US2479081A - Deflection circuits - Google Patents

Description

Aug. 16,1949. I WJQPOCH 2,179,081

' DEFLECTION CIRCUITS I Filed Sept. 7, 1944 2 V 55 SEA/ 5' mum/v0 .55 60/1.

INVENTOR WA 405/1442 J. Poc/ A 7'7'ORNEY Fatented Aug. 16, 194

DEFLECTION CIRCUITS Waldemar J. Pooh, Moorestown, N. J., assignor to Radio Corporation of America, a corporation of Delaware Application September '7, 1944, Serial No. 553,076

4 Claims. (Cl. 250-36) This invention is directed to television or oscillographic apparatus. It is primarily concerned with a relatively simple circuit comprising essentially the combination of a discharge tube for controlling the development of sawtooth wave energy and an output tube. This circuit is useful in connection with either the horizontal or the vertical scanning circuit, and the tube and circuit elements are so coordinated and arranged with regard to each other as to provide extremely high short time stability so that the frequency drift over several scanned rasters or fields is negligible.

Further than this, the present invention is directed to a form of system which is in the general nature of an improvement upon the circuit and arrangement disclosed and set forth by my copending application, Serial No. 473,666, filed on January 27, 1943, now Patent Number 2,418,425, issued April 1, 1947, for an improvement in Electrical circuits.

The invention herein to be disclosed includes, among other features, the combination in a deflection circuit of a discharge tube and an output tube serving to energize the electromagnetic deflecting coils or the electrostatic deflecting plates of the cathode ray tube so that the electron beam developed within the tube shall be caused appropriately to trace a scanning raster across the tube end wall or target area. Further than this, the present invention incorporates a circuit combination whereby through a resistance and capacity network, certain impulses occurring at the deflection frequency are fed back to control the oscillations developed within an oscillatory circuit, which, in turn, is arranged to control the operative periods of the discharge tube. Further provisions are made in accordance with the invention whereby the entire system may further be stabilized from an external source supplying impulses to control the periods at which the discharge tube functions.

In view of the foregoing, it will be apparent that an object of the present invention is that of providing a deflection circuit and control tube a portion of the load for the tube II.

system for use therein serving todevelop energy of suitable wave form to deflect a cathode ray beam and, at the same time, to provide in such a circuit a higher degree of frequency stability than has heretofore been possible.

Other objects of the invention and advantages thereof are those of providing a frequency stabilized deflection circuit which is capable of, being synchronized from an external source.

Other objects of the invention are those of providing a more efficient, a greatly simplified, and a somewhat less costly and less complicated deflecting circuit than has heretofore been customarily utilized.

Still other objects of the invention are those of providing a deflection circuit which will overcome one or more known difliculties in the prior art arrangements.

Still further objects and advantages of the invention will suggest themselves when the specification is read and considered in connection with the accompanying drawing, of which the single figure thereof represents a circuit arrangement, largely in schematic form, for carrying out the purposes of the invention.

Referring now to the drawing for a further understanding of this invention, there has been provided a combination of the discharge tube H and an output tube l5 which serves as an amplifier to supply deflection energy, by Way of a transformer, for instance, to control the current flowing in the deflection coil IS. The deflection coil IQ has been illustrated merely in schematic form but it is to be understood that such coil is of the general type that is customarily positioned to surround the neck of a cathode ray tube (not shown herein) to control the deflection of the usual cathode ray or scanning beam developed therein.

In the development of the controlling current fed through the deflection coil Hi, there has been provided a storage condenser 2| connected to the plate or anode of the discharge tube I. The condenser 2| is adapted to be charged from a source of voltage of which the positive terminal is connected at terminal point 23 so that the charge acquired by the condenser 2| is determined in accordance with the resistor 25 connected in series with the condenser and the terminal point 23, and serving also as at least To control further the rate at which the condenser 2| can charge, an adjustable resistor or potentiometer element 21 has been provided. This type of element is for the purpose of controlling the amplitude of the voltage built up across the condenser. Accordingly, such a resistor becomes known as the size controlling unit because it controls at least one dimension of the scanned raster. In the illustrated form of circuit, the lower end of the resistor 25 connects to the variable'tapping point on the size control unit and in series with this unit is a resistor 29 which connects to ground 3| as indicated.

Under these circumstances, there is developed ing periods when the discharge tube l is blocked or non-conducting and the rapid return portion or discharge period of the condenser occurs during periods when the tube II is triggered to become conductive in known manner.

Accordingly, the voltage appearing a-tthepoih't Y 33 may be transferred by way; of the capacitor 35 to control the output tube mar a thuscol 1etrols the current flowing in the primary winding 31 of the transformer IT. The transformer secondary Winding 39 is then connected to the deflecting coil Hi to control the current-flowing therethrough. The output tube i is usually of the multi-grid type with one grid connected directly to the terminal point 4! at which a positive voltage is provided and to which terminal point the lower end of the transformer primary winding 37 also connects. In this way, itj'will be appreciated that the transformer becomes polarized so that 'a pulse appears across the deflecting coil. The adjustable resistor 33 shown in series with the deflecting 'coil I9 and the transformer secondary. winding 39'is of known character and serves to center the beam 'within the cathode ray tube upon that portion 'of the target area or screen thereof w'hich'is desired.

In the operation of the system, th'e pulse which appears across the deflecting coil and which'has been shown diagrammatically and schematically by the wave form I) adjacent'toth'e'conde'nser'd'l which connects, as indicated, to the transformer secondary 39is then fed back'to control the circuit operation through the capacity'and resistance network formed from the capacitor 41 and the, resistor 49. These pulses, as indicated, are then supplied through the 'capac'ityeresistance circuit to an oscillatory circuit by way of the connection made'at the 'pointf5l.

The oscillatory circuitis prefei'ably'composed of parallelly connected, inductance "and "capacity elements 53 and 55,, respectively, which connects to ground 3| b'y way"ofthe'resistor element "57 It may be assumed that the developed wave energy of the'circuit already des'cribedisjtofbe utilized to control the deflection of a cathode ray beai'nin a horizont'al'direction that'is, the line deflection). Then, it "will, be appreciated that the tube H functions 'as'thehorizontal discharge tube of the system,'wni1e 'the tube functions as the horizontalfoutput tube. The tuned circuit comprising the parallelly connected inductance 53 and capacitor'55isftuned to'the horizontal or line frequncyso that a wave form which is substantiallysinusoidal in form, as in dicated schematically by the wave form 0, and which is developedat line frequency appears in the oscillatory circuit. It will be seen that the point 5| of the oscillatory circuit connects to the grid or control electrode of the discharge tube I .l by way of thecondenser 59 's0 that'the'peaks of the sinusoidal waves developedin the tuned circuit may be caused to control the discharge tube and to cause grid'current, as well'as plate current, to flow infthetube. In this connectiomthe resistor 6! then functions substantially in the usual manner as a leak resistor element. Accordingly, it can be appreciatedthat the, oscillator arrangement hereinabove "described functions on the feedback principleandits'operational cycle can be controlled in a large measure by the capacity resistance network, above described.

However, the oscillator may also be synchronized by introducing synchronizing pulses from an external source, such as those control pulses shown by the wave form d, which are introduced at the terminal "Q3 and are applied across the resistor element 51. In this connection, the

pulses applied to the terminal 63 will serve to control rigidly the operation in accordance with same-xterm operation such, for instance, as the rate at which signals are generated at a suitable trahsmittihg' point. Synchronization can also be effected by means of a reactance tube which may serve to change the reactance component across the tuned circuit by the incoming signal pulse in the wayin which the circuit has been shown, particularly by the drawings. The reactance tube may then'be controlled in accordance with known forms of controls heretofore utilized to provide automatic frequency and. phase control of synchronization in television apparatus, as have been explained, for instance, by Fredendall et al. Patent No. 2,344,810.

Oscillations will not normally be obtained if the tuned circuit is short circuited, Where the resistor 57 is of a relatively low value. However, if the value of the resistor '57 is increased, the tuned circuit can still be made to control the frequency of operation of the discharge tube 51 but oscillations occur even if the tuned circuit is shorted. If now the resistor 57 be changed to one of extremely high order, the circuit here inabove described will oscillate but the tuned circuit will be found to have practically no efiect onthe operational frequency. Accordingly, with in the purpose of this disclosure, it,'thereiore, becomes important that the size or" the resistor 51'shall be relatively small and, for normal operation, usually of a value not to exceed 1,600 ohms.

Having now described the invention, what is claimed "and desired to be secured by Letters Patent is the following:

1. A wave generating circuit comprising an electrical storage element, means to charge the electrical storage element along a substantially linear path, a thermionic device to discharge the storage element at predetermined time periods, an output tube connected to amplify the voltage appearing at the output of the storage element so as thereby to be adapted to energize a deflecting coil, a tuned circuit comprising parallelly connected inductive and capacity elements connected' to the input of the thermionic device serving to discharge thercapacity, a capacitative and resistive network for feeding back, from the output, tube to the oscillatory circuit pulse energy occurring at the, frequency of discharge of the stored chargein thestorage element, said energy fed back b'eing'of sumcient amplitude to develop substantially sinusoidal oscillations in the said tuned circuit having peaks of sufficient magnitude tocontrol the period of operation of said discharge'tube, and' means for energizing and controlling the periodof operation of the thermionic discharge tube in accordance with the peak voltage developedin the tuned circuit.

'2. The systemclaimed in claim 1 comprising, inaddition, means to. supply control energy pulses tothe tuned circuit fromanexternal source so as to'interlock the pulse development periods servingto control the oscillations in the tuned circuit withan'external circuit operation.

' '3. Adeflection control circuit'comprising an electrical storage element, means to charge the electrical storage element along a substantially linear path, a discharge tube to reduce the charge in the storage element to a predetermined value at predetermined time periods, an output tube connected to amplify the voltage developed across the storage element so as thereby to be adapted to energize a deflecting coil, a tuned circuit comprising parallelly connected inductive and capacity elements connected to the input of the discharge tube, a capacitative and resistive network connecting the output tube to the oscillatory circuit to supply thereto pulse energy occurring at the frequency of discharge of the stored charge in the storage element, said energy fed back being of sufiicient amplitude to develop substantially sinusoidal oscillations in the said tuned circuit having peaks of sufilcient magnitude to control the period of operation of said discharge tube, means for biasing the discharge tube to a predetermined operation, and means for energizing and controlling the period of operation of the discharge tube in accordance with the peak voltages developed in the tuned circuit.

4. A Wave generating circuit comprising a capacity element and means to charge the said element along a substantially linear charging path, discharge means to release the charge stored in the capacity element at predetermined time periods, an output circuit connected to receive an output voltage varied substantially in proportion to the charging voltage developed by charging the capacity and said output circuit being adapted to energize a deflecting coil of a cathode ray tube device, a tuned circuit comprising parallelly connected inductance and capacity elements connected to the discharge means to initiate its operation at selected time periods, a capacitative and resistive network for feeding back voltage from the output circuit to the tuned circuit pulse energy occurring at the frequency of discharge of the charge stored in the capacity element, said pulse energy fed back being of suflicient magnitude to develop substantially sinusoidal oscillations in the said tuned circuit having peaks of sufficient magnitude to control the period of operation of said discharge tube, and means for biasing the discharge means so that selected peak voltages developed in the tuned circuit initiate the said discharge.

WALDEMAR J. POCI-I.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,264,781 Wheeler Dec. 2, 1941 2,277,000 Bingley Mar. 17, 1942 2,363,822 Wendt Nov. 18, 1944

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