JPH0670193A - Parabolic voltage generating circuit - Google Patents

Abstract

PURPOSE:To generate a parabolic voltage of a vertical period and a parabolic voltage of a horizontal period used for the correction of left and right pincushion distortion and vertical pincushion distortion 'a cathode ray display device through digital control. CONSTITUTION:One vertical or horizontal period in a synchronization state is divided into a prescribed number of sections equally, and a digital level is set at every divided section through the adjustment of an adjustment signal generating section 3. A signal based on the adjustment is outputted by a control circuit 4. A digital output of the control circuit 4 is D/A-converted by a D/A converter circuit 6. An analog output by the D/A conversion is changed stepwise at every section and the envelope line becomes a voltage waveform to form a parabola shape. Then a vertical or horizontal parabolic voltage is obtained by passing a D/A conversion output through an LPF 7. The vertical or horizontal parabolic voltage is used similarly to the case with a conventional method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is adapted to digitally control a vertical period parabolic voltage and a horizontal period parabolic voltage for correction of left and right pincushion distortion and upper and lower pincushion distortion respectively in a cathode ray tube display. The present invention relates to a parabola voltage generation circuit.

[0002]

2. Description of the Related Art Conventionally, among the corrections of the above-mentioned thread winding distortion in a cathode ray tube display, for example, the correction of the left and right thread winding distortion has been performed as shown in FIG. Hereinafter, FIG. 4 will be described. FIG. 4 is a principle circuit diagram as one example of left and right pincushion distortion correction. 41 is a vertical sawtooth wave voltage, 42 is an integrating circuit, TR1 is a horizontal output transistor, X1 is a damper diode, and C1 is a resonance capacitor for setting a high voltage value. , DY is a horizontal deflection coil, T1 is a left and right pincushion distortion correction transformer, L1 is a horizontal size coil, L2 is a horizontal linearity coil, and C2 is a so-called S-shaped correction capacitor. A vertical sawtooth wave voltage 41 from a vertical deflection circuit (not shown) is integrated by an integrating circuit 42 to obtain a parabola voltage 43.

On the other hand, a left and right pincushion distortion correction transformer T1 consisting of a primary side N1 and a secondary side N2 is connected to the horizontal deflection coil HDY as shown in the figure, and the parabolic voltage 43 is applied to the primary side N1. Apply. This application changes the inductance Ls of the secondary side N2. This change is the parabolic voltage
At the beginning of 43 (the beginning of vertical scanning) and at the same end (at the same end), Ls is maximized, and at the same center (vertical scanning center) it is minimized, and during that time, it changes in a parabolic shape. As a result, the horizontal sawtooth current flowing through the horizontal deflection coil HDY decreases according to the parabolic voltage 43 as it goes to the upper or lower part of the screen, compared to the central part. This corrects the pincushion distortion on the left and right of the screen. Although not shown, the upper and lower pincushion distortions are also corrected by the same principle as above using a parabola voltage having a horizontal period. As described above, the parabola voltage is an essential voltage for correcting the horizontal and vertical pincushion distortions, and an integrating circuit has been conventionally used as a method for generating it.

[0004]

However, in a recent large-sized screen or a horizontally long screen having an aspect ratio of 16: 9 such as a high-definition television receiver, the large screen is obtained by the method of obtaining the parabola voltage by the integrating circuit. As a result, sufficient pincushion distortion correction has become incomplete. That is, in such a large screen and wide deflection angle, there is a limit in generating a parabola wave having a required waveform. According to the present invention, in order to sufficiently correct the pincushion distortion of such a large screen having a wide deflection angle or a horizontally long screen, the vertical or horizontal parabola voltage required for the correction is generated by digital control. An object is to provide a parabola voltage generation circuit.

[0005]

According to the present invention, a means for stepwise varying a digital level for each section, which is obtained by equally dividing a period of one vertical cycle into a predetermined number of sections, in each horizontal and vertical synchronization state. A D / A conversion circuit for converting digital level data to analog based on the means; a means for storing the digital level data; and a low frequency component of the analog signal from the D / A conversion circuit. The present invention provides a parabola voltage generating circuit configured by a low-pass filter for obtaining a parabolic voltage of a vertical cycle by a digital control to generate a parabolic voltage of a vertical cycle for correcting left and right pincushion distortion.

[0006]

The one vertical cycle period or one horizontal cycle period in the synchronized state is evenly divided into a predetermined number of sections, and the digital level is set by adjusting each of the divided sections. The digital level for each set section is D / A converted. The analog output by the D / A conversion changes stepwise for each section, and its envelope has a voltage waveform forming a parabolic shape. Therefore, a vertical or horizontal parabolic voltage can be obtained by passing the D / A converted output through the LPF.
This vertical or horizontal parabolic voltage is used as before.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A parabolic voltage generating circuit according to the present invention will be described below with reference to the drawings. 1 is a block diagram of an essential part of an embodiment of a parabolic voltage generation circuit for correcting left and right pincushion distortion according to the present invention, and FIG. 2 is a block diagram of an essential part of an example of a parabola voltage generator circuit used for correcting upper and lower pincushion distortion. FIG. 3 is an explanatory diagram of the parabola voltage generation in FIGS. 1 and 2. First, FIG. 1 will be described. In FIG. 1, reference numeral 1 is a horizontal sync signal or a horizontal drive signal (HD) of a horizontal cycle pulse, 2 is a PLL for generating a clock signal synchronized with the HD, 3 is an adjustment signal generator, and 4 is a PLL2.
A control circuit for outputting digital level data set for each section obtained by equally dividing one vertical cycle from the clock signal from the clock signal and the adjustment signal from the adjustment signal generating section 5, and a memory section for storing the digital level data. 6 is a D / A conversion circuit for converting the digital level data from the control circuit 4 into an analog voltage, and 7 is an LPF for obtaining a vertical parabola voltage by extracting only low frequency components from the signal from the D / A conversion circuit 6. (Low-pass filter) 8 is an output circuit for amplifying the vertical parabolic voltage to a level required for the left and right pincushion distortion correction transformer T1. In addition, other, T1,
TR1, X1, DY, L1, L2, etc. are the same as those in FIG. 4 described above.

Next, the operation of the present invention (FIG. 1) will be described. The essence of the present invention lies in that the generation of the parabolic voltage of the vertical period used for the correction of the left and right pincushion distortion is generated by digital control. For this purpose, one vertical cycle is evenly divided into a predetermined number. The number of divisions is arbitrary, but if it is subdivided too much, the correction accuracy will increase, but adjustment will take time, but if it is too rough, it will not be possible to generate the required parabolic wave, and the correction accuracy will drop, so both should be taken into consideration. Decide
Then, this division is predetermined (design stage). In this embodiment, one horizontal cycle is divided into 20 equal parts. The state of this division is shown in FIG. Although it is considered that this degree of division is sufficient, the number of divisions may be increased if the correction accuracy is further improved. As shown in FIG.
Digitally set the level for each divided position (P1 to P20). This setting is the adjustment of the left and right pincushion distortion correction. Specifically, specify the position (P1 to P20) and set the level for each specified position. Therefore, a function of designating this position and a function of outputting an adjustment signal for level setting are required. The adjustment signal generator 3 has these functions. The adjustment signal for each position output from the adjustment signal generator 3 as described above is input to the control circuit 4.

On the other hand, a clock signal synchronized with the horizontal drive signal (HD) is input to the control circuit 4 from the PLL 2. Therefore, the control circuit 4 outputs the digital data of the level corresponding to the adjustment signal for each position from the clock signal and the adjustment signal. This digital data is converted from digital to analog by the D / A conversion circuit 6. FIG. 3A shows an output voltage waveform of the D / A conversion circuit 6. This output voltage waveform is as shown
Since it has a step shape, the LPF must be removed to remove this step shape.
7 is used. The LPF 7 removes high frequency components from the staircase waveform to obtain a pure parabola voltage. The LPF7
Is the vertical parabola voltage shown in FIG. 3 (B).
In addition, "1V" in the figure means one vertical period.

This parabola voltage is supplied to the left and right pincushion distortion correction transformer T1 via the output circuit 8. After that, FIG.
The left and right pincushion distortion is corrected by the same action as in the above case. As described above, the present invention generates the parabolic voltage by digital control, and the optimum state of the parabolic wave is set by adjustment. It is preferable that a person looks at a screen (a test pattern signal such as a hatch signal) to determine whether or not this is optimal. This is because it is often difficult to make a judgment using only the oscilloscope. When the optimum state is set by the adjustment, each correction data for each position is stored in the memory 5. This storage is stored in the memory 5 by the control circuit 4 by the operation of the adjustment signal generator 3. At the time of normal use after being stored in the memory 5, the stored data is read from the memory 5, and the left and right pincushion distortion is corrected by the data.

Next, FIG. 2 will be described. FIG. 2 is a diagram in which the idea of the present invention is applied to upper and lower pincushion distortion correction, and differs from FIG. 1 in that the period of the generated parabola voltage is a horizontal period. Therefore, the block configuration (21 to 28) of the part related to the generation of the parabolic voltage is the same as that in FIG.
Except for (21) and PLL (22), the cycle handled by each block is changed from the vertical cycle in FIG. 1 to the horizontal cycle. The HD and PLL functions are the same as those in FIG. Figure 1
According to the above case, one horizontal period is divided into a predetermined number, and the number of divisions may be determined from the same viewpoint as in the case of FIG. For example, if the number of divisions is 20 divisions (P1 to P20), which is the same as the vertical parabola in FIG. 1, the output (concept) of the D / A conversion circuit 26 and the horizontal parabolic output (concept) of the LPF 27 are shown in FIG.
The period T in (A) and (B) is replaced with 1H (1 horizontal period). The level itself and the parabola amplitude at each position may differ between the case of FIG. 1 and the case of FIG. The level setting method for each position and its storage are the same as in FIG. The horizontal parabolic voltage from the LPF 27 is amplified to a predetermined level by the output circuit 28 and supplied to the upper and lower pincushion distortion correction circuit 30. The subsequent correction operation is the same operation as the conventional one which is generally performed.
The upper and lower pincushion distortion correction circuit 30 generally has a vertical deflection coil VDY through which a vertical sawtooth current from the vertical deflection output circuit 29 flows.
And the vertical parabolic current due to the horizontal parabolic voltage is superimposed on the vertical sawtooth current, and the upper and lower pincushion distortion is corrected.

[0012]

As described above, according to the present invention, the parabola voltage of the vertical or horizontal period necessary for correcting the horizontal or vertical pincushion distortion is generated by digital control,
Moreover, since the parabolic waveform can be arbitrarily changed for each point, the correction amount can be partially increased or decreased as compared with the conventional analog system (FIG. 4), and the correction accuracy can be improved. In particular, it is possible to effectively improve the pincushion distortion correction of a large CRT having a wide deflection angle or a horizontally long CRT for high definition.

[Brief description of drawings]

FIG. 1 is a block diagram of a main part showing an embodiment of a parabola voltage generation circuit used for correcting left and right pincushion distortion according to the present invention.

FIG. 2 is a principal block diagram showing an embodiment of a parabola voltage generation circuit used for upper and lower pincushion distortion correction.

FIG. 3 is an explanatory diagram of parabola voltage generation in FIGS. 1 and 2.

FIG. 4 is a circuit diagram of the principle of the conventional left and right pincushion distortion correction.

[Explanation of symbols] 1 horizontal drive signal (HD) 2 PLL 3 adjustment signal generator 4 control circuit 5 memory unit 6 D / A converter circuit 7 LPF (low pass filter) 8 output circuit T1 left and right thread winding distortion correction transformer TR1 horizontal Output transistor HDY Horizontal deflection coil L1 Horizontal size coil L2 Horizontal linearity coil 29 Vertical output circuit 30 Upper and lower pincushion distortion correction circuit VDY Vertical deflection coil

Claims (2)

[Claims] 1. A means for stepwise varying a digital level for each section obtained by equally dividing a period of one vertical cycle into a predetermined number of sections, and a digital level based on the means. D / A conversion circuit for converting the analog data to analog data, a means for storing the digital level data, and a low frequency component of the analog signal from the D / A conversion circuit to obtain a parabola voltage of a vertical cycle. A parabola voltage generation circuit comprising a low pass filter and digitally generating a parabolic voltage of a vertical cycle used for left and right pincushion distortion correction. 2. A means for stepwise varying the digital level in each horizontal and vertical synchronization state for each of a predetermined number of sections equally divided into one horizontal cycle period, and a digital level based on the means. D / A conversion circuit for converting the data of FIG. 4 into analog, a means for storing the digital level data, and a low frequency component of the analog signal from the D / A conversion circuit are passed to obtain a parabola voltage of a horizontal period. A parabola voltage generation circuit configured by a low-pass filter, wherein a parabola voltage of a horizontal cycle used for upper and lower pincushion distortion correction is generated by digital control.