JPH0750937B2 - Convergence or beam spot correction circuit - Google Patents

Description

The present invention relates to a convergence or beam spot correction circuit for correcting the beam spot on the screen of a color picture tube.

[Conventional technology]

In a color picture tube, for example, a one-gun, one-electron-lens, three-beam type picture tube, the horizontal static convergence is adjusted by the electrostatic deflection plate, and the fourth portion is provided outside the neck of the electrostatic deflection plate.
For the U-shaped convergence yoke as shown in the figure, 2
The dynamic convergence correction is adjusted by providing a correction coil (11) wound around the yoke and supplying a horizontal period parabolic current (or sine wave current) to the correction coil (11). Further, in an in-line type color picture tube, the shape of the beam spot is distorted due to the use of a vertical barrel type or horizontal pincushion type deflection magnetic field, which lowers the resolution. Similarly, a correction coil (11) provided on the outside of the neck and wound around this
A horizontal parabolic current (or sinusoidal current) is supplied to. The supply of the correction current of the horizontal cycle applied to these correction coils (11) is nothing but the correction amount at the central portion of the screen being zero and the correction amount being increased toward the peripheral portion. By the way, since the correction current of the horizontal period is formed on the basis of the horizontal pulse voltage taken out through the horizontal output transformer, it generally does not include a DC component. Therefore, in the central portion of the screen, the opposite correction is performed to the peripheral portion which is not originally necessary. In the conventional color picture tube which performs horizontal static convergence by the electrostatic deflection plate as described above, for example, this unnecessary correction is canceled by the horizontal static convergence correction. Further, in a color picture tube in which the horizontal static convergence is not adjusted by the electrostatic deflection plate, the variable DC current from the external DC power source is superposed on the current of the horizontal period for correction, so that unnecessary correction that occurs in the above-mentioned central portion is corrected. I was trying to cancel.

According to such a conventional configuration, when the correction amount of the dynamic convergence or beam spot correction in the peripheral portion of the screen is adjusted, it is necessary to readjust the horizontal static convergence etc. so that the correction amount becomes zero in the central portion of the screen each time. The adjustment operation was complicated.

Therefore, even if the correction amount in the peripheral portion of the screen is changed, the correction amount in the central portion of the screen is not changed, and as shown in FIG. 59-7270).

That is, in FIG. 5, (1) is a horizontal output transformer provided in, for example, a horizontal deflection circuit, and its secondary winding (2)
On the high potential side (point A), a negative-polarity pulse voltage having a horizontal period as shown in FIG. 6A is generated. The high potential side of the secondary winding (2) is connected to an integrator circuit in which a coil (3), a capacitor (4) and a series circuit of a variable resistor (5) are connected in parallel, and the output (B The sawtooth voltage shown in FIG. 6B is generated at the point). This sawtooth voltage is supplied to the base of the npn transistor (6) via a parallel circuit of a capacitor and a resistor, and the transistor (6) is switched by the sawtooth voltage.

The emitter of the transistor (6) is grounded, its collector is connected to the power supply terminal (+ B) via the yoke coil (7) and the variable resistor (8), and the damper diode (9) and A parallel circuit of capacitors (10) is connected. The variable resistor (8) is such that one end of its stator is open and its slider is connected to a power supply terminal (+ B) to which a positive DC voltage is supplied.
The power supply voltage supplied to the circuit is varied by the variable resistor (8). Collector of this transistor (6) (point C)
When the transistor (6) is turned off, the current flowing through the transistor (6) until then through the chain yoke coil (7) flows into the capacitor (10), so that the chain yoke coil (7) and the capacitor (10) are connected. ), A pulse voltage having a wide horizontal period (pulse width of about 30 μs) shown in FIG. 6C, which is determined by the resonance constant, is generated.

Further, (11) indicates a correction coil wound around a yoke for convergence correction, for example. As shown in FIG. 4, two correction yokes are provided in the object in a U shape, and the correction coils are wound around each of them, and the correction coil (11) is a combination of the correction coils of the respective yokes. The correction coil (11) and the first diode (12) form a first series circuit, and the correction coil (11) has a dummy coil (13) and a first diode (12) having substantially the same inductance value. On the other hand, a second diode (14) of opposite polarity constitutes a second series circuit, and the first and second series circuits are connected in parallel, and one end of this parallel circuit is connected to one end of the DC power supply. Is connected to the earth where it is and the other end is a capacitor (15)
Connected to the collector of the transistor (6).
Further, the inductance value of the correction coil (11) or the dummy coil (13) is set sufficiently smaller than that of the chioke coil (7), and the correction coil (11) or the dummy coil (13) and the capacitor (15). It is selected so that the series resonance frequency determined by is approximately equal to the horizontal periodic wave number. Furthermore, when these diodes are cut off between the connection point between the correction coil (11) and the diode (12) and the connection point between the dummy coil (13) and the diode (14), the correction coil (11) or the dummy coil. A capacitor (16) for protecting these diodes against the counter electromotive force generated in (13) is inserted. In this case, capacitors may be connected in parallel between the anode and cathode of diodes (12) and (14), but one diode is always on, so connect one capacitor (16). The diode can be protected just by Since the capacitance value of this capacitor (16) is sufficiently smaller than that of the capacitor (15), the correction coil (11) or the dummy coil (1
It has almost no effect on the resonant operation of 3) and the capacitor (15).

In the configuration of the conventional example described above, since the resonance frequency is approximately the horizontal frequency by supplying the pulse voltage of the horizontal period shown in FIG. 6C to the point C, the sine wave current of the horizontal frequency is applied to the correction coil ( 11) and the dummy coil (13) try to flow. Therefore, the diodes (12) and (14) are alternately turned on, and a sinusoidal current of horizontal frequency flows as a whole, but one dummy coil (13) has a positive direction in D shown in FIG. At this time, as shown in FIG. 6D, a current having a substantially sinusoidal horizontal period having a positive maximum on both sides of the horizontal scanning period and becoming zero at substantially the center thereof flows. When the direction indicated by E in FIG. 5 is positive, the other correction coil (11) has a positive maximum at approximately the center of the horizontal scanning period as shown in FIG. Then, a correction current having a substantially sinusoidal horizontal period flows. 6F shows the collector current waveform of the transistor (6), and the damper current by the damper diode (9) is shown by the broken line in the same figure. The waveforms in FIGS. 6C and 6 are slightly out of phase with respect to the center of the horizontal scanning period, which can be arbitrarily set by setting the resonance constants of the yoke coil (7) and the capacitor (10) as described above. so,
Therefore, it is of course possible to set it so as to coincide with the central portion.

As is clear from the above description, according to this conventional example, the adjustment of the dynamic convergence correction is performed by the tilt (TILT) adjustment by the variable resistor (5) and the amplifier (AMP) adjustment by the variable resistor (8). Above all, since the correction current shown in FIG. 6E is always zero on both sides of the screen, it is not necessary to readjust static convergence correction each time the dynamic convergence correction is adjusted, and the adjustment work is extremely simplified. There is a profit to be made. This also applies to the case where the deflection magnetic field corrects the distortion of the shape of the beam spot. Also, when a variable DC current is superimposed on the correction current by an external DC power source, a loss occurs in the coil for blocking the correction current in the horizontal period required for superimposing, and when the correction amount by the variable DC current is large. Was very inefficient because the voltage or current of the external DC power supply increased. However, according to this conventional example, since it is not necessary to superimpose a direct current on the correction current, the efficiency can be improved. Note that, as in the above-mentioned conventional example, the transistor (6)
If a pulse voltage with a wide pulse width that is close to 1/2 of the horizontal period is used in a switching circuit composed of, etc., the sine of the horizontal frequency will be more It is efficient because it contains many fundamental wave components. Further, it is conceivable to form the correction current and then clamp it so that the values on both sides of the screen become zero, but in this case, since the correction coil is a load, the configuration of such a clamp circuit is very complicated. However, in the example of FIG. 5, since the clamping is performed at the same time when the correction current is formed, such an inconvenience does not occur.

[Problems to be solved by the invention]

However, in the convergence or beam spot correction circuit as shown in FIG. 5, since uniform correction is performed from the upper part to the lower part of the screen of the color picture tube, for example, the upper part, the lower part and the central part of the screen are displayed. In the correction of the beam spots (1) and (2), inconvenience occurs when an optimum correction is attempted. That is, in the screen (17) of a color picture tube, the beam spots are generally distorted horizontally in the upper and lower left and right corners as shown in FIG. 7, and vertically distorted in the center of the center. . At this time, the beam response is reduced and the resolution is degraded as compared with the case where the beam spot is a perfect circle. When this case is corrected by the correction circuit in Fig. 5, it is necessary to change the clamp position of the central part current in the upper and lower parts of the screen, but this conventional correction circuit is uniform from the upper part to the lower part of the screen (17). However, when the central portion is optimally compensated, the upper and lower beam spots are not improved at all or rather deteriorated.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a convergence or beam spot correction circuit capable of making a beam spot substantially a circle over the entire screen.

[Means for solving problems]

In the convergence or beam spot correction circuit according to the present invention, for example, as shown in FIG. 1, a capacitor (1
Connect one end of 5), connect the other end of this capacitor (15) to the series circuit of the correction coil (11) and the diode (12), and connect this series circuit in parallel with the same inductance as this correction coil (11). The dummy coil (13) of the value is connected and the protection capacitor (16) is connected in parallel with the diode (12), and a predetermined vertical cycle is provided at the connection point between the correction coil (11) and the diode (12). The current is made to flow in, and the beam spot is corrected over the entire screen.

[Action]

According to the present invention, a substantially sinusoidal current with a horizontal cycle, which is current clamped, is passed through the correction coil (11), and a predetermined vertical cycle is externally applied to the connection point between the correction coil (11) and the diode (12). Since the current is supplied, the amount of the current clamp can be favorably controlled over the entire screen by a predetermined current having a vertical cycle from the outside, and thus the beam spot can be corrected over the entire screen.

〔Example〕

An embodiment of the convergence or beam spot correction circuit of the present invention will be described below with reference to FIGS. 1, 2 and 3. In FIG. 1, parts corresponding to those in FIG. 5 are designated by the same reference numerals, and detailed description thereof will be omitted.

In this example, the collector of the switching transistor (6) is connected to the power supply terminal + B to which a positive predetermined voltage is supplied via the chioke coil (7), and the collector of this transistor (6) is connected to the capacitor (15). , A convergence or beam spot correction coil (11) and a diode (12) for clamping are grounded through a series circuit, and the connection point of this capacitor (15) and this correction coil (11) is connected to this correction coil (11). It is grounded through a dummy coil (13) having an inductance value equal to the inductance value. A protective capacitor (16) is connected in parallel with the diode (12). In this case, if one of the diodes (12) and (14) in FIG. 5 is provided, for example, if the diode (12) is provided as shown in FIG. 1, the correction coil (11) → diode (12) → dummy coil Since it forms a closed circuit with (13), DC regeneration can be performed.

Reference numeral (18) denotes a vertical cycle current input terminal to which a predetermined current having a vertical cycle V from the outside, for example, a current having a polarity opposite to that of the parabolic current having a vertical cycle V as shown in FIG. 2A is supplied. The current input terminal (18) is connected to the base of the pnp transistor (20) via the capacitor (19), and the phase of this transistor (20) is connected to the bias resistor (2
1) is connected to the power supply terminal + B, and this base is grounded via a resistor (22).
The emitter of (0) is connected to the power supply terminal + B via the resistor (23), and the collector of this transistor (20) is connected via the resistor (24) to the correction coil (11) and diode (12).
Connect to the connection point of. Others are the same as those in FIG.

In this example, when the current supplied to the vertical cycle current input terminal (18) is zero, the correction coil (1
In 1), as shown in FIG. 6E, a correction current having a substantially sinusoidal horizontal period H that has a positive maximum at approximately the center of the horizontal scanning period and becomes zero on both sides thereof flows. Therefore, in FIG. 1, the same operation and effect as in FIG. 5 can be obtained, and further, by the correction current of the vertical cycle V supplied to the vertical cycle current input terminal (18), the correction coil (11) is supplied to the correction coil (11). It is possible to control the amount of the current clamp of the correction current having a horizontal period of a substantially sinusoidal waveform as shown in FIG. 6E, which allows the beam spot to be corrected over the entire surface of the screen (17) of the color picture tube.

For example, as shown in Fig. 7, the screen of this color picture tube (17)
When correcting the beam spot of the screen where the upper and lower left and right corners are distorted horizontally and the center is distorted vertically, use this vertical cycle current input terminal (18).
2A, a parabolic current having a vertical period V having a reverse polarity to that of the current is supplied to the connection point of the correction coil (11) and the diode (12) as shown in FIG. 2A.
The parabolic current ₁ is zero at the center of the screen (17) and is maximum on both sides thereof, that is, zero at the center of the screen (17) and at its upper and lower ends is maximum. In this case, the correction current of the substantially sinusoidal horizontal period H flowing through the correction coil (11) is at the center of the screen (17).
Since the correction current ₁ of the vertical period V supplied to the connection point of 1) and the diode (12) is zero, the correction current ₁ is the sixth as shown in FIG. 2B.
Similar to FIG. E, the correction current of the horizontal cycle has a positive maximum at the center of the horizontal scanning period, the beam spot at the center is corrected to be a perfect circle, and the correction current is zero on both sides of this horizontal scanning period. Therefore, the beam spot is not corrected and holds a perfect circle. Further, at the upper and lower ends of the screen (17), the correction current ₁ of the vertical period V supplied to the connection point of the correction coil (11) and the diode (12) becomes the maximum, and the correction current ₁ clamps the current. 2C, the correction current of the horizontal cycle flowing through the correction coil (11) is zero at the center of the horizontal scanning period and has a negative maximum on both sides of the horizontal cycle. The beam spots at the corners of the upper and lower ends are wavy and are corrected to form a perfect circle, and the beam spots at the centers of the upper and lower ends are not corrected and keep the perfect circle. The beam spots at other points on the screen (17) are similarly corrected, and the beam spots can be corrected over the entire screen as shown in FIG. 3 to form a perfect circle to improve the resolution and the like. The beam spot on screen (17) is number 7
Vertical period current input terminal (1
The beam spot can be similarly corrected over the entire screen by selecting the current of the vertical period V supplied to 8).

The present invention is not limited to the above-described embodiments, and it goes without saying that various other configurations can be adopted without departing from the gist of the present invention.

〔The invention's effect〕

According to the present invention, a substantially sinusoidal current having a horizontal cycle that is current clamped is passed through the correction coil (11) and the correction coil (1
Since an arbitrary correction current with a vertical cycle is applied from the outside to the connection point between 1) and the diode (12), an approximately sine wave with a horizontal cycle is applied over the entire screen by this arbitrary correction current with a vertical cycle. There is an advantage that the amount of current clamp of the current can be controlled well, and thus the beam spot can be corrected well over the entire screen.

[Brief description of drawings]

FIG. 1 is a connection diagram showing an embodiment of the convergence or beam spot correction circuit of the present invention, and FIGS. 2, 3, 6 and 7 are diagrams for explaining the present invention, and FIG. 4 respectively. Is a diagram for explaining an example of a convergence yoke or a beam spot correction yoke, and FIG. 5 is a connection diagram showing an example of a conventional convergence or beam spot correction circuit. (1) is a horizontal output transformer, (6) is a transistor for switching, (11) is a correction coil, (12) is a diode, (13) is a dummy coil, (15) is a capacitor, (1
8) is a vertical cycle current input terminal, and (20) is a transistor.

Claims (1)

[Claims] 1. A collector of a switching transistor (6), which is intermittently connected in a horizontal cycle, is connected to one end of a capacitor (15), and the other end of the capacitor (15) is connected in series with a correction coil (11) and a diode (12). A circuit is connected, a dummy coil (13) having an inductance value equal to that of the correction coil (11) is connected in parallel to the series circuit, and a protection capacitor (16) is connected in parallel to the diode (12). Convergence or beam spot correction, characterized in that a predetermined current having a vertical cycle is introduced into the connection point between the correction coil (11) and the diode (12) to correct the beam spot over the entire screen. circuit.