US3299343A - High voltage control arrangement - Google Patents

Description

J n-11,1961 M. HICKEY Em 3,2 9,3

HIGH VOLTAGE CONTROL ARRANGEMENT Filed June 5, 1963 .28 ?0 32 33 i ENERGY a? DETECTOR I I 40 38 .3 e DEFLECTION v GATING TRIGGER PULSE PuLs CIRCUIT GENERATOR GENERATOR FIG.

HIGH VOLTAGE REGULATED /42 POWER SUPPLY I I 'TO ACCELERATING ELECTRODE 4a 100 v 54 o U.D.P. 2o TO L.D.P. 22

+eoov +1ooov -s|ov -|ov o 0 0 I .79 80 8| as as v +aoov -4|ov 92 -8OOV I L 78 L 66 llil|+ v gm y|m+- leoov 94 I6OOV 64 lsoov INVENTORS HQ 2 JOHN J. HICKEY J- PfRRYJM/TH United States Patent 3,299,343 HIGH VOLTAGE CONTROL ARRANGEMENT John J. Hickey and J Perry Smith, Hawthorne, Calif., assignors, by mesne assignments, to TRW Inc., acorporation of Ohio Filed June 3, 1963, Ser. No. 285,013 6 Claims. (Cl. 32323) This invention relates to high voltage control arrangements, and in particular to simple and economical means for varying two or more high direct current voltages simultaneously without introducing excessive corona effects.

In certain electrical laboratory instruments which utilize relatively high direct current potentials, such as oscillographs or electronic cameras, it is desirable to be able to vary two or more of these potentials.

One type of electronic camera system for photographing ultrahigh speed luminous transient phenomena employs an electrostatically operated image converter tube. The image converter tube serves both as a high speed electronic shutter and as a means for amplifying the light image being photographed. The image converter tube comprises a photocathode for converting the light image into a corresponding electron image, a control grid for gating the electron image, a generally cylindrical focussing electrode for electrostatically focussing the electron image onto a fluorescent screen, a conical accelerating electrode for accelerating the electron image towardsthe fluorescent screen, and a pair of electrostatic deflection plates for moving the electron image across the fluorescent screen.

In order to operate the camera in different modes it is necessary to be able to change the supply potentials of the deflection plates relative to that of the accelerating electrode. For example, during initial focussing and alignment procedures it is customary to apply'equal potentials to the deflection plates and accelerating elect-rode. For framing operation, in which three side by side images are obtained by the application of properly timed voltage pulses to the deflection plates and control grid, it is desirable to apply opposite and equal supply voltages to the deflection plates relative to the accelerating electrode so that the first frame will appear off center on one side, the second frame centered, and the third frame oif center on the opposite side. For streak operation, in which a slit is imaged on the center of the photocathode and the resulting electron image then swept across the screen by applying'a linear ramp voltage to one or both deflection plates, the deflection plate supply voltages differ by a greater'amount than in framing operation in order that the image on the screen will cover the same over-all picture area.

While it is possible to vary the high potentials on the deflection plates relative to the accelerating electrode by switching the high voltages directly from a common power supply, such practice causes severe corona problems. To avoid corona problems by employing separate power supplies would entail extra cost.

Accordingly, it is an object of this invention to provide an arrangement for altering two or more high direct current voltages applied from a single source while minimizing corona effects.

A further object of the invention is to provide a simple and economical means for oppositely varying two high potentials about a third fixed high potential.

The foregoing and other objects are achieved according to an embodiment of the invention in a control arrangement which includes a high voltage power supply having two parallel branches in series therewith. Each branch includes a voltage regulator having an anode and a cathode and a current limiting resistor connected between the anode and the source. A voltage divider network, which 3,299,343 Patented Jan. 17, 1967 may consist of two resistors is connected between the anodes of the voltage regulators. The cathodes of the voltage regulators are connected to variable unidirectional voltages of much smaller magnitude than the supply voltage. The variable voltages may be produced by means of a phase splitter. The phase splitter consists of a vacuum tube whose anode is connected to the cathode of one of the voltage regulators and whose cathode is connected to the cathode of the other voltage regulator. Resistors of equal resistance value are connected in the anode and cathode circuits and to equal and opposite voltages.

The cathode circuit of the phase splitter operates like a cathode follower in that a direct current voltage applied to the grid will produce a corresponding voltage on the cathode of the same sign and nearly of the same magnitude. The voltage on the anode will be equal to and opposite that on the cathode since the anode current is equal to the cathode current. The appearance of these two voltages which are substantially smaller in magnitude than the supply voltage will be reflected by a corresponding change in the potentials on the anodes of the two voltage regulators. The anode potential on one regulator will increase and the anode potential on the other regulator will decrease by the same amount, while the potential at the midpoint of the voltage divider network connecting these two anodes will remain constant.

In the drawing:

FIG. 1 is a schematic diagram of an electronic camera system in which the voltage control arrangement of the invention finds utility; and

FIG. 2 is a schematic circuit of one embodiment of the voltage control arrangement according to the invention.

Referring now to the drawing, FIG. 1 is a schematic diagram of an electronic camera system employing a voltage control arrangement according to the invention. The electroniccamera system includes as one of its principal components an image converter tube 10 which functions primarily as a high speed shutter. Another function of the image converter tube 10 is that of providing light amplification for the extremely short frame times involved in its high speed photographic operation.

The image converter tube 10 comprises essentially a cylindrical evacuated envelope 12 containing a photoemissive cathode or photocathode 14 at one end, a fluorescent screen 16 at the other end, a control grid 18adjacent to the photocathode 14, and a pair of deflection plates 20 and 22 intermediate the control grid 18 and the fluorescent screen 16. Certain other parts and components essential to the operation of the tube 10 are omitted for simplicity, since these are well known. For example, the tube 10 ordinarily contains additional electrodes such as an anode and focussing electrodes and also requires a high voltage supply. It will suffice to say that the tube may be one of the kind manufactured by RCA and bearing the developmental type number C73435A.

In the operation of the electronic camera for the purpose of photographing high speed transient phenomena, light from an object 24 is focussed by a lens 26 onto the photocathode 14 of the image converter tube 10. The electron image emitted from the photocathode 14 is normally prevented from reaching the fluorescent screen 16 by the application of sufliciently high negative blanking voltage to the control grid 18 relative to the photocathode 14.

A rapid series of frames or exposures of the phenomenon or object 24 can be taken by applying a series of positive rectangular gating voltage pulses to the control grid 18. The gating voltage pulses are sufliciently large, such as 300 volts, to unblank the grid 18 and permit the electron image to be accelerated towards the fluorescent screen 16. The different frames or exposures may be reproduced side-by-side on the fluorescent screen 16 by applying deflection voltages to the deflection plates 20 and 22 respectively, between and during successive gating pulses. The amplified light images appearing on the fluorescent screen 16 are then projected onto a photographic film 28 by means of a lens system 30. In practice, the film 28 may be part of a camera of the type which allows rapid development of the exposed film 28.

A gating signal for actuating the image converter tube is developed in a circuit which includes an electromagnetic energy detector 32 exposed through a lens system 34 to the phenomenon or object 24 to be recorded. The beginning of the event for example, may be manifested by the initial emission of light from the object 24. In such case, the detector 32 may comprise a phototube circuit which converts the light into an electrical signal. The electrical signal is fed to a trigger circuit 36 to develop an amplified trigger pulse or a series of pulses of suflicient magnitude to drive a gating pulse generator 38 and a deflection pulse generator 40 which generate the desired gating and deflection pulses for operating the image converter tube.

For streak operation, a single gating pulse is applied to the control grid 18 while a linear ramp voltage is applied to one deflection plate or equal and opposite ramp voltages are applied to both deflection plates. The scene is viewed through a slit that is oriented perpendicular to the direction in which the beam is swept so that the film records the trace left by the moving slit image.

As mentioned previously, it is necessary that the high voltage supply potentials for the deflection plates 20 and 22 be varied for diflerent operating conditions. Focussing and alignment procedures for the camera tube and lens systems are carried out with the deflection plates at the same high positive potential. For framing operation, the supply potentials on the deflection plates must be changed so that they difler by one amount, while for streak operation the potentials are charged so that they differ by another amount.

A circuit for varying the supply potentials on the deflection plates relative to the anode is shown in FIG. 2. The positive side of a high voltage power supply 42 is connected in series with two parallel branches. One bran-ch includes a current limiting resistor 44 connected to the anode of a high voltage regulator tube 46 and the other branch includes a current limiting resistor 48 connected to the anode of a high voltage regulator tube 50. A voltage divider consisting of two resistors 52 and 54 of equal resistance value is connected between the anodes of the two regulator tubes 46 and S0. A vacuum amplifying tube 56, such as a triode, has its cathode connected at point 58 to the cathode of voltage regulator tube 46 and its anode connected at point 60 to the cathode of voltage regulator tube 50.

The cathode of the amplifying tube 56 is connected through a cathode resistor 62 to a negative potential. The negative potential, which is variable, is supplied from low voltage source 64 and voltage divider 66, the latter having a number of taps 68, 70, 72 from which a desired voltage can be selected through a selector switch 74.

The anode of amplifying tube 56 is connected through a plate resistor 76 to a positive potential. Plate resistor 76 has the same resistance value as cathode resistor 62. The positive potential, likewise variable, is supplied from a low voltage source 77 and voltage divider 78, the latter having a number of taps 79, 80, 81 selectable by a selector switch 82.

The control grid of the amplifying tube 56 is connected to a negative potential through a switch 84 whichcan select one of a number of taps 86, 88, 90 on a voltage divider 92 connected across a low voltage source 94. v

The junction point 96 between resistors 44 and 52 and the anode of voltage regulator tube 46 is connected through a resistor 98 to the lower deflection plate 22 of the image converter tube 10.- The junction point 100 between resistors 48 and 54 and the anode of voltage regulator tube 50 is connected through a resistor 102 to the upper deflection plate 20 of the image converter tube 10. The junction point 104 between the two resistors 52 and 54 is connected to the accelerating electrode of the image converter tube 10.

In accordance with one preferred set of conditions for operating the image converter camera system a voltage of 20 kilovolts is supplied to the parallel branches by the high voltage power supply42. The voltage regulator tubes 46 and 50 regulate the voltage across their electrodes within 2% of 15 kilovolts over a range of 5 00 microamperes. Switch 82 connects plate resistor 76 to a positive potential of 800 volts on tap 80, and switch 74 connects cathode resistor 62 to a negative potential of 800 volts on tap 70. For focussing and alignment, switch 84 connects the grid of amplifier tube 56 to a potential of about 10 volts on tap 90,

Tube 56 is connected as a phase splitter, which produces substantially equal and opposite voltages at, the cathode and anode (points 58 and 60), with the cathode following the voltage applied to the grid. However, the cathode voltage will always be slightly positive with respect to the grid unless grid current is drawn. Also the minimum anode potential will always be positive relative to the cathode by amount, for example 20 volts. Thus, when'the grid voltage is about l0 volts, the potential of point 58 will be 10 volts negative and the potential of point 60 will be 10 volts positive. The potential of point 96 is 15 kilovolts positive relative to point 58 and thus will be 14,990 volts. The potential of point 100 is 15 kilovolts positive. relative to point 60 and thus will be 15,010 volts. Point 104, which is at a potential midway between points 96 and 100, will be at 15 kilovolts. Thus, for practical purposes points 96, 100, and 104 are essentially at the same potential of 15 kilovolts.

For framing operation switch 84 is moved to tap 88 to connect the grid of tube 56 to a negative 410 volts. Since the cathode circuit of tube 56 operates like a cathode follower, the grid voltage will be substantially reproduced on the cathode, thereby placing point 58 at 400 volts negative. Since the same tube current flows through plate and cathode resistors 76 and 62 the drops across the equal resistances are equal, thereby placing point 60 at 400 volts positive. Point 96 is 15 kilovolts above point 58, and point 100 is 15 kilovolts above point 60. Thus, point 96 will connect about 14.6 kilovolts to the lower deflection plate and point 100 will connect about 15.4 kilovolts to the upper deflection plate. Point 104 remains fixed at 15 kilovolts, which is supplied to the accelerating electrode.

For streak operation, switch 84 is moved to tap 86 to connect the grid of tube 56 to a negative 610 volts. The voltage at point 58 now becomes 600 voltsnegative and point 60 becomes about 600 volts positive. Point 96 becomes 14.4 kilovolts and point 100 becomes 15.6 kilovolts. Point 104 remains at 15 kilovolts.

So long as equal and opposite voltages are at points 58 and 60, the potential at point 104 will remain fixed midway between the potentials at points 96 and 100. However, it is possible to switch the voltage at point 104 by making the voltages at points 58 and 60 unequal. For example, if switch 74 is moved to tap 68, which is 1000 volts negative, and switch 82 remains at 800 volts positive, then a grid voltage of 610 volts negative will produce a voltage of 600 volts negative at point 58, or a voltage drop of 400 volts across the cathode resistor 62. Since'there must be a 400 volt drop across the plate resistor 76 also, point 60 must be at 400 volts. Point 96 Will be at 14.4 kilovolts and point 100 will be at 15.4 kilovolts, there by placing point 104 at 14.9 kilovolts or 100 volts less than it was originally. An analogous ge in voltage at point 104 can be brought about by changing the voltage applied to the anode by source 77 through switch 82.

It will now be appreciated that the grid of tube 56 can be switched by relatively low voltages to produce changes in the high voltages furnished by the high voltage supply 42. A single low voltage on the grid is effective to produce changes in the two voltages applied to the deflection plates. Furthermore, a change in either the cathode or plate supply voltage will produce a change in the voltage (at point 104) supplied to accelerating anode. Thus, by reducing the number of components opearting at high potentials there has been a reduction in corona problems. In accordance with one operative embodiment the following circuit values and components were used:

Resistors 44, 48 megohms each 30 Resistors 52, 54 do 20 Tube 56 Type 12 AT7 Resistors 62, 76 kilohms each 200 Resistors 98, 102 megohms each 10 The regulators 46 and 50 were type Ml08-15 Corotron voltage regulators manufactured by Victoreen Instrument Co. of Cleveland, Ohio.

The embodiments of the invention in which an exclusive property or privilege is claimed as defined as follows:

We claim:

1. A high voltage control arrangement, comprising:

a source of relatively high unidirectional supply volt age;

a pair of parallel branches in series with said source,

each branch including a voltage regulator and a current limiting resistor connected between said source and the anode of said voltage regulator;

a voltage divider network connected between the anodes of said voltage regulators;

and means connecting the cathodes of said voltage regulators to variable unidirectional control voltages of substantially smaller magnitude than said supply voltage.

6 2. The invention according to claim 1 in which said last mentioned means includes a phase-splitting network whose outputs are coupled to said cathodes.

3. A high voltage control arrangement, comprising:

a source of relatively high unidirectional supply voltage;

a pair of parallel branches in series with said source,

each branch including a voltage regulator and a current limiting resistor connected between said source and the anode of said voltage regulator;

a voltage divider network connected between the anodes of said voltage regulators;

a vacuum tube having a cathode, a control grid, and an anode, with the cathode and anode connected across the cathodes of said voltage regulators;

two resistors connected in the anode and cathode circuit respectively of said vacuum tube;

means for applying operating potentials to that cathode and anode of said vacuum tube;

and means for selectively applying various potentials to said grid that are of substantially smaller magnitude than said supply voltage, thereby altering the potentials on the anodes of said regulators.

4. The invention according to claim 3, wherein the resistors in said anode and cathode circuit are of equal value and the supply voltages for said cathode and anode are equal and opposite in polarity.

5. The invention according to claim 3 and further including a connection to the mid-potential point of said voltage divider-network.

6. The invention according to claim 5 and further including means for selectively applying diiferent operating potentials to the anode and cathode of said vacuum tube, thereby altering the potential of said mid-potential point.

No references cited.

JOHN F. COUCH, Primary Examiner.

K. D. MOORE, Assistant Examiner.

Claims (1)

1. 3. A HIGH VOLTAGE CONTROL ARRANGEMENT, COMPRISING: A SOURCE OF RELATIVELY HIGH UNIDIRECTIONAL SUPPLY VOLTAGE; A PAIR OF PARALLEL BRANCHES IN SERIES WITH SAID SOURCE, EACH BRANCH INCLUDING A VOLTAGE REGULATOR AND A CURRENT LIMITING RESISTOR CONNECTED BETWEEN SAID SOURCE AND THE ANODE OF SAID VOLTAGE REGULATOR; A VOLTAGE DIVIDER NETWORK CONNECTED BETWEEN THE ANODES OF SAID VOLTAGE REGULATORS; A VACUUM TUBE HAVING A CATHODE, A CONTROL GRID, AND AN ANODE, WITH THE CATHODE AND ANODE CONNECTED ACROSS THE CATHODES OF SAID VOLTAGE REGULATORS; TWO RESISTORS CONNECTED IN THE ANODE AND CATHODE CIRCUIT RESPECTIVELY OF SAID VACUUM TUBE; MEANS FOR APPLYING OPERATING POTENTIALS TO THAT CATHODE AND ANODE OF SAID VACUUM TUBE; AND MEANS FOR SELECTIVELY APPLYING VARIOUS POTENTIALS TO SAID GRID THAT ARE OF SUBSTANTIALLY SMALLER MAGNITUDE THAN SAID SUPPLY VOLTAGE, THEREBY ALTERING THE POTENTIALS ON THE ANODES OF SAID REGULATORS.

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