Fig. 5 weiter entnimmt, haben in diesem Fall die in den Primärwicklungen 16 bzw. 26 fließenden Ströme I1 bzw. I2 nahezu den gleichen Maximalwert, d.h. die Strombelastung in den Schaltern 11 ... 14 ist etwa genauso groß wie in den Schaltern 21 ... 24, obwohl der Tastgrad von U1 etwa doppelt so groß ist wie der Tastgrad von U2, so daß auch die aus U1 abgeleitete Kathodenspannung etwa doppelt so groß ist wie die aus U2 abgeleitete Anodenspannung.Under this condition, the compensation currents are minimal and only a small reactive power is exchanged between the windings. 5, in this case the currents I 1 and I 2 flowing in the primary windings 16 and 26 have almost the same maximum value, ie the current load in the switches 11 ... 14 is approximately the same as in FIG the switches 21 ... 24, although the duty cycle of U 1 is approximately twice as high as the duty cycle of U 2 , so that the cathode voltage derived from U 1 is also approximately twice as large as the anode voltage derived from U 2 .

    Die Kathodenspannung bzw. die Anodenspannung hängen bei einem Arbeitspunkt mit konstantem Röhrenstrom weitgehend linear von dem Tastgrad bzw. der Pulsdauer der pulsbreitenmodulierten Signale PWM1 und PWM2 ab. Hingegen ergibt sich nur eine schwache Abhängigkeit der Kathodenspannung vom Tastgrad des Pulsdauer modulierten Signals PWM2; das gleiche gilt für die Abhängigkeit der Anodenspannung von dem Tastgrad des Signals PWM1. Die lineare Abhängigkeit der Hochspannung von dem Tastgrad ist für das Regelverhalten günstig.At an operating point with a constant tube current, the cathode voltage or the anode voltage depend largely linearly on the duty cycle or the pulse duration of the pulse-width-modulated signals PWM 1 and PWM 2 . In contrast, there is only a weak dependency of the cathode voltage on the duty cycle of the pulse duration modulated signal PWM 2 ; the same applies to the dependence of the anode voltage on the duty cycle of the PWM 1 signal. The linear dependence of the high voltage on the duty cycle is favorable for the control behavior.

    In den Figuren 4 und 5 sind die Pulsbreitenmodulatoren 103 und 203 als analog wirkende Schaltungen erläutert. Es ist jedoch auch möglich, die Pulsbreitenmodulation - und gegebenenfalls auch die Schaltimpulserzeugung durch die Bausteine 104 und 204 - mit Hilfe programmierbarer Kontrollerbausteine durchzuführen.The pulse width modulators 103 are shown in FIGS. 4 and 5 and 203 as analog circuits. It is however, pulse width modulation is also possible - and if necessary also the switching pulse generation by the blocks 104 and 204 - with the help of programmable controller modules perform.

    Claims (9)

    1. An X-ray apparatus, comprising a power supply section for powering an X-ray tube (4), which power supply section comprises a high-voltage transformer (3) with two groups of primary and secondary windings provided on the same transformer core, the coupling between the primary windings (16, 26) from different groups being weaker than that between the primary and secondary windings (16, 31; 26, 32) belonging to the same group, the primary windings of the two groups being connected to two inverters (1, 2) which operate at the same frequency,
      characterized in that there are provided means (53, 103, 203) for operating the inverters (1, 2) with a fixed frequency and with an independently controllable duty cycle.
    2. An X-ray apparatus as claimed in Claim 1, characterized in that the means for operating the inverters are constructed so that the voltage pulses (U1, U2) generated by the two inverters overlap in time in such a manner that the shorter one of the two voltage pulses (U2) occurs always within the period of the longer voltage pulse (U1), and that the two voltage pulses cause temporal variations in the same direction of the magnetic flux in the transformer core.
    3. An X-ray apparatus as claimed in Claim 2,
      characterized in that the means for operating the inverters are constructed in such a manner that the centers of the voltage pulses supplied by the two inverters coincide in time.
    4. An X-ray apparatus as claimed in Claim 1,
      characterized in that the means for operating the inverters comprise a pulse width modulator (103, 203) for each inverter.
    5. An X-ray apparatus as claimed in Claim 1,
      characterized in that the primary windings (16, 26) as well as the secondary windings (31, 32) of the two groups are arranged adjacent one another and that the secondary windings (31, 32) enclose the primary windings belonging to the respective same group.
    6. An X-ray apparatus as claimed in Claim 1,
      characterized in that rectifiers (6, 7) which are connected in series in respect of direct voltage are connected to the secondary windings (31, 32).
    7. An X-ray apparatus as claimed in Claim 1,
      characterized in that the inverters (1, 2) are constructed as series-resonant inverters and that the frequency at which the inverters operate corresponds at least substantially to the series-resonance frequency.
    8. An X-ray apparatus as claimed in Claim 7,
      characterized in that each inverter comprises a capacitance (15, 25) which forms a series-resonant circuit in conjunction with the reactance (L16, L26) of the associated primary winding (16,26).
    9. An X-ray apparatus as claimed in Claim 1,
      characterized in that the user is formed by an X-ray tube whose anode current deviates from its cathode current.
    EP95203284A 1994-12-07 1995-11-29 X-ray apparatus with a power supply unit for an x-ray tube Expired - Lifetime EP0716561B1 (en)

    Applications Claiming Priority (2)

    Application Number Priority Date Filing Date Title
    DE4443551A DE4443551A1 (en) 1994-12-07 1994-12-07 Arrangement for supplying power to an electrical consumer, in particular an X-ray apparatus
    DE4443551 1994-12-07

    Publications (2)

    Publication Number Publication Date
    EP0716561A1 EP0716561A1 (en) 1996-06-12
    EP0716561B1 true EP0716561B1 (en) 2004-02-18

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    EP95203284A Expired - Lifetime EP0716561B1 (en) 1994-12-07 1995-11-29 X-ray apparatus with a power supply unit for an x-ray tube

    Country Status (4)

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    US (1) US5731968A (en)
    EP (1) EP0716561B1 (en)
    JP (1) JP3683318B2 (en)
    DE (2) DE4443551A1 (en)

    Families Citing this family (15)

    * Cited by examiner, † Cited by third party
    Publication number Priority date Publication date Assignee Title
    DE19724931A1 (en) * 1997-06-12 1998-12-17 Philips Patentverwaltung Power supply unit with a pulse duration modulated inverter, in particular for an X-ray generator
    DE19940137A1 (en) * 1999-08-24 2001-03-01 Philips Corp Intellectual Pty Series-resonant converter with a control circuit
    US6178098B1 (en) * 1999-09-22 2001-01-23 Lucent Technologies Inc. Phase-shifted post-regulator, method of operation thereof and power converter employing the same
    US6738275B1 (en) * 1999-11-10 2004-05-18 Electromed Internationale Ltee. High-voltage x-ray generator
    DE10126256A1 (en) * 2001-05-29 2002-12-05 Philips Corp Intellectual Pty Power system
    DE10159897A1 (en) * 2001-12-06 2003-06-26 Philips Intellectual Property Power supply for X-ray generator
    JP4306209B2 (en) * 2002-09-09 2009-07-29 株式会社日立メディコ Neutral point ground X-ray generator and X-ray CT apparatus using the same
    JP4392746B2 (en) * 2003-05-23 2010-01-06 株式会社日立メディコ X-ray high voltage device
    EP1898510A4 (en) * 2005-04-22 2017-03-01 Daifuku Co., Ltd. Secondary-side power receiving circuit of noncontact power supplying equipment
    DE102007032199A1 (en) * 2007-07-11 2009-01-15 Sms Elotherm Gmbh Two resonant circuit inverters operating method for inductively operated heating device, involves synchronizing frequency of controlling of resonant circuit inverters, where frequency of controlling is dynamically adjusted
    JP2011522387A (en) * 2008-06-02 2011-07-28 コーニンクレッカ フィリップス エレクトロニクス エヌ ヴィ Rotary power transformer used in high voltage generator circuit to inductively transmit two or more independently controllable power supply voltages to the power supply electrode of the load
    US8861681B2 (en) * 2010-12-17 2014-10-14 General Electric Company Method and system for active resonant voltage switching
    US10305385B2 (en) 2016-09-27 2019-05-28 Texas Instruments Incorporated Interleaved resonant converter
    US11103207B1 (en) * 2017-12-28 2021-08-31 Radiation Monitorng Devices, Inc. Double-pulsed X-ray source and applications
    JP7577572B2 (en) * 2021-03-03 2024-11-05 富士フイルム株式会社 Radiation tubes and sources

    Family Cites Families (14)

    * Cited by examiner, † Cited by third party
    Publication number Priority date Publication date Assignee Title
    FR2507842A1 (en) * 1981-06-12 1982-12-17 Gen Equip Med Sa SEMICONDUCTOR VOLTAGE REGULATOR AND RADIOLOGY GENERATOR COMPRISING SUCH A REGULATOR
    DE3218535A1 (en) * 1982-05-17 1983-11-17 Philips Patentverwaltung HIGH VOLTAGE GENERATOR, ESPECIALLY FOR THE SUPPLY OF A X-RAY TUBE
    US4504895A (en) * 1982-11-03 1985-03-12 General Electric Company Regulated dc-dc converter using a resonating transformer
    US4574340A (en) * 1984-06-22 1986-03-04 Westinghouse Electric Corp. Inverter with constant voltage to frequency ratio output capability
    US4797908A (en) * 1984-09-14 1989-01-10 Kabushiki Kaisha Toshiba Voltage-resonance type power supply circuit for X-ray tube
    DE3567351D1 (en) * 1984-10-09 1989-02-09 Siemens Ag Medium-frequency x-ray generator power supply
    JPS61158698A (en) * 1984-12-28 1986-07-18 Hitachi Medical Corp Inverter-type x-ray plant
    US4823250A (en) * 1987-11-05 1989-04-18 Picker International, Inc. Electronic control for light weight, portable x-ray system
    FR2633115B1 (en) * 1988-06-17 1993-02-12 Gen Electric Cgr STABILIZED POWER SUPPLY WITH REDUCED ROPE RATE
    US5272612A (en) * 1989-06-30 1993-12-21 Kabushiki Kaisha Toshiba X-ray power supply utilizing A.C. frequency conversion to generate a high D.C. voltage
    DE3929888A1 (en) * 1989-09-08 1991-03-14 Philips Patentverwaltung X-RAY GENERATOR FOR THE OPERATION OF AN X-RAY TUBE WITH TUBE PARTS CONNECTED TO GROUND
    DE59003559D1 (en) * 1990-11-27 1993-12-23 Siemens Ag High frequency x-ray generator.
    FR2672166B1 (en) * 1991-01-25 1995-04-28 Gen Electric Cgr DEVICE FOR OBTAINING A CONTINUOUS VOLTAGE WITH LOW RESIDUAL Ripple.
    US5602897A (en) * 1995-06-29 1997-02-11 Picker International, Inc. High-voltage power supply for x-ray tubes

    Also Published As

    Publication number Publication date
    JP3683318B2 (en) 2005-08-17
    DE59510860D1 (en) 2004-03-25
    EP0716561A1 (en) 1996-06-12
    JPH08255694A (en) 1996-10-01
    US5731968A (en) 1998-03-24
    DE4443551A1 (en) 1996-06-20

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