GB2265532A

GB2265532A - Dynamic convergence correction

Info

Publication number: GB2265532A
Application number: GB9304088A
Authority: GB
Inventors: Keeyeon Nam; Hyeukchan Kwun; Doyoung Yang
Original assignee: Samsung Electron Devices Co Ltd
Current assignee: Samsung SDI Co Ltd
Priority date: 1992-03-09
Filing date: 1993-03-01
Publication date: 1993-09-29
Anticipated expiration: 2013-03-01
Also published as: GB2265532B; GB9304088D0; JPH0698339A; DE4306304A1; TW258850B

Description

2265532 1 Title: - Deflection Yoke having xis - convergence Correction

Device

DESCRIPTION

The present invention relates to a deflection yoke DY having a mis-convergence correction device for a colour picture tube CPT and, more specially to the defl-ection yoke provided with the device for correcting mis-convergence which can correct vertical coma error VCR by controlling nonlinearly a current itself passing through a correction coil using the correction coil.

Generally, a deflection yoke mounted on the neck portion of a colour picture tube is formed by combining a pair of horizontal deflecting coils, a pair of vertical defecting coils and ferrite cores. The deflection yoke is installed on the outer surface oil the neck of the colour iDicture tube to deflect electron beams ewitted from three electron guns. This deflection yoke structure is formed such that the horizontal deflecting coils are disposed in the saddle type on a separator and the vertical deflecting coils are disposed in the toroid type or in the saddle type on the seDarator.

2 After converging the three electron beams respectively emitted from the electron gun, the deflection yoke deflects them and at the same time, they are necessarily focused on an aperture of a shadow mask. If the three electron beams are mis-converged on the aperture of the shadow mask, 'the three electron beams can not reach the corresponding fluorescent layers, resulting in mislanding. Thus, there is performed the static -convergence such that the magnetic field is applied from the outside by a convergence purity magnet CPM to modify the track of the electron beam on the screen middle portion, resulting in converging the three electron beams on the shadow mask.

However, the static -convergence by the convergence purity magneit- can nolL be performed on the corner of the screen of a tube!a-rge colour picture tube for the face Of the colour p-,cr-u--.e L.

4 S L 1. L so nearly '!a' that its radius of curvature is to be very arge, and the radius of curvature of the trace of dots - L converging the three electron beams emitted from the electron gun is smaller than that of the face. Thus, though the three 3 electron beams are converged at the center of the screen, they are dispersed in the corner of the screen so that each beam passes through the respective different apertures of the shadow mask thereby emitting light to the different fluorescent -he colour purity. This materLal, resulting in lowering t phenomenon remarkably occurs according as the deflecting angle of L-he electron beam and the radius of curvature is to be larger.

Thus, to achieve the good convergence on the shadow mask of the electron beams at the center and the corner of the screen in the in-line ty L.

pe three electron beam colour picture tube of self-convergence type, the deflection yoke using the nonuniform magnetic field distribution such that the horizontal deflecting magnetic field of the deflection yoke is formed in the pincushion the type and 'the verti me d i n It.

cal deflecting magnetic field is for barrel type has been used since 1972. This method leads to the rough agreement of raster of the electron beam at the corner.

I However, despite the use of the nonuniform deflecting magnetic field, the agreement of raster by the outer electron

4 beams of the in-line type electron beams with that by the center electron beam can not be obtained. Namely, raster bv the center electron beam is to be smaller than that by the outer electron beams. Difference of the raster size is called a coma error. in a 14 inch colour picture tube, both of the vertical coma error and the horizontal direction coma error are 1 - 2mm.

In the above coma error, while the horizontal coma error can be overcome by studying the horizontal deflecting coil distribution, it is reasonably difficult to correct the vertical coma error.

A technology for achieving the good convergence of the in- ine type three electron beams is disclosed in Japanese Examined Publication No. Sho 57-45748. This invention is formed such that a pair of correcition coils wound on a ?[ [ " type core are disposed oppositely and in the vertical direction between the front end of the electron gun and the f- ront side of the main t_.1..1 deflecting coil. The operation of the above correction coil leads to the reduction of the vertical coma error of about 0.2mm in the 14 inch colour picture tube.

However, in the above technology, the vertical coma error is partially excessively corrected at the center of the screen.

According as the screen size of the colour picture tube is to be large and flat, this tendency is increased 1Chereby occurring to the colour change unpleasant to eyes among characters displayed on the screen in a high definition tube.

A technology for preventing the excessive correction of the vertical coma error at the center is disclosed in US Patent No.

07/4,8181,919 " Device for colour picture tube " The conventional deflection yoke of the above invention will be described.

FIG. 1 is an equivalent circuit diagram of the conventional de.flection yoke. As shown in this figure, the conventional deflection yoke structure has the vertical deflecting Coils W11, LV12; a pair of first auxiliary C0i1S CF11, CF12 in serial connected to the vertical deflecting coils W11, W12; a pair of second auxiliary coils CF13, CF14 in serial connected between the 6 firsi- auxiliary coils CF11, CF12 and a low potential side V-;and a current control elements D11, D12 'Darallel connected to the second auxiliary coils CF13, CF14.

Description of the operation of the conventional deflection - '1 1 owed. yoke will be 'Lo-- Voltages V-,, V- of saw-toothed wave type is applied to the vertical deflecting coils LVI1, LV12 from a vertical oscillation circuit(not shown) to generate the vertical deflecting magnetic Lield of barrel ttype, so that the three electron beams emitted he in-line type electron gun is vertically deflected. At from t %_ i..

thatl 'L-iine, the current passing through the vertical deflecting Coils LV11, W112 passes through a pair of the first auxiliary CoLls CF11, CF-12 which are in serial connected thereby generating t - firs' auxiliary the magnetic f-Jeld of pincushion type from the -- coils CF11, CF-312. The current Dassing through the first auxiliary coils CF11, CF12 continue to pass through a pair of the serially connected second auxiliary coils CF13, CF14 thereby generating the magnetic -field of barrel type from the second auxiliary coils

7 CF13, CF14.

Namely, the auxiliary coils CF11, CF12 makes the positive correction by the magnetic field of pincushion type with the same direction as that of a main deflecting magnetic field. The second auxiliary coils CF13, CF14 makes the negative correction by the magnetic field of barrel type with the same direction as that of the main deflecting magnetic field.

At that time, since most of the current passing through the second auxiliary coils CF13, CF14 passes through diodes Dil, D12 in case ithat the diodes D11, D12 of a current control element t - .urn on, the magnetic field by the second auxiliary coils CF13,

CF14 is to be constant, so that the negat-ive correction of the vertical coma error reaches the state oj- saturation.

The non-linear characteristic of the curreniC passing through the second auxiliary coils CF13, CF14 for the negative correction, which reaches the state of saturation in case of more than a predetermined current, leads to -Preventing the excessive correction on the middle portion o the screen to correct the 8 vertical coma error.

However, the conventional deflection voke has a disadvantage such that two pair of auxiliary coils for the negative correction and for the D0sitive correction should be required to prevent the excessive correction on the middle portion of the screen at the ste-D of correcting the vertical coma error. This disadvantage results in the non-efficient manufacturing process of the deflection yoke due to the use of many big size coils compared with the other circuit element and tt-he increased production cost due ELO the a high number of man-hours and fraction defective by 4k_he unnecessarily complicated terminal board.

TO solve the above problems, an object of the present invention is to provide a deflection yoke provided with a devIce or correcting mis-convergence which can prevent the excessive correction occurring on the middle portion of a screen at the step of correcting vertical coma error VCR of the vertical direction by controlling nonlinearly a current itself passing through a correction coil using the correction coil.

t_ 9 To achieve the object, one structure of this invention has a vertical deflecting coils connected to a high potential side for generating a vertical deflecting magnetic field of barrel type when applying voltage; a pair of correction coils in serial connected to a pair of the vertical deflecting coils for generating the deflecting magnetic field to correct a coma error; a non-linear current control element in serial connected to a pair o-L2 the correction coils for bypassing more than a predetermined current; a resistance parallel connected to the non-linear current control element for controlling the size of current passing through the current control element;and a current control means connected between the vertical deflecting coil and a low potential side.

Another structure of h i invention has the vertical deflecting coils connected to the high potential side for generating the vertical deflecting magnetic field of barrel type when applying voltage; a pair of resistances connected to the vertical deflecting coils for controlling the size and shape of the current passing through the correction coils; the non-linear current control element connected between a pair of resistances for bypassing more than a predetermined current; a pair of correction coils connected between the non-linear current control elemen't and cl-he low potential side for generating correction deflecting magnetic field to correct the vertical deflecting coma error;a-nd the resistance connected between the non-linear control element and ithe low potential side for controlling the size and shape of the current passing through the correction coils.

The present will now be described further, by way oLSexample only, with reference to the accompanying drawings in which: - FIG. 1 is an equivalent circuit diagram of a conventional deflection yoke; FIG. 2 is an equivalent circuit diagram of a deflection yoke provided with a device for correcting mis-convergence or an embodiment of the present invention; FIGs 3 to 9 are equivalent circuit diagrams of a deflection 11 yoke provided with a device for correcting mis-convergence of other embodiments of the present invention;and FIGs. 10A and 10B are waveform views of a current passing through a deflection yoke provided with a device for correcting mis-convergence of an embodiment oil 'the present invention.

FIG. 2 describes in an equivalent circuit diagram a deflection yoke provided with a device for correcting mis- convergence of an embodiment of the present invention. As shown in this figure, the deflection yoke has a vertical deflecting coils W21, LV22 whose each one terminal is connected to a high r)otential side V+ and another terminal is connected to each other; a pair of correction coils CF21, CF22 which are in serial connected to the connecting point of the vertical deflecting cails LV21, LV22; a pair off diodes D21, D22 which are in serial connected to the correction coils CF21, CF22 and disposed parallel and in the opposite direction to each other; a resistance R21 which is parallel connected to a pair of diodes D21, D22; the resistance R22 which is connected between the 12 connecting point of the vertical deflecting coils LV21, LV22 and a low -potential side V- An operation of the deflection yoke provided with a device for correcting mis-convergence of an embodiment of the present Lnvention will be disclosed.

L L_ - - Voltages V+, V- of saw-toothed type are applied to the vertical deflecting coils LV21, LV22 from a vertical oscillating circuit(not shown) to generate a vertical deflecting magnetic f J eld of barrel type thereby vertically deflecting three electron beams emL'L.4t-.ed from an in-line type electron gun. At that time, the current passing through the vertical deflecting coils LV21, LV22 passes through the correction coils CF21, CF22 which has a pair of one 'Layer coills serially connected to generate the field of pincushion type from the ve-rtical deflecting magnetic,correction coils CF21, CF22. The current passing through a pair of correction coils CF21, CF22 can be controlled by adjusting the value of resistances R21, R22. Namely, if the value of resistance R21 is to be large, the current passing through the correction 13 coils CF21, CF22 is changed into the current having a triangle wave shape formed by cutting off the middle portion in the saw- toothed wave shape. Also, if the value of resistance is to be set small, according as a -Pair of diodes D21, D22 slowly turn on, the size of the current passing through the correction coil CF21 can be reduced until the diodes D21, D22 turn on. Thus, according to the control of the value of resistan-ces R21, R22, the size and shape of the current passing through a pair of correction coils CF21, CF22 can be controlled.

Explanation of the above with current waveforms and formulas will be followed.

one cycle of the vertical deflectin g current is shown in FIG. 10A. The formula representing the waveform shown in FIG. 10A is as follows; i (t) = 10 - 2 10 t / T (0 < t < T) wherein T is represented as a cycle and 10 is represented as maximum value of the current. tl, t2 are represented as an instant when the diode of the current control element turn on.

14 Generally, a vertical deflecting frequency is to be low as 50 HZ, so that, as far as an inductance of the correction coils is not sufficiently large, impedance mainly depends on the value RCF of the resistance of the correction coils CF21, CF22. The current iC?(t) passing through the correction coils CF21, CF22 is divided into two cases as follows:

(1) in case of tl < t < t2, icE, k R22 i (2) in case of 0 < t < tl or t2 < 't- < T, iCF (t) --. R22 i(t) / (R22+RCF) - (t) / (R21+R22+RCp) The intensity Of the vertical coma error correction magnetic field is proportional to the amount of current passing through

L the correction coils CF21, CF22. As described above, the value of the resistance is controlled to adjusil- the current ieF(t) passing through the correction coils CF21, CF22, so that the intensity of current passing through the middle portion of the screen is weakened to prevent the excessive correction on the screen center thereby controlling the vertical coma error correction magnetic field. The inclination of the straight line shown in FIG. 10B is relatively indicated. Each inclination, ti and -L-2 may be determined according to the value of the used resistances R21, R22 and changed by the electrical characteristic of diodes D21, D22.

FIG. 3 describes in an equivalent circuit diagram the deflection yoke provided with the device for correcting mis- convergence of other embodiment of the present invention. As shown in this figure, the deflection yoke has the vertical deflecting CoilS LV31, LV32 whose each one terminal is connected to the high potential side V+ and another terminal is connected J_ Lo each other; a pair of correction coils CF31, CF32 which are in serial connected to the connecting point of the vertical deflecting coills LV31, LV32; two pairs of diodes D31, D32, D33, D34 which are in serial connected to a pair of correction coils CF31, CF32 and each pair is disposed parallel and in the opposite direction; the resistance R31 which is in serial connected to two pairs of the diodes D31, D32, D33, D34;and the resistance R32 which is connected between the connecting point and the low 16 Dotential side V- The operation of the deflection yoke provided with the device for correcting mis-convergence of other embodiment of the present invention is similar to that of the deflection yoke provided with the device for correcting mis-convergence of one embodiment of the present invention as shown in FIG. 2. This ooeration will be followed.

The saw-toothed voltage V+, V- are applied to the vertical deflecting coils LV31, LV32 from the vertical oscillating circuit to generate the vertical deflecting magnetic field of barrel type thereby vertically deflecting the three electron beams emitted from the in-line type electron gun. At that time, the current passing through the vertical deflecting coils LV31, LV32 passes through the correcition coils CF31, CF32 which has a pair of one layer coil to generate the vertical deflecting magnetic field of p.Lncushion type from the correction coils CF31, CF32.,The current passing through a pair of correction coils R31, R32 is controlled by adjusting the value of resistances R31, R32.

17 In the above case, more than two pairs of diodes D31, D32, D33, D34 are used at the paint where the vertical deflection coma error of the vertical portion of the screen is most deviated, so that the intensity of current at the middle portion of the screen is weakened to prevent the excessive correction on the middle portion of the screen 'hereby correcting the mis-convergence.

FIG. 4 describes in an equivalent circuit diagram the deflection yoke provided with the device for correcting mis- convergence of other embodiment of the present invention.

As shown in this figure, the deflection yoke has the vertical deflecting coils LV41, LV42 whose each one terminal is connected to the high potential side V+ and another terminal is connected to each other; a pair of correction coils CF41, CF42 which are in. serial connected to the connecting point of the vertical deflecting coils LV41, W42; a pair of diodes D41, D42 which are in serial connected to a pair of correction coils CF41, CF42 and are disposed parallel arid in the opposite direction to each other; the resistance R41 which is parallel connected to a pair 18 of the diodes D41, D42;and the resistance R42 and a coil CV43 which are connected between the connecting point of the vertical deflecting coils W41, LV42 and the low potential side v-.

The operation of the deflection yoke provided with the device for correcting mis-convergence of other embodiment of the -Present invention will be followed.

The saw-toothed voltage V+, V- are applied to the vertical deflecting coils LV41, LV42 from the vertical oscillating circuit to generate the vertical deflecting magnetic 1 L Lield of barrel type thereby vertically deflecting the three electron beams emitted from the in-line type electron gun. Att- that time, the current passing through the vertical deflecting coils LV41, LV42 Passes through it-he correction coils CF41, CF42 which has a pair of one layer coil to generate 'he vertical deflecting magnetic field of - L- from the correction coils CF41, CF42.

pincushion type L In -'L-.he above case, Che coil CV43 is used to correct the horizontal coma error of the middle portion of the screen to generate the non-linear current waveform such as the current 19 waveform shown in FIG. 10B thereby preventing the excessive correction at the middle portion and correcting mis -convergence.

FIG. 5 describes in an equivalent circuit diagram the deflection yoke provided with the device for correcting mis- convergence of other embodiment of the present invention.

As shown in this figure, the deflection yoke has the vertical deflecting coils LV51, LV52 whose each one terminal is connected to the high potential side V+ and another terminal is connected to each other; a pair of correction coils CF51, CF52 which are in serial connected to the connecting point of the vertical deflecting coils LV51, W52; a pair of diodes D51, D52 which are in serial connected to a pair of correction coils CF51, CF52 and are disposed parallel and in the opposite direction to each other; the resistance R51 which is parallel connected to a Dair oil the diodes D51, D52;and the resistance R52 and a choke coil CF53 which are in serial connected between the connecting point of the vertical deflecting coils W51, LV52 and the low potential side V-.

The saw-toothed voltage V+, V- are applied to the vertical deflecting coils LV51, LV52 from the vertical oscillating circuit to generate the vertical deflecting magnetic field of barrel type thereby vertically deflecting the three electron beams emitted from the in-line type electron gun. All: that time, the current passing through the vertical deflecting coils W51, LV52 passes through the correction coils CF51, CF52 which have a pair of one layer coil to generate the vertical deflecting magnetic field of pincushion type from the correction coils CF51, CF52.

in the above case, the choke coil CF53 and the resistance R52 are used to generate the non-linear current waveform shown in FIG. 10B thereby preventing the excessive correction at the middle portion and correcting the mis-convergence.

of the diodes, as current control element, disposed parallel and in the opposite direction as shown in FIGs. 2 to 5, a pair of zener diodes which are disposed in serial to each other are used to obtain the same effect. This case will be described in connection with FIG. 6.

21 FIG. 6 describes in an equivalent circuit diagram the deflection yoke provided with the device for correcting mis- convergence of other embodiment of the present invention.

As shown in this figure, the deflection yoke has the vertical deflecting coils W61, LV62 whose each one terminal is connected to the high potential side V+ and another terminal is connected to each other; a pair of correction coils CF61, CF62 which are in serial connected to the connecting point of the vertical deflecting coils LV61, LV62; a pair of zener diodes D61, D62 which are in serial connected to a pair of correction coils CF61, CF62; the resist-ance 61 which is parallel connected to a pair of the diodes D61, D62;and the resistance R62 which are in serial connected between the connecting point of the vertical deflecting 31S LV61, LV62 arid the low potential side V-.

CO.L L The operation of the deflection yoke provided with the device for correcting mis-convergence of other embodiment of the - invention will be followed.

iDresent The saw-toothed voltage V+, V- are applied to the vertical 22 deflecting coils W61, LV62 from the vertical oscillating circuit- ield off barrel type to generate the vertical deflecting magnetic E thereby vertically deflecting the three electron beams emitted from the in-line type electron gun. At that time, the current passing through the vertical deflecting coils LV61 LV62 passes CF62 which have a pair of one 1-hrough the correction coils CF61, laver coil to generate the vertical deflecting magnetic field o pincushion type from the correction Coils CF61, CF62. In this case, a pair of zener diodes D61, D62 turn on by adjusting the value of the resistance R61, R62 to generate the nonlinear current waveform, so that the excessive correction of the screen center is prevented to correct the vertical deflecting coma error.

FIG. 7 describes in an equivalent circuit diagram the deflection yoke provided with the device for correcting mis- convergence of other embodiment of the present invention.

As shown in this figure, the deflection yoke has the vertical deflecting coils W71, LV72 whose each one terminal is connected 23 L.o the high Potential side V+ and another terminal is connected to each other; the resistanceS R71, R72 whose each one terminal is connected the connecting point of the vertical deflecting coils LV71, W72; a pair of zener diodes D71, D72 which are connected between another terminals of the resistances R71, R72; a pair of correction coils CF71, CF72 which are in serial connected between the connecting point of the resistance R71 and L-he zener diode D71 and the low potential side V-;and the resistance R73 which is connected between the connecting point of the resistance R72 and the zener diode D72 and the low r)oten.1L.-ial side V-.

The operation of the deflection yoke provided with the device for correcting mis-convergence of other embodiment of the pr.esent invention will be followed.

The saw-toothed voltage V+, V- are applied to the vertical deflecting Coils W71, LV72 from the vertical oscillating circuit to crenerate the vertical deflecting magnetic field of barrel type thereby vertically deflecting the three electron beams emitted 24 from the in-line type electron gun.

All-- that -Lime, exPlanation of- the above with the current waveforms and formulas will be followed. one cycle of the vertical deflecting current is shown in FIG. 10A. The formula representing the waveform shown in FIG. 10A is as follows; i(t) = IC. -2 10 t / T (0 < t < T) wherein T -JS represented as the cycle and IC, is represented as maximum value of the current. tl, 'L-2 shown in FIG. 10A are represented as an instant when the zener diodes D71, D72 of the current control element turn on.

If the value of the resistance R72 is more than that of the resistance R73, part of the vertical deflecting current passing through the vertical deflecting coils W71, LV72 pass through the 0 zener diodes D71, D72 of current contro-2 element at ';he time Of ti, t2. At the same time, the current passing through the resistance R71 is combined with that passing through the zener diodes D71, D72 for the nonlinear current to pass through a pair of correction coils CF71, CF72 having a pair of one layer coils as shown in FIG. 10B. So, the correction magnetic field of misconvergence is generated from the correction coils CF71, CF72 to correct the vertical coma error.

In that case, the size and shape of the current passing t L-hrough the correction coils CF71, CF72 are controlled by adjusting the value of the resistance or by using the electrical characteristic oil the zener diodes D71, D72 to prevent the excessive correction of the screen center thereby correcting mis- the colour picture tube.

convergence oL Fig. 8 describes in an equivalent circuit diagram the deflection yoke provided with the device JEor correcting mis- convergence of other embodiment of the present invention.

As shown in this figure, the deflection yoke has the vertical de.flecting coils W81, LV82 whose each one terminal is connected to the high potential side V+ and another terminal is connected to each other; the resistances R81, R82 whose each one terminal is connected the connecting point of the vertical deflectincr coils W81, W82; the zener diodeS D81, D82 which are connected 26 between another terminals of the resistanceS R81, R82; a pair of corTrection coils CF81, CF82 which are parallel connected between the connecting point of the resistance R81 and the zener diode D81 and the low potential side V-;and the resistance R83 which is connected between the connecting point of the resistance R82 and the zener diode D82 and the low potential side V-.

The operation of,L--he deflection yoke Drovided with the device for correcting mis-convergence of other embodiment of the present invention will be followed.

The saw-toothed voltage V+, V- are applied to the vertical -deflecting coils LV81, LV82 from the vertical oscillating circuit to generate the vertical deflecting magnetic field of barrel type thereby vertically deflecting the three electron beams emitted from ',---.he in-line type electron gun.

At that time, one cycle of the vertical deflecting current passing through the vertical deflecting coils W81, LV82 is represented as the waveform shown in FIG. 10A. tl, t2 shown in FIG. 10A are represented as an instant when the zener diodes D81, 27 D82 of the current control element turn on.

if the value of the resistance R83 is more than that of the resistance R82, part of the vertical deflecting current passing through the vertical deflecting coils W81, LV82 pass through the zener diodes D81, D82 of current control element at the time of t2. At the same t-ime, the current passing through the resistance R81 is combined with thait- passing throughthe zener diodes D81, D82 for the nonlinear current to pass through a pair of correction coils CF81, CF82 having a pair of one layer coils as shown in FIG. 10B. So, the nonlinear current passes through the correction Coils CF81, CF82 to generate the correction magnetic field of mis-convergence from the correction coils CF81,

CF82 thereby correcting the vertical coma error.

in that case, the size and shape of the current passing through the correction coils CF81, CF82 are controlled by adjusting the value of the resistances R81, R82, R83 or by using the electrical characteristic of the zener diodes D81, D82 to prevent the excessive correction of the screen d thereby 28 correcting the xis-convergence of the colour picture tube.

FIG. 9 describes in an equivalent circuit diagram the deflection yoke provided with a device for correcting mis- convergence of other embodiment of the present invention.

As shown in t-his figure, the deflection yoke has the vertical deflecting coils LV91, LV92 whose each one terminal is connected to the high potential side V+ and another terminal is connected 1- L.o each other; the resistanceS R91, R92 whose each one terminal is connected the connecting point of the vertical deflecting coils LV91, W92; the zener diodes D91, D92, D93 which are connected between another terminals of the resistances R91, R92; a pair of correction coils CF91, CF92' which is in serial connected between,the connecting point of the resistance R91 and t zener dii the ode D91 and the low potential side V-;and the resistance R93 which is connected between the connecting point of the resistance R92 and the zener diode D92, D93 and the low poential side V-.

The operation of the deflection yoke provided with the 29 device for correcting mis-convergence of other embodiment of the present invention will be followed.

The saw-toothed voltage V+, V- are applied to the vertical deflecting coils W91, LV92 from the vertical oscillating circuit ield of barrel type to generate the vertical deflecting magnetic 1 thereby vertically deflecting the three electron beams emitted from the in-line type electron gun.

At that time, one cycle of the vertical deflecting current passing through the vertical deflecting coils W91, LV92 represented as the waveform shown in FIG. 10A. tl, t2 shown in FIG. lOA are represented as an instant when the zener diodes D91, D92, D93 of the current control element turn on.

If the value of the resistance R93 is more than that of the resistance R92, part of the vertical deflecting current passing through the vertical deflecting coils W91, LV92 pass through the zener diodes D91, D92, D93 of current control element at the time of tl, t2. At the same time, the current passing through the resistance R91 is combined with that passing through the zener diodes D91, D92, D93 for the nonlinear current to pass through a pair of correction coils CF91, CF92 having a pair of one layer coils as shown in FIG. 10B. So, the nonlinear current passes through the correction coils CF91, CF92 to generate the correction magnetic field of mis-convergence from the correction coils CF91, CF92 thereby correcting the vertical direction coma error.

in that case, ithe size and shape of the current passing through the correction coils CF91, CF92 are controlled by adjusting the value of the resistances R91, R92, R93 or by using the electrical characteristic of the zener diodes D91. D92, D93 to prevent the excessive correction of the screen center thereby correcting mis-convergence of the colour picture tube.

As described above, the present invention can provide the deflection yoke having the device for correction mis-convergence which can efficiently correct the vertical coma error without using many big size coils in such a manner that a pair of correction coils nonlinearly control the current itself passing 31 through the correction coils to prevent the excessive correction of the screen center.

Although several preferred embodiments of the present invention have been described in detail hereinabove, it should be clearly understood that many variations and/or modifications of the basic inventive concepts herein taught which may appear to those skilled in the pertinent art will still fall within the spirit and scope of the present invention, as defined in the appended claims.

32

Claims

- CLAIMS A deflection yoke having with a mis -convergence correction device comprising: a pair of vertical deflecting coils connected to the high -potential side for generating the vertical deflecting magnetic field of barrel type; a correction coil having a Dair of one layer coils serially connected to the vertical deflecting coils for generating the deflecting magnetic field to correct the vertical deflecting coma error; a non-linear current control element serially connected to the correction coil for bypassing more than a predetermined current; a first current control means paral 11 ell connected 'L.0 the non- linear current control element for controlling the size of current;and a second current control means connected between the vertical deflecting coil and a low potentia 1 side for controlling 33 the size of current.

1) J:1.

The deflection yoke as claimed in claim 1, wherein the non- linear current control element comprises more than at least a pair of inverse parallel diodes.

3. The deflection yoke as claimed in claim 1, wherein the non- linear current control element comprises a pair of inverse serial zener diodes.

4. The deflection yoke as claimed in claim 1, wherein the first current control means comprises more than at least one resistance.

5. The deflection yoke as claimed in claim 1, wherein the second current control means comprises a resistance and coils.

6. The deflection yoke as' claimed in claim 1, wherein the second current control means comprises only the resistance.

7. The deflection yoke as claimed in claim 1, wherein the second current control means comprises choke coils serially connected thereto and the resistance.

8. A deflection yoke having a mis-convergence correction device 34 comprising:

"lecting coils connected to the high.

a pair of vertical def potential side for generating the vertical deflecting magnetic field of barrel type; a pair of resistances connected to the vertical deflecting coils for controlling the size and shape of the current passing through the correction coils; non-linear current control element connected between a pair of resistances for bypassing more than a predetermined current; correction coils connected between the non-linear current control element and the low potential side for generating correction deflecting magnetic field to correct the vertical deflecting coma e.-ror;and a resistance connected between the non-linear control element and the low potential side for controlling the size and shape of the current passing through the correction coils.

9. The deflection yoke as claimed in claim 8, wherein the non- linear current control element comprises a pair of zener diodes where cathodes are connected in serial to each other and correction coils having a pair of one layer coils are connected in serial to each other.

10. The deflection yoke as claimed in claim 8, wherein the non- linear current control element comprises a pair of zener diodes where anodes are connected in serial to each other and correction coils having a pair of one layer coils are connected in Parallel to each other.

11. The deflection yoke as claimed in claim 8, wherein the non- linear current control element comprises a zener diode and a pair of zener diodes parallel connected to 'a cathode of the zener diode, the i:iair of the zener diodes being connected parallel to each other, one anode being connected to other cathode, one cathode being connected to other anode and the correction coils being in serial connected.

12. A deflection yoke constructed and arranged substantially as hereinbefore described with reference to and as illustrated in any one of the accompanying drawings of Figures 2 to 9.