JPH0323790A - Vertical deflection signal generating circuit - Google Patents

Abstract

PURPOSE:To keep the field period constant and to obtain stably an interlace scanning deflection signal by selecting alternately an output from a sawtooth wave generating means and an output from a delay means at odd and even number fields and supplying the selected signal to a vertical deflection amplifier in response to an identification signal. CONSTITUTION:A video signal is led to a vertical synchronizing signal generating circuit 12 and fed to a sawtooth wave generating circuit 13 and fed to an odd/even number field discrimination circuit 14. Moreover, a delay circuit 15 applies 0.5H delay and its output is fed to other terminal B of a switch 186. The switch 16 is controlled with an output of the odd/even number field discrimination circuit 14 and selects a terminal A in the period of an odd number field and selects a terminal B in the period of an even number field. Thus, a sawtooth wave deviated by 0.5H between the odd number field and the even number field is obtained at an output terminal 17. Thus, the field period is kept constant and stable interlace scanning deflection signal is obtained without the effect of S-shape correction or temperature change.

Description

Detailed Description of the Invention [Object of the Invention] (Industrial Application Field) This invention converts an NTSC television signal into a 525 scanning line signal per field by converting the number of scanning lines, for example. The present invention relates to a vertical deflection signal generation circuit that is effective when displaying in a non-interlaced manner (1050 scanning line signals per frame).

(Prior Art) Recently, in order to display high-quality images, television receivers have been developed that can obtain horizontal scanning of 525 lines per feed and 1050 lines per frame.

Additionally, a circuit has been developed that performs line interpolation using signals sent in the NTSC format to create 525 scanning line signals.

By the way, when the above-mentioned 525 scanning line signals are deflected as one field and displayed on a cathode ray tube screen, and interlaced scanning is performed, for example, in an even field, 0.5H (I
H: 1 horizontal synchronization period) It is necessary to shift the phase and perform vertical deflection.

FIG. 4 shows a conventional vertical deflection signal generation circuit that performs interlaced scanning of signals on 525 even lines as described above.

A video signal is supplied to an input terminal 1 and introduced into a vertical synchronization signal generation circuit 2. The vertical synchronization signal obtained by the vertical synchronization signal generation circuit 2 is supplied to the sawtooth wave generation circuit 3. In the sawtooth wave generation circuit 3, a vertically periodic triangular wave (sawtooth wave) is obtained,
This sawtooth wave is supplied to one of the comparators 4. The output of comparator 4 is supplied to deflection coil 6 via capacitor 5. The deflection coil 6 is provided at the neck of the cathode ray tube and generates a vertical deflection magnetic field.

The current flowing through the deflection coil 6 is supplied to a feedback impedance circuit 8, and the voltage generated here is supplied to the other power section of the comparator 4.

Here, the vertical synchronization signal generation circuit 2 is set to generate synchronization signals that are shifted by 0.5H between odd and even fields as shown in FIG.

By generating a vertical synchronization signal in this way, a vertical deflection signal (sawtooth wave) that enables interlaced scanning can be generated.

(Problems to be Solved by the Invention) The above-described vertical deflection signal generation method has the following problems.

The vertical deflection coil drive circuit includes a capacitor 5 in front of the deflection coil. This is to remove DC components in order to accurately transmit the waveform. However, this is not a problem if it is a wave cedar with a constant cycle, but it
．． If the sawtooth wave is shifted by 5H, the current value flowing through the coil will be shifted by a uniform 0.5H over one field period due to the circuit time constant caused by the capacitor 5, the vertical deflection coil 6, and the resistance of the coil. does not occur.

Then, the displacement of the horizontal line in the vertical direction will be different at the top and bottom of the screen. In other words, a pairing is created in which the horizontal lines of the odd field and the horizontal lines of the even field are partially integrated.

There is another way to perform interlaced scanning while keeping the period of the field constant.

In this method, when a sawtooth waveform of a constant period is supplied through the amplifier 4, a constant voltage is applied to the sawtooth waveform, for example, only during even field periods, as shown in FIG. In this case, the value of the constant voltage is set to such a value that a shift of 0.5H occurs in the sawtooth wave.

However, with this method, there is no problem if the sawtooth waveform is a linearly changing waveform, but the sawtooth waveform is S-shaped corrected. Therefore, originally, the voltage applied to some parts (center, bottom, and top of the screen) should be changed. Applying a constant voltage results in partial bearing. Furthermore, if the constant voltage supplied to the sawtooth wave changes due to temperature changes, etc.
Pairing will occur over the entire screen. Also, if for some reason the vertical amplitude of the television receiver is changed, this constant applied voltage must also be changed, or bearing will similarly occur across the entire screen.

SUMMARY OF THE INVENTION An object of the present invention is to provide a vertical deflection signal generation circuit that can maintain a constant field period and stably obtain a deflection signal for interlaced scanning without being affected by S-curve correction or temperature changes. .

[Structure of the Invention] (Means for Solving the Problems) The present invention provides a television that converts a non-interlaced scanning line signal into an interlaced scanning line signal at a constant cycle, and processes this signal for display on a cathode ray tube screen. In the signal processing device, an identification signal generation means for generating identification signals for odd fields and even fields for the interlaced scanning line signal using the vertical synchronization signal of the non-interlaced signal, and the vertical synchronization signal is supplied. a sawtooth wave generating means for generating a sawtooth wave for vertical deflection; a delay means for delaying the sawtooth wave from the sawtooth wave generating means by about half of one horizontal synchronization period; and in response to the identification signal,
The apparatus further includes a switch means for alternately selecting the output from the sawtooth wave generating means and the output from the delay means for odd and even fields and supplying the selected output to the vertical deflection amplifier.

(Operation) With the above means, the delay means outputs 0. Although a sawtooth wave delayed by 5H can be obtained, the overall period of this sawtooth wave does not change even if it is made continuous with the sawtooth wave obtained from the sawtooth wave generating means. For this purpose, 0 is applied uniformly across the entire screen.
．． Even field deflection signals shifted by 5H can be obtained. Further, since the delay means is used, even if the sawtooth wave is S-shaped corrected, the above-mentioned bearing will not occur.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention. A video signal composed of, for example, 525 scanning line signals per field is supplied to the input terminal 11 and introduced into the vertical synchronization signal generation circuit 12 . The vertical synchronization signal obtained by the vertical synchronization signal generation circuit 12 is supplied to the sawtooth wave generation circuit 13, and
The signal is supplied to the odd/even field discrimination circuit 14. The odd/even field discrimination circuit 14 is constituted by, for example, a circuit that is inverted/non-inverted by a vertical synchronizing signal.

It may be configured by a counter that counts horizontal synchronization signals.

The output of the sawtooth wave generation circuit 13 is sent to the delay circuit 15 and the switch 1.
is supplied to one terminal A of 6. The delay circuit 15 has a delay time of 0.
A delay of 5H is performed and the output thereof is supplied to the other terminal B of the switch 16.

The switch 16 is controlled by the output of the odd/even field discrimination circuit 14, and selects terminal A during the odd field period and selects the terminal B during the even field period.

As a result, a sawtooth waveform shifted by 0.5H between the odd and even fields is obtained at the output terminal 17. This sawtooth wave is applied to the vertical deflection coil via an amplifier such as that shown in FIG.

FIG. 2 is an example of the sawtooth waveform. Odd number fi? In the field, the sawtooth wave shown by the broken line obtained from the delay circuit 15 is selectively output, and in the even field, the sawtooth wave shown by the solid line obtained from the sawtooth wave generating circuit 13 is selectively output. The 0.5H delayed sawtooth wave that is output in the odd field is the voltage that always deflects the electron beam of the cathode ray tube to the position 0.5H earlier in the even field, and the relationship between the voltages is determined by S-curve correction, vertical amplitude, etc. It is completely unaffected by sawtooth waveform shape and temperature changes. Therefore, even-numbered lines of video can be completely interlaced scanned.

This invention is not limited to the embodiments described above, and various embodiments are possible.

Here, the delay circuit 15 does not need to have a delay amount of exactly 0.5H, but is adjusted to around 0.5H to adjust the vertical deviation between the odd field and even field lines. It is also possible.

Further, as the delay circuit 15, it is not necessary to delay the sawtooth wave in its complete waveform, and a sample and hold circuit shown in FIG. 3 may be used.

Here, a simple example using four switches and a capacitor is shown.

The human power terminal 22 is connected to one terminal A of the switch 31 via switches 23, 24, and 25.

The connection point between switches 23 and 24 is grounded via a capacitor 26, the connection point between switches 24 and 25 is grounded via a capacitor 27, and the connection point between switch 25 and terminal A is grounded via a capacitor 28. Ru. Further, the connection point between the switches 23 and 24 is connected to the terminal B of the switch 31 via the switch 29, and the connection point between the two switches and the terminal B is grounded via the capacitor 30.

The switches 23 and 24 switch intermittently at intervals of 0.5H. Switches 25 and 29 are switches 13 and 14
It switches intermittently when it is not conducting (for example, by 0.25H), which is slightly different from when it is conducting. and switch 3
1, odd-numbered fields are switched to the right side, that is, to the capacitor 28 side, and even-numbered fields are switched to the left side, that is, to the capacitor 3o side. Then, a delay difference of 0.5H can be provided as shown in FIG. 2, with a constant voltage during IH in both the odd and even fields.

In other words, since the sample timing of the switch 24 is deviated by 0.5H from the sample timing of the switch 23, an output delayed by that amount can be sent to the terminal A side.

[Effects of the Invention] As described above, the present invention keeps the field period constant and can stably obtain a deflection signal for interlaced scanning without being affected by S-curve correction or temperature changes.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing an embodiment of the present invention, FIG. 2 is a signal waveform diagram shown to explain the operation of the circuit of the present invention, and FIG. 3 is another example of the delay circuit shown in FIG. 1. Figure 4 is a diagram showing an example of a conventional vertical deflection circuit, Figure 5 is a waveform diagram for creating a conventional vertical deflection signal, and Figure 6 explains problems with the conventional vertical deflection circuit. FIG. 12... Vertical synchronization signal generation circuit, 13... Sawtooth wave generation circuit, 14... Odd/even field identification circuit, 1
5...Delay circuit.

Claims (1)

[Claims] Non-interlaced scanning line signals are transmitted at a constant period,
In a television signal processing device that converts the interlaced scanning line signal into an interlaced scanning line signal and processes the signal for display on a cathode ray tube screen, the vertical synchronization signal of the non-interlaced signal is used to distinguish odd and even fields for the interlaced scanning line signal. identification signal generating means for generating a field identification signal; sawtooth wave generating means for receiving the vertical synchronization signal and generating a sawtooth wave for vertical deflection; and a sawtooth wave from the sawtooth wave generating means for one horizontal synchronization period. and a delay means for delaying approximately half of the above, and in response to the identification signal, the output from the sawtooth wave generating means and the output from the delay means are alternately selected in odd and even fields and supplied to the vertical deflection amplifier. 1. A vertical deflection signal generating circuit, characterized in that it comprises a switch means for: