US3706908A - Horizontal deflection control means - Google Patents

Abstract

A saturable reactor for providing picture horizontal scan width and scan linearly control for a television horizontal deflection system is connected in series with standard cathode ray tube magnetic-deflection coils. A core of the saturable reactor is adjusted lengthwise of its encompassing coil to vary the scan width by directly altering the inductance of the coil. Independently therefrom, a permanent magnet is rotatably mounted adjacent to one end of the coil opposite of and spaced from an extended portion of the core, the magnet having a preselected one of its poles selectively rotated closer to and further away from the core to vary the scan linearity by directly altering the premagnetization level of the core. The magnet is effective to either add or to buck respectively the induced polarization of the core during periods of forward or reverse deflection current to give linearity control during both the initial and final portions of a sawtooth sweep current waveform having a zeroreference axis.

Description

a States Patent [451 Dec. 19,1972

[54] HORIZONTAL DEFLECTION CONTROL MEANS [72] Inventor: Chris A. Petri, La Grange, 111.

[73] Assignee: Motorola, Inc., Franklin Park, Ill.

[22] Filed: Aug. 3, 1970 [21] Appl. No.: 60,484

[52] US. Cl. ..3l5/27 SR, 315/27 GD [51] Int. Cl ..H01j 29/76 "[58] Field of Search ..3l5/27 SR, 27'GD [56] References Cited UNITED STATES PATENTS 3,153,174 10/1964 Claypool et al ..3l5/27 GD Primary ExaminerBenjamin A. Borchelt Assistant Examiner-R. Kinberg Att0rneyVincent Rauner and L. Arnold [5 7] ABSTRACT A saturable reactor for providing picture horizontal scan width and scan linearly control for a television horizontal deflection system is connected in series with standard cathode ray tube magnetic-deflection coils. A core of the saturable reactor is adjusted lengthwise of its encompassing coil to vary the scan width by directly altering the inductance of the coil. Independently therefrom, a permanent magnet is rotatably mounted adjacent to one end of the coil opposite of and spaced from an extended portion of the core, the magnet having a preselected one of its poles selectively rotated closer to and further away from the core to vary the scan linearity by directly altering the premagnetization level of the core. The magnet is effective to either add or to buck respectively the induced polarization of the core during periods of forward or reverse deflection current to give linearity control during both the initial and final portions of a sawtooth sweep current waveform having a zeroreference axis.

5 Claims, 10 Drawing Figures PATEN'IED DEC 19 I972 SHEET 2 BF 2 FIGGB FBG. 6A

FIGB

FIG]? INVENTOR CHRIS A. PETRl w-WM ATTY.

HORIZONTAL DEIFLECTION CONTROL MEANS BACKGROUND OF THE INVENTION This invention relates to a horizontal deflection system of a television receiver, and more particularly it relates to a novel means for controlling horizontal scan width and scan linearity for an image-reproducing cathode ray tube.

According to common practice, saturable reactors useful as deflection control means are connected in series or in shunt with the deflection coils of a television horizontal deflection system to provide a non-linear horizontal sweep rate for the tubes electron beam scanning guns in a technique widely known as S-shaping the normal exponential ramp type waveform of the sawtooth deflection current. Additionally, permanent magnets are often magnetically linked with the ferromagnetic core materials of the reactors to affect the level of premagnetization of the core.

Although it is perhaps more common to utilize this type of saturable reactor as merely a linearity control device, there are devices of this type being used as both width and linearity control. In one such known device, the saturable reactor is provided with two separate core members, one core member for width control and the other for linearity control, only the linearity control core member being magnetically linked with the magnet. Another existing device of this type has a slideable coil mounted on an elongated core and the combination coil and core are movable as a unit closer to or father away from the associated magnet. The coil is adjusted along the length of the core to vary the scan linearity by varying the slope of the inductance-instantaneous deflection current characteristic curve within the range of the useful current. The scan width is adjusted by moving the coil and core unit with respect to the magnet, which movement directly varies the inductance of the coil without affecting the slope of the inductance-current characteristic curve.

Furthermore, prior art methods of linearity control most commonly involve adjusting the final exponential slope of the deflection current waveform to obtain a slower rate of sweep. This single adjustment to the exponential current wave form however is generally unsatisfactory in of itself in that the initial rise of the deflection current must also be made slower. Prior art devices also utilize the imposed magnetic field of the associated magnet to shift the hysteresis loop characteristic curve of the core so as to allow the initial portion of the exponential curve waveform to be adjusted and leaving the proper slope of the final portion of the current waveform to be obtained by a judicious choice of the circuit parameters. While this latter type of device is an improvement of the former which failed to adjust the initial portion of the sweep current, it is nevertheless desirable to be able to adjust both the initial and the final portion of the sweep current waveform by means of the imposed magnetic field. This, of course, cannot be accomplished by a mere unindirectional shift of the hysteresis loop of the core. Also, it is desirable to provide a width-linearity control means having only one core member to allow for an improved device of low cost and compact size and construction.

SUMMARY It is therefore an object of this invention to provide an improved device wherein a single core member is adjustable axially with respect to an encompassing helical coil and is adjustably linked with a magnetic field of a magnet to control respectively the scan width and scan linearity of a television horizontal deflection system.

It is another object of this invention to provide a novel means of altering horizontal scan width and scan linearity respectively by directly varying the amount of additive series inductance of a helical coil and the premagnetization level of the core member.

It is still another object to provide scan linearity control by properly S-shaping the deflection coil current waveform both during the initial rise and during the final exponential portion thereof.

It is yet another object to provide an improved device having a magnet adjustable to compensate for the polarity with which the helical coil is connected in series with the deflection coil.

Further, it is an object of the invention to provide a much improved horizontal deflection control means having a simple construction of low cost and compact size.

In a preferred embodiment of the invention, a com bination horizontal width and linearity control means is connected in series with the deflection coils of the standard television horizontal deflection control system and has a helical inductor coil with a longitudinal axis, a ferromagnetic core member core member having a length greater than the longitudinal length of the coil with one end portion of the core member adjustably inserted within the coil and another end portion thereof extending from one end of the coil, said core member being movable along the longitudinal axis of the coil to provide a means of adjusting the scan width by directly varying the effective inductance of the coil, and a permanent magnet.

The permanent magnet has a rotational axis parallel to and spaced form the longitudinal axis of the coil and is mounted adjacent one end of the coil opposite of and spaced from the extending end portion of the core member in order to control the premagnetization level thereof. The magnet is magnetized so as to present poles of opposite polarity at two diametrically opposite points on its periphery. A selected one of these poles is aligned directly opposite said other end portion of the core member for maximum premagnetization thereof, and is rotated in either direction away therefrom for lessening the premagnetization level. Also, the magnet is effective to either add to or buck respectively the induced polarization of the core member during forward or reverse deflection current in order to provide scan linearity control during both the initial and final portions of the sawtooth sweep current waveform. The rotation of the magnet with respect to the core member further provides an adjustment to the linearity control in both the initial and final portions of the deflection current waveform.

Other objects and advantages of the invention will occur to those skilled in the art as the invention is described in connection with the accompanying drawing, in which:

THE DRAWING FIG. l is a simplified schematic illustration of a horizontal deflection system for a television receiver useful in explaining the principles of the present invention;

FIG. 2 is a schematic circuit diagram of the horizontal deflection system of FIG. 1, showing a schematic representation of the linearity and width control means in series connection with the horizontal deflection coils;

FIG. 3 is an elevational side view of a preferred embodiment of the linearity and width control means of the present invention;

FIG. 4 is an end view of the device of FIG. 3;

FIG. 5 is a perspective view of the device of FIGS. 3 and 4, having a cutaway portion of the coil and coil form for showing the adjustable end portion of the core;

FIG. 6 is an elevational side view of the isolated operable parts of the embodiment of FIG. 3;

FIG 6A is a diagram representation of the bucking magnetic fields of the embodiment of FIG. 6;

FIG. 6B is a diagram representation of the adding magnetic fields of the embodiment of FIG. 6;

FIG. 7 includes graphs of a normal deflection current waveform and two S-shaped deflection current waveforms illustrating the line scan linearity control of the present invention; and

FIG. 8 is a view taken along line 8-8 of FIG. 6.

DETAILED DESCRIPTION FIG. 1 shows a horizontal deflection system 10 as a part of a television receiver having a receiving antenna 11 and a cathode ray tube (CRT) 12, fed by a video amplifier l3 and a high voltage (I-IV) power supply 14 as is standard for television receivers. The yoke 12a of the tube 12 has horizontal magnetic-deflection coils, indicated at 15, which coils carry a sawtooth waveform deflection sweep current 17 supplied by the horizontal oscillator 19 and amplified by the horizontal output amplifier 21 in a well known manner.

FIG. 2 shows a more detailed schematic circuit diagram of the horizontal deflection system 10 wherein a horizontal driver circuit 19a of the oscillator 19 supplies the sawtooth waveform deflection current 17 to a transistorized deflection amplifier 21a of the horizontal output amplifier 21. The amplified sweep current 17 is provided a DC return by the primary winding 25-26 of the high voltage autotransformer 23 that is connected to the B+ high voltage power supply 14. The secondary winding 26-27 of the autotransformer 23 supplies the operating high voltage to the CRT 12 through the high voltage rectifier 28 and the anode terminal 29. The horizontal deflection coils a and 15b are connected in series with the horizontal width-linearity control means 30 of the present invention and an AC coupling capacitor 24. The control means 30 includes an inductance coil 31, ferromagnetic core member 32, and permanent magnet 33; the control means 30 is then connected to ground potential.

For wide angle tube screens, the ramp portion of the sawtooth deflection current common to horizontal deflection systems, is generally exponential in its waveform: the pattern characterized by a fast rising current initially, then slowly decreasing in its rate of rise as the deflection coils begin to build a counter electromagnetic force (EMF), and finally rapidly decreasing as the full counter EMF is developed. The deflection current is then said to be at its saturation level.

According to common practice, deflection control means comprising an additional inductance having a high permeability core, such as iron or a ferromagnetic material, is inserted in series or shunt with the deflection coils to vary the coil inductance by a desired amount. This additional inductance, as taken for example in a series connection, imparts to the deflection current waveform a slower initial rate of rise and therefore gives the desirable S-shaped waveform common to horizontal deflection systems. With the aid of the S- shaping inductor, the line scanning motion of the electron beam is slower at the beginning of its horizontal sweep, faster during the central portion of the trace, and slower at the end thereof, thus compensating for the tendency of a constantly moving beam to appear to be moving faster at both edge portions of a generally wide flat screen surface than that movement of the beam in the central portion of the screen.

A preferred embodiment of the control means 30 of the present invention is shown in FIGS. 3-5. The control means 30 utilizes a single piece holder member 35 made of a suitable insulating material. The holder member 35 has a magnet holding section 35a, a core holding section 3517, and a mounting base 350 with appropriate means for mounting the control means 30 to a circuit board as by apertures 35d. An elongated helical coil 37 having two electric connecting terminals 37a and 37b is wound about a coil form 38 and one end portion of the coil form 38 inserted into a channel 35e in the core holding section 35b of the holder member 35. Thereafter, a ferromagnetic core member 39 (alternatively, the core material could be made of iron) is inserted intothe coil form 38, which acts as an extension of the channel 352 through the helical coil 37.

The coil 37 is seen to have a longitudinal axis that is substantially concentric with that of the core member 39. The core member 39 preferably has a length greater than the helical coil 37 so that the core 39 has a substantial portion within the coil 37 and another preferably substantial opposite portion extending from the coil 37. The portion of the core member 39 that lies within the coil 37 (or, optionally, the opposite portion thereof) can be provided with a tool-accommodating aperture 39a for adjusting the core member 39 lengthwise with respect to the coil 37 along its longitudinal axis.

A permanent magnet 41, conveniently constructed in the form of an elongated cylinder and magnetized across its diameter to have two diametrically opposite magnetic poles on its periphery (a north (N) pole and a south (S) pole together with an accompanying magnetic field), is insertably mounted for retention in the magnet holding section 35a. The magnet 41 has a rotational axis parallel to and spaced from the longitudinal axis of the coil 37 and core member 39, which magnet 41 can as well be provided with a tool-accommodating aperture 41a for rotatably adjusting the magnetic field of the magnet 41 with respect to the opposite end portion of the core member 39.

l060ll 0620 The operation of the control means 30 to adjust horizontal scan width can best be illustrated by the isolated view of FIG. 6 wherein the holder member 35 and the coil form 33 have been omitted and the operable parts have been maintained in their normal orientation. If the core member 39 is adjusted to move along its longitudinal axis or, optionally along the longitudinal axis of the coil 37, in the direction of the arrow 43, the right-end of the core member 39 as viewed in FIG. 6 is caused to move through the coil 37. This movement rapidly reduces the length of the ferromagnetic core member 39 which lies internal to the coil 37. By reason of the well understood principles of saturable reactors, this results in a direct variation of the reactance or inductance of the coil 37. The change in inductance of the coil is utilized for providing the line scan width control.

It is obvious that while the exact length of the core member 39 is not critical, the approximate length should be such that a relatively small amount of movement of the core 39 in the direction of the arrow 43 causes the length of the core path within the coil 37 to vary. The exact length of the opposite extended portion also is not critical; the magnet 41 could overlie somewhat the adjacent end of the coil 37 without degrading appreciable the operation of the control means 30. Also, since the magnet 41 and the extended portion of the core 39 cooperate to affect line scan linearity rather independently of the line scan amplitude or width, as will be described more fully hereinafter, the magnet 41 could be removed at any convenient distance from the coil 37 along the length of the core 39 as long as the impractical effects of making the extended end portion of the core 39 too long are simultaneously considered.

The line scan width and line scan linearity controls are independent adjustments as is readily apparent when observing the movement of the core 39 with respect to the coil 37 during the adjustment of the line scan width. This is for the reasons that the length of the core member 39 adjacent the magnet 41 remains substantially a constant and that the cores movement is in a direction substantially perpendicular to the direction of the lines of force comprising the magnetic field of the magnet 41.

FIG. 7 shows variations of the ramp portion only, indicated at $5, 47 and 47, of the sawtooth deflection sweep current 17 centered about a zero reference so as to present forward i) and reverse i) current portions thereof. The dashed line 45 represents an approximation of the waveform that the ramp portion of the sweep current 17 would take through the deflection coils a and 15b if the linearity correction were not provided. As stated previously, the ramp portion of the deflection current has an initial fast rise, slower middle trace and still slower final exponential portion settling slowly to maximum forward current. This type of waveform is undesirable and requires correction to a slower initial rise. Also, in order to avoid undue difficulty in malting a judicious choice of circuit parameters the final exponential rise can be regulated by the control means 3th. The waveform would then require a slight correction to increase the slope of the final exponential rise. This correction is then called S-shaping because of the resemblance of the corrected ramp current waveform to the letter S.

With the proper S-shaping, line scan linearity control is obtained. The operation of the control means 30 to adjust horizontal scan linearity is best illustrated by FIG. 6A, 6B and 8. The permanent magnet 41 has its attendant magnetic field linked with the extended end portion of the core member 39 so long as the spacing between the magnet 41 and the core member 39 is not unduly large. This results in the common phenomenon known as premagnetization of the core member 39. Briefly, premagnetization of the core member 39 increases the flux density of the core tending to saturate the core more quickly with a given current in the coil 37.

As shown in FIG. 6A, when the instantaneous AC deflection current 17 begins its ramp portion in the form of the reverse current i), the reverse current fiows through the series additive coil 37 and induces a temporary magnetic field surrounding the coil 37, which field permeates the ferromagnetic core member 39. In accordance with well understood principles of electromagnetic field theory, the current flow though the coil 37 induces a magnetic field around the coil 37 having a magnetic polarity with north (N) and south (S) poles according to the direction of the windings of the coil 37 about the core member 39 and the direction of the current flow though the coils. Thus, the proximity of a selected pole of the magnet 41 to the adjacent end portion of the core member 39 will have an attraction or repulsion effect upon the adjacent portion of the magnetic field of the coil 37 depending upon whether the induced polarization of the core member 39 is an opposite or like pole to the selected pole of the magnet 41.

It is readily obvious that in the case of the reverse current i) flowing through the coil 37, the desired effect would be to create repulsion force between the two adjacent poles so as to buck the adjacent portion of the induced magnetic field of the core member 39 and thus slow the otherwise fast initial rise of the ramp current. Therefore, the direction of the coil windings about the core 39 should be such that the reverse current induces a magnetic field having a south (S) polarity if the magnet 41 has a south (S) pole aligned oppositely of the core 39, or alternatively, a north (N) polarity if the magnet 41 has a north (N) pole aligned oppositely of the core 39.

If the terminals 37a and 37b of the coil 37 are connected in reverse to the magnetic- deflection coils 15a and 15b, the correct polarities of the respective fields can be obtained by merely rotating the magnet 41 until the opposite pole is aligned with the core 39. For illustration purposes, the magnetic field of the magnet 41 as it links with the core 39 has been omitted in FIGS. 6A and 6B and only the diagrammatical representation of the effect of the repulsion forces between the two like poles (8-8) and the attraction forces between the two unlike poles (N-S) upon the induced magnetic field of the coil 37 is shown.

Obviously, as indicated by the diagrammatical representation in FIG. 6B of the additive effect of two unlike poles (N-S) upon the induced magnetic field of the coil 37, the forward (+1) deflection current induces a polarization in the core 39 wherein the opposite pole is located in the extended end portion thereof, thus the complementary magnetic fields of the coil-core and magnet-core combinations have the effect of increasing the slope of the exponential trace of the forward current.

In summary, it is readily seen that in FIG. 6A, the like adjacent poles (-8) of the core 39 and the magnet 41 repel to buck the induced magnetic field of the coilcore combination and slow the'initial rise of the reverse current, and that in FIG. 6B, the unlike adjacent poles (N-S) of the core 39 and the magnet 41 attract to add to or aid the same magnetic field and speed up slightly the final exponential trace of the forward current. Also, if the polarity of the coil 37 is reversed in its serial connection with the deflection coils a and 15b, the magnet 411 could simply be rotated 180 about its rotational axis to align the opposite poles adjacent to the core member 3 to obtain the desired bucking and adding effect of the two magnetic fields during reverse and forward current flow respectively.

Therefore, it is seen that by placing the magnet 41 in the position with respect to the core member 39 as indicated in the drawings, line scan linearity control is obtained. In FIG. 7, the current waveforms 47 and 47' are indicative of the linearity corrections realized by the S-shaping effect of the additive and diminutive magnetic forces upon the induced magnetic field of the coil 37. Further, the rotational capability of the magnet 41 about its axis, as best illustrated in FIG. 8, will result in increasing or decreasing, respectively, these corresponding additive or diminutive forces, and thus the level of premagnetization of the core member 39.

The current waveform 47 indicates the maximum amount of linearity correction and corresponds to the position of the magnet 41 where the full strength of the magnets appropriate pole is aligned directly opposite the core member 39. As the magnet is rotated in the direction of the arrows 51 and 51' to thus align points A or B directly opposite the core member 39, the effect of the magnets magnetic field upon the adjacent pole of the core member 39, and thus the field of the core 37, is gradually lessened and the S-shaped curve 47' is realized.

FIG. 8 shows line A B which represents the neutral or demagnetized portion of the magnet 41, and as the magnet is further rotated in the directions of the arrows 51 and 51 to align the points A or 8' directly opposite the core member 39, the effect of the magnets magnetic field upon the adjacent portion of the induced magnetic field of the coil 37 is at its minimum level. At this minimum level, the curve 45 is substantialy realized although in practice the effect of the magnets magnetic field is not entirely eliminated due to the narrowness of such a theoretical neutral point on the magnet 41. Therefore, the improved construction of the applicants control means 3&1 provides an adjustable range of linearity control by merely a slight rotation of the magnet 41 by means of its tool-receiving aperture 41a.

The invention has been described in detail with particular reference to the drawings, but it will be understood by those skilled in the art to which the invention pertains that various modifications and variation can be made without departing from the spirit and scope thereof, and to this extend the appended claims are intended to cover the same.

Iclaim:

1. A horizontal deflection control means for connection with a television magnetic-deflection coil having a bidirectional current therethrough of a type in which the control means provides both electron beam horizontal line scan width and scan linearity adjustmen'ts, said control means comprising: an elongated helical inductor coil having a longitudinal axis and adapted to be connected with the magnetic-deflection coil, a double-ended ferromagnetic core member having one end portion adjustably inserted within the helical coil and another end portion extending from one end of the helical coil, said core member being movable along the longitudinal axis of the coil to adjust the insertion of said one end portion within the coil for directly adjusting the inductance of the coil whereby the horizontal line scan width is controlled, and a permanent magnet rotatably mounted adjacent said core for varying the amount and polarity of magnetic flux linkage between said permanent magnet and said core with rotation of said permanent magnet and said magnet being operative upon rotation thereof to adjust the level of premagnetization of said core whereby the horizontal line scan linearity is controlled.

2. A horizontal deflection control means as claimed in claim 1 wherein: said magnet is an elongated generally cylindrical magnet having a longitudinal axis with said magnet being mounted for rotation thereabout, and said magnet is further mounted so that said longitudinal axis is in parallel alignment with and spaced from the longitudinal axis of said helical coil.

3. A horizontal deflection control means as claimed in claim 1 wherein said helical coil is connected in series with the magnetic-deflection coil.

4. A horizontal deflection control means as claimed in claim 1 wherein said magnet and said other end portion of the core member are mounted within a single piece holder member having a mounting base and a pair of parallel spaced channel-like openings for respectively receiving said magnet and said other end portion of the core member, a first of said pair of openings has a diameter slightly larger than the diameter of said magnet and has said magnet concentrically disposed therein whereby the magnet is free to rotate about its axis within said first opening, and a second of said pair of openings has a diameter slightly larger than the diameter of said core member and has said other end portion of the core member concentrically disposed therein whereby said core member is free for axial movement within said second opening.

5. A horizontal deflection control means as claimed in claim 4 wherein a generally tubular coil form has one end portion thereof inserted into said second opening and another end portion thereof extending outwardly from one end of said second opening whereby said other end portion of the coil form comprises an extension of said second opening, said coil is wound about said other end portion of the coil form with one end thereof adjacent said magnet, and said core member is concentrically disposed within said coil form and is free for axial movement with respect thereto whereby said core member has its one end portion encompassed by said coil and its other end portion extended in oppositely spaced relationship to said magnet.

Claims (5)

1. A horizontal deflection control means for connection with a television magnetic-deflection coil having a bidirectional current therethrough of a type in which the control means provides both electron beam horizontal line scan width and scan linearity adjustments, said control means comprising: an elongated helical inductor coil having a longitudinal axis and adapted to be connected with the magnetic-deflection coil, a double-ended ferromagnetic core member having one end portion adjustably inserted within the helical coil and another end portion extending from one end of the helical coil, said core member being movable along the longitudinal axis of the coil to adjust the insertion of said one end portion within the coil for directly adjusting the inductance of the coil whereby the horizontal line scan width is controlled, and a permanent magnet rotatably mounted adjacent said core for varying the amount and polarity of magnetic flux linkage between said permanent magnet and said core with rotation of said permanent magnet and said magnet being operative upon rotation thereof to adjust the level of premagnetization of said core whereby the horizontal line scan linearity is controlled.

2. A horizontal deflection control means as claimed in claim 1 wherein: said magnet is an elongated generally cylindrical magnet having a longitudinal axis with said magnet being mounted for rotation thereabout, and said magnet is further mounted so that said longitudinal axis is in parallel alignment with and spaced from the longitudinal axis of said helical coil.

3. A horizontal deflection control means as claimed in claim 1 wherein said helical coil is connected in series with the magnetic-deflection coil.

4. A horizontal deflection control means as claimed in claim 1 wherein said magnet and said other end portion of the core member are mounted within a single piece holder member having a mounting base and a pair of parallel spaced channel-like openings for respectively receiving said magnet and said other end portion of the core member, a first of said pair of openings has a diameter slightly larger than the diameter of said magnet and has said magnet concentrically disposed therein whereby the magnet is free to rotate about its axis within said first opening, and a second of said pair of openings has a diameter slightly larger than the diameter of said core member and has said other end portion of the core member concentrically disposed therein whereby said core member is free for axial movement within said second opening.

5. A horizontal deflection control means as claimed in claim 4 wherein a generally tubular coil form has one end portion thereof inserted into said second opening and another end portion thereof extending outwardly from one end of said second opening whereby said other end portion of the coil form comprises an extension of said second opening, said coil is wound about said other end portion of the coil form with one end thereof adjacent said magnet, and said core member is concentrically disposed within said coil form and is free for axial movement with respect thereto whereby said core member has its one end portion encompassed by said coil and its other end portion extended in oppositely spaced relationship to said mAgnet.

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