EP0179680A1 - Speiseanordnung für Röntgenstrahlenquelle, anwendbar bei Röntgenuntersuchungen - Google Patents

Speiseanordnung für Röntgenstrahlenquelle, anwendbar bei Röntgenuntersuchungen Download PDF

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Publication number
EP0179680A1
EP0179680A1 EP85401754A EP85401754A EP0179680A1 EP 0179680 A1 EP0179680 A1 EP 0179680A1 EP 85401754 A EP85401754 A EP 85401754A EP 85401754 A EP85401754 A EP 85401754A EP 0179680 A1 EP0179680 A1 EP 0179680A1
Authority
EP
European Patent Office
Prior art keywords
circuit
thyristors
capacitor
switch
current
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
EP85401754A
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English (en)
French (fr)
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EP0179680B1 (de
Inventor
Roberto Rovacchi
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.)
General Electric CGR SA
Original Assignee
General Electric CGR SA
Thomson CGR
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
Application filed by General Electric CGR SA, Thomson CGR filed Critical General Electric CGR SA
Publication of EP0179680A1 publication Critical patent/EP0179680A1/de
Application granted granted Critical
Publication of EP0179680B1 publication Critical patent/EP0179680B1/de
Expired legal-status Critical Current

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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
    • H05G1/18—Power supply arrangements for feeding the X-ray tube with polyphase AC of low frequency rectified
    • 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

Definitions

  • the present invention relates to a supply circuit for an X-ray emitter usable in radiology.
  • radiology it is necessary to power an X-ray emitter or source for a determined period. This duration corresponds to a duration of exposure or installation of a radio-sensitive plate.
  • radio cinema it is also necessary to modulate the activity of the X-ray emitting source as a function of the rate at which images are taken: in this way the dose of radiation that a patient receives during such an examination is reduced.
  • the transmitter supply circuit includes a transformer whose primary circuit is connected to a three-phase alternating electrical network, and whose secondary circuit is connected to the transmitter.
  • the primary circuit mounted in a star comprises, in place of a nodal connection, a switch for connecting together at the nodal point the three supply strands.
  • the duration of closure of this switch conditions the commissioning of the primary, therefore that of the transformer, and consequently fixes the duration of activity of the X-ray emitter.
  • the switch conventionally comprises a set of thyristors which are initiates upon desired power up. To obtain an opening of the switch, the thyristors are extinguished.
  • the reverse current which is established in the set of thyristors has a sinusoidal shape. That is, this current increases to a maximum and then decreases.
  • a sufficient reverse current must be established there for a period greater than their recovery time. This leads to choosing capacitors of significant value. Indeed, the useful life of the sufficient reverse current is greater the higher the maximum intensity of this reverse current. The latter is dependent on the capacitance of the capacitor. It follows that at the high point of the blocking operation the thyristors are traversed by an unnecessarily large current since it is primarily their recovery time which controls their blocking.
  • the object of the present invention is to remedy the drawbacks mentioned. It achieves a high rate using a circuit that does not require a special sequence to recharge the capacitor. Indeed, during blocking, the discharge of the capacitor causes its recharging in an opposite polarity. What the invention proposes is that for the following cycle the terminals of the capacitor are switched so that, without changing the polarity of this capacitor, the latter again becomes correctly connected.
  • the invention relates to a supply circuit for an X-ray emitter usable in radiology, of the type comprising a transformer whose primary circuit is connected to the three-phase electrical network and whose secondary circuit is connected to the emitter, in which the primary circuit is switched on and off by a controlled switch, said switch comprising a set of closing thyristors to close the primary circuit and thus activate the supply circuit, and a correctly charged capacity, connectable to this primary circuit, to reverse the direction of current flow in the closing thyristor set, to thereby open the switch and to stop the power supply accordingly, characterized in that it also includes a switching circuit for the connection of the capacity to said primary circuit .
  • FIG. 1 shows a supply circuit according to the invention.
  • This circuit includes a transformer 1 , the primary circuit 2, 3, 4 of which is connected to the three-phase electrical network 5.
  • the secondary circuit 6, 7, 8 of this transformer is connected to an emitter 9 of X-radiation.
  • the connection of this secondary circuit comprises a current rectifier 10.
  • the primary circuit is put into service by means of a switch 11 which receives its command on two access terminals 12, 13.
  • This switch comprises a set 14 of thyristors which ensure the closing of the switch coming almost short-circuited points A and B of this switch.
  • the switch 11 also includes a correctly charged capacitor 15 connectable to the primary circuit to reverse the direction of current flow in the set 14 of the thyristors.
  • the capacity 15 is connected to the set 14 of the thyristors by a switching circuit 50.
  • This switching circuit comprises the thyristors 16 to 19. These thyristors are controlled two by two (16-17 and 18-19) by common control terminals 20 and 2 1 respectively . By selecting one or the other of these terminals, the direction of connection of the capacity to the set 14 can be reversed.
  • Windings 2, 3 and 4 are the three primary windings of the three-phase transformers. They are magnetically coupled to the three secondary windings of the transformer 1. On the side opposite to the three-phase electrical network, the windings 2, 3 and 4 are connected to six diodes 22 to 27. Each end of each of the windings is connected to the midpoint respectively of the pairs of diodes 25-22, 26-23,27-24 connected in series. The three pairs are mounted in parallel between points A and B of the switch. To put the primary into service, simply short circuit point A, connected in common to the three cathodes of diodes 22 to 24, at point B connected in common to the three anodes of diodes 25 to 27. When the circuit is open, the DC voltage V R between points A and B is equal to ⁇ 2 times the voltage distributed by the network 5. To prevent the commissioning of the primary from causing overvoltages at the secondary, the connection from point A to point B is done in two stages.
  • thyristors 14 In the set of thyristors 14 one first opens, at an instant t, (figure 2-a), a thyristor 28 by sending a short duration pulse on its trigger by the control terminal 12. A resistor 29 connected in series with this thyristor 28 causes a voltage drop ⁇ v. The fall ⁇ v is moreover represented in FIG. 2a. Then at the end of a courtyard, instant (the instant separating a date t, from the date t,) a main thyristor 30 is started by a short pulse applied to its terminal. control 13. The two thyristors 28 and 30 are mounted in parallel between points A and B, the first via resistor 29 in series, the second via an inductor 31 in series.
  • the inductance 31 limits the variation of current so that the voltage V AB then tends towards 0 exponentially (Fig. 2-a).
  • the transformer is then energized. In radiology it is the beginning of the exhibition. In view of the fact that the thyristor 30 is on, the thyristor 28 placed in series with the resistor 29 is naturally blocked: the current which is likely to pass there is less than its holding current.
  • the thyristor 30 is forced to extinguish. For this, the electrical energy contained in the capacitor 15 is available.
  • This capacitor 15 in the invention is connected between the two midpoints 32 and 33 a switch bridge which has two branches in parallel.
  • a first branch comprises the thyristors 16 and 19 in series with one another and the second branch comprises the thyristors 18 and 17 also in series with one another.
  • the common ends of these two branches are connected in parallel to the terminals of the thyristor 30.
  • the capacitor 15 is in the electrical state shown in FIG. 1, namely that its armature close to terminal 33 is positively charged with respect to its other armature.
  • the thyristors 16 and 17 are primed at a date t ,, by a short pulse applied to their common control terminal 20.
  • the thyristors 18 and 19 remain blocked.
  • the capacitor 15 is discharged by passing through an inductor 34 connected in series with it between the points 32 and 33.
  • the current crosses the inductor 34 and begins to flow in the opposite direction to the normal current in the thyristor 30.
  • a charge current of intensity I ch passes through the thyristor 30.
  • an inverse current of value 1 begins to pass through thyristor 30.
  • the shape of this current as a function of time is shown in FIG. 2b. Due to the presence of inductance 34 the current l i at a sinusoidal shape: but only one alternation (the positive alternation) can pass because of thyristors 16 and 17. As soon as current 1 becomes higher, in absolute value , at current I ch the thyristor 30 begins to block. For the blocking of the thyristor 30 to be effective, the reverse current must be greater than the load current for a period t greater than a recovery time tq characteristic of the thyristor 30 used.
  • the reverse current follows a circuit passing through the thyristor 16, the capacitor 15, the inductance 34, the thyristor 17 and the thyristor 30.
  • the tail of discharge current of the capacitance passes through the circuit of the diodes 22 to 27 to close on the capacity 15.
  • the reverse current Towards the end of the half-wave the reverse current is canceled, it cannot become negative due to the presence of the thyristors 16 and 17 and the diodes 22 to 27.
  • the discharge current recharges the capacity 15 in reverse.
  • the circuit is open between points A and B, and the capacitor 15 is found charged, in reverse, at a voltage greater than the peak value of the network voltage due to the presence transformer leakage inductors.
  • the energy contained in the leakage inductors, at the time of blocking, is applied to the capacitor 15. This is the reason why the voltage V AB in Figure 2a takes during blocking, on date t ,. a value greater than the voltage V R found in steady state between points A and B. At terminals A and B this overvoltage relapses to return to the normal value in steady state when the switch 11 is open. On the other hand, at the terminals of the capacitor 15 the overvoltage could not decrease, within the limits of the leakage time of the capacitor 15. In fact the thyristor 16 then finds itself reverse biased and does not allow the discharge of the capacity 15.
  • the charging polarity of the capacitor 15 is therefore now the reverse of that shown in FIG. 1.
  • the thyristors 16 and 17 are no longer accessible via terminal 20 except the 'We will solicit but rather the thyristors 18 and 19 by sending a short-duration electrical pulse to their common control terminal 21.
  • the capacity, which was charged in reverse by the current which served to switching off thyristor 30, will then keep the polarity in which it is located.
  • the terminals 32 and 33 of this capacitor will be switched so that their connections to the thyristor 30 are the reverse of those they were previously. In other words, in the invention it is not necessary to provide a special sequence to restore the capacity to a single initial state.
  • the capacitance 15 When the supply circuit is put into service for the first time, or else after a too long time between two successive commissionings, the capacitance 15 is generally discharged. It must therefore be given a good starting charge.
  • the thyristors 18 and 19 are primed beforehand.
  • the voltage V R is applied to the terminals of the capacitor 15. The latter is charged as in the case presented in FIG. 1.
  • opening is controlled by switching on thyristors 16 and 17.
  • opening is controlled by switching on thyristors 18 and 19; so on as successive commissionings. If these successive commissionings are sufficiently close in time, in particular in the case of radiocinema, the capacitor 15 does not have time to discharge and the switching circuit operates normally. Therefore, the invention does indeed bring the two expected advantages, namely the time saving by eliminating the recharging sequence of the capacitor and the technological gain by removing the source intended to provide additional energy to the capacitors.
  • the invention also has another characteristic. To obtain defusing of the thyristor 30, it is necessary to send it in reverse a current greater than its direct charge current for a time greater than its recovery time tq. This current reverse is provided by the discharge of the capacitor 15.
  • the discharge circuit includes a single inductor 34 as shown in Figure 1 the shape of the discharge current is that shown in Figure 2b.
  • the condition indicated above can lead to a current peak inverse the major ic.
  • the capacitance / inductance pair 15-34 is replaced by a set of LC cells represented for example in FIG. 4, a discharge pulse having the form represented in FIG. 3 is obtained.
  • Each of cells 35 or 36 of the assembly 37 includes an inductor 38 in parallel with a capacitor 39.
  • the inductors of the different cells are slightly magnetically coupled together. We know how to calculate these cells and their number to obtain a desired pulse shape. What is important here is the duration during which this pulse lets pass a current whose intensity is greater than the charge intensity I ch .
  • this improvement brings a gain on the energy dissipated unnecessarily by the thyristor 30.
  • the energy dissipated unnecessarily corresponds approximately to the surface separating the curves I rh and li. These areas are hatched in FIGS. 2b and 3. As, ultimately, this useless energy had to be stored in the capacity 15, this makes it possible to significantly reduce the values of the cells capacities.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • X-Ray Techniques (AREA)
EP85401754A 1984-09-14 1985-09-09 Speiseanordnung für Röntgenstrahlenquelle, anwendbar bei Röntgenuntersuchungen Expired EP0179680B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8414153 1984-09-14
FR8414153A FR2570569A1 (fr) 1984-09-14 1984-09-14 Circuit d'alimentation pour emetteur de rayons x, utilisable en radiologie

Publications (2)

Publication Number Publication Date
EP0179680A1 true EP0179680A1 (de) 1986-04-30
EP0179680B1 EP0179680B1 (de) 1989-04-26

Family

ID=9307739

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Application Number Title Priority Date Filing Date
EP85401754A Expired EP0179680B1 (de) 1984-09-14 1985-09-09 Speiseanordnung für Röntgenstrahlenquelle, anwendbar bei Röntgenuntersuchungen

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Country Link
US (1) US4730352A (de)
EP (1) EP0179680B1 (de)
DE (1) DE3569865D1 (de)
FR (1) FR2570569A1 (de)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5077770A (en) * 1990-07-05 1991-12-31 Picker International, Inc. High voltage capacitance discharge system for x-ray tube control circuits
US5513093A (en) * 1994-03-11 1996-04-30 Miller Electric Mfg. Co. Reduced open circuit voltage power supply and method of producing therefor

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2608243A1 (de) * 1976-02-28 1977-09-01 Koch & Sterzel Kg Roentgenapparat
FR2389294A1 (fr) * 1977-04-30 1978-11-24 Philips Nv Circuit destine a un generateur de rontgen
DE2804591A1 (de) * 1978-02-03 1979-08-09 Koch & Sterzel Kg Roentgenapparat
US4200795A (en) * 1977-05-18 1980-04-29 Tokyo Shibaura Electric Co., Ltd. Pulsate X-ray generating apparatus
FR2481046A1 (fr) * 1980-04-18 1981-10-23 Siemens Ag Generateur radiologique pour appareil de radiodiagnostic, dans lequel la tension du tube radiogene est reglable par l'intermediaire du courant du tube radiogene

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3720868A (en) * 1972-01-10 1973-03-13 Zenith Radio Corp Multiple input voltage source power supply
JPS5910557B2 (ja) * 1976-11-15 1984-03-09 株式会社東芝 コンピユ−タ断層撮影装置
SU892612A1 (ru) * 1980-03-28 1981-12-23 Предприятие П/Я В-2156 Преобразователь посто нного напр жени
SU957434A1 (ru) * 1981-01-06 1982-09-07 Кемеровский государственный университет Прерыватель посто нного тока

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2608243A1 (de) * 1976-02-28 1977-09-01 Koch & Sterzel Kg Roentgenapparat
FR2389294A1 (fr) * 1977-04-30 1978-11-24 Philips Nv Circuit destine a un generateur de rontgen
US4200795A (en) * 1977-05-18 1980-04-29 Tokyo Shibaura Electric Co., Ltd. Pulsate X-ray generating apparatus
DE2804591A1 (de) * 1978-02-03 1979-08-09 Koch & Sterzel Kg Roentgenapparat
FR2481046A1 (fr) * 1980-04-18 1981-10-23 Siemens Ag Generateur radiologique pour appareil de radiodiagnostic, dans lequel la tension du tube radiogene est reglable par l'intermediaire du courant du tube radiogene

Also Published As

Publication number Publication date
US4730352A (en) 1988-03-08
EP0179680B1 (de) 1989-04-26
FR2570569A1 (fr) 1986-03-21
DE3569865D1 (en) 1989-06-01

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