EP0401901B1 - Generator for the operation of the rotating anode of an x-ray tube - Google Patents

Generator for the operation of the rotating anode of an x-ray tube Download PDF

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Publication number
EP0401901B1
EP0401901B1 EP90201378A EP90201378A EP0401901B1 EP 0401901 B1 EP0401901 B1 EP 0401901B1 EP 90201378 A EP90201378 A EP 90201378A EP 90201378 A EP90201378 A EP 90201378A EP 0401901 B1 EP0401901 B1 EP 0401901B1
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EP
European Patent Office
Prior art keywords
voltage
generator
alternating
stator
anode
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EP90201378A
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German (de)
French (fr)
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EP0401901A2 (en
EP0401901A3 (en
Inventor
Gerd Vogler
Wulf Müller
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Philips Intellectual Property and Standards GmbH
Koninklijke Philips NV
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Philips Patentverwaltung GmbH
Philips Gloeilampenfabrieken NV
Koninklijke Philips Electronics NV
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Publication of EP0401901A3 publication Critical patent/EP0401901A3/en
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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
    • H05G1/66—Circuit arrangements for X-ray tubes with target movable relatively to the anode

Definitions

  • the invention relates to a generator for operating a rotating anode X-ray tube, the rotating anode of which is connected to a rotor which interacts with a stator, the windings of which are coupled to a high voltage generator which supplies the high voltage for the rotating anode and the rotor, one with its primary winding to one AC voltage source connectable isolating transformer is provided.
  • a generator of the type mentioned is known from the US Pat. No. 4,107,535 as prior art.
  • the “air” gap between the rotor and the stator can be considerably smaller than in conventional X-ray tubes in which the rotor carries high-voltage potential and the stator is grounded; with a small gap, the drive efficiency is much better.
  • the multiphase isolating transformer is required, which must be designed for the anode-side high voltage (e.g. 75 kV) and at the same time a low frequency (e.g. 50 or 150 Hz) adapted to the desired speed.
  • Such an isolating transformer is relatively voluminous and complex.
  • the object of the present invention is to design a generator of the type mentioned at the outset in such a way that the outlay for the isolating transformer can be reduced.
  • the secondary winding of the isolating transformer is coupled to a rectifier for feeding an inverter, which generates the alternating currents for the stator windings from the rectified voltage, and that the inverter is galvanically connected to the high-voltage generator and is operated at the anode-side high-voltage potential.
  • stator currents with a high reactive component have to be transmitted via a multiphase isolating transformer
  • the invention only the active power for supplying an inverter which supplies the stator currents is transmitted via the isolating transformer.
  • An inverter is required anyway if the frequency of the stator currents deviates from the grid frequency. In the case of the invention, this inverter is operated at the anode-side high-voltage potential.
  • a preferred development of the invention provides that the frequency of the AC voltage, which is fed to the primary winding from the AC voltage source, is significantly higher than the frequency of the currents supplied by the inverter. Accordingly, if the frequency of the AC voltage source is between a few kHz and a few hundred kHz, for example, the construction volume of the isolating transformer can be significantly reduced. This isolating transformer can then contain an inexpensive ferrite core and a cast secondary coil and is only slightly larger than a line transformer for television receivers of similar design.
  • the alternating voltage source comprises a switching device for generating alternating voltage pulses from the direct voltage supplied by a direct voltage source.
  • Such AC voltage sources can be manufactured particularly inexpensively.
  • a control loop is provided for stabilizing the current drawn from the DC voltage source.
  • the direct current supplied by the direct voltage source is stabilized, with the result that the stator currents supplied by the inverter are also stabilized. They are therefore independent of fluctuations in the mains voltage and changes in the resistance of the stator windings.
  • stator currents and the high voltage for the rotating anode X-ray tube are transmitted together via a multi-core high-voltage cable.
  • a stator cable is required, via which the Stator currents are supplied, this cable can be omitted in this embodiment of the invention.
  • the stator currents are supplied via a multi-core high-voltage cable. With three stator windings, this cable must have three wires.
  • High-voltage cables for X-ray tubes have three wires from the outset in order to be able to feed two filaments on the cathode side.
  • the drawing shows a rotating anode X-ray tube 1, the rotating anode 11 of which is only schematically indicated, is connected to a rotor 12 (which is actually arranged inside the tube piston).
  • the rotor 12 is over three triangle-shaped windings 13, 14 and 15 of a stator (which are arranged outside of the tubular piston), which are offset with respect to one another by 120 °, the gap remaining between the rotor and stator being small, so that there is good drive efficiency.
  • the electrical energy for driving the rotating anode is fed to the mains connection terminals 2 of a bridge rectifier 21, the output voltage of which is smoothed by a capacitor 22; a 3-phase network with 6-valve rectifier can also be used for the supply.
  • the capacitor voltage is fed via a resistor 23 to a circuit 3 which converts the direct voltage into alternating voltage pulses with a sufficiently high frequency, for example 20 kHz, and thus feeds the primary winding 41 of an isolating transformer 4 connected to its output.
  • the circuit 3 has two parallel branches, each with two series-connected switch combinations 31, 32 and 33, 34. Each switch combination comprises the parallel connection of a diode operated in the reverse direction and a controllable semiconductor switch.
  • the primary winding 41 is connected between the connection points of the switch combinations 31, 32 and 33, 34 connected in series.
  • the switch combinations are controlled by a clock pulse generator 35 with a clock frequency which corresponds to the transmission frequency of the isolating transformer, that is to say with 20 kHz in the example.
  • the control of the switch combination or the controllable switch contained therein by the clock pulse generator 35 takes place in push-pull, so that in one phase an alternating current flows through the switch combination 31, the winding 41 and the switch combination 34 and in the other phase via the switch combination 32 the primary winding 41 (in the opposite direction as in the previous switching phase) and the switch combination 33.
  • the isolating transformer 4 isolates the low-voltage potential on its primary winding from the anode-side high-voltage potential on its secondary winding. Because of the relatively high frequency with which the isolating transformer is operated (20 kHz), it can comprise an inexpensive ferrite core with a small cross-section, the secondary winding of which is cast for insulation purposes.
  • the AC voltage on the secondary winding 42 is rectified by a bridge rectifier 51 in conjunction with a capacitor 52 which is connected in series with the primary winding 61 of a transformer 6 to the output of the bridge rectifier 51.
  • This switched-mode power supply allows the DC voltage on the capacitor 22 to be converted into a DC voltage on the capacitor 52 with good efficiency, the connections of the capacitor 22 approximately having ground potential, while those of the capacitor 52 carry approximately high voltage potential - as will be explained in more detail below.
  • the voltage across the capacitor 52 is fed to an inverter 7, which supplies the currents for the three stator windings 13, 14 and 15.
  • the inverter 7 is a three-phase inverter with three branches connected in parallel with the capacitor 52, which are made up of two switch combinations 71, 74; 73.76; 75.72 exist.
  • the three connection points between the Switch combinations in the three branches are connected to the three connections of the delta-connected stator windings 13..15 each via a line.
  • the switch combinations 71..76 can have the same structure as the switch combination 31..34, it being possible for the controlled switches to be formed by a bipolar transistor, a MOSFET or a GTO thyristor or combinations thereof. Normal thyristors, which only block after a current zero crossing, are unsuitable as switches.
  • the switch combinations 71..76 are controlled by a clock pulse generator 8 so that the switching combinations 74, 76, 72 or 71, 73, 75 located in the upper or lower part of the branches become conductive one after the other, while in the other part at the same time Switch combinations become conductive one after the other that are not in the same branch. For example, during the first half of the time switch 71 in the left branch is conductive, switch 72 in the right branch is conductive and during the second half switch 76 is in the central branch of the upper portion.
  • the clock pulse generator 8 supplies six clock pulses with a frequency of 150 Hz at its outputs 81..86, which are connected to the switch combinations 71..76, the potentials on the control lines 82, 84 and 86 for the three upper ones Switches 72, 74 and 76 are offset from the potentials on control lines 81, 83 and 85 for lower switches 71, 73 and 75 by an appropriate amount.
  • the clock pulses at the successive outputs 81..86 are each offset by 60 °, making the switches connected to them conductive for a third of each period. At the three Inputs of the stator windings therefore result in stepped voltages of 150 Hz, with the mutually offset course indicated above these windings.
  • the six phase-shifted clock pulses can be derived in the clock pulse generator 8, for example from an oscillator with six times the clock frequency (at 900 Hz) in conjunction with a binary counter, the outputs of which are linked via logic gates so that the phase-shifted clock pulses result; the oscillator, the binary counter and the logic gates are not shown in the drawing.
  • the supply voltage for the clock pulse generator 8 is generated by rectifying the output voltage of the secondary winding 62 of the transformer 6. Although the primary winding 61 of this transformer is located at the output of the rectifier 51, a direct current flows through it, but a transferable alternating voltage arises from the fact that the bridge rectifier (51) only supplies voltage periodically and acts as a freewheeling diode during breaks, in accordance with the switching regulator principle.
  • Direct current therefore flows through the winding 61 for recharging the capacitor 52 with a triangularly superimposed alternating current component.
  • the primary winding 61 of the transformer 6 thus has a double function in that it serves on the one hand as a storage inductor in the switching power supply 3, 4 etc. and on the other hand forms the primary winding of a transformer 6 transmitting the AC components for generating a supply voltage for the clock generator 8.
  • One of the three lines connecting the connection points in the three branches to the three stator connections is connected to the output of a high-voltage generator 91.
  • This high voltage generator delivers the High voltage (against ground) for the rotating anode, which is fed to it via the above-mentioned line.
  • the inverter 7 is also connected to the high voltage with the connection of the clock pulse generator 8 and the secondary winding 42.
  • the negative high voltage is generated by a high voltage generator 92.
  • the output of the high voltage generator 92 is connected to one of the three output lines of the heating current converter group 93, which supplies the currents for the two filaments of the X-ray tube.
  • the high voltage for the anode and the cathode as well as the stator currents and the filament currents are transmitted to the X-ray emitter via a high-voltage cable 94 and 95, which is indicated schematically in the drawing.
  • stator cable is still required to drive the rotating anode in conventional X-ray emitters with a stator operated at ground, via which the stator currents flow, such a cable can be omitted in the invention because the stator currents and the high voltage can be transmitted via the same high-voltage cable 94.
  • the direct current flowing from the capacitor 22 via the resistor 23 to the switching device 3 is a precise measure of the amplitude of the alternating currents flowing in the stator windings 13, 14 and 15, which in turn is the driving torque acting on the rotor 12 determine.
  • the rotating anode drive can therefore be stabilized from fluctuations in the mains voltage and against fluctuations in the line resistances in the high-voltage cable or in the stator windings, which can occur, for example, as a result of a change in temperature.
  • the power loss is kept to a minimum.
  • the control circuit required to stabilize the direct current contains a pulse duration modulator 36 which compares the voltage across the resistor 23, which is proportional to the direct current, with a predeterminable value and, depending on this, varies the duration of the switching pulses for the switch combinations 31..34 such that the direct voltage across the resistor 23 corresponds to the specified value.

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  • X-Ray Techniques (AREA)

Description

Die Erfindung betrifft einen Generator zum Betreiben einer Drehanoden-Röntgenröhre, deren Drehanode mit einem Rotor verbunden ist, der mit einem Stator zusammenwirkt, dessen Wicklungen mit einem die Hochspannung für die Drehanode und den Rotor liefernden Hochspannungserzeuger gekoppelt sind, wobei ein mit seiner Primärwicklung an eine Wechselspannungsquelle anschließbarer Trenntransformator vorgesehen ist. Ein Generator der eingangs genannten Art ist aus der US-PS 4 107 535 als Stand der Technik bekannt. Wenn sich die Statorwicklungen bzw. der Stator auf demselben Hochspannungspotential befinden wie der Rotor, kann der "Luft"-Spalt zwischen Rotor und Stator wesentlich kleiner sein als bei konventionellen Röntgenröhren, bei denen der Rotor Hochspannungspotential führt und der Stator an Masse liegt; bei einem kleinen Spalt ergibt sich ein wesentlich besserer Antriebswirkungsgrad. Nachteilig daran ist, daß zur Erzeugung der Ströme für die Statorwicklungen der mehrphasiger Trenntransformator erforderlich ist, der für die anodenseitige Hochspannung (z.B. 75 kV) und zugleich eine niedrige, der gewünschten Drehzahl angepaßte Frequenz (z.B. 50 oder 150 Hz) ausgelegt sein muß. Ein derartiger Trenntransformator ist relativ voluminös und aufwendig.The invention relates to a generator for operating a rotating anode X-ray tube, the rotating anode of which is connected to a rotor which interacts with a stator, the windings of which are coupled to a high voltage generator which supplies the high voltage for the rotating anode and the rotor, one with its primary winding to one AC voltage source connectable isolating transformer is provided. A generator of the type mentioned is known from the US Pat. No. 4,107,535 as prior art. If the stator windings or the stator are at the same high-voltage potential as the rotor, the “air” gap between the rotor and the stator can be considerably smaller than in conventional X-ray tubes in which the rotor carries high-voltage potential and the stator is grounded; with a small gap, the drive efficiency is much better. The disadvantage of this is that to generate the currents for the stator windings, the multiphase isolating transformer is required, which must be designed for the anode-side high voltage (e.g. 75 kV) and at the same time a low frequency (e.g. 50 or 150 Hz) adapted to the desired speed. Such an isolating transformer is relatively voluminous and complex.

Aufgabe der vorliegenden Erfindung ist es, einen Generator der eingangs genannten Art so auszugestalten, daß der Aufwand für den Trenntransformator verringert werden kann.The object of the present invention is to design a generator of the type mentioned at the outset in such a way that the outlay for the isolating transformer can be reduced.

Diese Aufgabe wird erfindungsgemäß dadurch gelöst, daß die Sekundärwicklung des Trenntransformators mit einem Gleichrichter zur Speisung eines Wechselrichters gekoppelt ist, der aus der gleichgerichteten Spannung die Wechselströme für die Statorwicklungen erzeugt, und daß der Wechselrichter mit dem Hochspannungserzeuger galvanisch verbunden ist und auf dem anodenseitigen Hochspannungspotential betrieben wird.This object is achieved in that the secondary winding of the isolating transformer is coupled to a rectifier for feeding an inverter, which generates the alternating currents for the stator windings from the rectified voltage, and that the inverter is galvanically connected to the high-voltage generator and is operated at the anode-side high-voltage potential.

Während also bei der bekannten Anordnung die Statorströme mit hohem Blindanteil über einen mehrphasigen Trenntransformator übertragen werden müssen, wird bei der Erfindung über den Trenntransformator lediglich die Wirkleistung für die Speisung eines Wechselrichters übertragen, der die Statorströme liefert. Ein Wechselrichter ist ohnehin erforderlich, wenn die Frequenz der Statorströme von der Netzfrequenz abweicht. Dieser Wechselrichter wird bei der Erfindung auf dem anodenseitigen Hochspannungspotential betrieben.Thus, while in the known arrangement the stator currents with a high reactive component have to be transmitted via a multiphase isolating transformer, in the invention only the active power for supplying an inverter which supplies the stator currents is transmitted via the isolating transformer. An inverter is required anyway if the frequency of the stator currents deviates from the grid frequency. In the case of the invention, this inverter is operated at the anode-side high-voltage potential.

Eine bevorzugte Weiterbildung der Erfindung sieht vor, daß die Frequenz der Wechselspannung, die der Primärwicklung von der Wechselspannungsquelle zugeführt wird, wesentlich höher ist als die Frequenz der von dem Wechselrichter gelieferten Ströme. Wenn demgemäß die Frequenz der Wechselspannungsquelle beispielsweise zwischen einigen kHz und einigen hundert kHz liegt, kann das Bauvolumen des Trenntransformators wesentlich reduziert werden. Dieser Trenntransformator kann dann einen kostengünstigen Ferritkern enthalten sowie eine vergossene Sekundärspule und ist nur geringfügig größer als ein in der Bauform ähnlicher Zeilentransformator für Fernsehempfänger.A preferred development of the invention provides that the frequency of the AC voltage, which is fed to the primary winding from the AC voltage source, is significantly higher than the frequency of the currents supplied by the inverter. Accordingly, if the frequency of the AC voltage source is between a few kHz and a few hundred kHz, for example, the construction volume of the isolating transformer can be significantly reduced. This isolating transformer can then contain an inexpensive ferrite core and a cast secondary coil and is only slightly larger than a line transformer for television receivers of similar design.

In weiterer Ausgestaltung ist vorgesehen, daß die Wechselspannungsquelle eine Schalteinrichtung zur Erzeugung von Wechselspannungsimpulsen aus der von einer Gleichspannungsquelle gelieferten Gleichspannung umfaßt. Solche Wechselspannungsquellen lassen sich besonders preisgünstig herstellen.In a further embodiment it is provided that the alternating voltage source comprises a switching device for generating alternating voltage pulses from the direct voltage supplied by a direct voltage source. Such AC voltage sources can be manufactured particularly inexpensively.

In noch weiterer Ausgestaltung der Erfindung ist vorgesehen, daß ein Regelkreis zur Stabilisierung des der Gleichspannungsquelle entnommenen Stromes vorgesehen ist. Dadurch wird der von der Gleichspannungsquelle gelieferte Gleichstrom stabilisiert, was zur Folge hat, daß auch die vom Wechselrichter gelieferten Statorströme stabilisiert werden. Sie sind damit unabhängig von Netzspannungsschwankungen und von Widerstandsänderungen der Statorwicklungen.In a still further embodiment of the invention it is provided that a control loop is provided for stabilizing the current drawn from the DC voltage source. As a result, the direct current supplied by the direct voltage source is stabilized, with the result that the stator currents supplied by the inverter are also stabilized. They are therefore independent of fluctuations in the mains voltage and changes in the resistance of the stator windings.

In weiterer Ausgestaltung der Erfindung ist vorgesehen, daß die Statorströme und die Hochspannung für die Drehanoden-Röntgenröhre gemeinsam über ein mehradriges Hochspannungskabel übertragen werden. Während die Röntgenstrahler mit Drehanoden-Röntgenröhre, bei denen in der üblichen Weise der Rotor Hochspannungspotential und der Stator - im zeitlichen Mittel - Massepotential führt, außer den beiden Hochspannungskabeln zum Zuführen der Hochspannungen für Anode bzw. Kathode noch ein Statorkabel erforderliche ist, über das die Statorströme zugeführt werden, kann dieses Kabel bei dieser Ausgestaltung der Erfindung entfallen. Die Statorströme werden dabei über ein mehradriges Hochspannungskabel zugeführt. Bei drei Statorwicklungen muß dieses Kabel drei Adern haben. Hochspannungskabel für Röntgenröhren besitzen aber von vornherein drei Adern, um zwei Heizfäden auf der Kathodenseite speisen zu können.In a further embodiment of the invention it is provided that the stator currents and the high voltage for the rotating anode X-ray tube are transmitted together via a multi-core high-voltage cable. While the x-ray emitter with rotating anode x-ray tube, in which the rotor carries high voltage potential and the stator - on average over time - has ground potential, in addition to the two high voltage cables for supplying the high voltages for anode and cathode, a stator cable is required, via which the Stator currents are supplied, this cable can be omitted in this embodiment of the invention. The stator currents are supplied via a multi-core high-voltage cable. With three stator windings, this cable must have three wires. High-voltage cables for X-ray tubes have three wires from the outset in order to be able to feed two filaments on the cathode side.

Die Erfindung wird nachstehend anhand der Zeichnung erläutert, die ein schematisches Prinzipschaltbild eines erfindungsgemäßen Generators zeigt.The invention is explained below with reference to the drawing, which shows a schematic block diagram of a generator according to the invention.

Die Zeichnung zeigt eine Drehanoden-Röntgenröhre 1, deren nur schematisch angedeutete Drehanode 11 mit einem (in Wirklichkeit innerhalb des Röhrenkolbens angeordneten) Rotor 12 verbunden ist. Der Rotor 12 wird von über drei im Dreieck geschaltete und räumlich um 120° gegeneinander versetzten Wicklungen 13, 14 und 15 eines Stators (die außerhalb des Röhrenkolbens angeordnet sind) angetrieben, wobei der zwischen Rotor und Stator verbleibende Spalt klein ist, so daß sich ein guter Antriebswirkungsgrad ergibt.The drawing shows a rotating anode X-ray tube 1, the rotating anode 11 of which is only schematically indicated, is connected to a rotor 12 (which is actually arranged inside the tube piston). The rotor 12 is over three triangle-shaped windings 13, 14 and 15 of a stator (which are arranged outside of the tubular piston), which are offset with respect to one another by 120 °, the gap remaining between the rotor and stator being small, so that there is good drive efficiency.

Die elektrische Energie für den Antrieb der Drehanode wird an den Netzanschlußklemmen 2 einem Brückengleichrichter 21 zugeführt, dessen Ausgangsspannung von einem Kondensator 22 geglättet wird; zur Speisung kann aber auch ein 3Phasen-Netz mit 6Ventil-Gleichrichter verwendet werden. Die Kondensatorspannung wird über einen Widerstand 23 einer Schaltung 3 zugeführt, die die Gleichspannung in Wechselspannungsimpulse mit genügend hoher Frequenz, beispielsweise 20 kHz umsetzt und damit die an ihrem Ausgang angeschlossene Primärwicklung 41 eines Trenntransformators 4 speist. Die Schaltung 3 besitzt zwei parallele Zweige mit je zwei in Serie geschalteten Schalterkombinationen 31, 32 bzw. 33, 34. Jede Schalterkombination umfaßt die Parallelschaltung einer in der Sperrichtung betriebenen Diode und eines steuerbaren Halbleiterschalters. Die Primärwicklung 41 ist zwischen die Verbindungspunkte der in Serie geschalteten Schalterkombinationen 31, 32 bzw. 33, 34 geschaltet.The electrical energy for driving the rotating anode is fed to the mains connection terminals 2 of a bridge rectifier 21, the output voltage of which is smoothed by a capacitor 22; a 3-phase network with 6-valve rectifier can also be used for the supply. The capacitor voltage is fed via a resistor 23 to a circuit 3 which converts the direct voltage into alternating voltage pulses with a sufficiently high frequency, for example 20 kHz, and thus feeds the primary winding 41 of an isolating transformer 4 connected to its output. The circuit 3 has two parallel branches, each with two series-connected switch combinations 31, 32 and 33, 34. Each switch combination comprises the parallel connection of a diode operated in the reverse direction and a controllable semiconductor switch. The primary winding 41 is connected between the connection points of the switch combinations 31, 32 and 33, 34 connected in series.

Die Schalterkombinationen werden durch einen Taktpulsgenerator 35 mit einer Taktfrequenz gesteuert, die der Übertragungsfrequenz des Trenntransformators entspricht, im Beispiel also mit 20 kHz. Die Ansteuerung der Schalterkombination bzw. der darin enthaltenen steuerbaren Schalter durch den Taktpulsgenerator 35 erfolgt im Gegentakt, so daß in der einen Phase ein Wechselstrom über die Schalterkombination 31, die Wicklung 41 und die Schalterkombination 34 fließt und in der anderen Phase über die Schalterkombination 32 die Primärwicklung 41 (in der entgegengesetzten Richtung wie in der vorigen Schaltphase) und die Schalterkombination 33.The switch combinations are controlled by a clock pulse generator 35 with a clock frequency which corresponds to the transmission frequency of the isolating transformer, that is to say with 20 kHz in the example. The control of the switch combination or the controllable switch contained therein by the clock pulse generator 35 takes place in push-pull, so that in one phase an alternating current flows through the switch combination 31, the winding 41 and the switch combination 34 and in the other phase via the switch combination 32 the primary winding 41 (in the opposite direction as in the previous switching phase) and the switch combination 33.

Der Trenntransformator 4 trennt das Niederspannungspotential an seiner Primärwicklung von dem anodenseitigen Hochspannungspotential an seiner Sekundärwicklung. Wegen der relativ hohen Frequenz, mit der der Trenntransformator betrieben wird (20 kHz) kann er einen preiswerten Ferritkern mit geringem Querschnitt umfassen, dessen Sekundärwicklung zu Isolationszwecken vergossen ist.The isolating transformer 4 isolates the low-voltage potential on its primary winding from the anode-side high-voltage potential on its secondary winding. Because of the relatively high frequency with which the isolating transformer is operated (20 kHz), it can comprise an inexpensive ferrite core with a small cross-section, the secondary winding of which is cast for insulation purposes.

Die Wechselspannung an der Sekundärwicklung 42 wird durch einen Brückengleichrichter 51 in Verbindung mit einem Kondensator 52 gleichgerichtet, der in Serie mit der Primärwicklung 61 eines Transformators 6 an den Ausgang des Brückengleichrichters 51 angeschlossen ist. Die Schalteinrichtung 3, der Trenntransformator 4, der Gleichrichter 51, der Kondensator 52 und die als Speicherdrossel wirksame Primärwicklung 61 des Transformators 6 bilden ein Schaltnetzteil vom Brücken-Gegentaktwandler-Typ. Dieses Schaltnetzteil gestattet es, die Gleichspannung am Kondensator 22 mit gutem Wirkungsgrad in eine Gleichspannung am Kondensator 52 umzusetzen, wobei die Anschlüsse des Kondensators 22 näherungsweise Massepotential führen, während die des Kondensators 52 annähernd Hochspannungspotential führen - wie noch näher ausgeführt wird.The AC voltage on the secondary winding 42 is rectified by a bridge rectifier 51 in conjunction with a capacitor 52 which is connected in series with the primary winding 61 of a transformer 6 to the output of the bridge rectifier 51. The switching device 3, the isolating transformer 4, the rectifier 51, the capacitor 52 and the primary winding 61 of the transformer 6, which acts as a storage choke, form a switching power supply of the bridge push-pull converter type. This switched-mode power supply allows the DC voltage on the capacitor 22 to be converted into a DC voltage on the capacitor 52 with good efficiency, the connections of the capacitor 22 approximately having ground potential, while those of the capacitor 52 carry approximately high voltage potential - as will be explained in more detail below.

Die Spannung am Kondensator 52 wird einem Wechselrichter 7 zugeführt, der die Ströme für die drei Statorwicklungen 13, 14 und 15 liefert. Der Wechselrichter 7 ist ein Dreiphasen-Wechselrichter mit drei dem Kondensator 52 parallelgeschalteten Zweigen, die aus der Serienschaltung von jeweils zwei Schalterkombinationen 71,74; 73,76; 75,72 bestehen. Die drei Verbindungspunkte zwischen den Schalterkombinationen in den drei Zweigen sind mit den drei Anschlüssen der im Dreieck geschalteten Statorwicklungen 13..15 über je eine Leitung verbunden.The voltage across the capacitor 52 is fed to an inverter 7, which supplies the currents for the three stator windings 13, 14 and 15. The inverter 7 is a three-phase inverter with three branches connected in parallel with the capacitor 52, which are made up of two switch combinations 71, 74; 73.76; 75.72 exist. The three connection points between the Switch combinations in the three branches are connected to the three connections of the delta-connected stator windings 13..15 each via a line.

Die Schalterkombinationen 71..76 können den gleichen Aufbau haben wie die Schalterkombination 31..34, wobei die gesteuerten Schalter durch je einen bipolaren Transistor, einen MOSFET oder einen GTO-Thyristor bzw. Kombinationen davon gebildet werden können. Normale Thyristoren, die erst nach einem Stromnulldurchgang sperren, sind als Schalter hingegen ungeeignet.The switch combinations 71..76 can have the same structure as the switch combination 31..34, it being possible for the controlled switches to be formed by a bipolar transistor, a MOSFET or a GTO thyristor or combinations thereof. Normal thyristors, which only block after a current zero crossing, are unsuitable as switches.

Die Schalterkombinationen 71..76 werden von einem Taktpulsgenerator 8 so gesteuert, daß die im oberen bzw. unteren Teil der Zweige befindlichen Schaltkombinationen 74, 76, 72 bzw. 71, 73, 75 nacheinander leitend werden, wobei gleichzeitig in dem jeweils anderen Teil die Schalterkombinationen nacheinander leitend werden, die sich nicht im gleichen Zweig befinden. Beispielsweise ist während der ersten Hälfte der Zeit, während der der Schalter 71 im linken Zweig unten leitend ist, der Schalter 72 im rechten Zweig oben leitend und während der zweiten Hälfte der Schalter 76 im mittleren Zweig des oberen Teils. Der Taktimpulsgenerator 8 liefert zu diesem Zweck an seinen Ausgängen 81..86, die mit den Schalterkombinationen 71..76 verbunden sind, sechs Taktpulse mit einer Frequenz von 150 Hz, wobei die Potentiale auf den Steuerleitungen 82, 84 und 86 für die drei oberen Schalter 72, 74 und 76 gegenüber den Potentialen auf den Steuerleitungen 81, 83 und 85 für die unteren Schalter 71, 73 und 75 um einen geeigneten Betrag versetzt sind. Wie schematisch angedeutet, sind die Taktpulse an den aufeinanderfolgenden Ausgängen 81..86 jeweils um 60° gegeneinander versetzt, wobei sie während eines Drittels jeder Periode die damit verbundenen Schalter leitend machen. An den drei Eingängen der Statorwicklungen ergeben sich daher stufenförmige Spannungen von 150 Hz, mit dem gegeneinander versetzten, oberhalb dieser Wicklungen angedeuteten Verlauf.The switch combinations 71..76 are controlled by a clock pulse generator 8 so that the switching combinations 74, 76, 72 or 71, 73, 75 located in the upper or lower part of the branches become conductive one after the other, while in the other part at the same time Switch combinations become conductive one after the other that are not in the same branch. For example, during the first half of the time switch 71 in the left branch is conductive, switch 72 in the right branch is conductive and during the second half switch 76 is in the central branch of the upper portion. For this purpose, the clock pulse generator 8 supplies six clock pulses with a frequency of 150 Hz at its outputs 81..86, which are connected to the switch combinations 71..76, the potentials on the control lines 82, 84 and 86 for the three upper ones Switches 72, 74 and 76 are offset from the potentials on control lines 81, 83 and 85 for lower switches 71, 73 and 75 by an appropriate amount. As indicated schematically, the clock pulses at the successive outputs 81..86 are each offset by 60 °, making the switches connected to them conductive for a third of each period. At the three Inputs of the stator windings therefore result in stepped voltages of 150 Hz, with the mutually offset course indicated above these windings.

Die sechs gegeneinander phasenversetzten Taktpulse können in dem Taktpulsgenerator 8 beispielsweise aus einem Oszillator mit der sechsfachen Taktfrequenz (an 900 Hz) in Verbindung mit einem Binärzähler abgeleitet werden, dessen Ausgänge über Logikgatter so verknüpft sind, daß sich die phasenversetzten Taktpulse ergeben; der Oszillator, der Binärzähler und die Logikgatter sind in der Zeichnung nicht näher dargestellt. Die Versorgungsspannung für den Taktpulsgenerator 8 wird durch Gleichrichtung der Ausgangsspannung der Sekundärwicklung 62 des Transformators 6 erzeugt. Die Primärwicklung 61 dieses Transformators befindet sich zwar am Ausgang des Gleichrichters 51, wird also von einem Gleichstrom durchflossen, jedoch entsteht eine übertragbare Wechselspannung dadurch, daß der Brückengleichrichter (51) nur periodisch Spannung liefert und in den Pausen als Freilaufdiode wirkt, entsprechend dem Schaltreglerprinzip. Durch die Wicklung 61 fließt also Gleichstrom zur Nachladung des Kondensators 52 mit dreieckförmig überlagerter Wechselstromkomponente. Die Primärwicklung 61 des Transformators 6 hat also eine Doppelfunktion, indem sie einerseits als Speicherdrossel in dem Schaltnetzteil 3, 4 usw. dient und andererseits die Primärwicklung eines die Wechselstromkomponenten übertragenden Transformators 6 zur Erzeugung einer Versorgungsspannung für den Taktgenerator 8 bildet.The six phase-shifted clock pulses can be derived in the clock pulse generator 8, for example from an oscillator with six times the clock frequency (at 900 Hz) in conjunction with a binary counter, the outputs of which are linked via logic gates so that the phase-shifted clock pulses result; the oscillator, the binary counter and the logic gates are not shown in the drawing. The supply voltage for the clock pulse generator 8 is generated by rectifying the output voltage of the secondary winding 62 of the transformer 6. Although the primary winding 61 of this transformer is located at the output of the rectifier 51, a direct current flows through it, but a transferable alternating voltage arises from the fact that the bridge rectifier (51) only supplies voltage periodically and acts as a freewheeling diode during breaks, in accordance with the switching regulator principle. Direct current therefore flows through the winding 61 for recharging the capacitor 52 with a triangularly superimposed alternating current component. The primary winding 61 of the transformer 6 thus has a double function in that it serves on the one hand as a storage inductor in the switching power supply 3, 4 etc. and on the other hand forms the primary winding of a transformer 6 transmitting the AC components for generating a supply voltage for the clock generator 8.

Eine der drei Leitungen, die die Verbindungspunkte in den drei Zweigen mit den drei Stator-Anschlüssen verbindet, ist an den Ausgang eines Hochspannungserzeugers 91 angeschlossen. Dieser Hochspannungserzeuger liefert die (gegenüber Masse positive) Hochspannung für die Drehanode, die dieser über die erwähnte Leitung zugeführt wird. Infolgedessen liegt auch der Wechselrichter 7 mit Anschluß des Taktpulsgenerators 8 und der Sekundärwicklung 42 auf Hochspannung.One of the three lines connecting the connection points in the three branches to the three stator connections is connected to the output of a high-voltage generator 91. This high voltage generator delivers the High voltage (against ground) for the rotating anode, which is fed to it via the above-mentioned line. As a result, the inverter 7 is also connected to the high voltage with the connection of the clock pulse generator 8 and the secondary winding 42.

Die negative Hochspannung wird von einem Hochspannungserzeuger 92 erzeugt. Der Ausgang des Hochspannungserzeugers 92 ist mit einer der drei Ausgangsleitungen der Heizstromwandlergruppe 93 verbunden, die die Ströme für die beiden Heizfäden der Röntgenröhre liefert. Über je ein in der Zeichnung schematisch angedeutetes Hochspannungskabel 94 bzw. 95 werden die Hochspannung für die Anode bzw. die Kathode sowie die Statorströme bzw. die Heizfadenströme zum Röntgenstrahler übertragen. Während bei konventionellen Röntgenstrahlern mit auf Masse betriebenem Stator zum Antrieb der Drehanode immer noch ein Statorkabel erforderlich ist, über das die Statorströme fließen, kann bei der Erfindung ein solches Kabel entfallen, weil die Statorströme und die Hochspannung über das gleiche Hochspannungskabel 94 übertragen werden können.The negative high voltage is generated by a high voltage generator 92. The output of the high voltage generator 92 is connected to one of the three output lines of the heating current converter group 93, which supplies the currents for the two filaments of the X-ray tube. The high voltage for the anode and the cathode as well as the stator currents and the filament currents are transmitted to the X-ray emitter via a high-voltage cable 94 and 95, which is indicated schematically in the drawing. While a conventional stator cable is still required to drive the rotating anode in conventional X-ray emitters with a stator operated at ground, via which the stator currents flow, such a cable can be omitted in the invention because the stator currents and the high voltage can be transmitted via the same high-voltage cable 94.

Es läßt sich zeigen, daß der Gleichstrom der vom Kondensator 22 über den Widerstand 23 zu der Schalteinrichtung 3 fließt, ein genaues Maß für die Amplitude der in den Statorwicklungen 13,14 und 15 fließenden Wechselströme ist, die ihrerseits das auf dem Rotor 12 wirkende Antriebsmoment bestimmen. Durch Stabilisieren des Gleichstroms, der der Schalteinrichtung 3 zufließt, kann daher der Drehanodenantrieb von Netzspannungsschwankungen und gegenüber Schwankungen der Leitungswiderstände im Hochspannungskabel oder in den Statorwicklungen stabilisiert werden, die beispielsweise als Folge einer Temperaturänderung auftreten können. Durch das Stabilisieren des Antriebsmomentes bzw. der Statorströme wird gleichzeitig die Verlustleistung auf einem Minimalwert gehalten.It can be shown that the direct current flowing from the capacitor 22 via the resistor 23 to the switching device 3 is a precise measure of the amplitude of the alternating currents flowing in the stator windings 13, 14 and 15, which in turn is the driving torque acting on the rotor 12 determine. By stabilizing the direct current flowing to the switching device 3, the rotating anode drive can therefore be stabilized from fluctuations in the mains voltage and against fluctuations in the line resistances in the high-voltage cable or in the stator windings, which can occur, for example, as a result of a change in temperature. By stabilizing the drive torque or the stator currents at the same time the power loss is kept to a minimum.

Der zur Stabilisierung des Gleichstroms erforderliche Regelkreis enthält einen Pulsdauermodulator 36, der die zu dem Gleichstrom proportionale Spannung am Widerstand 23 mit einem vorgebbaren Wert vergleicht und in Abhängigkeit davon die Dauer der Schaltimpulse für die Schalterkombinationen 31..34 so variiert, daß die Gleichspannung am Widerstand 23 dem vorgegebenen Wert entspricht.The control circuit required to stabilize the direct current contains a pulse duration modulator 36 which compares the voltage across the resistor 23, which is proportional to the direct current, with a predeterminable value and, depending on this, varies the duration of the switching pulses for the switch combinations 31..34 such that the direct voltage across the resistor 23 corresponds to the specified value.

Claims (8)

  1. A generator for operating a rotary-anode X-ray tube (1) whose rotary anode (11) is connected to a rotor (12) that cooperates with a stator whose windings (13, 14, 15) are coupled to a high-voltage generator (91) delivering the high-voltage for the rotary anode and the rotor, there being provided an isolating transformer (4) whose primary winding (41) can be connected to an alternating-voltage source (2, 3), characterized in that the secondary winding (42) of the isolating transformer is coupled to a rectifier (51) for feeding an inverter (7) that generates the alternating currents for the stator windings from the rectified voltage, and in that the inverter (7) is conductively connected to the high-voltage generator (91) and is operated at the high-voltage potential at the anode side.
  2. A generator as claimed in Claim 1, characterized in that the frequency of the alternating voltage applied to the primary winding by the alternating-voltage source (2, 3) is substantially higher than the frequency of the currents delivered by the inverter (7).
  3. A generator as claimed in Claim 2, characterized in that the alternating-voltage source includes a switching device (3) for generating alternating-voltage pulses from the direct voltage delivered by a direct-voltage source (2).
  4. A generator as claimed in Claim 3, characterized in that a storage choke (61), forming a switched-mode power supply in conjunction with the switching device, the isolating transformer (4) and the rectifier (51, 52), is arranged in the output circuit of the rectifier (51).
  5. A generator as claimed in Claim 3 or 4, characterized in that a control circuit is provided for stabilizing the current derived from the direct-voltage source.
  6. A generator as claimed in Claim 5, characterized in that the control circuit includes a resistor (23), being connected between the direct-voltage source (2) and the switching device (3), and a pulse-duration modulator (36) which varies the duration of the pulses delivered by the switching device as a function of the direct voltage across the resistor (23).
  7. A generator as claimed in Claim 4, characterized in that the storage choke is formed by the primary winding (61) of a transformer (6) whose secondary winding is coupled to a rectifier whose output voltage serves as the supply voltage for a clock pulse generator (8) for generating the clock pulses for the inverter (7).
  8. A generator as claimed in any one of the preceding Claims, characterized in that the stator currents and the high-voltage for the rotary-anode X-ray tube are transferred jointly via a multi-core high-voltage cable (94).
EP90201378A 1989-06-03 1990-05-30 Generator for the operation of the rotating anode of an x-ray tube Expired - Lifetime EP0401901B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE3918164A DE3918164A1 (en) 1989-06-03 1989-06-03 GENERATOR FOR OPERATING A TURNING ANODE TUBE
DE3918164 1989-06-03

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EP0401901A2 EP0401901A2 (en) 1990-12-12
EP0401901A3 EP0401901A3 (en) 1991-05-29
EP0401901B1 true EP0401901B1 (en) 1994-11-02

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EP90201378A Expired - Lifetime EP0401901B1 (en) 1989-06-03 1990-05-30 Generator for the operation of the rotating anode of an x-ray tube

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US (1) US5060252A (en)
EP (1) EP0401901B1 (en)
JP (1) JP2836196B2 (en)
DE (2) DE3918164A1 (en)

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US5265146A (en) * 1992-11-16 1993-11-23 General Electric Company X-ray tube rotor controller using the main high voltage inverters for acceleration and speed maintenance
DE4304760A1 (en) * 1993-02-17 1994-08-18 Philips Patentverwaltung Drive device for a rotating anode
US8804910B1 (en) * 2011-01-24 2014-08-12 Moxtek, Inc. Reduced power consumption X-ray source
ITRE20120021A1 (en) * 2012-04-02 2013-10-03 Igor Spinella METHOD AND APPARATUS FOR ELECTRIC POWER TRANSFER
US9173623B2 (en) 2013-04-19 2015-11-03 Samuel Soonho Lee X-ray tube and receiver inside mouth
US11103207B1 (en) * 2017-12-28 2021-08-31 Radiation Monitorng Devices, Inc. Double-pulsed X-ray source and applications
CN109914025A (en) * 2019-04-11 2019-06-21 北京大豪科技股份有限公司 Yarn storage send yarn driving device and method, horizontal loom, equipment and storage medium

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Also Published As

Publication number Publication date
EP0401901A2 (en) 1990-12-12
DE59007598D1 (en) 1994-12-08
EP0401901A3 (en) 1991-05-29
JP2836196B2 (en) 1998-12-14
DE3918164A1 (en) 1990-12-06
JPH0322400A (en) 1991-01-30
US5060252A (en) 1991-10-22

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