JPS6171770A - Horizontal deflection amplitude modulation circuit - Google Patents

Abstract

PURPOSE:To attain the accurate modulation of a horizontal deflection amplitude by producing a sawtooth wave current which is flowed to a horizontal deflection coil so that the amplitude of said sawtooth wave current in response to the shape of a reference waveform and therefore compensating a phase delay due to the nonlinearity of a transistor or a circuit element. CONSTITUTION:A harmonic wave detecting circuit 8 delivers a voltage equivalent to the modulated wave parabolic component of the sawtooth wave current which is flowed to a horizontal deflection coil. An operational amplifier 9 serving as a comparator compares a reference voltage obtained from a waveform shaping circuit 7 with a detection voltage obtained from the circuit 8 and applies an output voltage V0 to a horizontal amplitude modulation circuit 5 for horizontal deflection coil current IH. Thus the voltage V0 of the amplifier 9 is set automatically so as to secure the coincidence at all times between a parabolic voltage W1 obtained in proportion to the parabolic modulated wave component of the current IH and the reference parabolic voltage W2 set previously. Thus the circuit 5 modulates the horizontal amplitude.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a horizontal deflection-width modulation circuit for correcting the screen shape of an image display device such as a direct view type or projection type notelevision receiver using a picture tube. It is something.

(Prior Art) Conventionally, when trying to form a raster by passing a simple sawtooth wave current through the horizontal and vertical deflection coils in a normal picture tube, the raster does not form correctly, as shown in Figure 3. , so-called pincushion distortion may occur. Although the deflection angle of the picture tube is relatively large, this phenomenon tends to occur when the oil ratio on the image receiving surface is small.
When trying to make a straight line as shown by the broken line in the figure, the current that should be passed through the horizontal deflection coil is 1. will be as shown in Figure 4. That is, it is sufficient to modulate the sawtooth wave of the horizontal deflection coil H with the parabolic wave of the vertical deflection period V.

Further, in a projection type display device or the like, a trapezoidal raster as shown in FIG. 5 may be required depending on the arrangement of the picture tube. In such a case, as shown in FIG. 6, a sawtooth wave current having a horizontal deflection period H that is modulated by a sawtooth wave having a vertical deflection period V may be applied to the horizontal deflection coil.

In any case of n, in order to modulate the sawtooth wave flow of horizontal deflection with a different waveform of the vertical deflection period, a conventional configuration as shown in Fig. 7 has been used. Ta. That is, in this figure, 1 is a horizontal deflection output circuit, from which a horizontal deflection coil 3 and further a horizontal amplitude modulation circuit 5 are connected. is flowing. 2 is a vertical deflection output circuit,
A vertical deflection coil 4 is in contact with the load, and a sawtooth wave current with a vertical deflection period is applied thereto. Further, 6 is a waveform shaping circuit which obtains a part of the output of the vertical deflection output circuit 2, shapes it according to the signal, and applies it to the horizontal amplitude modulation circuit 5.

Although various methods are conceivable for the horizontal amplitude modulation circuit 5, an inductance modulation method using a saturable reactor, which is the most commonly used method, will be explained here as an example. Figure 8 shows the connection when a saturable reactor is used for this modulation2.
The modulated output current t from the waveform shaping circuit 6 is passed through the modulation winding 5α, and the modulated wire 5b is connected in series to the horizontal deflection coil 3. Figure 9 (-1) This is a diagram for explaining the structure of this saturable reactor. This saturable reactor is normally E-
An I or E-E type core 5C is used, the modulating winding 5a is wound on the center leg, and the modulated wire 5b is divided and wound on the left and right legs. In this way, when the current i is not flowing through the modulating winding 5α, the magnetic flux from the modulated winding 5b circulates through the core 5C as indicated by the broken line arrow. Here, the modulation winding 5α
When a current i is applied to the core 5 of Fig. 9, the magnetic flux due to this n is
As shown by the solid line arrow in c, the direction of the flow layer always coincides with the magnetic flux shown by the broken line due to the modulated winding 5b in either the left or right core leg. Therefore, core 5C is saturated in this part,
As a result, the inductance L of the modulated winding 5b decreases.

To illustrate this phenomenon, the relationship between the modulated output current i and the inductance L is as shown in FIG. Modulated! i5
When the inductance L of b decreases, the horizontal deflection coil 3
As the horizontal sawtooth current increases, the value of the current i is changed in a parabolic manner with a vertical deflection period V as shown in the parabolic waveform P in FIG. 10. The current that flows is as shown in Figure 4, and the third
The left and right ends of the rasku in the figure are corrected to straight lines.

(Inventive power; Solution, Derivation 11' et al. sinus is in the H layer) The most problematic problem in the conventional example detailed above is the i-
The relationship between L is not a straight line, and the slope is small both in the small portion and the large portion of the current i. Therefore, even if the parabolic waveform P in Figure 10 is a correct waveform, the envelope of the sawtooth waveform shown in Figure 4 does not necessarily become a parabolic waveform, and therefore the left and right ends of the correction result in Figure 3 are straight lines. In many cases, it would not move and would undulate. In order to prevent this, it is sufficient to use a sufficiently large core 5c so that the central straight portion of the i-L curve is sufficiently large compared to the amplitude of the parabolic waveform P. but,
Naturally, if this is done, there will be disadvantages in terms of weight and cost.

In addition, since this type of saturable reactor utilizes the saturation characteristics of the core, the i-L curve shown in Figure 10 has many variations, and it still changes easily depending on the degree of mixing. There was a problem in that it was not possible to accurately correct the vertical lines at the left and right ends of the raster shown in Figure 3.

Solution to Problem C) In order to solve the above-mentioned problems, the present invention provides a picture tube;
It has a deflection coil that electromagnetically deflects the electron beam in the horizontal direction, and a detection circuit that detects the modulated wave component (W1) of the vertical deflection period number of the sawtooth current synchronized with the horizontal deflection flowing through the deflection coil. A reference waveform (W
2), and means for generating each of the above two waveforms (W,
) , (w2), and a horizontal amplitude modulation circuit that modulates the sawtooth wave current flowing through the horizontal deflection coil (upper 3e) by the output of this comparison circuit. This will provide a horizontal deflection width modulation circuit configured so that the current has the shape of the reference waveform (W2) and its amplitude changes (Embodiment) FIG. 1 shows an embodiment of the present invention. This is an example, and the parts numbered 1 to 5 in FIG. 1 are the same parts as the same reference numerals in FIG. 7, and have essentially the same functions.

7 is a waveform shaping circuit, which obtains a part of the output of the vertical deflection output circuit 2 and uses it for correcting the desired waveform, for example, raster left and right pincushion distortion as shown in Figures 3 and 4.
A parabolic wave voltage with vertical deflection synchronization is obtained. Further, 8 is a modulated wave detection circuit which outputs a voltage corresponding to the modulated wave parabolic component of the sawtooth wave current flowing through the horizontal deflection coil as shown in FIG. , 9 is an operational amplifier serving as a comparison circuit, which uses the voltage obtained from the waveform shaping circuit 7 as a reference, compares this voltage with the detected voltage obtained from the modulated wave detection circuit 8, and calculates the result. Output voltage V. is applied to the horizontal amplitude modulation circuit 5 of the horizontal deflection coil current I++.

In this way, the parabolic voltage W obtained in proportion to the parabolic modulation portion of the horizontal deflection coil current IH is automatically calculated so as to always match the preset reference parabolic voltage W2. Output voltage V of amplifier 9. is determined n2
, this causes the horizontal amplitude modulation circuit 5 to perform horizontal amplitude modulation 1.
Go about your business. Therefore, even if there is some nonlinearity or variation in the horizontal amplitude modulation circuit 5 as in the conventional example described above, in the case of the present invention □, the shape of the modulation wave of the horizontal deflection coil current IH is determined completely regardless. n.ru.

What is shown in FIG. 2 is a specific example 1 of the modulated wave detection circuit 8.
Here, 10 is a current-voltage conversion resistor, 11 is a DC blocking capacitor, 12° and 13 are rectifier diodes, and 1
4 is a smoothing capacitor, 15 is a load resistor, and 16 is a coupling capacitor for exchange.

In this way, the voltage vR across both sides of the current-voltage conversion resistor 10, which is proportional to the horizontal deflection coil current II, is adjusted to the DC blocking capacitor 11, the rectifier diodes 12, 13, the smoothing capacitor 14, and the negative voltage VR. Since the fiT resistor 15 K is rectified in both waves and has the shape n, both ends of the load resistor 15 are at the peak and peak value of the voltage VR at both ends with parabolic ripple! ') Run n1, of which the above coupling capacitor 16
Therefore, only the parabolic voltage W corresponding to the ripple of the parabolic wave is applied to one of the input terminals of the operational amplifier 90.
, this is always the reference parabolic wave voltage W2 as mentioned above.
The entire circuit works to match.

In addition, in order to obtain the waveform of this reference parabolic wave 'wave pressure w2, the waveform obtained from the vertical deflection output circuit 2 is subjected to, for example, integration in the waveform shaping circuit 7, and the waveform of the waveguide voltage W2 becomes a parabolic wave. Therefore, in such a case, it is not necessary to provide a multi-H waveform shaping circuit. That is, since a direct current blocking capacitor is usually connected to the deflection coil, some vertical period parabolic waves are generated in this capacitor, so this wave is introduced to the operational amplifier by a coupling capacitor. By the way, this invention can be realized with an extremely simple configuration.

In addition, although the saturable reactor method has been described as an example of the horizontal amplitude modulation circuit 5 shown in FIG.
, for example, t may use an active element such as a transistor and utilize its voltage change. Even in such a case, according to the present invention, the non-linearity of the transistor and the circuit element can be It is possible to perform accurate modulation by compensating for the phase delay n, etc.

(Effects of the Invention) By providing the horizontal deflection amplitude modulation circuit as described above, the present invention can accurately and arbitrarily control the horizontal amplitude of the horizontal deflection of the electron beam of the picture tube with vertical deflection control. Since it is possible to modulate the image, it is extremely effective when applied to left and right pincushion distortion correction and trapezoidal correction of the image receiving screen.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the horizontal deflection amplitude modulation circuit according to the present invention, and FIG. 2 is a specific circuit diagram of a part thereof.
FIGS. 3 to 6 are explanatory diagrams for explaining the purpose and effects of the present invention, and FIGS. 7 to 9 are explanatory diagrams showing conventional examples.
FIG. 10 is a curve diagram showing the characteristics. 1...Horizontal deflection output circuit, 2...Vertical deflection output circuit, 3...Horizontal deflection coil, 4...Vertical deflection coil. 5... Horizontal amplitude modulation circuit, 7... Waveform shaping circuit, 8
...Modulated wave detection circuit, 9...Operation amplifier, 10...
・Resistance for current and current positive conversion, 11... DC blocking capacitor, 12.13... Rectifier diode, 14... Smoothing capacitor, 15... Load resistor, 16... Coupling capacitor. Patent applicant: Yudo Omata, representative of Victor Japan Co., Ltd.
Tomonosuke Araki Figure 1 Figure 2 Figure 3 Figure 4 Gate Figure 5 Figure 6 Figure 7 Figure 9 C Figure 8 Figure 10

Claims (2)

[Claims] (1) It has a picture tube and a deflection coil that electromagnetically deflects the electron beam in the horizontal direction, and the modulated wave component (
W_1), a means for generating a reference waveform (W_2) having a vertical deflection period, and a comparison circuit for comparing the two waveforms (W_1) and (W_2). By providing a horizontal amplitude modulation circuit that modulates the sawtooth wave current flowing through the horizontal deflection coil according to the output of the comparison circuit, the sawtooth wave current flowing through the horizontal deflection coil can be adjusted according to the shape of the reference waveform (W_2).
A horizontal deflection amplitude modulation circuit characterized in that the amplitude is configured to vary. (2) As a means for generating a reference waveform (W_2) having a vertical deflection period, a parabolic voltage waveform generated on a DC blocking capacitor connected in series with the vertical deflection coil is obtained as the reference waveform (W_2). 2. The horizontal deflection amplitude modulation circuit according to claim 1, wherein the horizontal deflection amplitude modulation circuit is configured to correct left and right pincushion distortion of a screen on a picture tube by using a parabolic voltage waveform as a reference waveform.