JPH1070671A - Deflection signal generating circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a V ramp waveform corrected precisely by means of a simple circuit. SOLUTION: A V ramp generator 12 is composed of an analog circuit to output an analog V ramp waveform. A DSP(digital signal processor) 14 outputs digital correction waveform data. A D/A converter 16 converts the corrected waveform data into an analog correction waveform. The V ramp waveform from a V ramp generator and the corrected waveform from a D/A converter 16 are given to an adder circuit 18, in which they are added to obtain a corrected V ramp waveform.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a deflection signal generating circuit for generating a deflection signal synchronized with scanning for deflection in a television.

[0002]

2. Description of the Related Art A video signal for television constitutes one frame by a predetermined number of horizontal lines, and must be scanned in the horizontal and vertical directions for display. For vertical scanning in a cathode ray tube, a ramp waveform is needed in which the voltage is gradually changed for one vertical period and then rapidly returns to the initial voltage. That is, using this ramp waveform, the electron beam is deflected in the vertical direction to achieve vertical scanning.

[0003] Such a ramp waveform can be generated in an analog manner using a capacitor, a coil, and the like, and various analog-type circuits are known. Also,
This ramp waveform can be easily generated digitally, and the obtained digital waveform data is D / A-converted.
Waveforms have also been obtained.

Here, if vertical deflection is performed using the ramp waveform that changes linearly as it is, the screen will be distorted. For this reason, in the case of actual vertical deflection, predetermined correction is applied to the ramp waveform, and vertical deflection is performed using the corrected waveform.

[0005] Such correction also requires delicate adjustment, and digital ramp waveform generating circuits that have a high degree of freedom for change have been widely used.

[0006]

As described above, according to the digital circuit, a desired waveform can be obtained by correcting the ramp waveform relatively freely. However, this ramp waveform is a voltage for actually performing vertical scanning,
The voltage must be obtained by A / D conversion. Further, the accuracy of the corrected ramp waveform must be considerably high. Therefore, in a circuit for obtaining a ramp waveform, a large value must be represented with high accuracy, and there is a problem that the circuit becomes very large. For example, assuming that the amplitude of the ramp waveform is Vpp, in order to obtain a resolution of Vpp / 256, a circuit for generating 8-bit data and this D / A converter are required.

The present invention has been made to solve the above problems, and has as its object to provide a vertical deflection signal generating circuit which can obtain an accurate ramp waveform with a relatively small circuit.

[0008]

SUMMARY OF THE INVENTION The present invention relates to a deflection signal generating circuit for generating a deflection signal in synchronization with scanning for electron beam scanning in a television. A fundamental wave generating circuit for generating a fundamental wave indicating a basic change state, a digital circuit, and a correction wave generating circuit for generating correction wave data for correcting the fundamental wave; and a correction wave generating circuit. A D / A converter for converting the correction wave data into an analog correction wave, and a synthesis circuit for synthesizing the fundamental wave generated from the fundamental wave generation circuit and the correction wave output from the D / A converter. It is characterized by having.

Thus, the fundamental wave is generated in analog,
Generates a correction wave digitally. The fundamental wave usually has a large amplitude, and the correction wave usually has a small amplitude. For example,
In the case of a V ramp waveform, the maximum amplitude of the correction wave is about 1/16 of the maximum amplitude of the V ramp waveform. Therefore, if the correction wave is represented by 4 bits, 1/25 with respect to the V ramp waveform
8, that is, the same as when the correction is performed using 8-bit data. Therefore, according to the present invention, more accurate correction can be performed with a simple circuit.

Further, the change of the correction wave can be easily performed by setting digital data. For example, ax ²
When using + bx ³ (a and b are constants and x is a vertical position), the constants a and b can be changed based on an external operation, and if the set values are stored, the change is easy and Reliable change of the correction wave can be performed.

Further, the invention is characterized in that the fundamental wave is a sawtooth V ramp waveform.

Further, the present invention is characterized in that the fundamental wave is a parabolic parabolic waveform.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention (hereinafter referred to as embodiments) will be described below with reference to the drawings. FIG. 1 is a block diagram showing the overall configuration of the present embodiment.
The H signal and the vertical synchronization signal Vsync are input to the V countdown circuit 10. This V countdown circuit 10
For vertical scanning, a signal about a vertical position is output. For example, in an NTSC television, one field is composed of 262.5 horizontal lines.
This count is performed by the countdown circuit 10. Then, the V countdown circuit 10 generates a timing pulse corresponding to the vertical position.

The timing pulse from V countdown circuit 10 is supplied to V ramp generator 12.
The V ramp generator 12 generates a linearly changing ramp waveform in an analog manner using a charging voltage to a capacitor or the like.

The timing pulse from the V countdown circuit 10 is also supplied to a DSP (Digital Signal Processor) 14. The DSP 14 generates correction data corresponding to each vertical position based on the timing pulse.

For example, ax ² + bx ³ (x is a vertical position,
Correction data is generated based on an equation (a and b are constants). The constants a and b can be changed based on an external operation, and the constants a and b based on the operation are stored.

The output of the DSP 14 is D / A
It is supplied to a converter 16. The digital correction data for each vertical position input to the D / A converter 16 is converted into an analog correction waveform.

The V ramp waveform from the V ramp generator 12 and the correction waveform from the D / A converter 16 are input to an addition circuit 18 where they are combined and corrected into a corrected V ramp waveform.

It is preferable that a predetermined offset voltage be supplied to the output of the D / A converter 16 to correct the DC voltage value of the correction waveform. Also, the D / A converter 16
Is a step-like waveform, and the output waveform of the adder circuit 18 also has a step-like component. Therefore, it is preferable that the waveform of the output of the adding circuit 18 be dulled by a predetermined integrating circuit or the like to obtain a smoothly changing V ramp waveform.

Here, the output of the DSP 14 is, for example, 4
Convert to digital data of bits. The maximum amplitude of the correction waveform may be about 1/16 of the maximum amplitude of the V ramp waveform. Therefore, one step of the 4-bit correction data is 1/256 of the maximum amplitude of the V ramp waveform. Therefore, 4
The bit DSP 14 and the D / A converter 16 provide a resolution of 1/256 with respect to the maximum amplitude of the V ramp waveform.

As described above, according to the present embodiment, the DSP 14 generates a correction waveform. Therefore, it is very easy to change the correction waveform. Then, only the correction waveform is DSP
14, full bits of the output of the DSP 14 can be used for correction, and 4-bit data is 1/256, that is, 8 bits for the entire V ramp waveform.
The same correction as the bit data can be performed. For this reason, D /
The A converter 16 may also be a 4-bit one, and the circuit can be simply reduced in size.

In this embodiment, only the correction for the V ramp waveform is described, but the above circuit can be used as it is for the correction of the parabolic waveform. That is, the V ramp generator 12 may be replaced with a generator of a parabolic basic waveform, and the DSP 14 may generate parabola waveform corrected waveform data.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the overall configuration of a circuit according to the present invention.

[Explanation of symbols]

10 V countdown circuit, 12 V ramp generator, 14 DSP, 16 D / A converter, 18 addition circuit.

Claims (3)

[Claims] 1. A deflection signal generation circuit for generating a deflection signal in synchronization with scanning for electron beam scanning in a television, comprising: an analog circuit; a fundamental wave indicating a basic change state required for deflection. , A correction wave generation circuit configured to generate correction wave data for correcting the fundamental wave, and an analog correction wave generated by the correction wave generation circuit. And a combining circuit for combining a fundamental wave generated from the fundamental wave generating circuit and a correction wave output from the D / A converter. Generator circuit. 2. The deflection signal generation circuit according to claim 1, wherein the fundamental wave is a sawtooth ramp waveform. 3. The deflection signal generating circuit according to claim 1, wherein the fundamental wave is a parabolic parabolic waveform.