US2225469A - Relaxation arrangement for deflecting cathode rays - Google Patents

Description

RELAXATION ARRANGEMENT FOR DEFLECTING CATHODE RAYS Filed Oct. 7, 1938 Patented Dec. 17, 1940 UNITED STATES RELAXATION ARRANGEMENT FOR DEFLECTING CATHODE. RAYS Hugo Diebold, Berlin, Germany, assignor to C. Lorenz Aktiengesellschaft, Berlin-Tempelhof,

Germany, a company Application October 7.

1938, Serial No. 233,764

In Germany September 3, 1937 6 Claims.

In television arrangements it is necessary to employ symmetric deecting voltages or deflecting currents in order to avoid the cathode ray when deflected causing distortions of the spot of light. For the production of symmetric relaxation voltages of this kind mainly two methods are available. One of these consists in producing a normal, that is, an asymmetric relaxation voltage by means of a customary generator and to amplify such voltage by a push-pull connected arrangement, the counterphasal input voltage intended for the push-pull tube located at the output end of the relaxation generator being in well known manner taken from the anode circuit of the other or symmetric tube. The second method consists in producing the relaxation Voltage directly with the aid of relaxation generators fed in counterphasal fashion and whose symmetry point is connected to earth. These arrangements have two condensers which are charged over resistances or charging tubes and in most cases are discharged through an electron tube common to them. To one of these condensers positive charging voltage is supplied While the charging voltage supplied to the other condenser is negative. The discharge tube common to the two condensers may be periodically opened by synchronizing impulses. However, the relaxation voltages generated by the relaxation condensers are not sufcient in television tubes to deflect the cathode ray suiliciently. These deecting voltages therefore require to be amplied, and they are so by a push-pull connected arrangement. Such amplilier, arranged after the relaxation generator in series connection therewith, is necessary espe-. cially if the deection is effected by means of coils, since these consume current and hence should not be connected to the relaxation condenser, as no power should be taken from this condenser. In addition, a push-pull connected arrangement here employed allows of compensating the direct anode current of the tubes.

The invention will be understood from the following description, reference being had to the accompanying drawing in which Fig. 1 is a wiring diagram of a known arrangement while Fig. 2 is a wiring diagram of one embodiment of the invention.

Referring more particularly to Fig. l, I, 2 denote the charging resistances, while 3, 4 indicate charging condensers. Condenser 3 is arranged to be charged positively whereas condenser 4 will be charged negatively, as will be seen from the drawing, and both condensers are conjointly discharged through an electron tube 5, this tube being periodically rendered vpermeable to currents in a manner that need not be explained here more fully. In order tov amplify the counterphasal relaxation voltages originated at condensers 3, 4 the ampliiier tubes 6, 1 are connected in (Cl. Z50-36) push-pull after'these condensers. The input end of the tube arrangement E, 'I is through condensers 8, 9 and grid leak resistances Il), II joined to the relaxation condensers 3, 4. It will be seen that the usual push-pull connected amplifying f arrangement having a symmetric input end is employed here.

This arrangement, however, has a great disadvantage due to the fact that the grid leak resistance Il) or II is through coupling condenser 8, or 9 connected in parallel with the relaxation condenser 3 or il, respectively. As a result the peak value of the relaxation voltage at condenser 3 or 4 is diminished as the charging voltage is decreased in the ratio of the two resistances. It may be thought that such disadvantage might be overcome by diminishing the charging resistances I, 2. In this way, however, the portion of that part of the characteristic curve used for deflection would be greater and therefore the proportionality would be worse than otherwise.

In order to avoid this drawback the invention proposes to couple the tubes S, l' galvanically to the condensers 3, In this way only the gridcathode path of the tubes li, 'l will be connected in parallel with these condensers. This path if the tubes are working in the negative region takes no current and the capacity thereof is not detrimental since it may be implied in the capacity of the relaxation condensers. This feature of the invention is not so self-evident as it may appear at the rst glance, for to carry this feature into eiiect involves diiiiculties not at once appreciable. The main dimculty lies in the fact that in consequence of the coupling condenser 8, Fig. l, missing, the positively charged condenser 3 will cause the grid of tube 5 likewise to assume positive potential, thus causing a grid current which is located in parallel with condenser 3 and is in the nature of a detrimental current consuming means. In order to do away with this drawback another feature of the invention consists in interposing in the cathode lead of tube t a comparatively high cathode resistance 2l), Fig. 2, namely a'resistance by which the cathode potential is so increased that even if the peak voltage of condenser 3 is attained this cathode potential shall be higher than the grid potential, the tube thus always operating in the negative region.

This feature is likewise not self-evident because it entails another disadvantage, which consists in this that the operative part of the characteristie curve of tube 6 is flattened by the insertion oi resistance 2l! so that this tube will no longerl be able to eiect the same amplication as tube l. This disadvantage is in accordance with a third feature of the invention overcome by supplying to tube E a higher input voltage than is supplied to tube 'l'. Such higher input voltage may be obtained by diminishing the capacity of condenser 3 or less suitably by diminishing the appertaining charging resistance I or finally by increasing the appertaining feeding voltage. It is of course possible also to employ several such means in conjunction. Taking all in all, the circuit arrangement as a whole becomes asymmetrical, such asymmetry however resulting in attaining the aim, that is, producing a symmetric deflecting voltage or symmetric deilecting currents.

From the fact that the tubes 6, 1 require to be supplied with input voltages which are different from each other still another difliculty results, namely a difficulty which is overcome by employing in accordance with a further feature of the invention a screen grid tube as discharging means. This difculty results in the fact that the charges supplied to condensers 3, 4 should be different from each other. If the discharging tube isa triode the two condensers 3, 4 cannot be discharged perfectly because the discharge current of both condensers is the same and therefore the condenser lesscharged will have to take over part of the charge of the other condenser, thus becoming charged in the opposite sense. In acy cordance with the invention this drawback is overcome by employing a screen grid tube 5' as discharge means. In this way the negatively charged larger condenser 4 can be made to dis- ,charge with a greater current intensity than the positively charged condenser 3. Since the ungrounded sideof condenser 4 is connected to the cathode of tube 5', the discharge current of this condenser ows both to the anode and screen, being equal to the full cathode current of the tetrode which as is well known is generally considerably greater than the anode current thereof. The discharge current side of condenser 3, on the contrary, is merely the anode current of tube 5 since the ungrounded side of this condenser is connected solely to the anode and not to the' screen. In this way an extremely rapid discharge of the negatively charged larger condenser 4 is attained. As is well known, such rapid discharge is necessary for the cathode ray to return as quickly as possible.

Fig. 2 at the rst glance merely differs from Fig. 1 by the mode in which the tubes 6, 'I are coupled to the relaxation condensers 3, 4. However, there are also differences as regards the dimensions of certain individual parts, such parts being dimensioned asymmetrically, as will appear from the numerical values given by way of example in Fig. 2 and which approximately indicatethe size of these special parts. It will be `seen that resistance 20 is considerably greater than resistance 2l in order to raise the cathode potential of tube 6, as stated before. The resistances 2D, 2| are preferably Variable in order to afford a convenient possibility of regulating the amplitude of the deecting voltage or de- Afleeting currents.

What is claimed is:

1. A relaxation arrangement for supplying symmetric deecting Waves whose instantaneous potentials are substantially equal but of opposite sign with respect to a given reference level of potential, comprising a rst condenser and means for supplying thereto positive voltage with respect to said reference level of potential, a second condenser and means for supplying thereto negative voltage with respect to said reference level of potential, a first electron tube having a cathode, an anode and a grid, a galvanic connection between said grid and the positive terminal of said first condenser, a second electron tube having a cathode, an anode and a grid, a galvanic connection between said grid of said second tube and the negative terminal of said second condenser, connecting means connecting said two tubes in push-pull to constitute an amplifier, means for biasing the cathode of said second tube to a potential above that of said grid of said second tube, and means for biasing the cathode of said first tube to a potential substantially higher than said bias potential first mentioned and sufficiently high so that said cathode of said rst tube is at all times more positive than the grid of said first tube.

2. A relaxation arrangement for supplying symmetric deiiecting waves whose instantaneous potentials are substantially equal but of opposite sign with respect to a given reference level of potential, comprising a first condenser andmeans for supplying thereto positive Voltage with respect to said reference level of potential, a second condenser and means for supplying thereto negative voltage with respect to said reference level of potential, a first electron tube having a cathode, an anode and a grid, a galvanic connection between said grid and the positive terminal of said iirst condenser, a second electron tube having a cathode, an anode and a grid, a galvanic connection between said. grid of said second tube and the negative terminal of said second condenser, connecting means connecting said two tubes in push-pull to constitute an amplifier, a cathode resistor associated with said second tube and connected in series with the cathode thereof to bias the cathode of said second tube to a potential above that of said grid of said second tube, a cathode resistor associated with said rst tube and connected in series with the cathode thereof to bias the cathode of said first tube to a potential substantially higher than said bias potential iirst mentioned and sufficiently high so that said cathode of said first tube is at all times more positive than the grid of said first tube.

3. An arrangement according to claim 2, wherein said condensers and means for supplying voltages thereto are asymmetrically proportioned to supply to the first said tube an input voltage higher than the voltage supplied to the second said tube.

4. An arrangement according to claim 2, wherein the first said condenser is of smaller capacity than the other condenser.

5. An arrangement according to claim 2, wherein said means for supplying voltages to said first and second condensers are asymmetrically proportioned so as to supply to the first said condenser a positive voltage higher than the negative voltage supplied to the second said condenser.

6. An arrangement according to claim l, further comprising a screen grid tube common to the two condensers and having a cathode, a control grid, a second grid and an anode, and connections from said anode to one of said condensers and from said cathode to the other of said condensers, and from said screen grid to the opposite sides of said two condensers to effect a discharge thereof.

HUGO DIEBOLD.

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