EP0405399A2 - Apparat zur Erzeugung von Röntgenstrahlen - Google Patents

Apparat zur Erzeugung von Röntgenstrahlen Download PDF

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Publication number
EP0405399A2
EP0405399A2 EP90112038A EP90112038A EP0405399A2 EP 0405399 A2 EP0405399 A2 EP 0405399A2 EP 90112038 A EP90112038 A EP 90112038A EP 90112038 A EP90112038 A EP 90112038A EP 0405399 A2 EP0405399 A2 EP 0405399A2
Authority
EP
European Patent Office
Prior art keywords
voltage
frequency
transformer
high voltage
frequency converting
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.)
Granted
Application number
EP90112038A
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English (en)
French (fr)
Other versions
EP0405399A3 (en
EP0405399B1 (de
Inventor
Toyoshige C/O Intell. Property Division Harada
Kenichi C/O Intell. Property Division Tanbo
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.)
Toshiba Corp
Original Assignee
Toshiba Corp
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Priority claimed from JP2150458A external-priority patent/JPH0395898A/ja
Application filed by Toshiba Corp filed Critical Toshiba Corp
Publication of EP0405399A2 publication Critical patent/EP0405399A2/de
Publication of EP0405399A3 publication Critical patent/EP0405399A3/en
Application granted granted Critical
Publication of EP0405399B1 publication Critical patent/EP0405399B1/de
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • 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
    • 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 present invention relates to an X-ray generator apparatus having an X-ray tube which generates X-rays when applied with a high voltage obtained by increasing an input A.C. voltage by means of a step-up transformer or the like and rectifying the increased voltage.
  • a frequency converter 2 for converting the frequency of a voltage supplied from an input power source is connected to the primary side of a high voltage transformer 3.
  • An output voltage of the frequency converter 2 is increased by the high voltage transformer 3 and an output voltage of the high voltage transformer 3 is rectified by a high voltage rectifier 4.
  • a rectified output of the high voltage rectifier 4 is applied between the anode and cathode of an X-ray tube 5 serving as an X-ray source.
  • the frequency converter 2 is generally formed of a rectifier for converting an input A.C. voltage to a D.C. voltage, a capacitor for filtering the D.C. voltage, and an inverter for converting the D.C. voltage from the capacitor to an A.C. voltage of a desired frequency.
  • the frequency converter 2 converts the frequency fo (which is a commercial frequency and is generally 50/60 Hz) of the input A.C. voltage to a frequency f1 which is higher than the frequency fo and then applies the voltage to the high voltage transformer 3.
  • the output frequency f1 of the frequency converter 2 is set to be higher, the size and weight of the frequency con­verter 2 and high voltage transformer 3 can be reduced.
  • the capacitance and inductance can be reduced as the frequency is set higher if the impedances are kept unchanged. Since the capaci­tance and inductance vary in proportion to the size of the capacitor and coil, the size and weight of the fre­quency converter 2 and high voltage transformer 3 using the coil and capacitor can be reduced as the frequency becomes higher.
  • Fig. 2 shows an equivalent circuit of the device shown in Fig. 1 in view of the secondary portion of the trans­former 3.
  • L1, L2 and M respectively denote the primary inductance, secondary inductance and mutual inductance of the high voltage transformer 3.
  • N denotes the turn ratio (the number of turns of the secondary windings/the number of turns of the primary windings) of the transformer 3.
  • the high voltage transformer 3 in order to obtain a high output voltage, is so designed that the number of turns of the secondary winding is set to be very larger than that of the pri­mary winding, and thus the secondary inductance L2 is very larger than the primary inductance L1 and mutual inductance M. Therefore, the inductance of the secon­dary portion of the high voltage transformer 3 which is actually equal to (L2 - M) as shown in Fig. 2 can be regarded as being equal to the secondary inductance L2 by neglecting M, and in the following explanation, it is assumed that the inductance of the secondary portion is equal to L2.
  • the impedance Z2 becomes higher as the output fre­quency f1 of the frequency converter 2 becomes higher, causing a problem that the voltage Ex applied to the X-ray tube 5 is lowered.
  • the output frequency f1 of the conventional frequency converter 2 has an upper limit of approximately 10 KHz and a higher frequency exceeding the upper limit cannot be attained. If the frequency is set to approximately 10 KHz, it is difficult to greatly reduce the size and weight of the transformer and rectifier circuit and noise may be gen­erated from the transformer 3. The reason why the out­put frequency f1 of the frequency converter 2 can be increased only to approximately 10 KHz at most is that the secondary inductance L2 of the high voltage transformer 3 is very large.
  • a capacitor C1 is serially connected to the primary winding of the high voltage transformer 3 to attain a series resonance operation on the primary portion.
  • a capacitor C2 is connected in parallel with the primary winding of the high voltage transformer 3 to attain a parallel reso­nance operation on the primary portion.
  • a voltage on the primary portion of the high voltage transformer 3 is equivalently increased by the series resonance or parallel resonance operation.
  • the inductance L1 of the primary portion is originally small and the resonance voltage is low, and therefore, in order to obtain the same voltage applied to X-ray tube 5 as that obtained in a case wherein no resonance circuit is connected, it is only possible to increase the output frequency of the frequency converter 2 to two or three times the output frequency set in a case wherein no resonance circuit is connected.
  • the secondary winding of the high voltage transformer is divided into a plurality of sub-windings to increase the frequency of the high voltage trans­former, the sub-windings are connected to rectifier circuits are serially coupled and applied to an X-ray tube.
  • the high voltage transformer is not divided and the high voltage transformer can be regarded as being a single transformer, and an output of one frequency converter is simply connected to a single high voltage transformer. Therefore, like the conventional case shown in Fig. 1, it is only possible to increase the frequency to approximately 10 KHz at most.
  • An object of the present invention is to provide an X-ray generator apparatus in which the frequency of a voltage from an A.C. power source is increased by a fre­quency converter, then the voltage is increased by means of a transformer, and the increased voltage is rectified by means of a rectifier and applied to an X-ray tube, and in which the output frequency of the frequency con­verter is increased and the size and weight of the transformer and rectifier are reduced.
  • An X-ray generator apparatus comprises frequency converter means con­nected to an A.C. power source, for increasing the frequency of an A.C. voltage; plural transformer means connected to an output of the frequency converter means, for increasing the output A.C. voltage from the fre­quency converter means; and rectifier means for convert­ing the output A.C. voltages from the plural transformer means to D.C. voltages, serially adding all of the D.C. voltages, and applying the result of addition of the D.C. voltages to an X-ray tube.
  • FIG. 5 is a block diagram showing the construction of a first embodiment.
  • An A.C. power source 11 serving as an input power source is connected to the input terminal of an frequency converter 12.
  • the frequency converter 12 increases the frequency of an A.C. voltage supplied from the A.C. power source 11.
  • High voltage transformers 131, 132, ... 13 n are connected in parallel with one another between output terminals of the frequency con­verter 12. That is, one end of the primary winding of each of the high voltage transformers 131, 132, ...
  • 13 n is connected to one of the output terminals of the fre­quency converter 12 and the other end of the primary winding of each of the high voltage transformers 131, 132, ... 13 n is connected to the other output terminal of the frequency converter 12.
  • the secondary windings of the high voltage transformers 131, 132, ... 13 n are respectively connected to high voltage rectifiers 141, 142, ... 14 n .
  • the output terminals of the high voltage rectifiers 141, 142, ... 14 n are serially connected and the result of serial addition obtained by the series connection is applied to an X-ray tube 15.
  • the positive output terminals of the high voltage rectifiers 141 is connected to the anode of the X-ray tube 15
  • the negative output terminals of the high voltage rectifiers 141, 142, ... 14 n-1 are connected to the positive output terminals of the high voltage rectifiers 142, 143, ... 14 n
  • the negative output terminal of the high volt­age rectifier 14 n is connected to the cathode of the X-ray tube 15.
  • the number of turns of each of the primary windings of the high voltage transformers 131, 132, ... 13 n is set to be equal to that of the primary winding of the conventional high voltage transformer 3 shown in Fig. 1 and the number of turns of each of the secondary windings of the high voltage transformers 131, 132, ... 13 n is set to 1/n of that of the secondary winding of the conventional high voltage transformer 3 in order to simplify the description.
  • Fig. 6A is an equivalent circuit diagram of a secondary portion (a portion from the secondary winding to the X-ray tube with the rectifier being neglected) of the conventional transformer 3 of Fig. 1.
  • Fig. 6B is also the equivalent circuit diagram of the secondary portions of the transformers 131, 132, ... 13 n of the first embodiment shown in Fig. 5.
  • the number of turns of the secondary winding of each of the high voltage transformers 3, 131, 132, ... 13 n is extremely larger than that of the primary winding thereof, and the secondary inductance L2 is set to a large value. Therefore, the equivalent circuit diagrams can be expressed only by the secondary inductance L2 as shown in Figs. 6A and 6B.
  • the frequency converter is generally on/off operated by the switching pulse and outputs a pulse signal. Therefore, the voltage E2 is also expressed by a pulse.
  • the number of turns of the secondary winding of each of the high voltage transformers 131, 132, ... 13 n is set to 1/n of that of the high voltage transformer 3 in the conventional device (Fig. 1). Since the inductance of a coil varies in proportion to the square of the number of turns, the secondary induc­tance becomes L2/n2 and the secondary voltage becomes E2/n in each of the high voltage transformers 131, 132, ... 13 n . Further, the load of each of the high voltage transformers 131, 132, ... 13 n is substantially the same as a value obtained by dividing the load Rx in the con­ventional device by n, that is, it becomes Rx/n. As a result, the equivalent circuit diagram of the embodiment of Fig. 5 can be expressed as shown in Fig. 6A.
  • the time constant in the device of this embodiment (Fig. 5) is set to 1/n of that of the conventional device (Fig. 1), and therefore, it is understood that the frequency of the transformers 131, 132, ... 13 n can be increased by n times since the same voltage is obtained if the pulse width of the out­put of the frequency converter 12 is set to ⁇ b.
  • the high voltage transformer is divided into a plurality (for example, n) of transformers 131, 132, ... 13 n having a small capacity (the number of turns of the primary winding is kept unchanged and the number of turns of the secondary winding is reduced to 1/n times the original value), the primary windings of the divided transformers 131, 132, ... 13 n are connected in parallel with one another between the output terminals of the frequency converter 12 and a voltage obtained by serially adding together the rectification results of the outputs of the respective transformers is applied to the X-ray tube 15.
  • the apparatus including the frequency converter 12 can be made small and lightweight. Since the output frequency of the frequency converter 12 can be increased up to approximately 100 KHz or to a frequency which exceeds the audio frequency, generation of noise which is a problem in the conventional device can be pre­vented. Further, since the output control of the fre­quency converter 12 can be effected at a higher speed as the output frequency thereof increases, a high volt­age applied to the X-ray tube 15 can be more precisely set by using the feedback operation.
  • the rising characteristic of the tube voltage can be improved as shown by the curve B of Fig. 7, it becomes easy to apply a high voltage in a pulse form to the X-ray tube 15 and generate X-rays only at necessary timings, thereby making it possible to reduce the amount of X-ray radiation to an object.
  • the frequency converter can change the output voltage in addition to the output frequency by means of a pulse width modulation (PWM) for changing the pulse width of the switching pulse.
  • PWM pulse width modulation
  • the high voltage transformer and high voltage rectifier are disposed in a container filled with insulating oil. Since the container is substantially entirely filled with insulating oil, the volume and weight thereof become very large. In this case, the maintenance therefor is troublesome and there occurs a problem that oil leaks out of the container and stains the surrounding.
  • the transformer since the transformer is divided into a plurality of trans­formers of small capacities the high voltage trans­former and high voltage rectifier are disposed in a container of small capacity and can be molded into one unit with solid insulation material including gel insu­lating material.
  • Each molding unit may be constructed by a single transformer 131 and a single rectifier 141 as shown in Fig. 8 or by a plurality of transformers 131 to 13 i and a plurality of rectifiers 141 and 14 i as shown in Fig. 9. Further, as shown in Fig. 10, only the secondary winding of the transformer 131 and the rectifier 141 are molded and it is not always necessary to mold the primary winding of the transformer.
  • the high voltage transformer and the rectifier may be sepa­rately molded and they are connected by connectors or cables. Thus, various combinations of the molds can be selectively made.
  • Fig. 11 is a block diagram of the second embodiment. Portions which are the same as those of the first embodiment are denoted by the same reference numerals and the detail description thereof is omitted.
  • Inverters 121, 122 ... 12 n which are connected in par­allel with one another are connected to the A.C. power source 11.
  • Outputs of the frequency converters 121, 122, ... 12 n are supplied to rectifiers 141, 142, ... 14 n via high voltage transformers 131 132, ... 13 n .
  • Capacitors C R are respectively connected in series with the secondary windings of the high voltage transformers 131, 132, ... 13 n to constitute series resonant circuits on the secondary portion of the transformers.
  • the same effect as that of the first embodiment can be obtained.
  • the tube voltage can be roughly controlled by controlling the number of frequency converters which are set in the rest state.
  • the frequency con­verters are PWM-controlled, the tube voltage can be pre­cisely controlled.
  • the defective frequency converters are set into the rest state and other frequency converters which are otherwise set in the rest or nonoperative state can be used instead of the defective frequency converters. There­fore, it becomes possible to prevent the whole X-ray generator apparatus from being set into the inoperative state.
  • the maximum output is lowered by an amount cor­responding to the number of defective frequency con­verters, but it is seldom to use the maximum output and the device can be used without receiving practical interference while the defective frequency converter is being replaced.
  • the resonance capacitor C R is connected to the secondary winding of each of the high voltage transformers 131, 132, ... 13 n to cause an LC series resonance so as to prevent the voltage applied to the X-ray tube 15 from being lowered and to further increase the frequency of the frequency converters.
  • E2 and L2 in the respective resonant circuits can be reduced to E2 / n and L2 / n2 as shown in Fig. 6B as in the first embodiment.
  • L2 varies inversely with the square of the dividing number n, it becomes extremely small. In this way, since the voltages E L and E C across L2 and C R can be suppressed to small values, the advantage of the resonance on the secondary portion of the transformer can be effectively used.
  • the secondary inductance L2 becomes smaller, making it possible to attain a high frequency operation.
  • influence by the secondary inductance L2 can be completely neglected, making it possible to attain a higher frequency operation.
  • the dividing number can be reduced within the permissibie range of the breakdown voltage of the transformer and the capacitor.
  • the secondary resonance is not limited to the series resonance described above but may be a parallel resonance attained by connecting a capacitor in parallel with the secondary winding of the high voltage transformer.
  • Fig. 13 shows the characteristic of the voltage applied to the X-ray tube 15 obtained when the secondary portion is set in the resonant mode.
  • solid lines indicate Ex, and curves A and B among them respec­tively indicate the case of the conventional device and the case wherein the transformer is divided into n por­tions like the curves A and B of Fig. 7, and a curve D indicates a characteristic obtained when the high volt­age transformer of the second embodiment is divided and the secondary portion is set in the resonant mode.
  • the raising characteristic of the curves A and B which is suppressed by the secondary inductance of the transformer is improved by means of the resonance as indicated by the curve D. Therefore, a higher frequency operation can be attained, and the voltage applied to the X-ray tube can be further increased.
  • Fig. 13 fr indicates the reso­nant frequency.
  • broken line curves indicate the voltages obtained by multiplying the terminal volt­ages E L and E C of the secondary inductance L2 and the capacitor C R with the dividing number n.
  • the operation frequency can be further enhanced and the dividing number can be reduced by use of the secondary resonance in comparison with a case wherein the high voltage transformer is simply divided.
  • the transformers and rectifiers can be selectively molded into respective units with solid insulation material. It is not necessary to respectively connect the trans­formers to the frequency converters. It is possible to connect several transformers to a single frequency converter.
  • the output fre­quency of the frequency converter can be increased by dividing the transformer for increasing an output A.C. voltage of the frequency converter which increases the frequency of an A.C. voltage into a plurality of trans­formers of small capacity in which the number of turns of the secondary winding is smaller than that of the original transformer, adding outputs of the transformers together, and applying the result of addition to the X-ray tube.
  • the apparatus can be made small and lightweight, the control speed of the voltage can be enhanced if the frequency is increased, and the output voltage can be precisely controlled by feeding back the output.
  • the assembling and mainte­nance can be simplified by molding the divided trans­formers and the rectifiers into respective units with solid insulating material (including gel insulating material).
  • ripple components included in the output voltage can be easily suppressed and stabi­lized by the high frequency operation and the X-rays can be easily generated in a pulse form.
  • the fre­quency is increased, the frequency of the switching pulse of the frequency so that noise can be prevented from being generated.
  • each frequency converter can be easily and independently controlled so that the preci­sion of generation of the X-rays can be enhanced, and even if one or some frequency converters become defec­tive, the apparatus can be continuously operated by using the remaining frequency converters.
  • the frequency can be further increased by connecting the capacitor to the secondary winding of the transformer to form an LC resonance circuit and effect the resonance operation.

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  • X-Ray Techniques (AREA)
EP19900112038 1989-06-30 1990-06-25 Apparat zur Erzeugung von Röntgenstrahlen Expired - Lifetime EP0405399B1 (de)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
JP169645/89 1989-06-30
JP16964589 1989-06-30
JP150458/90 1990-06-08
JP2150458A JPH0395898A (ja) 1989-06-30 1990-06-08 Ｘ線発生装置

Publications (3)

Publication Number Publication Date
EP0405399A2 true EP0405399A2 (de) 1991-01-02
EP0405399A3 EP0405399A3 (en) 1991-06-05
EP0405399B1 EP0405399B1 (de) 1995-04-12

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Family Applications (1)

Application Number Title Priority Date Filing Date
EP19900112038 Expired - Lifetime EP0405399B1 (de) 1989-06-30 1990-06-25 Apparat zur Erzeugung von Röntgenstrahlen

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EP (1) EP0405399B1 (de)
DE (1) DE69018525T2 (de)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4107199A1 (de) * 1991-03-06 1992-09-10 Siemens Ag Hochfrequenz-roentgengenerator
WO1995009520A1 (en) * 1993-09-27 1995-04-06 Eagle Lcs Limited A mobile x-ray unit
DE102006052285A1 (de) * 2006-11-03 2008-05-08 Dr. Simon Consulting Gmbh Hochspannungsnetzgerät

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102013212099B4 (de) * 2013-06-25 2020-03-05 Trumpf Laser Gmbh Hochspannungsmodulation ohne Schleppfehler

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4317039A (en) 1978-07-14 1982-02-23 Siemens Aktiengesellschaft X-ray diagnostic generator
EP0286678A1 (de) 1985-12-20 1988-10-19 Yokogawa Medical Systems, Ltd Röntgenstrahlentomograph

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4338657A (en) * 1974-05-21 1982-07-06 Lisin Vladimir N High-voltage transformer-rectifier device
DE2814320C2 (de) * 1978-04-03 1984-02-16 Siemens AG, 1000 Berlin und 8000 München Röntgendiagnostikgenerator mit einer seinen Hochspannungstransformator aus einem Netzgleichrichter speisenden, zwei Wechselrichter aufweisenden Wechselrichterschaltung
FR2507842A1 (fr) * 1981-06-12 1982-12-17 Gen Equip Med Sa Regulateur de tension a semi-conducteur et generateur de radiologie comportant un tel regulateur
US4504895A (en) * 1982-11-03 1985-03-12 General Electric Company Regulated dc-dc converter using a resonating transformer
US4823250A (en) * 1987-11-05 1989-04-18 Picker International, Inc. Electronic control for light weight, portable x-ray system

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4317039A (en) 1978-07-14 1982-02-23 Siemens Aktiengesellschaft X-ray diagnostic generator
EP0286678A1 (de) 1985-12-20 1988-10-19 Yokogawa Medical Systems, Ltd Röntgenstrahlentomograph

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4107199A1 (de) * 1991-03-06 1992-09-10 Siemens Ag Hochfrequenz-roentgengenerator
US5210780A (en) * 1991-03-06 1993-05-11 Siemens Aktiengesellschaft Low ripple x-ray generator
WO1995009520A1 (en) * 1993-09-27 1995-04-06 Eagle Lcs Limited A mobile x-ray unit
DE102006052285A1 (de) * 2006-11-03 2008-05-08 Dr. Simon Consulting Gmbh Hochspannungsnetzgerät

Also Published As

Publication number Publication date
DE69018525T2 (de) 1995-08-10
DE69018525D1 (de) 1995-05-18
EP0405399A3 (en) 1991-06-05
EP0405399B1 (de) 1995-04-12

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