GB1572326A

GB1572326A – Circuit arrangement for an x-ray generator
– Google Patents

GB1572326A – Circuit arrangement for an x-ray generator
– Google Patents
Circuit arrangement for an x-ray generator

Download PDF
Info

Publication number
GB1572326A

GB1572326A
GB16746/78A
GB1674678A
GB1572326A
GB 1572326 A
GB1572326 A
GB 1572326A
GB 16746/78 A
GB16746/78 A
GB 16746/78A
GB 1674678 A
GB1674678 A
GB 1674678A
GB 1572326 A
GB1572326 A
GB 1572326A
Authority
GB
United Kingdom
Prior art keywords
voltage
circuit
current
tube
resistor
Prior art date
1977-04-30
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)

Expired

Application number
GB16746/78A
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.)

Koninklijke Philips NV

Original Assignee
Philips Gloeilampenfabrieken NV
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.)
1977-04-30
Filing date
1978-04-27
Publication date
1980-07-30

1978-04-27
Application filed by Philips Gloeilampenfabrieken NV
filed
Critical
Philips Gloeilampenfabrieken NV

1980-07-30
Publication of GB1572326A
publication
Critical
patent/GB1572326A/en

Status
Expired
legal-status
Critical
Current

Links

Espacenet

Global Dossier

Discuss

239000003990
capacitor
Substances

0.000
claims
description
28

230000003213
activating effect
Effects

0.000
claims
description
2

238000007599
discharging
Methods

0.000
claims
description
2

238000000034
method
Methods

0.000
claims
description
2

238000004804
winding
Methods

0.000
description
14

230000007423
decrease
Effects

0.000
description
5

230000001052
transient effect
Effects

0.000
description
5

238000010791
quenching
Methods

0.000
description
3

230000000171
quenching effect
Effects

0.000
description
3

230000003247
decreasing effect
Effects

0.000
description
2

230000001419
dependent effect
Effects

0.000
description
2

229910001219
R-phase
Inorganic materials

0.000
description
1

230000004913
activation
Effects

0.000
description
1

230000015572
biosynthetic process
Effects

0.000
description
1

238000010276
construction
Methods

0.000
description
1

230000001934
delay
Effects

0.000
description
1

230000003111
delayed effect
Effects

0.000
description
1

238000002955
isolation
Methods

0.000
description
1

238000005259
measurement
Methods

0.000
description
1

238000007493
shaping process
Methods

0.000
description
1

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

H05G1/56—Switching-on; Switching-off

Description

PATENT SPECIFICATION ( 11
< 4 z( 21) Application No 16746/78 ( 22) Filed 27 Apr 1978 ( ( 31) Convention Application No 2719373 ( 32) Filed 30 Apr 1977 in M ( 33) Federal Republic of Germany (DE) CA ( 44) Complete Specification Published 30 Jul 1980 tn ( 51) INT CL 3 H 05 G 1/56 " ( 52) Indexat Acceptance H 2 H 22 G 23 G RX ( 54) CIRCUIT ARRANGEMENT FOR AN X-RAY GENERATOR ( 71) We, N V PHILIPS' GLOEILAMPENFABRIEKEN, a limited liability Company, organised and established under the laws of the Kingdom of the Netherlands, of Emmasingel 29, Eindhoven, the Netherlands do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The invention relates to a circuit arrangement for an X-ray generator, comprising at least a first electronic switch for switching on the tube voltage, which switch is included in the primary circuit of the high-voltage transformer for the power supply of the X-ray tube. Such a circuit arrangement is known (DT-PS 63 553; Fig 1) and will hereinafter be termed "The kind referred to" In this circuit the primary windings of a three-phase transformer are switched on via a three-phase rectifier bridge circuit and a thyristor which serves as an electronic switch, which thyristor is included in the diagonal branch of the rectifier bridge circuit. When the high voltage transformer is switched on the inevitable capacitances in the high-voltage generator and the stray inductance of the high-voltage transformer produce transient effects, which temporarily cause the tube voltage to increase beyond the preset value The magnitude of the excess voltage thus produced decreases with increasing tube current. In order to avoid such overshoot it is known to include resistors in the lines to the primary windings of the high-voltage transformer Depending on the tube current setting one of these resistors is included in the line to the primary winding for a specific time interval at the beginning of the exposure By suitably proportioning the resistors to be included in the input lines in the different current ranges the excess voltages can be eliminated at all tube currents. However, this solution is very intricate The resistors to be included in the primary circuit should be designed for handling high loads, because during an X-ray exposure they may have to handle a few hundred Amps for a short time The contactors by which the resistors are included should have corresponding current or power ratings However, such re 50 sistors and contactors are very expensive. Moreover, the known solution is economically justified only in those X-ray generators which comprise a separate tube current control In X-ray generators without such a con 55 trol, in which the tube current is controlled automatically depending on the tube-voltage setting, the rated load of the X-ray tube and, as the case may be, the exposure time, the inclusion of resistors depending on the tube 60 current, which is the result of the specified values of tube voltage, tube load, etc, is impracticable. It is an object of the present invention to provide a circuit arrangement of the type men 65 tioned in the preamble, which in an advantageous and simple manner can reduce or suppress excess voltages when the high voltage is switched on. In accordance with the invention there is 70 provided a circuit arrangement of the kind referred to in which the series connection of a second electronic switch and a resistor is connected in parallel with the first electronic switch, that the second switch can be activated by the 75 high-voltage starting signal, and that the first switch can be activated by the output signal of a timing network, which is started by the high-voltage starting signal and is adapted so that the delay time between the high-voltage 80 starting signal and its output signal is greater at a small current in the high-voltage circuit than at a large current. The current in the high voltage circuit is the result of the current through the X-ray 85 tube and the current through any filter elements, voltage dividers etc in the highvoltage circuit The last-mentioned current component is constant at a specific high voltage and therefore it suffices when solely the tube 90 1 572326 1 572 326 current, which is adjustable within wide limits (for example from 10 m A 1500 m A) is covered If desired, the constant current component may also be included. In a circuit arrangement embodying the invention the resistor which is connected in series with the second electronic switch remains included in the primary circuit of the high-voltage transformer for a relatively long time at small tube currents, at average or larger tube currents for a relatively short time only and under certain conditions not at all In order to eliminate excess voltages in conventional X-ray generators. the value of the resistor which is included in the primary circuit is changed depending on the tube current (this resistor being included for a constant time), whereas in an embodiment of the invention the time during which the resistor, which is of the same value for all tube currents, is included in the primary circuit is changed depending on the tube current in such a way that this time interval decreases at increasing tube current Therefore, in addition a power resistor and an electronic power switch are required in an embodiment of the invention This (second) electronic switch may have a lower rating than the first electronic switch, because the current flowing through it is limited by the resistor connected in series with it and because it is loaded practically only until the first electronic switch is switched on The further components which are needed, in particular those of the timing element, are not loaded by the current in the primary circuit; therefore, inexpensive components with a lower current rating may be used. The time interval during which the resistor which is connected in series with the second electronic switch is included in the primary circuit and which is equal to the delay time do between the high voltage starting signal and the output signal of the timing element, can essentially be varied depending on the tube current in two different manners: The delay time is controlled depending on the tube current setting This value is already determined before the high voltage is switched on and is set either directly by a control for the tube current or indirectly by another control, for example the tube voltage control and the focus spot selector One or more timedetermining elements included in the timing network, for example a variable resistor or a plurality of resistors or capacitors, one of which can be included depending on the tube current setting, may be coupled to said controls A particularly simple construction of a timing network of this type is obtained in a modified embodiment of the invention in that the timing network comprises a plurality of elements which determine the delay time, of which each time one element can be included by means of the tube current control. The second possibility, of varying the time interval during which the resistor in series with the second electronic switch is included in the high-voltage circuit depending on the tube current, is to measure the tube current or the current in the high-voltage circuit and to change the time interval depending on the measured current Such a measurement is possible only 70 after the high voltage has been switched on, because prior to this there is no tube current. In a variant using this principle the timing network comprises a comparator circuit, which produces the output signal for activating the 75 first switch and which compares the charging or discharging voltage across a capacitor with a reference voltage, either the potential on the low end of the capacitor or the reference voltage being variable by an amount which is 80 proportional to the current measured in the high-voltage circuit of the X-ray generator or the tube current. The value of the resistor in series with the second electronic switch may be comparatively 85low, if in accordance with a variant of the invention a filter network consisting of the series connection of a resistor and a capacitor is connected to the output of the high-voltage rectifier circuit When this voltage RC network 90 is proportioned so that a time constant of the order of magnitude of the transient duration is obtained and the resistor has such a value that the charging current flowing at the starting instant substantially corresponds to the average 95 tube current (approx 10 m A in the case of an X-ray generator for tube currents between 10 m A and 1 5 m A), a current corresponding to the average tube current will flow in the high voltage circuit at the beginning of X-ray ex 100 posures with a small tube current, whilst the greater part flows via the RC element and not via the X-ray tube Therefore, the magnitude of the excess voltages is substantially independent of the value of the tube current in the 105 lower tube current range Thus, it becomes particularly simple to proportion the timing network and the resistor so that excess voltages can be suppressed uniformly at all tube current values 110 In principle, the delay time between the activation of the two switches should not exceed the duration of the transient effect (approx 2 msec) However, in X-ray generators with a filter network, whose time constant is shorter 115 than the transient duration, longer delay times are also permissible (though not required) for tube currents which are so small that they produce no significant voltage drop across the resistor At tube currents which are so large that 120 substantially no overshoot occurs, the delay time should be minimal If the delay time is too great, or when the resistance is too high, the starting voltage will vary stepwise. Various embodiments of the invention will 125 now be described by way of example, with reference to the accompanying drawings, of which:Figure 1 shows a circuit arrangement embodying the invention, 130 1 572326 Figure 2 a and 2 b show different example of the timing network, Figures 3 a to 3 c represent the variation in time of the input voltages at different tube currents for a timing network in accordance with Figs 2 a, and Figure 4 shows the primary section of a different embodiment. In Figure 1 a three-phase high-voltage transformer 1, of which only the primary windings 2 are shown, is designated 1 The high voltage transformer may comprise two sets of secondary windings, which are connected in star and in delta respectively, and whose output voltages are each rectified by a three-phase rectifier bridge 3 and 4 respectively, as is described in the book "Principles of Diagnostic X-ray Apparatus", Philips Technical Library 1975, pages 156 The two three-phase rectifier bridges 3 and 4 are connected in series and are connected to earth directly and via a measuring resistor respectively The output direct voltage of each of the two three-phase rectifier bridges is each applied to a filter network, consisting of a resistor 6 and 7 respectively (approx 80 k Ohms) and a capacitor 8 and 9 respectively (approx. n F) An X-ray tube 35 is connected between the outputs of the rectifiers 3 and 4 which carry the negative and the positive high voltage respectively. The primary windings 2 of the high-voltage transformer 3 are connected to a control transformer, not shown, for adjusting the tube voltage, and to a three phase rectifier bridge 10. In the diagonal branch of the rectifier bridge 10 a thyristor 11 is included, which (at least partly) serves for switching on the tube voltage and which is connected in parallel with a quenching thyristor 12 in series with a quenching capacitor 13 and a linmiting resistor 14 The quenching thyristor 12 receives an ignition pulse from a generator 15 when the exposure is terminated by an automatic exposure control or a timer. The capacitor then inter alia also discharges via the thyristor 11, so that said thyristor is extinguished The capacitor is subsequently re-charged by a direct voltage generator 16, which may also be constituted by a three-phase bridge Moreover, there is provided a generator 17, which supplies a pulse-shaped high voltage starting signal. The parts of the circuit described so far is known (DT-PS 15 63 553) In the present embodiment, the series connection of a further thyristor 19 and a resistor 19: is connected in parallel with the thyristor 11 and that the thyristor 18 is turned on by the high-voltage starting signal supplied by the generator 17 and that the thyristor 11 is not turned on until after a delay time which is dependent on the tube current For the delayed turn-on of the thyristor 11 a timing network 20 is used, which is started by a high-voltage starting pulse supplied by the generator 17 and which under control of the voltage drop across the resistor 5, which drop is proportional to the tube current produces an output pulse for the ignition of the thyristor 11 with a delay, which decreases at increasing current through the X-ray tube or in the high voltage circuit respectively or which 70 increases at decreasing current. For realizing a timing network, which upon a starting signal produces an output pulse with a delay, which depends on the current in a suitable manner, there are a multiplicity of 75 possibilities One of these possibilities is represented in Fig 2 a. The timing work comprises a comparator circuit 21, which compares a reference voltage UR taken from the voltage divider 22, 23 with 80 the voltage on the junction point of a resistor 24 and a capacitor 25, whose low end is connected to earth via the low-ohmic output of an operational amplifier 26 and via a resistor 27, and which produces an output pulse when the 85 voltage uc on the said junction point becomes equal to or exceeds the reference voltage UR. The capacitor 25 and the resistor 27 are shortcircuited by an electronic switch 28 before the beginning of the exposure, which switch as 90 is indicated by dashed lines is opened by the high-voltage starting signal supplied by the generator 17, so that charging of the capacitor begins at the same time that the high voltage is switched on The input of the amplifier 26 is 95 connected to the measuring resistor 5, through which a current flows which is proportional to the tube current. The operation of the timing network can be described with reference to Figs 3 a to 3 c, which 100 show the variation of the voltage on the junction point of the capacitor 25 and the resistor 24 as a function of time At very large tube currents the voltage drop across the resistor 5, or the output voltage of the operational amplifier, 105 26, is so high, that the low end of the capacitor is brought at a potential which is positive relative to the reference voltage UR, so that the voltage uc on the junction point of the resistor 24 and the capacitor 25 immediately ex 110 ceeds the reference voltage (Fig 3 c) If the fact is neglected that the tube current cannot rise as steeply as is shown in Fig 3 c, and if the switching delays of the switches 28 and the comparator circuit 21 are neglected, the output 115 signal produced by the comparator circuit 21, which via a stage 34 which serves for pulse shaping and potential isolation turns on the thyristor 11, will coincide with the high-voltage starting signal which turns on the thyristor 18 120 The resistor 19 in series with the thyristor 18 is thus short-circuited by the thyristor 11 and thus cannot become operative This is neither necessary at large tube currents, because in that case the resonant circuit consisting of the stray 125 inductances of the high-voltage transformer and the generator capacitances is damped so strongly that substantially no excess voltages can occur If by-passing by 11 were effected at a later instant, the high-voltage rise would be 130 1 572326 stepwise in accordance with the delay. Therefore, the gain of the amplifier 26 and the reference voltage UR should be adapted to each other in such a way that at large currents the output voltage of the amplifier 26 is higher than the reference voltage UR. At average currents (Fig 3 b) the output voltage of the amplifier 26 is smaller than the reference voltage Consequently, the voltage UC does not reach the reference voltage a R until the capacitor 25 has been charged to a specific degree (instant tl), so that a certain delay AT (for example 1 msec) is obtained between turnon of the thyristor 18 (instant to) and turn-on of the thyristor 11 The magnitude of the delay time then also depends on the time constant of the RC network which is constituted by the resistor 24 and the capacitor 25 This time constant and the resistor should be proportional so that in particular in the medium tube-current range, no excess voltages occur On the other hand, no voltage decrease should occur as a result of the brief inclusion of the resistor. At still smaller tube currents (Fig 3 a) the capacitor voltage u% will reach the reference voltage UR even later, so that the delay time (AT) between the highwvoltage starting signal of the generator 17 and the output signal of the comparator circuit 21, ie between tum-on of the thyristor 18 and the thyristor 11, becomes even greater If the tube current is smaller than the current through the filter chain 6 9 (Fig 1), a variation of the tube current has practically no more influence on the total tube current flowing in the high-voltage circuit and thus on the overshoot behaviour when the high voltage is switched on Therefore, it is effective and permissible, to measure the current through the filter chain in addition to the tube current (in this case the low end of the capacitor 8 is to be connected to earth) instead of being connected to resistor 5 so that at a further decreasing tube current substantially no change of the total current measured in the high-voltage circuit results and hence no change of the delay time. In many cases for example in the case of tube-current control it is undesirable to measure the current through the filter networks 6 9, and in these cases the filter network 6 should be connected directly to the output of the bridge rectifier 4 This leads to an in itself unnecessary prolongation of the delay time, but this does not present any problems, because even if the thyristor 11 would not be turned on at all during an exposure with a very small tube current, the voltage drop produced across the resistor 19 ( 0 3 to 1 ohm) by the tube current, which has been transformed to the primary side, will be so low that it would hardly give rise to a reduction of the tube voltage. The filter networks 6 9 in the highvoltage circuit may also be dispensed with, but then a resistor 19 of higher value is to be used, in order to avoid excess voltages at small tube currents. It is alternatively possible, to connect the low end of the capacitor 25 directly to earth and to change the reference voltage UR by an amount which is dependent on the current in the high-voltage circuit It is also possible to 70 utilize the capacitor discharge instead of its charging, in which case the switch 28 is to be opened before the tube voltage is switched on and is to be closed after this, so that the capacitor can discharge via said switch Instead 75 of the capacitor voltage the voltage across the charging resistor 24 may also be used The charging resistor 24 may be replaced by a constant-current source, for example by the collector-emitter junction of a transistor, whose 80 base is connected to a constant potential. Figure 2 b shows a different version of a timing network The network again comprises a comparator or a threshold-valve circuit 21, a voltage divider 22, 23, which defines a reference 85voltage, and the capacitor 25, which is shortcircuited by the switch 28 before the start of the exposure and is thus discharged Furthermore, there is provided a group of charging resistors 30 of which each time one resistor 90 is included via a switch which is coupled to the tube current control 31 The delay between the high-voltage starting signal and the turn-on of the thyristor 11 and thus the interval during which the resistor 19 is included in the primary 95 circuit, is determined by the value of the included charging resistor The charging resistors are therefore proportioned so that, for the tube current or tube current range for which they are included, neither an excess voltage 100 nor a reduction of the voltage results Instead of the resistor group 30 a potentiometer may be used, whose wiper is coupled to the tube-current control 31 and to which a connection of the potentiometer is connected Instead of a 105 capacitor and a group of charging resistors it is alternatively possible to use a charging resistor and a group of capacitors. It is also possible to realize the timing network by digital means Such a digital timing 110 network may for example comprise an oscillator, a counter, and a digital comparator circuit The counter counts the pulses supplied by the oscillator starting with the high voltage starting signal and the comparator cir 115 cuit compares the count with a predetermined value and when said predetermined value is reached produces a signal for turning on the thyristor 11 The oscillator comprises a voltagefrequency converter, which converts a voltage 120 which is proportional to the tube current or the current in the high-voltage circuit into a frequency which is proportional thereto or into a frequency which increases with increasing voltage and, as the case may be also with the dif 125 ferential quotient of the voltage At a larger tube current the frequency is consequently high and the predetermined value is reached very rapidly, whilst at a smaller tube current the oscillator frequency is low and the prede 130 1 572326 termined value is reached comparatively slowly. In Fig 1 an embodiment of the invention has been described in conjunction with a threephase transformer, but embodiments of the invention may also be used in X-ray generators which only comprise an a c transformer for a single-phase alternating voltage In the case of the three-phase transformer shown in Fig 1 a three-phase rectifier bridge 10 is connected to the star point of the three windings, the diagonal branch of said bridge including thyristors 11 and 18 However, an embodiment of the invention may also be used in X-ray generators with a high-voltage transformer whose primary windings is connected differently. A example of this is shown in Fig 4 In this case 1 ' designates a three-phase transformer, of which only the primary windings 2 ', which are connected in delta, are shown and whose secondary windings (not shown) may be connected in a same way as explained with reference to Fig 1 The three-phase voltages R, S, T of the three-phase mains are each applied to the three primary windings 2 ' of the three-phase transformer 1 ' via a triac 11,32 and 33 respectively The triac 11 ' is connected in parallel with the series connection of a triac 18 ' and a resistor 19 ' The triacs 18 ', 32 and 33 can only be turned on at a specific instant with respect to the phase of one of the phase voltages Such an arrangement of the primary windings is in principle known from DT-PS 11 83 998 However, in this circuit electromechanical switches are used instead of triacs. The thyristors 18 ', 32 and 33 are always turned on in the case of a phase relationship of the mains voltage, for which the windings connected to the R-phase contribute longest to the formation of the direct voltage on the output of the high-voltage rectifier bridge; if the secondary winding of the three-phase transformer 1, not shown, is also connected in delta, for example when the phase-voltage T, which leads the phase-voltage R by 1200, has its zero passage, or shortly before this The timing network, which may be of the same design as described with reference to the preceding Figures, ignites the triac 11 ' after a time which depends on the tube current or the current in the high-voltage circuit, and which increases as the tube current or the current in the high-voltage circuit decreases When the high voltage is switched on the resistor 19 ' damps the resonant circuit which is constituted by the stray inductances of the high-voltage transformer and the generator capacitances, and if the timing network is proportioned so that the time interval during which the resistor 19 ' is included suitably depends on the tube current or the current in the high-voltage circuit, the turn-on transient may also be reduced or eliminated with the arrangement shown in Fig 4, without the high voltage being reduced below the preset value during the inclusion of the resistor 19 '. Claims (4) WHAT WE CLAIM IS: 65 1 A circuit arrangement for an X-ray generator, comprising at least a first electronic switch for switching on the tube voltage, which switch is included in the primary circuit of the high-voltage transformer for the power-supply 70 of the X-ray tube, characterized in that the series connection of a second electronic switch and a resistor is connected in parallel with the first electronic switch, that the second switch can be activated by the high-voltage starting signal, and 75 that the first switch can be activated by the output signal of a timing network, which is started by the high-voltage starting signal and is adapted so that the delay time between the highvoltage starting signal and its output signal is 80 greater at a small current in the high-voltage circuit than at a large current. 2 A circuit arrangement as claimed in Claim 1, characterized in that the timing network comprises a plurality of elements which 85 determine the delay time, of which each time one element can be included by means of the tube current control. 3 A circuit arrangement as claimed in Claim 1, characterized in that the timinig network corm 90 prises a comparator circuit, which produces the output signal for activating the first switch and which compares the charging or discharging voltage (us) across a capacitor with a reference voltage (UR) either the potential on the low end of 95 the capacitor or the reference voltage being variable by an amount which is proportional to the current measured in the high-voltage circuit of the X-ray generator or the tube current. 4 A circuit arrangement as claimed in any 100 of the Claims 1 to 3, comprising at least one rectifier circuit which is connected to the secondary circuit of the high-voltage transformer, characterized in that a filter network consisting of the series connection of a resistor and a 105 capacitor is connected to the output of the high-voltage rectifier circuit. A circuit arrangement for an X-ray generator, substantially as herein described with reference to Figure 1 or to Figure 1 as modified 110 by any of Figures 2 a, 2 b and 4 of the accompanying drawings. RJ BOXALL, CHARTERED PATENT AGENT, BERKSHIRE HOUSE, 168-173 HIGH HOLBORN, LONDON, WC 1 V 7 AQ AGENT FOR THE APPLICANTS. Printed for Her Majesty's Stationery Office by MULTIPLEX techniques ltd, St Mary Cray, Kent 1980 Published at the Patent Office, 25 Southampton Buildings, London WC 2 l AY, from which copies may be obtained. GB16746/78A 1977-04-30 1978-04-27 Circuit arrangement for an x-ray generator Expired GB1572326A (en) Applications Claiming Priority (1) Application Number Priority Date Filing Date Title DE2719373A DE2719373C2 (en) 1977-04-30 1977-04-30 Circuit arrangement of an X-ray generator with an electronic switch controlled by a timing control element in the primary circuit of a high-voltage transformer Publications (1) Publication Number Publication Date GB1572326A true GB1572326A (en) 1980-07-30 Family ID=6007725 Family Applications (1) Application Number Title Priority Date Filing Date GB16746/78A Expired GB1572326A (en) 1977-04-30 1978-04-27 Circuit arrangement for an x-ray generator Country Status (6) Country Link US (1) US4208584A (en) JP (1) JPS5923080B2 (en) BE (1) BE866579A (en) DE (1) DE2719373C2 (en) FR (1) FR2389294A1 (en) GB (1) GB1572326A (en) Families Citing this family (7) * Cited by examiner, † Cited by third party Publication number Priority date Publication date Assignee Title DE2900623C2 (en) * 1979-01-09 1986-03-27 Siemens AG, 1000 Berlin und 8000 München X-ray diagnostic generator with switching means for switching the high-voltage transformer on and off at predetermined phase angles of the supply voltage EP0025688A3 (en) * 1979-09-13 1981-05-27 Pfizer Inc. Process for rapidly achieving stabilized X-ray emission from an X-ray tube JPS5797399U (en) * 1980-12-08 1982-06-15 FR2570569A1 (en) * 1984-09-14 1986-03-21 Thomson Cgr POWER SUPPLY CIRCUIT FOR X-RAY EMITTER FOR USE IN RADIOLOGY DE3541612A1 (en) * 1985-11-25 1987-05-27 Siemens Ag X-RAY DIAGNOSTIC DEVICE JPS6489198A (en) * 1987-09-30 1989-04-03 Toshiba Corp X-ray high-voltage device US5008912A (en) * 1989-10-05 1991-04-16 General Electric Company X-ray tube high voltage cable transient suppression Family Cites Families (10) * Cited by examiner, † Cited by third party Publication number Priority date Publication date Assignee Title US2420845A (en) * 1944-06-15 1947-05-20 Westinghouse Electric Corp Short exposure x-ray apparatus US3130312A (en) * 1961-07-26 1964-04-21 Profexray Inc X-ray timer system to produce short duration radiation pulses DE1144409B (en) * 1961-08-26 1963-02-28 Siemens Reiniger Werke Ag X-ray apparatus with dampening means that can be switched on briefly at the beginning of the X-ray recording DE1155867B (en) * 1961-12-02 1963-10-17 Siemens Reiniger Werke Ag Circuit arrangement for an X-ray diagnostic apparatus GB1032306A (en) * 1964-08-28 US3636355A (en) * 1969-09-24 1972-01-18 Cgr Medical Corp Starting voltage suppressor circuitry for an x-ray generator DE2053670A1 (en) * 1970-10-31 1972-05-10 Siemens Ag X-ray diagnostic apparatus DE2333015C3 (en) * 1973-06-28 1979-05-10 Siemens Ag, 1000 Berlin Und 8000 Muenchen X-ray diagnostic apparatus with a switching device having a semiconductor switching element DE2608243A1 (en) * 1976-02-28 1977-09-01 Koch & Sterzel Kg X:ray appts. synchronised with AC mains - has variable attenuator and performs one exposure per cycle of mains supply DE2637064A1 (en) * 1976-08-18 1978-02-23 Siemens Ag ROYAL DIAGNOSTIC DEVICE WITH AN ROYAL TUBE WITH CONTROL GRILL 1977 1977-04-30 DE DE2719373A patent/DE2719373C2/en not_active Expired 1978 1978-02-02 US US05/874,527 patent/US4208584A/en not_active Expired - Lifetime 1978-04-27 FR FR7812558A patent/FR2389294A1/en active Granted 1978-04-27 GB GB16746/78A patent/GB1572326A/en not_active Expired 1978-04-28 BE BE187287A patent/BE866579A/en unknown 1978-04-28 JP JP53050195A patent/JPS5923080B2/en not_active Expired Also Published As Publication number Publication date FR2389294B1 (en) 1984-02-24 JPS53136496A (en) 1978-11-29 DE2719373C2 (en) 1982-10-21 DE2719373A1 (en) 1978-11-02 BE866579A (en) 1978-10-30 FR2389294A1 (en) 1978-11-24 US4208584A (en) 1980-06-17 JPS5923080B2 (en) 1984-05-30 Similar Documents Publication Publication Date Title US4051425A (en) 1977-09-27 Ac to dc power supply circuit US6970365B2 (en) 2005-11-29 Controlled frequency power factor correction circuit and method GB2090702A (en) 1982-07-14 Method and circuit for controlling the switching of an inductive load GB992828A (en) 1965-05-19 Improvements in or relating to inverters JPH07274513A (en) 1995-10-20 Power supply device GB2122389A (en) 1984-01-11 Controlling temperature of an electric resistor GB1572326A (en) 1980-07-30 Circuit arrangement for an x-ray generator US3090017A (en) 1963-05-14 Smoothing filter having shunt capacitor charged via diode from output and discharged via second diode into input WO2004107546A1 (en) 2004-12-09 Power factor correction circuit and method of varying switching frequency EP0188570A1 (en) 1986-07-30 Switch-mode power supply GB1563838A (en) 1980-04-02 Regulated high voltage dc supply US4171488A (en) 1979-10-16 X-ray diagnosis generator comprising an inverter feeding the high voltage transformer GB2153556A (en) 1985-08-21 Ac line voltage regulator US4065805A (en) 1977-12-27 Circuit arrangement in an electrical device operated with direct-current, especially in a timing relay EP0301815B1 (en) 1993-06-16 Control device for switching a thyristor EP0008539A1 (en) 1980-03-05 Regulated DC power supply circuits GB2183967A (en) 1987-06-10 Constant power telephone line circuit US3955131A (en) 1976-05-04 Circuit for controlling the reverse current in a controlled rectifier US3331014A (en) 1967-07-11 Regulated power supplies with selfcommutating switching US4171487A (en) 1979-10-16 X-ray diagnostic generator in which the X-ray tube voltage is regulated via the X-ray tube current EP0120258B1 (en) 1989-03-22 Energy economising circuit US3522522A (en) 1970-08-04 Dual charging of a capacitor to produce a constant a.c. voltage EP1454405B1 (en) 2006-11-22 Controlled frequency power factor correction circuit and method US3346780A (en) 1967-10-10 Controllable supply or feed circuit for electromagnetic vibrators US4238681A (en) 1980-12-09 X-ray diagnostic generator Legal Events Date Code Title Description 1980-10-15 PS Patent sealed [section 19, patents act 1949] 1993-12-22 PCNP Patent ceased through non-payment of renewal fee Effective date: 19930427
Download PDF in English