JPH04316280A - Picture display device - Google Patents

Abstract

PURPOSE:To reduce the power consumption of a convergence amplifier by converting a composite video signal to a digital video signal and writing it in a line memory with one horizontal line as the unit and compressing the time base and reading out it to convert it to an analog video signal. CONSTITUTION:The composite video signal subjected to signal processing is converted to the digital video signal by an AD converter 11. This converted signal is stored in a memory 12 and has the time base compressed with one horizontal line as the unit in accordance with a horizontal synchronizing signal and is read out with the read period a prescribed time shorter than the write period of one horizontal line. The read-out digital video signal is converted to the analog video signal by a DA converter 13 to obtain a lightness signal. A deflecting signal generating means generates a triangular wave signal, which is increased in the read period and is reduced in the period of one horizontal line except the read period, as the horizontal deflecting signal. Thus, the power consumption of the convergence amplifier is reduced.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image display device that displays an image obtained by signal processing a composite video signal using a CRT.

0002

BACKGROUND ART CRT display devices that display image information from a signal source such as broadcast radio waves or an image recording medium on a cathode ray tube are widely known. FIG. 4 shows a part of the configuration of a conventional example of this device. An image information signal from a signal source (not shown) is subjected to processing such as demodulation and detection, and the resulting composite video signal is supplied to a signal processing circuit 1 and a synchronization signal separation circuit 2. In the signal processing circuit 1, processing such as gain adjustment, DC reproduction, and amplification is performed to obtain a video signal. If the image information signal is a color signal, the signal processing circuit 1 demodulates the color signal to obtain an RGB signal. Hereinafter, the video signal and the RGB signal will be collectively referred to as a brightness signal. This brightness signal is supplied to the CRT drive circuit 3, power amplified, and then supplied to the cathode or grid (none of which is shown) of the CRT 4. An electron beam whose light intensity is modulated by a brightness signal is emitted from the cathode to the display surface 41 of the CRT 4.
The image is displayed according to the brightness signal.

On the other hand, horizontal and vertical synchronization signals obtained from the synchronization separation circuit 2 are supplied to a horizontal deflection circuit 5 and a vertical deflection circuit 6, respectively. In the horizontal deflection circuit 5, a horizontal deflection signal is generated and supplied to the horizontal deflection coil 42 of the CRT 4. Similarly, a generated vertical deflection signal is supplied from the vertical deflection circuit 6 to the vertical deflection coil 43. Deflection currents are passed through the horizontal and vertical deflection coils by horizontal and vertical deflection signals to generate horizontal and vertical deflection magnetic fields. In response to this horizontal and vertical magnetic field, the electron beam
Deflection or scanning is performed on the display surface 41 of TR4 in the horizontal and vertical directions.

One horizontal line of the brightness signal shown in FIG. 5(a) is formed by a period T1 in which the signal exists and a horizontal blanking period T2. In the case of an NTSC composite video signal, the period of one horizontal line, that is, T1+T2, is 6
3.5μs, T1=52.5μs, T2=11μs
It is s. The horizontal deflection signal for scanning the brightness signal of one horizontal line in the horizontal direction of the display surface 41 is shown in FIG.
As shown in (b), the period of T1 increases gradually, and the period of T2
The period is a sawtooth current that rapidly decreases.

In FIG. 6, an electron beam deflected by a horizontal deflection signal is intensity-modulated by a brightness signal and scans the display surface from left to right in the figure during a period T1. Therefore, the brightness signal is displayed by the horizontal scanning line L1. Next, during period T2, the electron beam is rapidly returned from right to left in the figure as shown by horizontal retrace line B1. This period T2 is a blanking period, and no brightness signal is displayed on the display screen 41.

During the period T2, the rate of change of the current flowing through the horizontal deflection coil 42 is large, so a high back electromotive force proportional to the rate of change of the current is generated in the horizontal deflection coil 42. Therefore, there is a problem in that the output circuit (not shown) of the horizontal deflection circuit 5 must have a high breakdown voltage. In addition, if the CRT 4 is of a shadow mask type, three electron beams are connected to the R. G. When irradiating the B fluorescent dots, the trajectory of each electron beam is shifted in the periphery of the display screen, so it is necessary to provide a convergence coil to correct the trajectory of the electron beam. The current that drives this convergence fluctuates according to the current changes in the horizontal and vertical deflection coils, so the current increases rapidly during the T2 period, causing a problem in that the power consumption of the convergence amplifier that drives the convergence coil increases. .

[0007]

[Object of the Invention] Therefore, an object of the present invention is to be able to set the withstand voltage of the output circuit low in a circuit that generates a horizontal deflection signal, and to use a convergence amplifier to correct the trajectory of the electron beam. An object of the present invention is to provide an image display device that can reduce power consumption when the power consumption is low.

[0008]

SUMMARY OF THE INVENTION An image display device according to the present invention includes a deflection signal generating means for separating horizontal and vertical synchronizing signals from a composite video signal to generate horizontal and vertical deflection signals, and processing the composite video signal to determine brightness. An image display device comprising a brightness signal generating means for generating a signal, and a CRT that displays while scanning a display surface with an electron beam according to the horizontal and vertical deflection signals and the brightness signal, the image display device comprising: a brightness signal generating means for generating a signal; The means includes: an AD converter for converting the signal-processed composite video signal into a digital video signal; a memory for storing the digital video signal; a write control means for writing in units, a read control means for compressing the digital video signal from the memory in a read period that is a predetermined time shorter than the write period of one horizontal line; and a DA converter that converts a video signal into an analog video signal and uses this as the brightness signal, and the deflection signal generating means increases the horizontal deflection signal during the readout period from the period of the one horizontal line to the brightness signal. The configuration is characterized in that a triangular wave signal that decreases during periods other than the read period is generated.

[0009]

[Operation of the invention] In the image display device according to the present invention,
Converts the composite video signal to a digital video signal, writes it to the line memory one horizontal line at a time, compresses the written digital video signal in the time axis, reads it out in a reading period shorter than the writing period, and converts it into an analog video signal. After converting and amplifying the power, it is supplied to the CRT.

[0010] Also, during the reading period, the number of
A triangular wave horizontal deflection signal that decreases during a period excluding the readout period from the period of the horizontal line is generated, and this is CR
The electron beam is supplied to the horizontal deflection coil of T, and an image is displayed while scanning the display surface with an electron beam.

[0011]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 3. In this embodiment, a circuit as shown in FIG. 1 is added to the signal processing circuit 1 of the conventional configuration shown in FIG. A signal that has undergone conventional signal processing such as gain adjustment, DC reproduction, and color signal demodulation is supplied to the AD converter 11, and is converted into a digital video signal. This digital video signal is supplied to the line memory 12,
A write controller (not shown) serving as a write control means in the memory controller 14 writes data for each horizontal line during the period T1 (=52.5 μs) in FIG. 5(a).

The written digital video signal is time-base compressed and read out for each horizontal line by a read controller (not shown) as read control means in the memory controller 14. This reading period T3 is
31.75μs, and the period of one horizontal line is 63.5μs.
The period is half of s. As mentioned above, since the writing period T1 is 52.5 μs, the time axis compression ratio η is
=T3/T1=0.6, which means that the time axis has been compressed by 60%. A period in which a digital video signal is not read out from the line memory 12 within one horizontal line,
That is, the blanking period T4 is T4=(T1+T2)−
T3=63.5μs-31.75μs=31.75μs
becomes. Therefore, in the format of the read digital video signal, as shown in FIG. 2(a), the period T3 in which the brightness signal exists and the blanking period T4 have the same time length.

From the memory controller 14, FIG. 2(a)
A high-speed horizontal synchronizing signal synchronized with the brightness signal shown in FIG. 2 is supplied to the horizontal deflection circuit 5, and a horizontal deflection signal as shown in FIG. 2(b) is generated. That is, a triangular horizontal deflection signal that gradually increases at a constant rate of change during the reading period T3 and gradually decreases at the same rate of change during the blanking period T4 is generated and supplied to the horizontal deflection coil 42.

On the other hand, the digital video signal read from the line memory 12 is converted into an analog video signal by the DA converter 13 and supplied to the CRT 4 via the CRT drive circuit 3. Therefore, on the display surface 41 of the CRT 4, the horizontal deflection coil 42 receiving the triangular wave horizontal deflection signal performs horizontal scanning with a longer retrace time than in the conventional example, and the image is displayed. It will be done.

In this way, in the horizontal deflection circuit 6,
Since the generated horizontal deflection signal is a signal that repeatedly increases and decreases gradually, there is no sudden change in current during the blanking period as in the conventional example. Therefore, the back electromotive force generated in the horizontal deflection coil 42 is reduced, and the withstand voltage of the output circuit of the horizontal deflection circuit can be set low. At the same time, the power supply voltage of the convergence amplifier can be lowered, so
Its power consumption can be reduced.

[0016]

As explained above, in the image display device according to the present invention, a composite video signal is converted into a digital video signal, and is written into a line memory for each horizontal line, and the written digital video signal is It is compressed and read out in a reading period shorter than the writing period, converted to an analog video signal, power amplified, and then sent to a CRT.
supply to.

[0017] Further, a triangular horizontal deflection signal that increases gradually during the readout period and gradually decreases during the period excluding the readout period from the period of the one horizontal line is generated, and is applied to the horizontal deflection coil of the CRT. The image is displayed. As a result, there is no sudden change in the deflection current during the flyback period, and the back electromotive force generated in the deflection coil is reduced, so that the withstand voltage of the horizontal deflection circuit can be set low. In addition, when a convergence amplifier is used to correct the trajectory of the electron beam, such as in a shadow mask type CRT, the correction current for trajectory correction becomes smaller, so the power consumption of the convergence amplifier can be reduced. This makes it possible to do so.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a part of an image display device according to the present invention.

[Figure 2] (a) Signal format diagram in Figure 1 (b)
) A diagram showing a horizontal deflection signal in an image display device according to the present invention.

FIG. 3 is a diagram showing horizontal scanning lines of a CRT of an image display device according to the present invention.

[Figure 4] Block diagram of a conventional image display device

[Figure 5] (a
) A diagram showing a signal format in a conventional image display device (b) A diagram showing a horizontal deflection signal in a conventional image display device

FIG. 6 is a diagram showing horizontal scanning lines of a CRT of a conventional image display device.

[Explanation of symbols]

1...Signal processing circuit 4...CRT 5...Horizontal deflection circuit 11...AD converter 12...Line memory 13...DA converter 14...Memory controller 42...Horizontal deflection coil

Claims (2)

[Claims] 1. Deflection signal generation means for separating horizontal and vertical synchronization signals from a composite video signal to generate horizontal and vertical deflection signals; and brightness signal generation means for processing the composite video signal to generate a brightness signal. and a CRT that displays while scanning a display surface with an electron beam according to the horizontal and vertical deflection signals and the brightness signal, wherein the brightness signal generating means is configured to display the An AD converter for converting a composite video signal into a digital video signal, a memory for storing the digital video signal, and a write control means for writing the digital video signal in the memory in units of horizontal lines in accordance with the horizontal synchronization signal. a read control means for compressing the digital video signal from the memory in a read period that is a predetermined time shorter than a write period for one horizontal line; and converting the read digital video signal into an analog video signal. and a DA converter that uses this as the brightness signal, and the deflection signal generating means increases as the horizontal deflection signal during the readout period and decreases during a period excluding the readout period from the period of the one horizontal line. An image display device characterized by generating a triangular wave signal. 2. The image display device according to claim 1, wherein the readout period is approximately half the period of the one horizontal line.