JPH0560037U - Horizontal linearity correction circuit for television receiver - Google Patents

Abstract

(57) [Abstract] [Purpose] With a simple circuit configuration, the conventional horizontal linearity defect of shrinking at both ends and the center of the screen and extending at other parts is corrected, and even if the horizontal deflection frequency changes. The change in the correction amount is relatively small. [Structure] A saturable reactor with a direct current bias applied to the core of a coil by a permanent magnet, with different direct current superposition characteristics
It is characterized in that two or more a, 3b) connected in series are connected in series to the horizontal deflection coil 2. As a result, the conventional series resonance circuit for horizontal linearity correction is not required, the circuit configuration is simple, and the resonance circuit is not used, the frequency dependence of the correction amount is extremely small.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a horizontal linearity correction circuit of a television receiver for correcting horizontal screen distortion on a screen.

[0002]

[Prior Art]

 In the horizontal deflection circuit of a television receiver, there are mainly two types of factors that deteriorate the linearity. One is the contraction of the central part on the screen of the cathode ray tube caused by the difference between the center of curvature and the center of deflection of the phosphor screen, the extension at both ends, and the other is the series resistance of the circuit causing the deflection current to become a saturation curve instead of being a straight line Because of this, the left stretches and the right shrinks.

In the former, the series resonance current of the horizontal deflection coil and the horizontal linearity correction capacitor connected in series to the horizontal deflection coil is superimposed on the sawtooth wave current, and the deflection current is bent into an S-shape for correction.

The latter is connected to a horizontal deflection coil in series with a saturable reactor biased with a DC magnetic field, and the fact that the self-inductance changes depending on the degree of saturation at each point of the deflection current flowing through this is used for scanning. The deflection current is made small at the beginning of and corrected at the end.

FIG. 3 is a known horizontal linearity correction circuit for a television receiver. Reference numeral 1 is a horizontal output transistor, whose base is supplied with a horizontal drive pulse (not shown), and the emitter is at a reference potential point. Connected. Between the collector of the horizontal output transistor 1 and the reference potential point, a horizontal deflection coil 2, a saturable reactor 3 for horizontal linearity correction, and a horizontal linearity correction capacitor (hereinafter referred to as an S-shaped correction capacitor) 4 are provided. It is connected in series. Here, the saturable reactor 3 has a structure in which a direct current bias is applied to a coil core by a permanent magnet as shown in FIG. 4 (a), and its operation characteristics are as shown in FIG. 4 (b). ing. In Fig. 4 (b), the horizontal axis represents the coil current, and the vertical axis represents the coil inductance. The coil is given a direct current bias (center value of inductance change) according to the magnetic field of the permanent magnet. If a horizontal deflection current is applied to the coil and the deflection current flows from the top to the bottom of the deflection coil 2 in FIG. The inductance is large, and the inductance of the coil is small when the deflection current is flowing from the bottom to the top of the deflection coil 2 (forward direction) near the end of scanning.

When a saw-tooth wave current is passed through the horizontal deflection coil 2 of the above circuit, the deflection current is decreased at the beginning of scanning and increased at the end of scanning due to the change in the inductance of the saturable reactor 3, and the left side is increased. It stretches and corrects the contraction on the right.

Further, due to the DC resonance current of the horizontal deflection coil 2 and the S-shaped correction capacitor 4, a parabolic voltage is generated in the S-shaped correction capacitor 4, which modulates the sawtooth wave current, So-called S-shaped correction is performed to correct the contraction at the center and the elongation at both ends.

By the way, according to the S-shaped correction method as described above, as the correction amount is increased, the rising and falling edges of the correction waveform only become sharp, and the correction amount increases near the center of the screen. Even if it was done, the slope did not become steep, so there was a drawback that only the left and right extremes on the screen were extremely shrunk, and the shrinkage was still near the center of the screen.

As a means for solving this drawback, Japanese Patent Publication No. 51-19730 proposes a horizontal linearity correction circuit as shown in FIG.

The circuit of FIG. 5 is provided with a series resonance circuit composed of a coil 5 and a capacitor 6 in parallel with the S-shaped correction capacitor 4 of the horizontal linearity correction circuit shown in FIG. 3, one end of which is saturable. It is connected to the connection point between the reactor 3 and the S-shaped correction capacitor 4, and the other end is connected to the reference potential point. The resonance frequency of the series resonance circuit (5, 6) is selected to be about three times the horizontal deflection frequency. With such a configuration, the correction waveform is further superimposed on the parabolic voltage generated in the S-shaped correction capacitor 4 to improve the linearity.

By the way, the resonance frequency of the series resonance circuit in FIG. 5 does not necessarily need to be selected to be about three times the horizontal deflection frequency, and in order to improve the S-shaped correction, it is rather twice the horizontal deflection frequency. The ingredients are considered important.

This will be described with reference to FIG. In FIG. 6, the horizontal axis represents time and the vertical axis represents normalized voltage. Curve A is a sine wave curve having a period from time a to time e, and curve B is a sine wave curve having a period half the time from time a to time e. That is, the curve B is a sinusoidal curve having a frequency twice that of the curve A. Curve C is a parabolic curve that is a combination of curve A and curve B.

Here, in the horizontal linearity correction circuit described in FIG. 3, it is considered that the parabola voltage generated in the S-shaped correction capacitor 4 can be approximated by the curve C. The sinusoidal waveform of curve A is similar to the parabolic waveform shown in curve C, which is similar to the waveform in which the voltage at the portion (corresponding to times b and d) corresponding to the approximate center between the center and the end of the CRT screen is reduced. ing. Therefore, in order to correct the above-mentioned defect that only the left and right ends are extremely shrunk and still shrink near the center of the screen, for example, a low voltage is applied at both times b and d in FIG. It is considered that a different waveform, that is, a waveform similar to the curve A is required. That is, by obtaining the curve B by the series resonance circuit (5, 6), it is possible to obtain an ideal correction waveform (curve A). Therefore, the resonance frequency of the series resonance circuit may be set to twice the horizontal deflection frequency.

However, in FIG. 5, the resonance frequency of the coil 5 and the capacitor 6 cannot be selected to be twice the horizontal deflection frequency. This is because the voltage generated in the S-shaped correction capacitor 4 in FIG. 3 and the current flowing in the horizontal deflection coil 2 are 90 ° out of phase with each other. If a resonance circuit with a resonance frequency that is twice the horizontal deflection frequency is connected, the current and voltage will be in phase in the resonance state, so there will be a 90 ° phase shift with respect to the originally required correction waveform. This is a correction.

For this reason, the resonance frequency of the resonance circuit composed of the coil 5 and the capacitor 6 is deviated from the component of twice the horizontal deflection frequency, that is, the absolute value of impedance at resonance becomes small to some extent. , It is necessary to select an appropriate value so that the phase shift due to resonance rarely occurs. Therefore, conventionally, the resonance frequency is set to the horizontal deflection frequency of 2. It was general to select from 2 to 3 times.

However, there are some recent wide-angle deflection type cathode ray tubes that require a considerably large amount of correction by the resonance circuit. In order to increase the correction amount, the capacitance of the capacitor 6 with respect to the S-shaped correction capacitor 4 may be increased, but it is also an effective means to bring the resonance frequency close to twice the horizontal deflection frequency to some extent.

Here, when the resonance frequency is close to twice the horizontal deflection frequency, not only the value of the resonance current greatly changes due to a slight change in the circuit constant, but also if the horizontal frequency is changed due to some reason, When the deflection frequency fluctuates and the frequency component that is twice the horizontal deflection frequency approaches the resonance frequency of the resonance circuit, the resonance current becomes extremely large compared to that during normal operation.

As a case where such an inconvenience occurs, it can be considered that a signal different from the standard is input to a display monitor or the like. For example, it is assumed that the resonance circuit is used in a display monitor having a horizontal deflection frequency of 31.5 KHz and the resonance frequency is set to 67.725 KHz, which is 2.15 times the horizontal deflection frequency. If a signal with a horizontal deflection frequency of 33.75 KHz is erroneously input to this display monitor, there will be no problem if the horizontal deflection circuit pull-in frequency range is narrow enough and it cannot be synchronized with the input signal. If the circuit has a wide pull-in frequency range and operates at a horizontal deflection frequency of 33.75 KHz in synchronization with the input signal, then the resonance frequency becomes almost twice the horizontal deflection frequency and the resonance current becomes extremely large. ..

By the way, in recent display monitors, what is called a free scan type capable of receiving signals of all deflection frequencies within a specified range is sold. In such a free-scan display monitor, prepare several sets of horizontal linearity correction elements such as a S-shaped correction capacitor and a saturable reactor for horizontal linearity correction, or connect them in series with the basic element. Alternatively, it is general that elements to be inserted in parallel are prepared and used by appropriately switching them according to the horizontal deflection frequency.

In such a configuration, one type of combination of horizontal linearity correction elements is not optimized for a particular input signal, but for a range of horizontal deflection frequency signals. It is necessary to set so that almost proper horizontal linearity correction can be obtained.

However, when the horizontal linearity correction by the resonance circuit is applied to the free scan type display monitor, the following problems occur. Now, in FIG. 5, when the values of the coil 5 and the capacitor 6 which give the optimum horizontal linearity correction for a certain horizontal deflection frequency are given, it is possible to give an almost proper correction by these circuit constants. It is possible only when the deflection frequency that actually operates is within a very narrow range centered on the given frequency. For this reason, it is possible to prepare an extremely large number of switching elements and switch the constants for a slight difference in deflection frequency, but this circuit is a part that handles a relatively large current, so it is large. A current element is required, which causes a significant cost increase.

Here, it is conceivable that the image standards that can be received by the free scan display monitor are limited to, for example, about 3 to 4, and switching is performed so as to obtain the optimum correction for each signal standard. However, this is undesired because it significantly impairs the commercial characteristics of the free scan display monitor that can receive signals of all standards.

Further, as in many free-scan display monitors, the horizontal and vertical swings and the screen position can be controlled by the user by the front adjustment knobs or the like. It may be possible to make the correction controllable by the user, but it is difficult and unrealistic for a general user without specialized knowledge to properly adjust such complicated deflection distortion.

Further, even in the case of a display monitor corresponding to only two relatively close horizontal deflection frequencies such as the horizontal deflection frequencies of 31.5 KHz and 33.75 KHz, when the above resonance circuit is adopted, the circuit based on the horizontal deflection frequency is used. Switching constants becomes essential, which complicates the circuit.

[0025]

[Problems to be solved by the device]

 As described above, in the conventional horizontal linearity correction circuit of a television receiver, a horizontal linearity correction circuit of a type in which a series resonance circuit is connected in parallel with an S-shaped correction capacitor is used to detect signals of a plurality of horizontal deflection frequencies. When it is applied to a television receiver or a display monitor compatible with the above, the circuit constant of the series resonance circuit must be switched for each horizontal deflection frequency of the signal to be received, and the circuit configuration becomes complicated. There was the inconvenience of becoming a cost-up.

The present invention has been made to solve the above-mentioned conventional problems, and has a simple circuit configuration, which has the conventional horizontal linearity of contracting at both ends and the center of the screen and extending at other places. An object of the present invention is to provide a horizontal linearity correction circuit for a television receiver, which corrects a defect and has a relatively small change in the correction amount even if the horizontal deflection frequency of the received signal changes.

[0027]

[Means for Solving the Problems]

 In order to achieve the above object, the present invention is to connect two or more saturable reactors with different DC superposition characteristics connected in series to each other in series to a horizontal deflection coil in series with a horizontal deflection coil. It is characterized by being connected. Here, the combined DC superposition characteristics of this saturable reactor are for correcting the expansion of the left part of the screen and the contraction of the right part of the screen as a whole, and for correcting the contraction of the center part of the screen and the left and right ends of the screen. It is characteristic.

[0028]

[Action]

 According to the configuration of the present invention, the linearity correction by the conventional series resonance circuit is not necessary, and the linearity correction by the saturable reactor of the present invention does not utilize the resonance phenomenon, and therefore the frequency dependence of the correction amount. Is as small as the linearity correction by the conventional saturable reactor.

[0029]

【Example】

 An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing a horizontal linearity correction circuit of a television receiver according to an embodiment of the present invention. The same parts as those in FIG. 3 are designated by the same reference numerals.

In FIG. 1, reference numeral 1 denotes a horizontal output transistor, a horizontal drive pulse (not shown) is supplied to its base, and its emitter is connected to a reference potential point. A horizontal deflection coil 2, a saturable reactor 3a, a saturable reactor 3b, and an S-shaped correction capacitor 4 are connected in series between the collector of the horizontal output transistor 1 and the reference potential point. Here, the saturable reactors 3a and 3b are obtained by applying a direct current bias to the coil core with a permanent magnet, and different DC magnetic fields are applied to the saturable reactors 3a and 3b. Is as shown by the curves 10a and 10b in FIG. 2 (a). In FIG. 2, the horizontal axis represents the current input to the saturable reactor and the vertical axis represents the inductance of the saturable reactor. Here, the time when the horizontal deflection coil 2 in FIG.

With such a configuration, the combined DC superposition characteristic of the saturable reactors 3a and 3b is as shown by the curve 11 in FIG. 2 (b). Here, if we consider the hypothetical characteristic for only correcting the left-right balance, which is the effect of the conventional saturable reactor, as a straight line 12 in Fig. 2 (b), the characteristic of the curve 11 is a straight line. It can be considered as a combination of the characteristics of 12 and the characteristics of the curved line 13 of FIG. Here, the curve 13, which is a component of the curve 11, is a component that expands both ends and the center of the screen and contracts the others, and performs the same correction as the conventional series resonant circuit. There is.

Since this correction action does not utilize the resonance phenomenon, the frequency dependency of the correction amount is extremely small, which is the same level as that of the conventional saturable reactor. Therefore, it is no longer necessary to prepare a large number of switching elements and perform constant switching even for slight differences in deflection frequency, and a television receiver that receives signals at multiple horizontal deflection frequencies. Also, the circuit can be simplified in the display monitor.

Although two saturable reactors are used in the above embodiment, three or more saturable reactors may be used, and a plurality of saturable reactors connected in parallel may be used in plural sets. You may prepare them and connect them in series, or you may connect several sets of those connected in series in parallel, and replace some of these saturable reactors with ordinary coils. ..

Further, linearity correction by the series resonance circuit shown in FIG. 5 may be used in combination with the above embodiment.

Further, S-shaped correction means other than the S-shaped correction capacitor may be used in the circuit of the above embodiment, and instead of the horizontal output transistor 1, a charge effect transistor, an electron tube, or another switching device. Elements may be used.

Although the above embodiments have been described on the assumption of an ordinary television receiver in which horizontal scanning is performed from the left to the right of the screen, a display device in which the direction of horizontal deflection is the opposite direction, or a scanning line is used. The same applies to the vertical deflection circuit of the display device which is oriented in the vertical direction.

[0037]

[Effect of the device]

 As described above, according to the present invention, a plurality of saturable reactors connected in series is used to correct the shrinkage at the left and right edges and the central portion of the screen during horizontal deflection. Even in a television receiver and a display monitor that receive the image, the correction amount has little frequency dependence, and the correction can be performed by a relatively simple circuit.

[Brief description of drawings]

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

FIG. 2 is a diagram showing a DC superposition characteristic of the saturable reactor of FIG.

FIG. 3 is a circuit diagram showing a horizontal linearity correction circuit of a conventional television receiver.

FIG. 4 is a diagram illustrating a saturable reactor in FIG. 3 and horizontal linearity correction using the same.

FIG. 5 is a circuit diagram showing a horizontal linearity correction circuit of another conventional television receiver.

6 is a graph for explaining the circuit operation of FIG.

[Explanation of symbols]

 2 Horizontal deflection coil 3a Saturable reactor 3b Saturable reactor 4 S-correction capacitor

Claims (1)

[Scope of utility model registration request] 1. A horizontal linearity of a television receiver characterized in that a plurality of saturable reactors, which are DC biased with different DC magnetic fields, are connected in series to a horizontal deflection coil. Correction circuit.