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Publication numberUS3631527 A
Publication typeGrant
Publication dateDec 28, 1971
Filing dateJul 9, 1968
Priority dateJul 9, 1968
Also published asDE1934630A1
Publication numberUS 3631527 A, US 3631527A, US-A-3631527, US3631527 A, US3631527A
InventorsWalter E Splain
Original AssigneePicker Corp
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
X-ray tube kilovoltage control system
US 3631527 A
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Description  (OCR text may contain errors)

United States Patent Inventor Walter E. Splain Solon, Ohio Appl. No. 743,421

Filed July 9, 1968 Patented Dec. 28, 1971 Assignee Picker Corporation White Plains, N.Y.

X-RAY TUBE KILOVOLTAGE CONTROL SYSTEM 30 Claims, 5 Drawing Figs.

U.S.Cl 250/103, 315/276, 323/435 Int. Cl H05g 1/32, G03b 41/16 Field olSearch 250 102,

[56] References Cited UNITED STATES PATENTS 2,840,718 6/l958 Wright et a1. 250/103 X 3,255,403 6/1966 Beaver et al. 323/435 Primary Examiner-James W. Lawrence Assistant Examiner-A. L. Birch Attorney-Watts, Hoffmann, Fisher & i-ieinke ABSTRACT: A system for automatically supplying a preselected kilovoltage to an X-ray tube is provided with a transformer having a plurality of binary-coded secondary windings. Switching devices are connected to the secondary windings to provide various combinations of secondary windings. A control system automatically changes the combination of secondary windings to correct for changes in system parameters to insure that a selected kilovoltage is actually applied to the X-ray tube at the start of an exposure.

PATENTED 0:328 IBTI SHEET 5 OF 5 IN VENTOR.

WQLTE? E. SPLA/N M A TOQNEm X-RAY TUBE KILOVOLTAGE CONTROL SYSTEM BACKGROUND OF THE INVENTION 1. Field of the Invention.

The present invention relates generally to X-ray systems, and more particularly, to a control system for selecting kilovoltages to be supplied to an X-ray tube, while taking into account various losses and fluctuations to insure that a selected kilovoltage is actually applied to the tube at the start of an exposure.

2. Description of the Prior Art. n

In X-ray apparatuses the kilovoltage (KV) supplied to an X- ray tube is adjustable so that different intensities of X-rays can be provided, and so that the system can be used for different X-ray procedures, such as fluoroscopy and radiography. The demands for flexibility and reliability of KV are continually increasing as new procedures are developed, and devices such as image intensification tubes with television and/or cine cameras are more frequently used.

In prior X-ray systems, adjustment of the KV was often provided by an autotransformer between the power supply and the usual high-tension transformer connected to the X-ray tube. These prior systems are quite complex generally and are not sufficiently flexible and reliable for the may uses demanded of present day X-ray systems. For example, an X-ray system should be usable for at least fluoroscopy, radiography, and cinematography.

The power requirements for fluoroscopy are quite different from those necessary for radiography and for cinematography. During the examination of a patient, these procedures are often alternately and sequentially used. For this reason, it is necessary for the X-ray system to be easily and substantially instantaneously adjustable from one use to another.

A typical prior system, which attempted to provide this flexibility, had two variable-tap autotransformers or the equivalent. One autotransformer was set usually for its secondary winding to meet the requirements of radiography, and the other was set to a compromise setting which sought to satisfy the requirements of both fluoroscopy and cinematography. The medical practitioner in examining a patient switched the primary terminals of an X-ray tube high-voltage transformer from the secondary terminals of one autotrans former to those of the other autotransforrner, when changing between fluoroscopy or cinematography and radiography studies. In order to perform this switching function, complex switching mechanisms are necessary between the autotransformers and the high-voltage transformer. The switching problem is complicated by the use of only one KV level for both cinematography and fluoroscopy, even though the power levels are different.

With the prior systems, automatic adjustment of the KV applied to the X-ray tube for a given study was not provided. It has generally been necessary to adjust the autotransformer secondary winding settings manually in order to change the applied KV. In radiography, precise power levels must be used to obtain proper exposure. Accordingly, a kilovoltage meter has been provided in prior X-ray systems for indicating voltage measurements during radiographic procedures. Thus, another shortcoming of the prior art has been the need to observe the KV meter and manually adjust the KV for a desired level.

In the past, a kilovoltage meter has not usually been used for providing voltage measurements during fluoroscopy procedures, because the stability requirements have not been as great as in radiography and the meter was not of appropriate voltage range for fluoroscopy. Because no kilovoltage meter was used during fluorosc py, the operator was not aware of changes that might have taken place in desired kilovoltage caused, for example, by line voltage changes. Thus, such prior systems were not generally capable of accurately providing desired power levels when line voltage changes occurred prior to fluoroscopic examinations.

SUMMARY OF THE INVENTION The present system provides for automatic control of the voltage applied to an X-ray tube at the start of an exposure, regardless of whether the X-ray system is being utilized for fluoroscopy, radiography, cinematography or any other procedure. The present system does not require even one kilovoltage meter, because any change in the voltage supplied to the X-ray tube is corrected automatically prior to the exposure being made. The present system corrects for direct current voltage losses caused by the resistance of the secondary windings of the high-tension transformer. It also compensates for voltage losses which occur across the rectifier tubes in the secondary of this high-tension transformer. It further compensates for supply line voltage changes. Finally, it compensates for current changes caused by a change in applied line voltage by making a percentage voltage change.

The present system also provides for rapid and automatic changes in the kilovoltage selected to be applied to the X-ray tube. In addition, changes in voltage settings required to switch from fluoroscopy to radiography or to cinematography are automatically and rapidly provided with one autotransformer. The present system is particularly adapted for use in a preprogrammed system, wherein several kilovoltage settings for several different studies using radiography, fluoroscOPY or cinematography are preset prior to the beginning of an examination procedure and are automatically changed from one to another when running the several different studies.

In the present system, an autotransforrner is provided having a plurality of secondary windings, all wound differently to provide different secondary voltages. The secondary windings are binary coded in a series, in that each winding provides twice the secondary voltage of a previous winding, so that the secondary windings provide voltages which by a common factor are the elements of the binary geometric series, 1, 2, 4, 8, l6, etc. Thus, a second winding provides twice the voltage of a first winding and a third winding provides twice the voltage of the second winding, and so forth, each succeeding winding providing twice the secondary voltage of a next preceding winding.

Suitable switching devices are provided to interconnect these secondary windings. The switching devices selectively connect the secondary windings in various combinations to provide virtually any desired output voltage from the autotransformer secondary. The output voltage can be varied from a minimum voltage which is the voltage across a secondary reference winding, to the voltage across the combination of all of the secondary windings, the latter being a maximum voltage setting. The particular combination of secondary windings necessary to provide a selected voltage is provided automatically in response to the setting of a particular kilovoltage level by an X-ray control system. This control system also changes the selected combination of secondary windings to automatically correct the kilovoltage to be applied, prior to the start of an exposure, for changes that occur in supply line voltage, losses in the secondary circuit of the high-voltage transformer, current changes due to a change in the applied line voltage, and other losses.

Other advantages, features and objects of the invention and a fuller understanding of it, may be had by referring to the following description and claims taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a partially block and partially schematic diagram of an autotransformer and its voltage selector relays in an X- ray system embodying the invention;

FIG. 2 is a block diagram of a relay control for controlling the voltage selector relays shown in FIG. 1;

FIG. 3 is a schematic diagram of a relay driver used in the relay control of FIG. 2; FIG. 4 is a schematic diagram of an accumulator used in the relay control of FIG. 2; and

FIG. 5 is a schematic diagram of various other circuits shown as blocks in the relay control of FIG. 2.

As shown in FIG. 1, an X-ray system embodying the invention includes a pair of input terminals 14, 12 which are connected to a suitable conventional alternating current voltage source (not shown). The input terminals 111, 12 are respectively connected to a primary winding 141 of an autotransformer 14 through ganged, normally open contacts 16A, 16B of an input power switch, indicated generally by the numeral 16. The transformer primary winding 141 is provided with a plurality of input terminals 14P1-14P10 to accommodate input line voltages of various levels. In practice, the switch 16 would probably be a power relay whose actuation is controlled by an ON-OFF control.

The autotransformer 14 includes a plurality of secondary windings 1481, 1482, 1484, 1488, 14816, 14832, 14864, 148A, 1488, 148C, 148R, the windings 14832, 14864, 148R being defined by taps on the primary winding 141. The secondary windings 1481-14864 are wound to provide different respective output voltages. The output voltage appearing across the terminals of one of the secondary windings 1481-14864 is twice the output voltage appearing across the output terminals of the immediately preceding secondary winding taken in numerical order, as indicated by their reference numerals. In other words, the voltage appearing across the terminals of the winding 1482 is twice that appearing across the winding 1481. The voltage across the winding 1484 is twice that across the winding 1482, and so forth, such that the voltages across the windings 1481-14864 are equal, by a common factor, to the elements of a binary, geometric series, i.e., 1,2,4,8,l6,32,64. 1f the voltage across the first winding 1481 is arbitrarily designated as having a value of 1, then the voltage across the winding 1482 has a value of 2, the voltage across the winding 1484 has a value of 4, the voltage across the winding 1488 has a value of 8, the voltage across the winding 14816 has a value of 16, the voltage across the winding 14832 has a value of 32, and the voltage across the winding 14864 has a value of 64. A particular voltage is provided by adding the output voltages of selected ones of the windings 1481-14864 to a base or reference voltage provided from the winding 148R, so that the total output indicates the particular selected voltage. If a common voltage factor of the arbitrary values 1, 2, 4, etc. is 1.0 volts, then a voltage range of 1-127 volts can be selected form the secondary windings 1481-14864 and added to the reference voltage from the winding 148R of, for example, 20 volts. In the system shown, a common voltage factor of 1.0 kv. is preferably used to represent the voltage ultimately supplied to an X-ray tube. Thus, that voltage may be varied from a base or reference level of 20 kv. up to 147 kv. in single-kv. steps.

The secondary windings 148A, 148B, 148C are exemplary of a plurality of auxiliary windings for energizing power supplies, etc. One of them, for example the winding 148A, is pro vided with a pair of terminals 18A, 1813, that are connected to a reference voltage power supply to be later described in connection with F168. 2 and 5.

A plurality of relays 20, 22, 24, 26, 28, 311, are provided for connecting together in series various ones of the secondary windings 1481, 1482, 1484, 14811, 14816, 14832, 14864, 148R to provide a selected output voltage. Each of the relays 26-32 is provided with two sets of normally open contacts, one set of normally closed contacts, and an actuating coil. in the case of the relay 20, the normally open contacts are designated as 211A and 20D, the normally closed set of contacts is designated as 21113, and the actuating coil is designated as 20C. Similar contacts and coils of the other relays 22-32 are similarly designated. Each of the relay coils 2(1C-32C has one end connected to a lead 34, which is in turn connected to ground through a normally open set of relay contacts 36A. The other ends of the relay coils 20C32C are respectively connected by means of leads 38-50 to a relay driver shown in FIGS. 2 and 5.

Output from the selected combination of secondary windings of the transformer 14 is provided on a pair of condoctors 52, 54. The conductor 52 is connected directly to one input terminal of a conventional high-voltage transformer and rectifier circuit 56. The conductor 54 is connected to another input terminal of the high-voltage transformer and rectifier circuit 56 through a silicon controlled rectifier switch 58. The silicon controlled rectifier (SCR) switch 58 is entirely conventional in design and is controlled in conventional manner by a signal applied to an input lead 60. The derivation of the control signal applied to the lead 61) will be later described in conjunction with FIG. 2. Two output terminals of the high-voltage transformer and rectifier circuit 56 are connected respectively to the anode and cathode of a conventional X-ray tube 62 to provide high-voltage to the tube.

Looking now at the specific connections of the transformer secondary windings and the relays, it is seen that the contacts 2110-321) serve as holding contacts for their respective relays. Even more specifically, each of the contacts 20D-32D is connected to a lead 64, which is in turn connected to a source of positive potential (not shown). Each of the contacts 20D-32D is connected to that end of its corresponding relay actuating coil ZOE-32C that is remote from the lead 34. Thus, once one of the relay coils 211C-32C is energized by a signal being applied to its corresponding lead 38-51), the corresponding contacts 260-321) close to maintain the corresponding relay coil energized so long as the relay section 36A is closed to provide a current path to ground.

The output line 52 is connected to the contact 2081 of the relay 20, and the output line 54 is connected to both of the contacts 32A2 and 32132 of the relay 32. The conditions of the A and B contacts of the relays 211-32 determine which of the secondary windings 1481-14864 are connected between the output lines 52-54. The relay contact 20B2 is connected directly to the contact 2281, and the contact 2282 is connected to the contact 2451, the contact 24132 is connected to the contact 2681, the contact 2682 is connected to the contact 21181, and the contact 28132 is connected to the contact 31181. It is particularly pointed out that the contact 30B2 is not connected directly to the contact 3231, but rather is connected to that contact through the secondary winding 148R. Thus, even if all the relays 20-32 are deenergized and all the B contacts are closed, the secondary winding 148R will still be connected between the output leads 52-54. It will be recalled that this is the secondary winding that provides a base or reference voltage to which the voltages from selected other ones of the secondary windings are added.

Various ones of the transformer secondary coils 1481-1486 4 are connected in series with the reference voltage secondary 148R by opening selected ones of the B sections of the relays 211-32 and closing corresponding A sections. As shown, one end of the secondary winding 1481 is connected directly to the output lead 52, and the other end of that line is connected to the relay contact 20A1l. One end of the secondary winding 1482 is connected to the contact 20.42 and to the contact 20132. The other end of that winding is connected to the contact 22.41. One end of the secondary winding 1484 is connected to the contacts 22A2, 22B2, and the other end of that winding is connected to the contact 24A]. One end of the winding 1481" is connected to the contacts 24A2, 24B2, and the other end of that winding is connected to the contact 26A1. One end of the winding 14816 is connected to the contacts 26A2, 2682, and the other end of that winding is connected to the contact 28All. The relay contacts 28A2, 28132, 311A1, 31181 are all connected together. One end of the secondary winding 14832 is connected to the contact 30A2, and the other end of that winding is connected to the contact 3082. The secondary winding 14864 is connected between the contacts 321 11, 32131 and, as previously mentioned, the output lead 54 is connected to the contacts 32A2, 3282.

Assume for purpose of illustration that it is desired to add 1 volt to the voltage produced by the secondary winding 148R. ln that situation, a signal would be provided on the lead 38 to energize the relay 20. The contacts D would close to maintain the coil 20C in energized condition, the contacts IZ EB would open, and the contacts 20A would close. If all of the other relays remain deenergized, the current path between the output conductors 52, 54 would be through the secondary winding'l4Sl, the contacts 20A, 22B, 24B, 26B, 28B, 30B, the secondary winding 148R, and the relay contacts 328. This assumes, of course, that the relay contacts 36A are closed so that the relay-actuating coils may be energized.

Assume now as a second example that it is desired to add 27 volts to the base or reference voltage provided by the secondary winding 148R. In that situation, signals would be received on the leads 38, 40, 44 and 46. This would cause the relays 2b, 22, 26 and 28 to change their conditions. This would connect the output lead 52 to the lead 54 through the secondary winding 1481, relay contacts 20A, secondary winding M82, relay contacts 22A, relay contacts 248, secondary winding 1488, relay contacts 26A, secondary winding 14816, relay contacts 28A, relay contacts 30B, secondary winding 148R, and relay contacts 328. Thus, it is apparent that various ones of the relays 20-32 may be energized to connect selected ones of the secondary windings 1451-14864 in series between the output leads 52-54 to provide selected output voltages variable in 1- volt steps over a range of 127 volts, the selected volts being added to those provided by the secondary winding 148R.

FIG. 2 illustrates in block diagram form a relay control for controlling and driving the relays 20-32 shown in FIG. 1. The various elements of the system including leads that are common to various figures are identified by the same reference numerals throughout.

As shown in FIG. 1, the actuating coils 20C-32C of the relays 20-32 are respectively energized through the leads 38-50. Those leads are shown in FIG. 2 as output leads from a relay driver 70. Basically, the relay driver 70 serves to connect selected ones of the leads 38-50 to a source of positive potential in response to a command signal from a first multivibrator 72 on a lead 73. The selection of which one or ones of the leads 38-50 are energized is controlled by an accumulator 74.

The accumulator 74 is, in effect, a binary counter. It counts pulses supplied to it on a lead 75 from a clock pulse generator 76 through a gate 78. When the accumulator is receiving pulses from the pulse generator 76, it counts continuously from 127 to 0 and then recycles. For each count, two types of output signals are provided. First, output signals are provided on one or more of a plurality of leads 80-92 that enable the relay driver 70 to provide signals on corresponding ones of the leads 38-50 when so commanded by the multivibrator 72. Second, current output signals are provided through one or more of a plurality of resistors 94-106 connected together in a current adder configuration. The sum of the currents through the resistors 94-106 is supplied as one input to a current comparator 108 on a lead 110.

Energizing voltage for the accumulator 74 is provided by a power supply 112 on a lead 114. Input to the power supply 112 is from the terminals 18A, 1813, which are connected to the secondary winding 148A of the autotransformer 1141 described in connection described in connection with FIG. 1. Thus, the voltage output of the power supply 112 to the accumulator 74 on the lead 114 will reflect any variations in the line voltage input to the entire system. Consequently, the currents through the resistors 94-106 and through the lead 110 will reflect any such line variations as a percentage variation. Current is also supplied from the lead 1 14 through a lead 116 and a variable resistor 118 to the lead 110. The variable resistor 118 provides current to the comparator 103 that corresponds to the minimum KV to be applied to the X-ray tube as determined by the transformer secondary winding 148R. The variable resistor 118 is referred to as the Low KV Adjust.

The voltage supplied by the power supply 112 is also adjusted in accordance with three other factors, which cause various voltages to be added to the output voltage of the power supply.

First, an adjustable voltage is added to the power supply voltage so that the maximum current output of the accumulator 74 on the lead 1ll0 corresponds to the maximum KV that is to be applied to the X-ray tube. This voltage is controlled by the setting of an adjustable arm of a potentiometer 120 connected between a positive direct current source and ground. This is known as the High KV Adjust.

Second and third, the potential controlled by the setting of the potentiometer 120 is modified by potential drops across an adjustable portion of a potentiometer 122 and across an MA adjustment 124. The variable arm of the potentiometer 122 is set to compensate for the line voltage drop occurring between no loa and full load" conditions, and may represent a voltage drop of 2.5 percent-l0 percent in the line voltage when the X-ray tube is energized. This would not be compensated for by a change in the AC input (at terminals 18A, 188) to the power supply, because that change would occur when the exposure starts after the autotransformer secondary windings had been selected and could not be changed.

The MA adjustment 124 may be thought of as a variable resistor connecting the movable arm of the potentiometer 122 to ground and whose resistance varies inversely with the selected X-ray tube current. Inasmuch as variation in its value varies the voltage applied to the accumulator 74, the current output of the accumulator 74 varies as a function of both KV and X-ray tube current; those variations are proportional to losses that vary as the'product of KV and X-ray tube current (KV MIA). Such losses are primarily those that occur in the autotransformer primary and in the powerline and are dependent on both RV and MA.

The voltage appearing across the MA adjustment 124 and the selected portion of the potentiometer 122 is applied to the negative side of the power supply 112 through an impedancematching device 125 interposed in a lead 126. The impedance-matching device 125 draws no current through the potentiometer 122 and hence isolates the power supply 112 from the potentiometers I20, 122 and the MA adjustment 124. The voltage added to the power supply voltage is actually provided from the impedance-matciing device 125, under control of the potentiometers 120, 122 and the MA adjustment 124. In a particular example, about +1 2 volts DC may be provided by the power supply 112, and about +12 volts DC may be provided from the impedance-matching device 125. These voltages of course vary in accordance with the factors previously mentioned.

As previously mentioned, current is supplied to one comparison input of the comparator 108 through the lead 110. Current is taken from a second comparison input of the comparator through a lead 127. Current is supplied through the lead 127 to an MA adjustment 128, and to either one of a programmed KV (fluoroscopic) control or a programmed KV (radiographic) control 132. Determination of whether the control i319 or the control 132 receives current through the lead 127 is controlled by a signal applied to them from a mode control switch 134.

The MA adjustment 128 represents a variable impedance, and its value is selected so that current through it is proportional to high-voltage transformer secondary losses that are directly proportional to the X-ray tube current and not to KV. These losses are static for each selected tube current, and once an X-ray tube current is selected the current through the MA adjustment 128 remains constant for that setting. Thus, the setting of the MA adjustment 128 provides a current drain from the comparator 108 through the lead 127 proportional to X-ray tube current.

The programmed KV controls 130-132 respectively drain currents from the lead 126 that are proportional to various values of KV to be applied to the X-ray tube for fluoroscopy and radiology. The fluoroscopic KV control 130 contemplates the drain of a current that is continuously adjustable in value over a predetermined range of values under the manual control of a radiologist. The radiographic KV control 132 contemplates the drain of a current that is adjustable in steps,

each step corresponding to a change of one KV in the voltage applied to the X-ray tube. Both the fluoroscopic ICV control ll3tl and the radiographic lKV control 132 will be later described in more detail in connection with FIG. 5.

The comparator 108 is essentially a current comparator that compares the currents through the lead 1110, 127 and, if those currents are substantially equal, provides a high output signal. If the currents through those leads are unequal, the comparator provides a low output signal. The sensitivity of the comparator ltlh may be adjusted to provide a desired dead zone, so that minor differences between the comparison currents will not cause the comparator to provide a low output signal. This is done by adjustment of the resistance of a variable resistor 1136 connected between the lead llllt) and another input to the comparator 1%. Of course, this will be explained in more detail in connection with the circuit diagram of the comparator shown in FIG. 5.

The output signal from the comparator h appears on a lead 1138, which is connected to a first control input of the gate 78 interposed between the clock pulse generator 76 and the accumulator 7 3, and to an input of a relay driver M0. A second input of the gate 7% is connected by a lead Ml to receive an output signal from the relay driver Mil. The clock pulse generator 7d runs continuously while the equipment is energized. However, its output pulses are only transmitted through the gate 7% to the accumulator 74 when the signals on the leads 138, Ml are low. When the signal appearing on either of the leads 138, Ml is high, the gate 78 is closed and no clock pulses are permitted to reach the accumulator 7 1.

The gate 7% may be maintained in a closed condition once it has attained that condition and regardless of later-occurring output signals from the comparator 11.08, by grounding an input to the relay driver 140 through a normally open switch M2. This switch when open prevents a high output signal from the comparator 108 from actuating the relay driver 140. Thus, when the switch 142 is open, a high output signal from the comparator Mid can close the gate 78. However, the gate will open if the input signals to the comparator become unequal for any reason and will remain open until the inputs to the comparator become equal again.

The switch 142 serves as the exposure control or command switch. When it is in its normal, open position, a low or ground level signal is supplied on the lead Ml. to permit the gate 78 to be open or closed under the control of the accumulator. When the switch M2 is closed, the next-appearing high signal from the comparator actuates the relay driver to provide a high signal on the lead Ml. This signal will continue and maintain the gate 78 closed until the switch 1142 is opened at the end of an exposure.

When the switch 142 is first closed, the output signal from the comparator 1108 applied to the input of the relay driver 114MB and to the gate 78 may be either high or low. if the current comparison signals to the comparator 10% on the leads iii], R27 are not equal, the output of the comparator is low. The low output signal appearing on the lead 1133 opens the gate 78 and permits the clock pulses from the clock pulse generator 76 to be provided to the accumulator 74. As the accumulator counts the clock pulses applied to it, various ones of the leads hilt-92 and M-lltld are energized in conventional binary counting fashion. Current through various combinations of the resistors M406 changes the current being provided to the input of the comparator 108 on the lead llltl. When the currents in the leads 110, 127 are equal, the output signal of the comparator lllii changes from low to high. This high signal on the lead Mid causes the gate 78 to close so that no further pulses are provided to the accumulator 74 That high signal on the lead 138 also actuates the relay driver M0 and a high signal appears on the lead Mil to maintain the gate 7% closed regardless of further signals from the comparator. Thus, the accumulator is in effect frozen" at its last count. Of course, these effects occur immediately if the comparator is balanced and is providing a high output signal at the time the switch M2 is first closed. This may well be the case, unless there are changes in the input line voltage occurring at the time the switch M2 is closed.

When the relay driver M0 is actuated, it energizes a relayactuating coil 36C. The relay coil 36C controls relay sections 36A, 36B. The relay section 36A, which is normally open, is shown in FIG. l as connecting the conductor 34 to ground. It will be recalled that the conductor 34 is common to all of the relay actuating coils INC-32C. The relay section 363, when the coil 303C is energized, connects an input of the multivibrator 72 to ground, thus energizing that multivibrator.

The multivibrator 72 is essentially a delay element, whose function is to insure that the relay section 36A has completely pulled in before a positive firing pulse is supplied on the lead 73 to the relay driver 7% to energize a selected one or ones of the output leads 385ll. As previously pointed out in connection with FIG. ll, energization of the leads 3850 causes energization of corresponding ones of the relay coils 20C32C to provide a selected voltage from the secondary windings 14811-14864 of the autotransformer 14 through the SCR switch 58 to the HV transformer and rectifier circuit 56 for the X-ray tube 62. When selected ones of the relays 20-32 are energized, their corresponding contacts 20A-32A and ZtiD-32D are closed. As previously noted, the contacts 2ilD-32ll) serve as holding contacts, so that once the selected relays are momentarily energized the leads 3850 may be deenergized.

it is essential that the selected ones of the relays 20-32 have their contacts 20A-32A fully closed before power is applied through the SCR switch 58 to the HV transformer and rectifier circuit 56. To this end, a second delay multivibrator 144 is provided. It is actuated by a pulse from the first multivibrator 72 that occurs simultaneously with the relay driver firing pulse on the lead 73. This multivibrator provides a second delay after the thing pulse is provided from the multivibrator 72 to the relay driver 70 before it provides a positive signal on the lead so to close the SCR switch 58 and apply voltage from the lead 54 to the HV transformer and rectifier circuit 56.

The delay multivibrators 72, 144 are entirely conventional one-shot multivibrators, and are well known in the art. Hence, they are not shown schematically.

FIG. 3 is a schematic diagram of the relay driver 70 shown in block form in FIG. 2. Fundamentally, the relay driver 70 is composed of seven individual driver sections, indicated generally by the reference numerals l50A-G. The sections A-G are associated with corresponding ones of the relays 20-32 and are connected to them by means of corresponding leads 38-50. inasmuch as the driver sections l50AG are identical to each other, one general description will be given that is applicable to all sections with corresponding elements in the seven sections being designated by the same reference numerals with sufiixes A-G.

Each of the driver sections ll5tl comprises a silicon controlled rectifier (SCR) 152. The anodes of all of the SCRs l52A-G are connected together and through a common lead 154 to a source of positive DC potential (not shown). The cathodes of the SCRs are connected through corresponding disconnect diodes l56A-G to corresponding ones of the leads Bi -fit), shown also in FIG. l as connected to the actuating coils ZilC-32C of the relays 204%). Current through the lead 1541 from the positive power supply through selected ones of the SCRs l52A-G and the disconnect diodes l56A-G is used to energize the relays 20452 initially before their corresponding holding contacts Mill-32D close.

Each of the SCR's l52A-G has a gate electrode, which receives signals from two different sources. Coincidence of the two signals is required in order to fire the corresponding SCR. First, each gate electrode is connected through a resistor 158 to a lead 160. Signals are provided on the lead 160 from the lead 73 through a capacitor 162. As previously mentioned in connection with the description of FIG. 2, a positive pulse is provided on the lead 73 from the first multivibrator 72 a short time after the relay section 36B closes. The lead 160 is connected to ground through a resistor 164, so that the capacitor 162 and the resistor 164 act as a ditferentiator to apply a positive spikelike pulse through the resistors 158 to the gate electrodes of the SCRs 152 each time a positive output pulse is provided from the multivibrator 72. Thus, the SCRs 152 are pulsed, rather than continual power being supplied into their gate electrodes.

As previously mentioned, signals also can appear on various ones of the leads 80-92 from the accumulator 74 shown in block form in FIG. 2. Which of these leads bear positive signals depends on the particular count in the accumulator 74 at any given instant. Those leads 80-92 which do not bear positive signals are effectively grounded through the accumulator 74, so that a positive firing pulse appearing on the lead 160 is dissipated to ground and does not fire any of the corresponding SCR's.

The gate electrodes of the SCRs 152A-G are connected to their cathodes through resistors l66A-G connected in parallel with capacitors 168A-G.

When one or more of the leads 80-92 have positive signals thereon from the accumulator 74 and a positive firing pulse is received on the lead 160, those SCRs whose gate electrodes are positive due to signals on the leads 80-92 are fired. This effectively connects the positive voltage on the lead 154 to the output lead or leads 38-50 of those SCRs that have fired. This energizes a selected one or ones of the relays 20-32 (FIG. 1). When a relay 20-32 is energized, its holding contacts close. This removes any current through its corresponding SCR 152, and that SCR extinguishes. Thus, it is seen that the relay driver 70 is only operative during the pull-in times of the relays 20-32.

The diodes 156 serve to prevent any reverse current flow from the relay coils into the driver 70. The resistor 166 and the capacitor 168 provide a finite gate impedance, so that the gate does not appear to be open, which might cause noise to fire the SCRs. They also serve to suppress any leakage current that might be in their corresponding SCR. The resistors 158 serve to isolate the firing pulse appearing on the lead 160 from the accumulator 74, and also act as current dividers for the firing pulse appearing on the lead 160. Were the resistors 158 not in the circuit, only one of the he SCRs 152 would fire because its gate electrode-cathode junction would present a very low impedance.

The accumulator 74, shown schematically in FIG. 4, fundamentally comprises seven conventional direct-coupled, bistable multivibrators 170A-170G. Inasmuch as all of the multivibrators 170 are identical, only one description will be given which is applicable to all of them. Corresponding elements in the seven multivibrators are designated by the same reference numerals with A-G suffixes.

Each multivibrator comprises a pair of NPN-transistors 172, 174, and is provided with an NPN-transistor 176 that serves as an output or clamping transistor. The emitters of the transistors l76A-G are connected directly to ground, and their collectors are respectively connected to the leads 80-92 that connect the accumulator 74 to the relay driver 70. Thus, when one of the transistors l76A-176G is conducting, a corresponding one of the leads 80-92 is effectively connected to ground to prevent a firing pulse on the lead 160 (F16. 3) from firing any one of the SCRs 152. When the transistors 176 are nonconducting, the gate electrodes of the corresponding transistors 152 in the relay driver 70 are enabled to respond to a positive firing pulse on the lead 160 provided from the multivibrator 72.

Referring momentarily to FIG. 2, it is seen that the clock pulses from the clock pulse generator 76 are provided through the gate 78 on a lead 75 to the accumulator 74. As seen in FIG. 4, the lead 75 is connected to one side of a capacitor 178, whose other side is connected to ground through a resistor 180. The capacitor 178 and the resistor 180 serve to differentiate the relatively square clock pulses received on the lead 75 and provide relatively sharp negative pulses to the accumulator 74. A diode 181 provides a discharge path for the capacitor 178.

In each section 170A-170G of the accumulator 74, the negative-going input pulse is provided to the cathodes of a pair of steering diodes 182, 183. The negative-going input pulse is coupled from the anode of the diode 182 through a resistor 184 and capacitor 186 connected in parallel to the base of the transistor 172. it is also coupled from the anode of the diode 183 through a resistor 188 and capacitor 190 connected in parallel to the base of the transistor 174. The base of the transistor 172 is also connected through a resistor 192 and a lead 193 to a source of negative DC potential (not shown). The anode of the diode 182 is also connected to the next stage in the accumulator through a capacitor 194. The emitters of the two transistors 172, 174 in each stage are connected together and directly connected to ground. The collector of the transistor 172 is connected to the lead 114 from the power supply 112 through a load resistor 196. The collectors of the transistors l72A-172G are also connected to an end of the corresponding output resistor 94-106. The collector of the transistor 172 is also connected through the parallel combination of the resistor 188 and the capacitor 190 to the base of the transistor 174 in that stage. The base of the transistor 174 is connected to the negative potential lead 193 through a resistor 198. The collector of the transistor 174 is connected to the positive lead 114 from the power supply 112 through a load resistor 200, and is also connected to the side of the coupling capacitor 194 remote from the next-succeeding stage. The collector of the transistor 174 is also connected through a resistor 202 to the base of the transistor 176 that was previously mentioned as being the output or clamping transistor that controls a corresponding section of the relay driver 70.

it is apparent that for current to flow through any one of the output resistors 94-106 a corresponding transistor l72A-G must be nonconductive. Otherwise, current would flow from the lead 114 through the resistor 196, and directly through the transistor 172 to ground. If a transistor 172 is nonconductive, current will flow from the lead 114 through the resistor 196, and through a corresponding output resistor 94-106. The values of the resistors 94-106 are chosen in accordance with the desired current flow corresponding to the binary code 1, 2, 4, 8, 16, 32, 64. In other words, if the resistor 94 is assumed to have a value of unity, the resistor 96 would have a value of one-half, the resistor 98 a value of one-quarter, the resistor 100 a value of one-eighth, the resistor 102 a value of one-sixteenth, the resistor 104 a value of one thirty-second, and the resistor 106 a value of one sixty-fourth. Therefore, current through the resistor 96 would be twice that through the resistor 94, and so on progressively throughout the binary series.

It is pointed out that the accumulator 74 counts backwards. That is, it starts with a count of I27 and counts down to zero, at which time it recycles. This is completely immaterial to the operation of the control system of the invention, because at some time during each counting cycle the output current on the lead to the comparator 108 (FIG. 2) will be equal to the current on the lead 127. At that time, the proper ones of the clamping transistors 176 will release the clamps on the leads 80-92 and condition the corresponding driver sections A-G to energize the corresponding relays 20-32 upon receipt of a firing pulse from the multivibrator 72.

As an aid to understanding the operation of the accumulator 74, assume that at some instant it has reached a zero count, so that the current output on the lead 110 from the accumulator is substantially zero. Of course, there will be an output current on the lead 110 because of current through the low-KV- adjust resistor 118 which corresponds to the base or reference applied KV of approximately 20 kv.

At that time when the accumulator 74 registers zero, all of the transistors 172 are conductive, which maintains the bases of the transistors 174 at a negative potential and hence the latter transistors nonconductive. This causes the emitters of the transistors 174 to be high, which, in turn, causes the transistors 176 to be conductive. Thus, all of the leads 80-92 to the relay driver 70 are clamped to ground and none of the llll sections ldllA-G of the relay driver can be fired. All of the sections l'rllA-G are now in a state.

If now a first negative-going clock pulse is received on the lead 75, it will drive the base of the transistor 3172A negatively, thus causing that transistor to become nonconductive and its collector potential to rise. This rise in collector potential is transmitted through the resistor lhdA and the capacitor 1196M. to the base of the transistor 174A. That causes that transistor to become conductive and its collector potential to go low. This has two effects. First, it causes the clamping transistor ll76A to become nonconductive, thus releasing the clamp on the lead Ell to the relay driver section 150A. Second the drop in potential of the collector of the transistor 1170A is transmitted through the capacitor 194A and the diode ltlZB to the base of the transistor i728 in the second stage lli'ilh. Thus, the stage i708 flips, which similarly causes the stage l7tlC to flip, and so on down the line until all stages assume a l state. in this condition, the current on the output lead 1110 from the accumulator 74l corresponds to 127 plus the current through the resistor lllh corresponding to 20 kv. At the same time, all of the leads lib-592 to the relay driver 7i]! are unclamped to enable all of the driver sections lllA-G to be fired upon the receipt of the next firing pulse from the multivibrator '72. it is noted that at this time the diodes 182 are reverse biased, and the diodes 1183 are forward biased.

The next or second negative-going clock pulse received on the lead 75 is transmitted through the diode ltiBlA and through the resistor 188A and the capacitor ldliA to the base of the transistor ll7lA. This causes that base to go low and cuts off the transistor 174A. This causes the potential of the collector of the transistor ll74A to rise. This rise in potential is transmitted through the resistor 184A and the capacitor llEitSA to the base of the transistor 1172A, and causes that transistor to become conductive. Also, the rise in potential of the collector of the transistor 174A causes the transistor 176A to become conductive and clamps the lead till to ground potential. The rise in potential of the collector of the transistor 1174A has no effect on the next-succeeding stage 1708, because the diode M328 is reverse biased and the diode WEB is forward biased. Thus, the positive pulse transmitted through the steering diode to the already-positive base of the transistor 17413 has no effeet. At this point in time, because the transistor l72A is conductive, current does not flow through the output resistor 94 so that the total current in the lead lid to the accumulator is reduced by one unit and corresponds to 126 units plus the current due to flow through the resistor 118.

When a third clock pulse is received, the base of the transistor 172A will be driven negatively. This causes the transistor 172A to become nonconductive and the transistor ll'MA to become conductive. The drop in potential of the collector of the transistor 17 5A is transmitted through the capacitor 1194A, the diode 11833, and the resistor W818 and the capacitor was to the base of the transistor 1748. This causes that transistor to become nonconductive, which in turn cuts oh the transistors 1728, 1768. Thus, the total current from the accumulator on the lead lllll is reduced by two units and corresponds to 125 plus the current through the resistor lid.

The next-incoming clock pulse will cause the section 1170A to flip, but will not afiect the section 1768. Thus, the total output current will correspond to 1% plus the current through the resistor lllh. As successive input pulses are received, the counting proceeds in the conventional manner of binary counters until the count reaches zero. At that time, there is no current through the resistors 94406, and all of the leads hll92 are grounded through their respective transistors ll76A-G. As previously noted, the next-incoming clock pulse resets the accumulator to provide output current corresponding to 1127, plus the base or reference current through the resistor lit it will be recalled that it was mentioned in connection with F181. 2 that the voltage supplied to the accumulator 7 3 on the lead 114 from the power supply llZ reflects variations in a number of factors. Among these, are alternating current line variations and changes in the current through the X-ray tube. These changes in the voltage supplied on the lead 114 are reflected as percentage changes in the output currents supplied to the lead lllltl through the resistors 94-106. In other words, a 10 percent change in the voltage supplied on the lead 11M- will result in a 10 percent change in the current in the lead lid for each of the various KV levels. Thus, if the voltage on the lead lllld decreases, a higher count will be required in the accumulator 74 to provide the same output current on the lead lllll as before the change in voltage occurred. This means that if, for example, the line voltage for the system decreases, at different combination of autotransformer secondary windings lldSlllldS6d will be selected (higher KV selection) to maintain the actual KV supplied to the X-ray tube at its predetermined desired value. Of course, the converse is also true.

lFllG. 5 shows schematically the remainder of the control circuitry shown in block form in FlG. 2. Various portions of the schematic diagram of FM}. 5 have been identified generally by the same reference numerals as their corresponding blocks in H6. 2.

The clock pulse generator 76 is shown toward the left-hand side of FIG. 5. The pulse generator 76 comprises a freerunning, collector-coupled multivibrator, and is entirely conventional in design. Therefore, it will be described only in general terms. it comprises two NPN-transistors 210, 2H2, whose emitters are respectively grounded through forwardbiased diodes 2M, 216. The base of the transistor 2H0 is connected through a resistor 218 and a line 2H9 to a positive DC source (not shown) of, for example, +20 volts, and the base of the transistor 212 is similarly connected through a resistor 220. The collector of the transistor 2W is connected to the +DC line 2119 through a load resistor 222, and the collector of the transistor 2112 is similarly connected through two seriesconnected resistors 224, 226. Regenerative action is provided by connecting the collection of the transistor 212 to the base of the transistor 21MB through a capacitor 228, and by connecting the collector of the transistor 2m to the base of the transistor 212 through a capacitor 234).

The pulse generator 76 oscillates at a frequency of approximately 2 kilocycles per second. Its essentially square wave output signals are provided from a juncture between the resistors 224i, 226 through a capacitor 232 to the cathode of a diode 234 in the gate 7%. The anode of the diode 234i is connected to ground through a resistor 236 and directly to the lead 75, which provides negative-going clock pulses to the accumulator 7 8 when the gate 73 is open. Whether the gate 7 8 is open or closed is determined by signals provided to the cathode of the diode 234 on a lead 238 connected from a juncture point 246 to the cathode of the diode through a resistor 242. if the signal at the juncture point 240 is low, the diode 2% will be forward biased and will pass the negative portions of the pulses provided form the pulse generator 76. lf, however, the signal at the juncture point 240 is high, the diode 234 will be reverse biased and no clock pulses will be passed to the accumulator 743. Signals are provided to the juncture point 24% through a resistor 2% from an output lead 246 of the accumulator llld, and/or from the output of the relay driver Mill on a lead 1M8.

Looking now at the comparator i108, it is seen that the current comparison leads lllll, ll27 are respectively connected to emitters of a PNP-transistor 250 and an NPN-transistor 252. That is, current is fed into the comparator on the lead ll10 from the accumulator 7d, and is taken from the comparator on the lead 127 through the MA adjustment, variable resistor 12%, and the fluoroscopic KV control 230 or the radiographic KV control i332. The MA adjustment and the fluoroscopic and radiographic KV controls will be later discussed in detail.

The collectors of the transistors 250, 252 are connected directly together and similarly to the bases of an NPN- transistor 25d and a PNP-transistor 256. The base of the PNP- transistor 25@ is connected to the HM: line 2119 through a resistor 253 connected in series with the high-KV-adjust potentiometer 120. The base of that transistor is also connected to ground through two series-connected resistors 260, 262. Thus, it is seen that the transistor 250 is connected in a commonbase configuration so that its collector current is substantially equal to its emitter current. The base of the transistor 252 is connected directly to ground, so that that transistor is also connected in a common-base configuration.

The comparator sensitivity adjustment resistor 136 is connected between a juncture point 264 between the resistors 260, 262 and the emitter of the transistor 250. That juncture point is also connected directly to the emitters of both of the transistors 254, 256. The collector of the transistor 254 is connected to the +DC line 219 through a load resistor 266, and the collector of the transistor 256 is connected to ground through a load resistor 268. The load resistors 266, 268 have substantially equal resistance values.

The collector of the transistor 254 is also connected through a resistor 270 to the base of a PNP-transistor 272. The collector of the transistor 256 is connected directly to the base of an NPN-transistor 274. The emitter of the transistor 272 is connected directly to the +DC line 219, and its collector is connected to ground through a load resistor 276. The collector of the transistor 274 is connected directly to the +DC line 219 and its emitter is connected to ground through a load resistor 278. The collector of the transistor 272 is also connected through a resistor 280 to the base of an NPN-transistor 282. The emitter of the transistor 274 is connected through a resistor 284 to the base of an NlPN-transistor 286. The NEW- transistors 282, 286 comprise an AND gate that serves as the output stage for the comparator 108.

The emitters of the transistors 282, 286 are both connected directly to ground. The collector of the transistor 282 is connected to the +DC line 219 through a load resistor 288. The collector of the transistor 282 is also connected to the cathode of a diode 290, whose anode is connected to the +DC line 219 through a resistor 292. A juncture between the diode 200 and the resistor 292 is connected to the output lead 246.

The collector of the transistor 286 is connected to the +DC line 219 through a load resistor 294. It is also connected to the cathode of a diode 296, whose anode is connected to the output lead 246. it is apparent that, if either of the transistors 282, 286 is conducting, the potential on the output lead 246 will be low, that is, it will be virtually at ground potential. However, if both of the transistors 282, 286 are nonconductive, the potential on the output lead 246 will be high, that is, it will be at virtually the potential of the +DC line 219.

ln operation, if the current being pumped into the comparator from the lead 110 through the transistor 250 is equal to that current drained from the comparator on the lead 127 through the transistor 252, neither of the transistors 254, 256 is forward biased and neither is conducting. Therefore, the base of the transistor 272 will be high, the base of the transistor 274 will be low, and neither of the transistors 272, 274 will be conducting. This, in turn, causes the base of the transistor 282 to be low, and the base of the transistor 206 to be low. Thus, neither of the transistor 282, 286 is conductive and the output lead 246 will be high. This high signal trans mitted to the juncture point 240 and thence to the gate 78 causes the gate 78 to close so that no clock pulses are transmitted through the gate to the accumulator 70.

if more current is being pumped into the comparator through the transistor 250 than is being drained from the comparator through the transistor 252, the transistor 25 1 will be forward biased while the transistor 256 will remain reverse biased. This causes the transistors 274, 286 to remain nonconductive, but causes the transistors 272, 288 to become conductive. Thus the output lead 246 will be substantially at ground potential due to current flow through the transistor 282. Similarly, if more current is being drained through the transistor 252 than is being supplied through the transistor 250, the transistor 254 will be reverse biased while the transistor 256 will be forward biased. Thus the transistors 272, 282 will be nonconductive, but the transistors 274, 286 will be conductive. Again, the output lead 246 will be substantially at ground potential. When either of the transistors 282, 286 is conducting and the output lead 246 is low, the low signal transmitted to the gate 78 will cause the gate to open and permit negative-going clock pulses to be transmitted on the lead 75 to the accumulator M. This can be prevented, however, by an overriding high signal on the lead 248 from the relay driver M0.

As previously mentioned, the purpose of the sensitivity adjustment resistor 136 is to provide a desired dead zone, so that minor variations in the balance between input current and output current of the comparator will not cause the comparator to become unbalanced. This is necessary because current is being supplied from the accumulator to the comparator in discrete steps. Thus, it would be possible to attain a condition where the accumulator could not provide exactly the correct amount of current to balance the comparator. Therefore, the dead zone is provided so that if the input current is within one unit of equaling the output current the comparator would respond as though it were balanced. If the resistance of the variable resistor 136 is increased, the sensitivity of the comparator is increased. if the value of the resistor 136 is made smaller, a greater current differential must be seen by the transistors 254, 256 to indicate an unbalance. The dead zone may be made as many current units wide as desired by adjusting the resistor 136, although a zone approximately one current unit wide is preferred.

As was previously mentioned, a high signal may be provided from the relay driver 160 on the lead 248 to override any low signal provided from the accumulator 108 and to maintain the gate 78 closed. This cannot occur, however, when the exposure control or command switch 142 is open.

As is shown at the left of FIG. 5, the relay driver 140 comprises two NPN-transistors 300, 302 and a PNP-transistor 304. The emitter of the transistor 300 is connected directly to ground, and its collector is connected directly to the base of the transistor 302. Thus, if the transistor 300 is conducting, the base of the transistor 302 is effectively grounded and no signals appearing on it can afiect the state of that transistor. Conduction or nonconduction of the transistor 300 is controlled by the position of the exposure control switch 142. A positive DC voltage of, for example, +28 volts, is provided on a line 306 from a voltage source (not shown). The +DC line 306 is connected to one end of a resistor 308, whose other end is connected to the anode of a diode 310. The cathode of the diode 310 is connected to ground through the switch 142. A juncture between the resistor 308 and the diode 310 is connected to the anode of another diode 312, whose cathode is connected to the base of the transistor 300. The base of the transistor 300 is also connected to ground through a resistor 310. When the switch 142 is open, the base of the transistor 300 is maintained at a positive potential because of the voltage divider action of the resistor 308, the diode 312 and the resistor 314. Thus, when the switch 142 is open, the diode 300 is conducting heavily and effectively grounding the base of the transistor 302. Signals from the comparator 108 provided to the juncture point 240 are provided to the base of the transistor 302 through the lead 248 and a resistor 316. However, when the transistor 300 is conducting, these signals have no effect on the state of the transistor 302. When the switch M2 is closed, as when it is desired to make an exposure, the base of the transistor 300 is effectively grounded, which stops conduction in that transistor. Thus, the ground is removed from the base of the transistor 302 and it is free to vary in potential in response to any signals received from the comparator on the lead 268.

The transistors 302, 304 act together to energize the relay coil 36C, when the base of the transistor 302 is not grounded through the transistor 300 and a high signal is received from the comparator 108 through the lead 248. The collector of the transistor 302 is connected to the +DC line 306 through a load resistor 318 and to the base of the transistor 304 through a resistor 320. The emitter of the transistor 302 is connected to the +DC line 3% through. a resistor 322 and to ground through a Zener diode 324. The emitter of the transistor 3% is connected to +DC line 3% through a Zener diode 326. Its collector is connected to ground through the relay-actuating coil 36C across which a diode 32% is connected to short circuit any transients induced in the coil 36C when current through the coil is abruptly stopped. The collector of the transistor 30% is also connected to the anode of a diode 33th. The cathode of the diode 330 is connected through a resistor 332 to the lead 248, whereby, when the transistor 3% conducts, a high signal is placed on the lead 248 to reverse bias the diode 23 in the gate 78.

When the exposure control switch M2 is closed and the base of the transistor 302 ungrounded, a high signal present at the juncture point 240 indicating balance in the comparator W3 is transferred to the base of the transistor 3&2. This turns on the transistor 302, which decreases its collector potential and turns on the transistor 3%. When the transistor 3% conducts, the relay-actuating coil 36C is energized and, simultaneously, a high signal is transferred through the diode 3th and the resistor 332 to the juncture point 24M) and thence by way of the lead 238 to the gate 78. The high signal transferred through the diode 330 and the resistor 332 also maintains the base of the transistor 302 at a positive potential, so that any low signals received from the comparator W8, which might occur if the system input voltage changed during a exposure, will not affect the conditions of the transistors 3tl2, 3134. The only way that the high signal on the lead 243 from the relay driver 140 can be removed is by opening the switch 142 at the termination of an exposure. In addition, the high signal present on lead 243 from the relay driver maintains the gate 73 in an open condition so that variations in the state of the comparator I08 during an exposure have no effect on the gate 78. In other words, the gate 78 remains open during an exposure to maintain the combination of autotransformer secondary windings 11481-141864 selected at the beginning of the exposure.

The exposure switch M2 is shown diagrammatically as a simple manually operated switch. It will be realized, however, that in actual practice the exposure control switch M2 would in all probability be an electronic switch such as a phototimer or other known device that would control the X-ray exposure accurately.

As was previously mentioned in connection with the description of the comparator 108, the comparator compares the current through the transistor 250 with the current through the transistor 252. As described with reference to FIG. 4, the level of current in the conductor 110 from the accumulator 7d depends on the current through the resistors 941-1015 and the resistor I18, and the voltage supplied to the accumulator on the lead 114 from the power supply line 1112. In turn, the voltage supplied from the power supply M2 depends on the line voltage supplied to the power supply and on the voltages added to that voltage from the highdtV-adjust potentiometer 120, the line voltage compensation potentiometer I22 and the MA adjustment I24.

The power supply 1112 is shown in the lower right-hand portion of FIG. 5. It comprises a conventional full-wave rectifier bridge, shown generally by the reference numeral 340, having a pair of input terminals and a pair of output terminals. The input terminals are connected to the terminals 13A, 18B of the secondary winding MSA of the autotransforrner lid shown in FIG. ll. Thus, the input voltage to the bridge rectifier 340 will vary with the line voltage supplied to the autotransformer M. The positive output terminal of the bridge rectifier 340 is connected to ground through a choke 342 and a capacitor 344 connected in series to filter the output of the bridge. The lead 11114 to the accumulator 74! is connected to the juncture of the choke 362 and the capacitor 344.

The negative output terminal of the bridge rectifier 3410 is connected by way of the lead 126 to the impedance-matching device I25. The impedance-matching device comprises two NPN-resistors 3%, 348. The collector of the transistor 3 is connected to the HM: line 306 through a resistor 350. The emitter of the transistor 346 is connected directly to the base of the transistor 3% and through a resistor 352 to ground. The collector of the transistor 348 is connected to the +DC line 3% through a resistor 35d, and its emitter is connected directly to the lead 126 to the power supply I112. The potential on the base of the transistor 3% determines the degree of conductivity of the transistor 3%, and hence the level of voltage added to that provided by the power supply 112 to the accumulator 741 on the lead M41.

The base of the transistor 3% in the impedance-matching device is connected to one end of the line voltage compensation potentiometer 122. The other end of the potentiometer 122 is connected to the movable arm of the high-KV- adjust potentiometer 12th. The adjustable arm of the compensating potentiometer 1122 is connected to the collector of an NPN-transistor 356. The base of the transistor 356 is grounded, and the emitter of that transistor is connected through the MA adjustment 1124 to a regulated source of negative direct current (not shown). The MA adjustment 124 is shown diagrammatically as a simple variable resistor, although it is pointed out that in practice it could well comprise a plurality of resistors of different values that are connected into the circuit one at a time as various currents through the X-ray tube are programmed. its function is to provide a current drain through the transistor 356 that varies inversely with the X-ray tube current selected. In other words, if 0 milliamps are programmed into the equipment, the variable resistor 124 would represent an infinite resistance. Similarly, as the milliamperage programmed for the X-ray tube increases, the resistance value of the variable resistor 124i decreases. This causes more current to flow through the transistor 356, which reduces the voltage applied to the base of the transistor 346. When the voltage applied to the base of the transistor 346 is reduced, condition through that transistor decreases, thus reducing the voltage drop across the resistor 352 and decreasing the potential on the base of the transistor 348. This, in turn, decreases conduction of the transistor 348 and results in less voltage being added by the impedance-matching device 125 to that supplied by the power supply 112.

As previously pointed out in connection with FIG. 2, the maximum voltage that is added to the voltage from the power supply H2 is determined by the adjustment of the movable arm of the high-KV-adjust potentiometer 1120. The potentiometer 124) would be initially adjusted with the variable resistor I24 set to provide infinite resistance to obtain the maximum lKV desired to be applied to the X-ray tube with all of the transformer secondary windings 1451-14864 connected in series in the high-voltage transformer and rectifier input circuit. That adjustment would then remain constant for any particular equipment whose components are not changed.

As previously described with reference to FIG. 2, the current output lead 127 of the comparator 108 is connected to supply current to an MA adjustment R28 to either a fluoroscopic KV control 130 or a radiographic KV control I32. In FIG. 5, the MA adjustment 123 is shown as a simple variable resistor connected between the emitter of the transistor 252 and the regulated negative DC source previously mentioned. In fact, the MA adjustment I28 may be the same type of device as the MA adjustment I24 and, in some instances, even a single device can serve to provide both adjustments.

The lead 1127 from the comparator MP8 is also connected to supply current to the radiographic KV control 132, shown in the upper right-hand portion of FIG. 5, and to the fluoroscopic KV control 136) shown just below the control 132. Whether the current is provided to the fluoroscopic control 130 or to the radiographic control 132 is determined by the mode control switch 13 i, shown in the lower right-hand portion of FIG. 5.

The mode control switch 134 comprises a PNP-transistor 360 and three NPN-transistor 362, 364, 366. The conditions of the transistors 362, 364i, 366 are controlled by the condition of the transistor 360 which, in turn, is controlled by the condition of a switch 368. The switch 368 is manually opened or closed by a radiologist in accordance with whether a fluoroscopic exposure is to be made or a radiographic exposure is to be made. if a radiographic exposure is to be made the switch 368 is closed, and if a fluoroscopic exposure is to be made the switch 368 is opened. It is, of course, understood that the switch 368 is shown only in a diagrammatic sense. in practice, the switch 368 may well be an electronic device that is responsive to equipment primary logic circuitry to perform the function described hereinafter.

1n the mode control switch 134, the base of the transistor 360 is connected through a resistor 370 to the l-DC line 386, and to ground through a resistor 372 and the switch 368 connected in series. The emitter of the transistor 360 is connected directly to the ADC line 219 which is less positive than the line 306. The collector of the transistor 360 is connected through two series-connected resistors 374, 376 to a line 378. A negative DC potential (approximately 8 volts) is provided on the line 378 from a voltage source (not shown). When the switch is closed as shown, the base of the transistor 360 is less positive than its emitter and the transistor 360 conducts heavily. When the switch 368 is open, the base of the transistor 360 is positive with respect to its emitter, and the transistor is nonconductive. Thus, the transistor 360 is conductive during a radiographic mode of exposure, and is not conductive during a fluoroscopic mode of exposure.

As previously mentioned, the condition of the transistor 360 controls the conditions of the transistors 362, 364, 366. The transistor 362 switches the radiographic KV control 132 into and out of the circuit. The transistor 366 controls the condition of another PNP-transistor 380, which switches the fluoroscopic KV control 130 into and out of the circuit. if the transistor 362 is conducting, the radiographic KV control is in the circuit, and if the transistor 366 is conducting the fluoroscopic KV control 130 is in the circuit. Obviously, the transistors 362, 366 cannot both be in the same state at the same time.

The current lead 127 from the comparator 108 is connected to the anode of a diode 382, which serves as an input element for the fluoroscopic KV control 130. The lead 127 is also connected to the anode of another diode 384, which serves as an input element for the radiographic KV control 132.

in the fluoroscopic KV control 130, the collector of the transistor 380 is connected directly to the DC line 378. The emitter of that transistor is connected through a resistor 386 to the cathode of the input diode 382. The base of the transistor 380 is connected to the movable arm of a potentiometer 388 that serves as the fluoroscopic KV adjustment. One end of the potentiometer 388 is connected through a variable resistor 390 to ground, and the other end of the potentiometer is connected directly to the collector of the transistor 366. The emitter of the transistor 366 is connected directly to the DC line 378. Therefore, if the transistor 366 is nonconductive, the base of the transistor 380 will be essentially at ground potential, and the transistor 380 will be nonconductive. Therefore, the fluoroscopic KV control channel will be closed. If the transistor 366 is conductive, the base of the transistor 380 will be at a negative potential determined by the setting of the movable arm of the potentiometer 388. Thus, current flow through the transistor 380 will be determined by the setting of the movable arm of the potentiometer 388. The variable resistor 390 serves as a calibration adjustment for the fluoroscopic KV control.

The radiographic KV control 132 comprises a plurality of normally open switches 392A-H and a plurality of fixed resistors 394A-H. Corresponding ones of the switches 392A-G and the resistors 394A-G are connected in series between input and output leads 396, 398. The lead 396 is connected to the cathode of the input diode 384, and the lead 398 is connected directly to the collector of the transistor 362 and to ground through a resistor 400. The emitter of the transistor 362 is connected directly to the DC line 378. Therefore, if the transistor 362 is conductive, those resistors 394 whose corresponding switches 392 are closed are connected in parallel between the lead 127 and the DC line 378. The purpose of the input diode 384 is to insure that, when the transistor 362 is nonconductive and one or more of the switches 392 is closed, current cannot flow back through the resistor 400 and into the lead 127.

The resistors 394A-G are chosen to permit various numbers of units of current to flow through them, when their corresponding switches 392A-G are closed. For example, the resistor 394A could have a relatively large value, so as to permit one unit of current to flow through it, when its corresponding switch 392A is closed. The resistor 3941) could have a value half that of the resistor 394A to permit two units of current to flow through it when the switch 3928 is closed. The values of the resistors 394(1-6 would become progressively smaller to permit increasing numbers of units of current to flow through them when their corresponding switches are closed. It is pointed out that eight switches 392 are resistors 394 are shown in a diagrammatic sense only. in practice, there might well be 23 such combinations. In such an arrangement, the 23 resistors might well be sized to permit current flow of l, 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 30,40, 50, 60, 70, 80, 90, 100, I10, 120, and units. These units of current, of course, would correspond to selected KV levels of 1 kv., 2 kv., Alternatively, eight combinations of switches and resistors might be used, with the resistors so sized that current through them would correspond to voltages applied to the X-ray tube of l 2 kv., 4 kv., 8 16 32 kv., 64 kv., and 128 kv. The first example given is probably preferably, however, because only two switches need be closed to obtain any desired KV value. in the second example, various combinations of switches would have to be closed and could be confusing to an operator.

Attention is drawn to the fact that the control system will not respond to permit an exposure to be made if any of the switches 392'are closed that represent a total selected KV of less than that represented by current through the low-KV-adjust resistor 118 shown in FIG. 4. in other words, if the total KV selected by closing the switches 392 in a combination that calls for less than that predetermined by the setting of the resistor 118, more current will be pumped into the comparator 108 on the lead 110 from the accumulator 74 than will be drained from the comparator on the lead 127 through the radiographic KV control 132. In that instance, the accumulator 168 will never balance to provide a high output signal, so that the relay driver 140 will never be energized and no X-ray exposure can be made.

Turning again to the mode control switch 134, it is seen that the base of the transistor 362 that opens and closes the radiographic KV control channel is connected to a point intermediate between the resistors 374, 376 in the collector circuit of the transistor 360. The base of the transistor 364 is connected through a resistor 402 to the collector of the transistor 360, and is connected through a resistor 404 to the DC line 378. The collector of the transistor 364 is connected directly to the base of the transistor 366 and to ground through a load resistor 486. The emitter of the transistor 364 is connected directly to the DC line 378.

As previously noted, when the mode control switch 134 is in the radiographic mode of operation the switch 368 is closed. This causes the transistor 360 to conduct and provide a voltage drop across the load resistors 374, 376. The potential drop across the resistor 376 causes the base of the transistor 362 to be positive with respect to its emitter and causes that transistor to become conductive. This enables the radiographic l(V control channel and permits current flow through those resistors 394A-H whose corresponding switches 392A-H are closed. At that same time, the base of the transistor 364 is also positive with respect to its emitter, because of the potential drop across the resistor 404. This causes the transistor 364 to become conductive. The potential on the collector of the transistor 364 and hence on the base of the transistor 366 is essentially the same as the potential of the DC line 378. This causes the transistor 366 to be nonconductive and disables the fluoroscopic KV control channel.

When the radiologist opens the switch 356% in order to malre a fluoroscopic examination, the potential at the base of the transistor 36% rises and that transistor cease conducting. This causes the potential at the base of the transistor 36?; to drop and cuts off that transistors to disable the radiographic lKV control channel. At that same time, the potential at the base of the transistor 364 goes negative and that transistor cuts off. This causes its collector and the base of the transistor 3% to go to ground potential and causes the transistor 3366 to become conductive. This enables the fluoroscopic ltV control channel by permitting current through the fluoroscopic liV adjust potentiometer 3%.

Although the various portions of an embodiment of a control system embodying the invention have been described in detail, it is believed that a brief description of the overall operation of the system will be helpful. The following descrip tion is primarily of a functional nature, and is made principally with reference to FIGS. ll 2 and 5. Only incidental reference will be made to the detailed circuitry shown in W63. 3 and t.

The equipment is initially energized by closing the input power switch 16. This provides primary power to the autotransformer M and energizes the various power supplies that are connected to the transformer secondary windings MSA, MSB, MSC. When the various power supplies are energized, several things occur. For example, the second multivibrator 1144 is energized to provide an inhibit signal on the lead 69 to the SCR switch 58 so that that switch is maintained open and no voltage can be applied through the leads 52, 54 to the high-voltage transformer and rectifier circuit 565. The clock pulse generator 76 is energized to provide clock pulses to the gate 7% and thence to the accumulator 74 if the gate 7% is open. The relay driver 70 is energized, and voltage is applied to the accumulator 74 on the lead 1M from the power supply 1112. Likewise, the comparator 11% is energized to provide output signals on the lead l38 to the gate 78 and to the relay driver 141). At this time, the exposure control switch 1l4l2 is open, so that the relay driver M is inoperative.

Assume now that the switch 36% in the mode control switch 134 ((FlG. has been left open from a previous exposure. In that case, a certain amount of current will be drained from the comparator 1% through the lead 127 and through the transistor 380 in the fluoroscopic KV control 130. An additional current drain will occur through the MA adjustment 12% depending on what its previous setting was. Assume also that the high KV adjustment potentiometer B20, the line voltage compensation potentiometer ll22, and the MA adjustment 12d are providing a certain voltage that is added to the voltage provided by the power supply 112 on the lead lid to the accumulator. Assume further that when the equipment was last deenergized the accumulator 74 was provided a certain level of current through the resistors 94-11% to the lead llltt connected to the current input of the comparator lldd. if that current is not the same as the current being drained from the current output on the lead ll27 from the comparator, the com parator will provide a low output signal on the lead 113% to the gate 78 to open the gate. The clock pulses transmitted from the clock pulse generator 76 through the gate 78 to the accumulator 74 will then cause the accumulator to start counting as previously described and vary the current supplied to the lead ill) in steps of one current unit to the comparator. When the current input to the comparator on the lead lllli'i equals the current output on the lead 1127, the comparator will provide a high output signal on the lead 138 which will cause the gate 78 to close. This signal will have no effect on the relay driver because the exposure control switch 142 is still open.

Because the relay driver 114% is not actuated, the relay coil 36C is not energized and the first multivibrator 72 is not actuated. Therefore, although various ones of the leads hill-92 from the accumulator to the relay driver 70 are being energized, it will have no effect on the relay driver 7d because no firing pulse will be received from the first multivibrator 72. Thus, there will be no output on the leads M l-5h from the relay driver to the relays 20-332 to provide energizing current to their actuating coils EGG-32C. Furthermore, the relay con- Zli tacts 36A will be open, so that the relay coils 2tiC-32C would not be energized even though the leads 33-50 were energized.

The same functions would occur were the switch 368 in the mode control switch 134 in a closed position. The only difference would be that the comparator ltltl would provide a high output signal on the lead 138 when the current drain through the lead 1127 (controlled by the condition of the switches 392 in the radiographic KV control 132) was equal to the current input from the accumulator on the lead 110.

The radiologist would then adjust the various controls for the exposure that he desired to make. if the exposure was to be of the radiographic type, the switch 368 in the mode con trol switch 1134 would be closed. This would open the radiographic KV control channel through the transistor 362 and close the fluoroscopic KV control channel through the resistor 366. One or more of the switches 392 in the radiographic KV control 132 would then be closed to correspond to the desired KV level to be applied to the X-ray tube. The desired current through the X-ray tube would then be selected and the MA adjustments 1%, 12% made accordingly, high resistance values for low tube current and low resistance values for higher tube currents. Thus, a certain voltage would be subtracted from the voltage provided the accumulator on the lead llld from the power supply M2 in accordance with the selected MA value, and a certain current drain would be provided through the MA adjustment 128 to provide for losses in the system that are proportional to X-ray tube current. As these adjustments are made, the current output from the comparator MM on the lead ll27 is changed. The comparator thus provides a low output signal on the lead 138 to open the gate 73 and permit clock pulses to be provided to the accumulator 74. The accumulator 74! then counts until the currents supplied through its output resistors 94-196 (and the current provided trough the low ltV adjustment resistor 118) on the lead llltb equal the current drained from the comparator on the lead 127. When those two currents are equal, the comparator again provides a high output signal on the lead 138 which closes the gate 78 and maintains the accumulator 74 at its last count condition.

If, during that period of time between initial energization of the equipment and closing of the exposure command switch M2, the input line voltage to the system changes that change will be reflected in the voltage supplied to the power supply M2 and in the voltage supplied from the power supply to the accumulator 74 on the lead M. As previously noted, if the input voltage decreases, the voltage supplied to the accumulator will decrease and a higher count will be required from the accumulator to provide a current on the lead 1110 to the comparator 108 that equals the current on the lead 127 drained from the accumulator through the RV controls 130, 132 and the MA adjustment 12%. Of course, the converse is true. If the input voltage increases, a lower count will be required from the accumulator to cause the comparator to balance.

After the KV adjustments and the MA adjustment and the mode control selection has been made, the exposure command switch M2 may be closed. At that time, if the current to the comparator ltitl on the lead llllh is equal to the current from the comparator on the lead 127, a high output signal will be provided on the lead 138 to the relay driver 140 and to the gate 78. This will cause the gate 78 to close and maintain the accumulator at that particular count. As previously described, closing the switch M2 releases the clamp on the input to the relay driver M0 and the high signal provided on the lead 138 will actuate the relay driver. This will simultaneously cause the relay-actuating coil 3M: to be energized and a high signal provided on the lead l lll to the gate 78 to maintain the gate in its last-attained condition regardless of any further changes in the output from the comparator W8. Thus, any changes in the input line voltage during the course of an exposure cannot cause the various relays 2042 to change their conditions. In other words, those autotransformer secondary windings lest-M364 that are connected in series at the beginning of an exposure remain so connected throughout the exposure.

This is necessary because the contacts of the relays 2 11-32 cannot be open and closed while current is flowing through them because of their physical or structural limitations.

When the relay actuating coil is energized, it closes the normally open relay contacts 36A, 3613. The contacts 36A, when closed, complete a current path from the relay-actuating coils 20C-32C to ground, so that those relays whose leads 38-561 from the relay driver 70 are energized can be actuated. When the relay contacts 3613 close, the first multivibrator 72 is actuated to provide a positive firing pulse on the lead 73 to the relay driver 70, after a very short time delay.

At the time the positive firing pulseis received on the lead 73 by the relay driver 70 from the first multivibrator 72, selected ones of the leads h-92 have signals thereon. Those SCRs 152A-G that are receiving high signals on the leads 80-92 are fired by the firing pulse from the multivibrator to energize corresponding ones of the output leads 3840. This energizes corresponding ones of the relays 20-32 and connects corresponding ones of the autotransformer secondary windings 1481-14864 in series with the reference voltage winding 145R to the input of the high-voltage transformer and rectifier circuit 56.

The second multivibrator 144 receives a signal from the first multivibrator 72 simultaneously with the firing pulse provided on the lead 73 to the relay driver 70. After a relatively short time delay, the multivibrator 144 removes the inhibit signal provided on the lead 60 to the SCR switch 58 to permit voltage to be supplied to the high-voltage transformer and rectifier circuit 56 and an exposure to be made. The exposure is terminated by opening the exposure command switch 142 which, as previously pointed out, would in practice probably be an electronic control which would function as a switch to provide exposures of variable desired durations.

At the end of an exposure, when the switch 142 is opened, the control system assumes essentially the same condition as initially described. The relay driver 140 becomes inoperative, and the gate 78 will close or remain closed when the input current on the lead 1 to the comparator 108 is equal to the output current on the lead 127. The various controls may then be adjusted for the next exposure.

if a fluoroscopic mode of exposure is desired, the switch 368 in the mode control switch 134 is opened, this causes current in the lead 127 from the comparator to be provided to the fluoroscopic control 130 and to the MA adjustment 128 rather than to the radiographic KV control 132 and the MA adjustment 128. Outside of the different current path from the lead 127, the operation of the system is exactly the same as that described with respect to the radiographic mode of operation.

Although one embodiment of the invention has been illustrated and described in detail, it is apparent that many modifications and variations can be made by one skilled in the art departing from the true spirit and scope of the invention.

llclaim:

1. An X-ray control system for selecting energizing voltages to be supplied to an X-ray tube comprising:

a. a transformer having a primary winding for connection to a source of voltage, and having a plurality of secondary windings for providing said energizing voltage to said X- ray tube, said secondary windings respectively providing different voltage outputs;

b. voltage selection means for connecting selected ones of said secondary winding to the X-ray tube to provide different selected energizing voltages thereto;

0. X-ray tube energization control means interposed between the X-ray tube and the secondary windings for selectively connecting the X-ray tube across the secondary windings; and

d. inhibit control means connected to the X-ray tube energization control means and to the voltage selection means, said inhibit control means permitting the Xray tube energizafion control means to connect the X-ray tube to the secondary windings only after the secondary windings have been connected in the combination required to provide the voltage selected by the voltage selection means.

2. An X-ray control system for selecting energizing voltages to be supplied to an X-ray tube comprising:

a. a transformer having a primary winding for connection to a source of voltage, and having a plurality of secondary windings for providing said energizing voltage to said X- ray tube, said secondary windings respectively providing different voltage outputs; and

b. voltage selection means for connecting selected ones of said secondary windings to the X-ray tube to provide different selected energizing voltages thereto, and comprismg i. a plurality of switching devices;

ii. a ltilovoltage selector having a plurality of kilovoltage settings;

iii. control circuit means for causing said switching devices to connect the secondary windings progressively in different combinations to scan the kilovoltage range selectable from the transformer; and

iv. comparison means for comparing the kilovoltage level selected on said kilovoltage selector to the voltage output of the secondary windings connected together, and providing a signal indication when the voltage output of the connected windings is the voltage selected.

3. The system of claim 2 wherein the secondary windings are sized and arranged so that their respective voltage outputs are proportional to elements in a geometric series.

d. The system of claim 3 wherein the geometric series is binary.

5. The system of claim 4 wherein the binary-coded windings are sized and connected to scan in equivalent voltage steps corresponding to approximately 1.0 kv. each as provided to the X-ray tube.

6. The system of claim 5, wherein seven binary-coded secondary windings are provided and have output voltage values equivalent to l, 2, 4, 8, 16, 32 and 64 kv. as supplied to the X-ray tube.

7. An X-ray control system for selecting energizing voltages to be supplied to an X-ray tube comprising:

a, a transformer having a primary winding for connection to a source of line voltage, and having a plurality of secondary windings for providing said energizing voltage to said X-ray tube, said secondary windings respectively providing different voltage outputs; and

b. voltage selection means for connecting selected ones of said secondary windings to the X-ray tube to provide different selected energizing voltages thereto and comprismg i. a plurality of switching devices for selectively connecting the secondary windings in different series combinations to provide different selected X-ray tube energizing voltages.

kilovoltage selector means settable to any one of a plurality of kilovoltage settings of an available kilovoltage range and having an output providing a first signal indication which varies according to the kilovoltage settings,

iii. binary-coded winding selection means connected to said switching devices and causing said switching devices to connect said binary-coded windings progressively in a plurality of combinations which will provide the kilovoltage range selectable on said kilovoltage selector,

iv. said binary-coded winding selection means having an output providing a second signal indication which varies according to the voltage provided to the connected binary-coded windings,

v. comparison means comparing the first and second signal indications from the outputs of the kilovoltage selector means and the binarycoded winding selection means and providing a control signal when the signal indications are equal, and

vi. energizing circuit control means for initiating energization of the X-ray tube in response to said control signal.

8. The system of claim 7, wherein said voltage selection means further comprises:

vi. loss compensator means connected to said kilovoltage selector means to modify the first signal indication provided by said kilovoltage selector means in accordance with direct current losses so that another combination of the binary-coded secondary windings must be selected to cause the first and second signal indications to be equal.

9. The system of claim 8, wherein the signal indication from one of said outputs is dependent upon said source of line voltage so that changes in supplied line voltage cause corresponding changes in the selected combination of binary-coded secondary windings necessary to maintain a preselected KV to be supplied to the X-ray tube.

10. The system of claim 7, wherein said kilovoltage selector means comprises a plurality of kilovoltage selectors selectively connectable to said comparison means for selecting one of a plurality of kilovoltages to be supplied to the X-ray tube.

11. An X-ray system comprising:

a. a transformer having a primary winding and a plurality of binary-coded secondary winding, each succeeding secondary winding providing twice the output voltage of a preceding winding;

b. a like plurality of switching devices for connecting selected binary-coded winding in series;

c. circuit means for connecting the series-connected windings to the input of the high-voltage transformer and for connecting an output of the high-voltage transformer to an X-ray tube;

d. kilovoltage selection means for selecting a kilovoltage to be supplied to the X-ray tube; and

e. winding selection control means including i. sequencing means for sequentially selecting ditferent combinations of binary-coded windings;

ii. signal means for indicating the binary-coded windings selected;

iii. comparison means connected to said signal means and to said kilovoltages selecting means for comparing the kilovotlage providable by the binary-coded windings selected to the selected kilovoltage and providing a control signal when the voltage providabie by the selected binary-coded windings equals the selected voltage; and

iv. energization control means connected to said switching devices and to said comparison means and energizing selected switching devices for connecting the selected binary-coded windings in series in response to said control signal.

112. The system of claim lli, wherein said sequencing means comprises a binary counter, said counter having a plurality of first outputs equal to said plurality of secondary windings and switching devices which first outputs are energized to provide binary indications of the total pulse count received by the counter at its input for a pulse generator, said first outputs being connected to said switching devices so that only those switching devices connected to an energized first output can be energized by said energization control means.

13. The system of claim 12, wherein said signal means is a current adder comprising a plurality of resistors having respective one ends connected to respective second outputs of said binary counter and their other ends connected to a common conductor, the resistance of each succeeding resistor is one-half that of its next preceding resistor and the resistors are energized through the second outputs of the binary counter from a common voltage supply, whereby the current in the common conductor is representative of the voltage providable by the binary-coded windings selected.

M. The system of claim li, wherein said sequencing means comprises:

i. a binary counter;

ii. a clock pulse generator providing bits to a input of said counter;

iii. a gate interposed between said counter and said pulse generator for controlling passage of said bits to said input of said counter;

iv. said counter having a plurality of outputs equal to said plurality of switching devices which are selectively energized to provide a binary indication of total bit count received by said counter, said outputs being respectively connected to said switching devices so that only those switching devices connected to an energized output can be energized by said energization control means; and I v. said gate being connected to said comparison means and stopping passage of said bits to said counter in response to said control signal.

15. In an X-ray control system for selecting energizing voltages to be supplied to an X-ray tube, the combination comprising:

a. a transformer having a primary winding for connection to a source of line voltage, and having a plurality of secondary windings for providing said energizing voltages to said X-ray tube, said secondary windings respectively providing different voltages outputs;

b. a clock pulse generator for providing clock pulses;

c. selecting means responsive to said clock pulses for sequentially and cyclically connecting various ones of said secondary windings to provide various energizing voltages for said X-ray tube, and to provide a first current signal that varies in accordance with said voltages provided to said X-ray tube;

d. kilovoltage selector means for said X-ray tube, having a plurality of kilovoltage settings to provide a second current signal that varies in accordance with a kilovoltage selected thereby;

e. current comparator means connected to receive and compare said first and second current signals and provide a control signal when said first and second current are equal;

f. gate means interposed between said pulse generator and said selecting means responsive to said control signal to prevent transmission of said clock pulses to said selecting means; and

g. switch means actuatable for connecting, to energize said X-ray tube, that combination of secondary windings existing when said transmission of clock pulses is interrupted by said gate means.

116. The combination of claim 15, wherein said selecting means includes a counter.

17. The combination of claim 16, wherein said counter is a binary counter.

18. The combination of claim 15 wherein said selecting means includes a counter having a plurality of output leads corresponding to said plurality of secondary windings which, when selectively energized, permit various ones of said secondary windings to be connected together to provide said various voltages for said X-ray tube.

19. The combination of claim 18, wherein said selecting means further includes driver means connected between said counter output leads and said secondary windings and said driver means is responsive to a firing signal to actuate said switch means to connect in series those secondary windings that correspond to energized output leads from said counter.

20. The combination of claim 19, further including means for providing said firing signal in delayed response to said control signal.

211. The combination of claim 15, further including h. milliampere selector means having a plurality of settings,

each setting corresponding to a desired current through said X-ray tube and providing a third current signal that varies in accordance with a milliarnperage selected thereby; and

i. circuit means connecting said milliamperage selector means to said kilovoltage selector means whereby said third current signal modifies said second current signal.

22. The combination of claim 15, further including h. milliamperage selector means having a plurality .of settings, each setting corresponding to a desired current through said X-ray tube and providing a voltage signal that varies inversely with a milliamperage selected thereby; and

i. circuit means connecting said milliamperage selector means to said selecting means, whereby said voltage signal modifies said first current signal.

23. The combination of claim 15, further including h. first milliampere selector means having a plurality of settings, each setting corresponding to a desired current through said X-ray tube and providing a third current signal that varies in accordance with a milliamperage selected thereby;

. first circuit means connecting said first milliamperage selector means to said kilovoleage selector means, whereby said third current signal modifies said second current signal;

j. second millamperage selector means having a plurality of settings, each setting corresponding to a desired current through said X-ray tube and providing a voltage signal that varies inversely with a milliamperage selected thereby; and

k. second circuit means connecting said second milliamyerage selector means to said selecting means, whereby the voltage signal modifies said first current signal.

24. The combination of claim 15, further including h. X-ray tube energization control means interposed between said secondary windings and said X-ray tube and selectively actuatable to connect said X-ray tube across said secondary windings.

25. The combination of claim 24, further including i. means for actuating said energization control means in response to said control signal from said comparator means.

26. The combination of claim 25, wherein said energization control means is actuated after said switch means is actuated.

27. The combination of claim 15, further including means for energizing said selecting means from said source of line voltage, whereby said first current signal varies in accordance with said line voltage.

28. The combination of claim 21, further including means for energizing said selecting means from said source of line voltage, whereby said first current signal varies in accordance with said line voltage.

29. The combination of claim 22, further including means for energizing said selecting means from said source of line voltage, whereby said first current signal varies in accordance with said line voltage.

30. The combination of claim 23, further including means for energizing said selecting means from said source of line voltage, whereby said first current signal varies in accordance with said line voltage.

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Citing PatentFiling datePublication dateApplicantTitle
US3750005 *Sep 20, 1971Jul 31, 1973Us ArmyHigh efficiency constant voltage to constant current converter for energy storage
US3828194 *May 3, 1973Aug 6, 1974Siemens AgX-ray diagnosing apparatus with a regulating device for the x-ray tube voltage
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Classifications
U.S. Classification378/112, 315/276, 323/911
International ClassificationH05G1/58
Cooperative ClassificationY10S323/911, H05G1/58
European ClassificationH05G1/58