JP2001119600A - Dynamic horizontal linearity correction circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correct M-shaped distortion and inner pin distortion in a cathode ray tube over the entire screen with high accuracy. SOLUTION: The dynamic horizontal linearity correction circuit is provided with a horizontal deflection coil 11, a horizontal deflection circuit 13, a transformer 14 whose secondary winding 14b is connected to the horizontal deflection coil 11, a waveform generating circuit 15 that is provided to a primary winding 14a of the transformer 14 and outputs a correction waveform to cancel distortion in response to a distortion characteristic of the cathode ray tube synchronously with a vertical synchronizing signal 18 and a horizontal synchronizing signal 17 received by the cathode ray tube and a current amplifier 16. The current amplifier 16 amplifies the correction current with the correction waveform generated in the waveform generating circuit 15 and supplies the amplified current to the horizontal deflection coil 11 via the transformer 14 so as to adaptively correct distortion at an optional position on the display screen with respect to the distortion characteristic of the cathode ray tube so as to locally correct the horizontal linearity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dynamic horizontal linearity correction circuit for correcting linearity of horizontal deflection in a cathode ray tube display.

[0002]

2. Description of the Related Art A cathode ray tube display device used for a television receiver, a computer display, and other various monitors includes a correction circuit for correcting the linearity of horizontal deflection and vertical deflection when scanning and deflecting an electron beam. Have.
In general, the center of the curvature of the inner wall of the cathode ray tube is different from the center of deflection of the magnetic field generated by the deflection coil, and the horizontal linearity (horizontal linearity) resulting from this difference is as follows:
The pattern shrinks at the center of the screen and extends toward the left and right peripheral portions. In order to correct the horizontal linearity pattern and obtain a display screen with less distortion, various horizontal linearity correction circuits have been conventionally proposed.

FIG. 7 is a block diagram showing a configuration example of a conventional horizontal linearity correction circuit. This circuit includes a supersaturation circuit between a horizontal deflection unit in which a horizontal deflection coil 51, a capacitor 52, and a horizontal deflection circuit 53 are connected in series, and a vertical deflection unit in which a vertical deflection coil 54 and a vertical deflection circuit 55 are connected in series. It has a configuration in which a reactor 56 is provided. The supersaturated reactor 56 is mounted on the deflection yoke. In this configuration, a resonance circuit is formed by the inductance of the horizontal deflection coil 51 and the capacitor 52 connected in series thereto,
The horizontal linearity is corrected by superimposing a cosine waveform current on the horizontal deflection current output from the horizontal deflection circuit 53 and increasing the deflection speed in the central portion with respect to the left and right peripheral portions of the screen. This correction is generally called S-shaped correction.

With respect to vertical pin inner pin distortion (pincushion distortion) caused by the characteristics of the deflection yoke, the saturation point of a supersaturated reactor 56 inserted in series with the horizontal deflection coil 51 is modulated by a magnetic field generated by a vertical deflection current. Then, the inductance of the supersaturated reactor 56 is dynamically changed at the vertical deflection position, and the S-shaped correction amount at the upper and lower portions of the screen is made smaller than that at the center portion, thereby correcting the inner pin distortion.

[0005]

In a flat cathode ray tube (flat cathode ray tube) which has recently become widespread, the center of the curvature of the inner wall of the tube surface is almost infinite, and the center of the curvature of the magnetic field generated by the deflection coil is different from the center of the deflection. Since the difference is large and the modulation amount of the cosine waveform when performing the S-shaped correction is large, the difference between the waveform originally required for the correction and the cosine waveform is becoming apparent. As a result, as shown in FIG. 8, the horizontal linearity pattern is substantially equal at the center, the right end, and the left end of the screen, and the middle portion of the horizontal M is slightly extended.
A distortion in the shape of a letter (hereinafter, referred to as an M-shaped distortion) occurs.

As for the inner pin distortion, other correction items (particularly, convergence) are prioritized in a flat cathode ray tube having a large difference between the center of the curvature of the inner wall surface of the cathode ray tube and the deflection center of the magnetic field generated by the deflection coil. When designed in such a manner, the size becomes larger than that of a curved cathode ray tube. When the inner pin distortion as shown in FIG. 9A is corrected using a supersaturated reactor which is a non-linear element as in the conventional correction circuit, a local change occurs before and after the supersaturated reactor is saturated, On the screen as shown in FIG. 9B, an unnatural distortion of an irregular shape is observed.

As described above, the conventional horizontal linearity correction circuit cannot sufficiently correct the M-shaped distortion and the inner pin distortion over the entire screen, particularly when used for a flat cathode ray tube. There is a problem that local distortion occurs.

The present invention has been made in view of the above circumstances, and is capable of accurately correcting M-shaped distortion and inner pin distortion in a cathode ray tube over the entire screen to obtain a high-quality display screen without distortion. It is an object of the present invention to provide a dynamic horizontal linearity correction circuit capable of performing the above.

[0009]

SUMMARY OF THE INVENTION A dynamic horizontal linearity correction circuit according to the present invention is connected to a horizontal deflection coil and has a horizontal deflection circuit for generating a horizontal deflection current for a cathode ray tube, and a primary winding and a secondary winding. A transformer having a secondary winding connected to the horizontal deflection coil; and a transformer provided on the primary winding of the transformer and synchronizing with a vertical synchronization signal and a horizontal synchronization signal input to the cathode ray tube. Correction waveform generating means for outputting a correction waveform for correcting the linearity of horizontal deflection so as to cancel the distortion according to the distortion characteristic of the tube.

Further, the output stage of the correction waveform generating means is provided with the correction waveform generating means and the transformer at a predetermined phase position in a horizontal retrace period or a horizontal retrace period and a vertical retrace period of the cathode ray tube. It is preferable to provide a switch for opening the primary winding.

A dynamic horizontal linearity correction circuit according to the present invention is connected to a horizontal deflection coil and generates a horizontal deflection current for a cathode ray tube.
A correction waveform for outputting a correction waveform for correcting the linearity of horizontal deflection so as to cancel the distortion according to the distortion characteristics of the cathode ray tube in synchronization with the vertical synchronization signal and the horizontal synchronization signal input to the cathode ray tube. Generating means, and correction current supply means for connecting the correction waveform generating means, the horizontal deflection coil and the horizontal deflection circuit in an insulated state, and supplying a correction current based on the correction waveform to the horizontal deflection coil. .

The correction waveform generating means includes a storage means for storing correction data set in advance according to a distortion characteristic of the cathode ray tube, and the correction data at a predetermined timing synchronized with the vertical synchronizing signal and the horizontal synchronizing signal. Output control means for reading out the data.

The correction waveform generating means corrects the M-shaped distortion by changing the correction amount in the horizontal position so that the correction amount is small at the center, right end, and left end, and large at the middle. At the same time, it is preferable to output a correction waveform signal for correcting the inner pin distortion by changing the correction amount at the vertical position so as to be larger at the center and smaller at the upper and lower ends.

In the above arrangement, the correction waveform generating means outputs a correction waveform for canceling the distortion in accordance with the distortion characteristics of the cathode ray tube, and outputs the horizontal deflection from the horizontal deflection circuit via the correction current supply means such as a transformer. A correction current is supplied to the horizontal deflection coil together with the current. Thereby, the distortion characteristic of the cathode ray tube is adaptively corrected at an arbitrary position on the display screen, and local horizontal linearity can be corrected. As a result, even for complicated horizontal linearity distortions such as M-shaped distortion and inner pin distortion caused by the difference between the center of the inner wall curvature of the tube face and the deflection center of the magnetic field generated by the deflection coil, the accuracy can be improved over the entire screen. High correction is performed, and a high-quality display screen without distortion is obtained. Also,
Since the correction of the inner pin distortion can be performed without using a saturable reactor having a non-linear characteristic, the occurrence of local distortion on the display screen and a decrease in the efficiency of horizontal deflection are prevented.
The power consumption of the correction circuit is reduced.

Further, the switch means causes the correction waveform generating means to operate at a predetermined phase position in the horizontal retrace period of the cathode ray tube, or in the horizontal retrace period and the vertical retrace period, preferably in the entire retrace period. By opening the primary winding of the transformer, even if the flyback pulse generated during the flyback period is excited in the transformer, no voltage is applied to the correction waveform generating means. The amplification circuit provided in the waveform generating means does not load the horizontal deflection circuit, and the power consumption of the circuit is suppressed.

The correction waveform generating means stores correction data preset according to the distortion characteristics of the cathode ray tube in the storage means, and outputs the correction data at a predetermined timing synchronized with the vertical synchronizing signal and the horizontal synchronizing signal by the output control means. By reading the, the distortion can be appropriately canceled at any position on the display screen according to the characteristics of the cathode ray tube,
A correction waveform having a predetermined correction amount is output at a timing corresponding to a position on each screen of the horizontal scanning and the vertical scanning.

The correction waveform generating means generates and outputs a correction waveform in which the correction amount is changed at the horizontal position so that the correction amount is small at the center, right end, and left end, and is large at the middle. M-shaped distortion on the display screen is properly corrected. Also, by generating and outputting a correction waveform in which the correction amount is changed to be larger at the center and smaller at the upper and lower ends at the vertical position, the inner pin distortion on the display screen is properly corrected. .

[0018]

Embodiments of the present invention will be described below with reference to the drawings. [First Embodiment] FIG. 1 is a block diagram showing a configuration of a horizontal linearity correction circuit according to a first embodiment of the present invention. The horizontal linearity correction circuit of the present embodiment generates a predetermined correction waveform set in advance corresponding to the characteristics of the cathode ray tube, and supplies the correction waveform to the horizontal deflection circuit, thereby arbitrarily adapting the correction of the horizontal linearity. (Dynamic).

The horizontal linearity correction circuit has a horizontal deflection section in which a horizontal deflection coil 11, a capacitor 12, and a horizontal deflection circuit 13 are connected in series. The secondary winding 14b is connected in series. The horizontal sync signal (H.
Sync) 17 and a vertical synchronizing signal (V.Sync) 18 and a waveform generating circuit 15 for outputting a predetermined correction waveform, and a current amplifier 16 which is an amplifying circuit for current amplifying the output of the waveform generating circuit 15. The output terminal of the current amplifier 16 is connected to the primary winding 14a of the transformer 14. That is, the correction waveform generator corresponding to the correction waveform generator having the waveform generator 15 and the horizontal deflection unit including the horizontal deflection coil 11 and the horizontal deflection circuit 13 are controlled by the transformer 14 corresponding to the correction current supply. They are electrically separated and are insulated via this transformer 14.

The transformer 14 preferably has a sufficiently high degree of coupling, and it is desirable that characteristics such as inductance are flat and do not change during the horizontal scanning and vertical scanning of a cathode ray tube (not shown). Horizontal deflection circuit 13
A known circuit having an AFC circuit or the like may be used as appropriate.

Next, the operation of the horizontal linearity correction circuit configured as described above will be described. In the present embodiment, the waveform generation circuit 15 generates a correction waveform according to the distortion characteristics of the cathode ray tube mounted on the display device in synchronization with the horizontal synchronization signal 17 and the vertical synchronization signal 18, and generates the correction waveform. The power is supplied to the horizontal deflection coil 11 and the horizontal deflection circuit 13 via the transformer 14.

A current (hereinafter, referred to as a correction current) based on a correction waveform signal output from the waveform generation circuit 15 is amplified by a current amplifier 16 and then amplified by a primary winding 14a of a transformer 14.
Flows to Accordingly, the correction current having undergone the impedance conversion flows through the secondary winding 14b of the transformer 14, and the correction current is superimposed on the deflection current output from the horizontal deflection circuit 13 and applied to the horizontal deflection coil 11. With this correction current, a desired horizontal linearity correction can be obtained.

Here, an example of the waveform generating circuit 15 will be described. FIG. 2 is a block diagram showing a configuration example of the waveform generation circuit.

The waveform generating circuit of the present embodiment comprises a microcomputer 21 or a DSP for generating waveform data, and a waveform R as a storage means for storing waveform data.
AM22, a multiplying circuit 23 for multiplying the horizontal synchronizing signal 17,
A column address counter 24 that generates a column address signal of the waveform RAM 22 based on the output of the multiplying circuit 23 and the horizontal synchronization signal 17, and a row address counter 25 that generates a row address signal of the waveform RAM 22 based on the horizontal synchronization signal 17 and the vertical synchronization signal 18. Digital-analog conversion circuit 2 for converting the data output from waveform RAM 22 into an analog signal
6 is provided.

In this waveform generation circuit, the control circuit 21 converts the waveform data of the correction waveform to be generated in advance into the waveform RA.
It is stored in M22. At this time, for example, the control circuit 2
By applying a write address and write data to the waveform RAM 22 from step 1, two-dimensional waveform data in the horizontal and vertical directions is written. The waveform data is obtained by previously measuring distortion characteristics of a cathode ray tube to be used in a state where no correction is performed, and calculating a correction waveform that can cancel the distortion. That is, in accordance with the characteristics of the cathode ray tube (especially, the curvature of the inner wall of the tube surface and the characteristics of the deflection yoke) and the like, waveform data that can obtain an optimum correction result at each position of horizontal scanning and vertical scanning on the display screen is obtained and adopted. .

The horizontal synchronizing signal 17 is input to a multiplying circuit 23 and also to a reset input of a column address counter 24. The multiplication circuit 23 multiplies the horizontal synchronization signal 17 to generate a clock for the column address counter 24,
Input to clock input. The multiplier circuit 23 can be realized by a combination of a general phase lock loop (PLL) and a counter. The column address counter 24 stores the column address (R) of the waveform RAM 22 synchronized with the horizontal synchronization signal 17.
AM address). That is, the column address counter 24 is reset for each horizontal scanning period (1H period) of the horizontal synchronizing signal 17, and a column address sequentially added for each clock output from the multiplying circuit 23 is generated and input to the waveform RAM 22. Is done.

The horizontal synchronizing signal 17 is input to a clock input as a clock of a row address counter 25,
The vertical synchronization signal 18 is input to a reset input of the row address counter 25. The row address counter 25 outputs a waveform R synchronized with both the horizontal synchronizing signal 17 and the vertical synchronizing signal 18.
A row address (lower RAM address) of AM22 is generated. That is, one vertical scanning period (1
The row address counter 25 is reset every V period), and a row address sequentially added for each clock by the horizontal synchronization signal 17 is generated and input to the waveform RAM 22.

The multiplying circuit 23, column address counter 2
4. An output control means is constituted by the row address counter 25. By giving these column address and row address to the waveform RAM 22 as read addresses, the waveform RA
Digital waveform data corresponding to the correction waveform is sequentially output to the data output of M22 in a time-division manner at a timing synchronized with the horizontal synchronization signal 17 and the vertical synchronization signal 18. By converting this waveform data into an analog signal by the digital-analog conversion circuit 26, a predetermined corrected waveform signal can be obtained.

FIG. 3 shows an example of a correction current used in the horizontal linearity correction circuit of the present embodiment. FIG.
(A) is a horizontal correction current (horizontal rate correction current)
FIG. 3B shows a vertical correction current (vertical rate correction current). The correction current has a waveform shape as shown in FIG. 3 and the magnitude is appropriately changed at the horizontal position and the vertical position so that appropriate correction is always performed. Waveform data corresponding to the correction current is set in the waveform generation circuit 15.

By applying a correction current as shown in FIG. 3 to the horizontal deflection coil 11 via the transformer 14, the horizontal linearity is arbitrarily and locally corrected. That is, while performing the S-shaped correction in the horizontal direction, the correction amount is appropriately changed at the horizontal position (to be small at the center, the right end, and the left end, and to be large at the middle thereof).
M-shaped distortion generated in a flat cathode ray tube or the like is corrected.
In the vertical direction, the correction amount of the inner pin distortion is appropriately changed according to the vertical position (large in the center portion, upper end portion,
By making it smaller at the lower end), the inner pin distortion is appropriately corrected, and a straight display screen without distortion in the vertical direction can be obtained.

FIG. 4 shows an example of correcting the inner pin distortion in this embodiment. For the inner pin distortion having the maximum distortion amount D (for example, 1.5 mm) at the center as shown in FIG. 4A, the distortion is completely removed by using the correction current as described above. As shown in (B), a display screen on which the optimum correction has been made is obtained.

As described above, according to the present embodiment, the distortion characteristic of the cathode ray tube is adaptively corrected, and the local horizontal linearity, which has been difficult in the related art, can be corrected. As a result, even for complicated horizontal linearity distortions such as M-shaped distortion and inner pin distortion caused by the difference between the center of the inner wall curvature of the tube face and the deflection center of the magnetic field generated by the deflection coil, the accuracy can be improved over the entire screen. High correction can be performed, and a high-quality display screen without distortion can be obtained. In addition, since a saturable reactor having nonlinear characteristics, which has been conventionally used for correcting inner pin distortion, can be eliminated, it is possible to prevent local distortion on a display screen and a decrease in efficiency of horizontal deflection, thereby reducing power consumption. A small number of correction circuits can be configured.

[Second Embodiment] FIG. 5 is a block diagram showing a configuration of a horizontal linearity correction circuit according to a second embodiment of the present invention. The second embodiment has a configuration in which a switch circuit 31 for turning on and off a correction current is provided at an output stage of the waveform generation circuit 15 and the current amplifier 16. Other parts are the same as those of the first embodiment, and the same components are denoted by the same reference numerals and description thereof will be omitted.

In the second embodiment, the switch circuit 31 corresponding to the switch means is turned off in the horizontal retrace period, or in the entire period of the horizontal retrace period and the vertical retrace period, or in a predetermined phase position during these periods. Then, the primary winding 14a side of the transformer 14 is opened. The switching control of the switch circuit 31 is performed by a blanking circuit generally provided in a display device for processing and controlling a video signal, a microcomputer used in the above-described waveform generation circuit, or a DS or the like.
On / off by a switching signal using a synchronizing signal (preferably a blanking signal) generated in a built-in circuit of the display device, such as a control circuit constituted by P, a drive processor for generating a horizontal scanning drive signal, and the like. Should be performed.

FIG. 6 is a time chart showing an example of the switching operation of the switch circuit. In the present embodiment, for example, during a horizontal flyback period in which a flyback pulse is generated, the switching signal is turned off to turn off the switch circuit 31, and the primary winding 14a of the transformer 14 is opened so that the correction current is not output. I do. Thus, even if the flyback pulse generated during the horizontal retrace period in the transformer 14 is excited on the primary winding 14a side, the current amplifier 1
6 can be prevented from being applied with a voltage. In addition,
Switch circuit 3 in both horizontal retrace period and vertical retrace period
When 1 is turned off, the switching control may be performed in the same manner as in the case of only the horizontal flyback period.

When a flyback pulse is generated during the horizontal retrace period and excited on the primary winding 14a side of the transformer 14, an electromotive force by excitation is applied to the current amplifier 16 connected in series to the primary winding 14a. Current amplifier 1
6 increases. In order to prevent this, the primary amplifier 14a side of the transformer 14 is opened so that the current amplifier 16 does not become a load of the horizontal deflection circuit 13 during the horizontal retrace period. 1
It is possible to reduce the circuit power consumption in both the current amplifier 3 and the load-side current amplifier 16.

As described above, in the second embodiment, similar to the first embodiment, local horizontal linearity can be adaptively corrected for the distortion characteristics of the cathode ray tube, and the M-shaped distortion and the inner pin distortion can be corrected. In addition to the effect of being able to perform high-precision correction even for complicated horizontal linearity distortions, such as by opening the primary side of the transformer during the horizontal retrace period using a switch circuit, the power consumption of the circuit can be reduced. Therefore, an effect of realizing a low power consumption correction circuit can be obtained.

The horizontal linearity correction circuit according to the present invention is particularly effective and preferable when used in a display device having a flat cathode ray tube in which large M-shaped distortion and inner pin distortion occur. Even when the present invention is applied to a curved cathode ray tube, highly accurate correction can be similarly performed, and the present invention can be applied to any cathode ray tube display device.

[0039]

As described above, according to the present invention, M-shaped distortion and inner pin distortion in a cathode ray tube can be accurately corrected over the entire screen, and a high-quality display screen without distortion can be obtained. There is a possible effect.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a horizontal linearity correction circuit according to a first embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration example of a waveform generation circuit according to the embodiment;

FIG. 3 is a waveform chart showing an example of a correction current used in the horizontal linearity correction circuit of the present embodiment.

FIG. 4 is an operation explanatory view showing an example of correcting inner pin distortion in the present embodiment.

FIG. 5 is a block diagram illustrating a configuration of a horizontal linearity correction circuit according to a second embodiment of the present invention.

FIG. 6 is a time chart illustrating an example of a switching operation of a switch circuit according to the second embodiment.

FIG. 7 is a block diagram illustrating a configuration example of a conventional horizontal linearity correction circuit.

FIG. 8 is an explanatory diagram showing M-shaped distortion generated in a cathode ray tube.

FIG. 9 is an explanatory diagram showing inner pin distortion generated in a cathode ray tube.

[Explanation of symbols]

 Reference Signs List 11 horizontal deflection coil 12 capacitor 13 horizontal deflection circuit 14 transformer 14a primary winding 14b secondary winding 15 waveform generation circuit 16 current amplifier 17 horizontal synchronization signal 18 vertical synchronization signal 21 control circuit 22 waveform RAM 23 multiplier circuit 24 column address counter 25 Row address counter 26 Digital-analog conversion circuit 31 Switch circuit

Claims (5)

[Claims] 1. A horizontal deflection circuit connected to a horizontal deflection coil for generating a horizontal deflection current for a cathode ray tube, a primary winding and a secondary winding, and a secondary winding side is connected to the horizontal deflection coil. A transformer provided on the primary winding side of the transformer, in synchronization with a vertical synchronization signal and a horizontal synchronization signal input to the cathode ray tube,
A dynamic horizontal linearity correction circuit comprising: a correction waveform generation unit that outputs a correction waveform for correcting the linearity of horizontal deflection so as to cancel the distortion according to the distortion characteristic of the cathode ray tube. 2. An output stage of the correction waveform generating means, wherein a predetermined phase position of the cathode ray tube in a horizontal retrace period, or a horizontal retrace period and a vertical retrace period, is set between the correction waveform generator and the transformer. 2. The dynamic horizontal linearity correction circuit according to claim 1, further comprising switch means for opening the primary winding. 3. A horizontal deflection circuit connected to a horizontal deflection coil for generating a horizontal deflection current for the cathode ray tube; and a distortion of the cathode ray tube synchronized with a vertical synchronization signal and a horizontal synchronization signal input to the cathode ray tube. Correction waveform generating means for outputting a correction waveform for correcting the linearity of horizontal deflection so as to cancel the distortion according to the characteristic; and connecting the correction waveform generating means, the horizontal deflection coil and the horizontal deflection circuit in an insulated state. And a correction current supply means for supplying a correction current based on the correction waveform to the horizontal deflection coil. 4. A correction waveform generating means, comprising: storage means for storing correction data set in advance according to a distortion characteristic of the cathode ray tube; and correction data at a predetermined timing synchronized with the vertical synchronizing signal and the horizontal synchronizing signal. 4. The dynamic horizontal linearity correction circuit according to claim 1, further comprising: an output control unit that reads out the data. 5. The correction waveform generating means corrects an M-shaped distortion as the correction waveform by changing a correction amount at a horizontal position to be small at a center portion, a right end portion, and a left end portion, and to be large at a middle portion thereof. 4. The dynamic horizontal linearity correction according to claim 1, wherein a correction waveform signal for correcting an inner pin distortion is output by changing the correction amount at the vertical position so as to be large at the central portion and small at the upper and lower ends. circuit.