JPH10145631A - Horizontal linearity corrector for television receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the generation of distortion at the joint part of right and left pictures when simultaneously displaying two pictures by switching the frequency of a resonance current composed of an S curve correction capacitor and a serial resonance circuit means. SOLUTION: When displaying one picture on a cathode-ray tube(CRT), a switching transistor 14 is turned to non-conducted state and M-shaped distortion is corrected by superimposing the resonance current (2fH) of double horizontal synchronizing frequency fH onto sawtooth wave currents flowing through deflection coils 54 and 55 while using a an S curve correction capacitor 56, inductances 11 and 12 and capacitor 13 of a serial resonance circuit provided parallelly with this capacitor 56. When displaying two pictures on the CRT, the switching transistor 14 is turned to conducted state, the inductance 12 is bypassed and the resonance current (4fH) of four-times horizontal synchronizing frequency fH is superimposed on sawtooth wave currents flowing through the deflection coils 54 and 55 by the S curve correcting capacitor 56, inductance 11 and capacitor 13 of the serial resonance circuit provided parallelly with this capacitor 56.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the correction of horizontal deflection linearity (linearity) in a television receiver, and more particularly, to the horizontal adjustment of a television receiver effective for reproducing and displaying two different images on the same cathode ray tube. This is a linearity correction device.

[0002]

2. Description of the Related Art Recently, television receivers have become larger and wider screens, and have been used not only for reproducing images but also for receiving various kinds of information using characters and figures. It is also used as a device for reproducing a plurality of different videos or information.

[0003] In such a television receiver, a screen displayed by a CRT for reproducing and displaying video or information is as follows.
It is necessary to faithfully reproduce signals on the video and information transmission side. In particular, due to the enlargement and widening of the screen, the distance from the electron gun of the cathode ray tube to the phosphor screen differs between the central part and the peripheral part of the screen, and the screen reproduced by the enlargement of the deflection angle of the electron beam. In particular, when the electron beam is deflected in the horizontal direction, the screen is significantly distorted, and various correction means are implemented to eliminate the distortion.

As an example of the correction means, a horizontal deflection linearity correction circuit as shown in FIG. 4 is used.
In the drawing, a damper diode 52, a capacitor 53, and a series circuit of horizontal deflection coils 54 and 55 and an S-shaped correction capacitor 56 are connected in parallel between the collector electrode and the emitter electrode of the horizontal output transistor 51. A square wave voltage synchronized with a horizontal synchronizing signal 15.75 KHz (hereinafter referred to as fH) generated from a television signal receiving and reproducing unit (not shown) is applied to a base electrode of the horizontal output transistor 51. Horizontal output transistor 5
When the square-wave voltage is applied to one base electrode, a conduction state occurs and a collector current flows. However, a deflection coil 5 having a large inductance is applied to the load of the collector electrode.
Due to the connection of 4, 55, this collector current does not increase rapidly, but produces a positive half cycle of the sawtooth current which increases linearly with time. When the square-wave voltage is not applied to the base electrode of the horizontal output transistor 51, the collector current stops flowing, a negative voltage is generated by the resonance between the inductances of the deflection coils 54 and 55 and the parallel capacitor 53, and the damper diode 52 becomes conductive. In this state, a negative half cycle of the sawtooth current is generated, and a sawtooth current of fH flows through the deflection coils 54 and 55 for horizontal deflection, and scans and deflects the electron beam in the horizontal direction.

At this time, as described above, since the distance from the electron to the phosphor screen is different between the left and right peripheral portions and the central portion of the screen, the electronic components are not located at the central portion and the peripheral portion of the screen. Since the distortion due to the difference in the arrival time of the beam is generated and the linearity of the horizontal plane of the screen is impaired, the S-shaped correction capacitor 56 connected in series to the deflection coils 54 and 55 applies an S-shaped In addition, the linearity is corrected by accelerating the electron beam in the left and right peripheral portions of the screen.

However, as the screen of the television receiver becomes larger and wider, the deflection angle of the electron beam also becomes larger. With the S-shaped correction condenser 56 alone, the start and end of the electron beam scanning are required. Shrinking M-shaped distortion occurs on the screen. In order to eliminate the M-shaped distortion, a series resonance circuit of an inductance 57 and a capacitor 58 is added in parallel with the S-shaped correction capacitor 56,
A resonance current of about twice (2fH) the horizontal synchronization frequency fH is generated and superimposed on the sawtooth wave current to correct the M-type distortion.

In a television receiver having such a linearity correction means, when two screens are displayed on the screen of a cathode ray tube, the right portion of the screen displayed on the left side shrinks as shown in FIG. The left part of the displayed screen shrinks, that is, distortion occurs at the joint between the left and right screens at the center of the CRT. That is, as shown in FIG.
A video signal displayed on the left side of the CRT screen by superimposing a 2fH S-shaped correction resonance current (thin solid line waveform) on a sawtooth wave current (thick solid line waveform) which is a horizontal deflection current flowing through the horizontal deflection coils 54 and 55. Is scanned in the first half of the sawtooth current, and the video signal displayed on the right side is scanned in the second half of the sawtooth current. The scanning speed of the electron beam is accelerated in the central portion of the screen of the cathode ray tube, and FIG. As shown in FIG. 5, distortion occurs at the joint portion between the left and right images at the center of the screen, and the linearity characteristic becomes non-uniform as shown in FIG.

As a cause of the distortion due to the non-uniformity of the linearity characteristic, as shown in FIG. 6, the distance from the electron gun in the cathode ray tube to the fluorescent screen (display tube surface) is the peripheral portion of the screen and the central portion. There are differences between the two. That is, the distance from the electron gun, which is the source of the electron beam, to the center of the CRT display surface is short, and the distance from the electron gun to the left and right peripheral portions of the screen is long. Therefore, even when the electron beam is deflected at the same angle α in the central portion and the peripheral portion of the screen, the scanning distances L1 and L3 on the left and right sides of the display surface are equal, but the scanning distance L2 on the central portion of the display surface is , L1 and L3. In other words, L1 = L3> L2, and the screen at the center of the display surface becomes a screen that shrinks in the horizontal direction.

When a video signal is reproduced in a state where the above-mentioned screen distortion occurs, the image of the central portion of the cathode ray tube becomes unnatural, and when a character or a figure is displayed on one of the screens. There are problems such as difficulty reading character figures.

[0010]

When two screens are simultaneously displayed using a conventional large screen or a wide screen, distortion occurs at the joint between the left and right screens at the center of the display screen, and the linearity characteristic of the horizontal deflection is reduced. There is a problem that the screen becomes uneven.

[0011]

SUMMARY OF THE INVENTION The present invention relates to a series resonance circuit comprising an inductance and a capacitor provided in parallel with an S-shaped correction capacitor connected in series with a horizontal deflection coil constituting a horizontal deflection circuit means of a television receiver. Means, and switching switch means for switching the impedance of the series resonance circuit means. The frequency of the resonance current formed by the S-shaped capacitor and the series resonance circuit means is switched by the changeover switch means, and two screens are displayed on the cathode ray tube. This is a horizontal linearity correction device for a television receiver that corrects the horizontal linearity of two screens displayed on the left and right by causing a resonance current having a resonance frequency twice as high as that when displaying one screen to flow.

[0012]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a circuit configuration diagram showing an embodiment of a horizontal deflection linearity correction apparatus according to the present invention, and the same parts as those in FIG. 4 are denoted by the same reference numerals.

The difference between the present invention and the conventional horizontal deflection linearity correction device lies in the series resonance circuit connected in parallel to the S-shaped correction capacitor 56. The direct resonance circuit of the present invention has the inductances 11, 12 and A collector 13 and an emitter electrode of a switching transistor 14 are connected to both ends of the inductance 12, and a switching signal is supplied to a base electrode. The value of each circuit element of the series resonance circuit composed of the inductances 11 and 12 and the capacitor 13 is a value having a relationship of Expression 1 when the switching transistor 14 is non-conductive and a value of Expression 2 when the switching transistor 14 is conductive. Set.

[0014]

(Equation 1)

(Equation 2) Where fH is the horizontal frequency and L11 is the inductance 1
The value of 1, L12 is the value of the inductance 12, and C13 is the value of the capacitor 13.

When displaying one screen on the cathode ray tube, the switching transistor 14 is turned off,
S-shaped correction capacitor 56 and S-shaped correction capacitor 5
6, an inductance of a series resonance circuit provided in parallel with 6,
12 and the capacitor 13 superimpose twice the resonance current of fH (2fH) on the saw-tooth wave current flowing through the deflection coils 54 and 55 to correct the M-type distortion. Next, when two screens are displayed on the cathode ray tube, the switching transistor 14 is turned on, the inductance 12 is bypassed, an S-shaped correction capacitor 56, and a series resonance circuit provided in parallel with the S-shaped correction capacitor 56. With the inductance 11 and the capacitor 13, the resonance current of four times fH (4fH) is superimposed on the sawtooth current flowing through the deflection coils 54 and 55.

When displaying such two screens,
As shown in FIG. 2A, the resonance current of 4 fH is superimposed during the scanning period of the sawtooth current for horizontal deflection, and a screen without distortion can be displayed on the left and right screens as shown in FIG. 2B. In addition, as shown in FIG. 2C, the linearity characteristics can be made uniform. Generally, a television receiver capable of displaying this type of two screens is provided with a display screen switching mode switch, and the mode switch can be used to selectively switch the display screen to one screen or two screens. Since the operating voltage applied to the base electrode of the switching transistor 14 is switched in conjunction with the mode switch, the switching of the switching transistor 14 between conduction and non-conduction can be easily realized.

Next, another embodiment of the present invention will be described with reference to the horizontal deflection circuit configuration diagram of FIG. FIG.
4 and 4 are denoted by the same reference numerals. The series resonance circuit connected in parallel to the S-shaped correction capacitor 56 includes the inductance 21 and the capacitors 22 and 23, and the switching transistor 14 is provided at both ends of the capacitor 23.
Are connected to a collector electrode and an emitter electrode, and a switch signal is applied to the base electrode in the same manner as in FIG. The inductance 21 and the capacitor 22,
The value of each circuit element of the series resonance circuit 23 has the relationship of Equation 3 when the switching transistor 14 is on, and Equation 4 when the switching transistor 14 is off.
Is set to a value having the relationship

[0018]

(Equation 3)

(Equation 4) Where fH is the horizontal frequency and L21 is the inductance 2
The value of 1, C22 is the value of the capacitor 22, and C23 is the value of the capacitor 23.

When one screen is displayed on the cathode ray tube, the switching transistor 14 is turned on, the capacitor 23 is bypassed, the S-shaped correction capacitor 56, and the series resonance capacitor provided in parallel with the S-shaped correction capacitor 56 are provided. Double the fH with the circuit inductance 21 and capacitor 22
The (2fH) resonance current is superimposed on the sawtooth current flowing in the deflection coils 54 and 55 to correct the M-type distortion. Next, when two screens are displayed on the cathode ray tube, the switching transistor 24 is turned off, the S-shaped correction capacitor 56, and the inductance 21 and the capacitor 22 of the series resonance circuit provided in parallel with the S-shaped correction capacitor 56. ,
23, the resonance current of 4 times fH (4fH) is applied to the deflection coil 5
The linearity correction in the case where the two screens are displayed as described with reference to FIG. Note that the switch signal applied to the base electrode of the switching transistor 14 performs the reverse operation of the case of FIG. In this case, the switching transistor 14 is turned off.

As described above, according to the present invention, in a television receiver capable of displaying one screen or two screens, a series resonance circuit including an inductance and a capacitor is formed in parallel with an S-shaped correction capacitor, and the resonance frequency is reduced. Switching between single-screen display and dual-screen display. In dual-screen display, a resonance current having a resonance frequency approximately twice that of the single-screen display is generated, and the resonance current is deflected by a horizontal deflection coil. By superimposing the current on the sawtooth wave current, the horizontal linearity characteristics of the left and right screens can be improved, and the distortion of the junction between the left and right screens at the center of the CRT display surface can be eliminated.

[0021]

According to the present invention, when the resonance current of the series resonance circuit composed of the inductance and the capacitor connected in parallel with the S-shaped correction capacitor is displayed on two screens, the resonance current is reduced to about twice the one-screen display character. By switching, the horizontal scanning linearity of the central part of the cathode ray tube can be improved, the distortion of the central part of the screen can be eliminated, and the screen faithful to the signal transmitted can be reproduced. Further, even when an information signal such as a character or a figure is displayed, it is possible to perform a clear display without distortion of the character or figure.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of a horizontal deflection linearity correction device according to the present invention.

FIGS. 2A and 2B are waveform diagrams showing an operation state of the present invention and a display screen state, wherein FIG. 2A is a waveform diagram of a horizontal scanning sawtooth wave current, and FIG. 2B is a plan view showing a screen display state; And (c)
7 is a characteristic diagram showing characteristics of linearity.

FIG. 3 is a circuit configuration diagram showing another embodiment of the horizontal linearity correction device according to the present invention.

FIG. 4 is a circuit diagram showing a conventional horizontal deflection linearity correction device.

5A and 5B show waveforms indicating an operation state of a conventional horizontal deflection linearity correction device and a display screen state, and FIG.
FIG. 3B is a waveform diagram of a horizontal scanning sawtooth wave current, FIG. 3B is a plan view showing a display state of a screen, and FIG. 3C is a characteristic diagram showing characteristics of linearity.

FIG. 6 is a plan view showing a relationship between an electron gun of a cathode ray tube and a display surface.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 ... Inductance, 12, 13 ... Capacitor 14 ... Switching transistor 51 ... Horizontal output transistor 52 ... Damper diode 53 ... Parallel capacitor 54, 55 ... Horizontal deflection coil 56 ... S-shaped correction capacitor

Claims (4)

[Claims] 1. A television receiver capable of displaying two screens on the same cathode ray tube, wherein a damper diode, a capacitor, and an S-shaped capacitor connected in series with a horizontal deflection coil are connected in parallel between a collector electrode and an emitter electrode of a horizontal output transistor. Horizontal deflection circuit means provided, series resonance circuit means comprising an inductance and a capacitor provided in parallel with the S-shaped capacitor, and changeover switch means for switching the impedance of the series resonance circuit means. The resonance frequency of the resonance current formed by the resonance circuit means is switched by the changeover switch means, and when displaying two screens on the cathode ray tube, a resonance current having a resonance frequency twice as high as when displaying one screen is caused to flow. TV that compensates for horizontal linearity Horizontal linearity correction apparatus in an image device. 2. The series resonance circuit means comprises two inductances and one capacitor, one of the two inductances is short-circuited by the changeover switch means, and is formed by the S-shaped capacitor and the series resonance circuit means. The horizontal linearity correction device for a television receiver according to claim 1, wherein the resonance frequency to be switched is switched. 3. The series resonance circuit means comprises one inductance and two capacitors, one of the two capacitors is short-circuited by the changeover switch means, and is formed by the S-shaped capacitor and the series resonance circuit means. The horizontal linearity correction device for a television receiver according to claim 1, wherein the resonance frequency to be switched is switched. 4. The horizontal linearity correction device for a television receiver according to claim 1, wherein said changeover switch means is changed over in accordance with a screen mode displayed on said cathode ray tube.