JPH07135577A - Television receiver provided with scanning speed modulation circuit and contour emphasis circuit including the modulation circuit - Google Patents

Abstract

PURPOSE:To prevent power consumption from being considerably increased even when a signal having lots of high frequency components such as a noise is received by a scanning speed modulation circuit 100 being a component of a video image contour emphasis circuit. CONSTITUTION:A video signal received at an input terminal 10 is processed by a scanning speed modulation signal processing circuit 20 and amplified by a variable gain amplifier circuit 30 and an amplifier circuit 40 and the amplified signal is fed to a scanning speed modulation coil 200 by an output circuit 50 to emphasize a contour of a video image. A current detection circuit 70 detects a mean current of the output circuit and a comparator circuit 80 compares the current with a reference voltage. When the former exceeds the latter as the result of comparison, the gain of the amplifier circuit 30 is reduced to suppress a current flowing to the output circuit 50.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a television receiver provided with a contour emphasizing circuit for emphasizing the contour of an image displayed on a cathode ray tube display device, and more specifically, it constitutes such a contour emphasizing circuit. The present invention relates to a scanning speed modulation circuit as a constituent element.

[0002]

2. Description of the Related Art As one of the methods for improving the sharpness of a television image and improving the image quality, as described in Japanese Patent Publication No. 55-37903, the scanning of a cathode ray tube electron beam for scanning at a constant speed. A scanning speed modulation method is known in which the speed is modulated to enhance the contour of an image displayed on a cathode ray tube. This method utilizes the fact that in a cathode ray tube electron beam, the image becomes darker when the scanning speed is increased and becomes brighter when the scanning speed is slowed down. Therefore, the resolution does not deteriorate due to the increase of the beam spot diameter.

Here, the configuration of a television receiver including the above-described contour enhancement circuit adopting the conventional scanning velocity modulation method as a contour enhancement circuit for enhancing the contour of an image will be described with reference to FIG. . In the figure, 0 is an input terminal, 1
00 is a scanning speed modulation circuit, 200 is a scanning speed modulation coil, 300 is a video signal processing circuit, 400 is a video circuit,
Reference numeral 500 is a cathode ray tube cathode, and 600 is a cathode ray tube (Braun tube).

In FIG. 2, the video signal input to the input terminal 0 is subjected to various required video signal processing in the video signal processing circuit 300, amplified in the video circuit 400, and input to the cathode 500 of the cathode ray tube 600. It is displayed as an image. In addition, the video signal input to the input terminal 0 is input to the scanning speed modulation circuit 100 to create a scanning speed modulation signal to be applied to the scanning speed modulation coil 200.

In Japanese Patent Publication No. 55-37903, a signal obtained by quadratic differentiation of a video signal is applied to a scanning velocity modulation coil, and is supplied as a correction current for enhancing the contour, whereby the contour according to the above scanning velocity modulation method is applied. The emphasis is realized. The specific method will be briefly described with reference to FIG.
3 is a signal waveform diagram showing the waveform of each signal in FIG.

Please refer to FIG. 2 and FIG. Input terminal 0
When a video signal as shown in (a) is input, a signal as shown in (b) of FIG. 3 is applied to the scanning velocity modulation coil 200, and a correction current as shown in (c) of FIG. 3 is applied. As a result, the luminance change of the image on the cathode ray tube 600 becomes as shown in FIG. Here, (b) is the secondary differential waveform of the video signal (a), and (c) is the primary differential waveform of the video signal (a). As a result, the contour of the image is emphasized and the sharpness is improved.

[0007]

[Problems to be Solved by the Invention] Japanese Patent Publication No. 55-37
In the scanning velocity modulation circuit disclosed in Japanese Patent No. 903, for example, when a video signal containing a large amount of high frequency components such as noise is input to the input terminal 0, the effective value of the correction current increases and the power consumption significantly increases. There was a problem. Here, a video signal containing a lot of high-frequency components such as noise is a television signal in a weak electric field, or a signal for measurement output from a measuring instrument during multiburst measurement and applied to a television receiver (not noise However, there are many high-frequency components) and so on.

Japanese Examined Patent Publication No. 55-37903 does not particularly mention or consider the problem of increase in power consumption due to the high frequency component. In the present invention,
Considering such a problem, a television receiver including a scanning speed modulation circuit and a contour enhancement circuit including the modulation circuit, which does not significantly increase power consumption even when a signal having many high frequency components such as noise is input. The purpose is to provide a machine.

[0009]

In order to achieve the above object, the present invention provides a cathode ray tube display device with a modulation coil for modulating the scanning speed of an electron beam, and displays an image on the cathode ray tube display device. In this case, the scanning speed modulation circuit supplies the scanning speed modulation signal created therein to the modulation coil to flow the signal, thereby enhancing the contour portion of the image displayed on the cathode ray tube display device. As a scanning speed modulation circuit,

A scanning speed modulation signal processing circuit for generating the scanning speed modulation signal from the video signal to be displayed, and a variable gain amplifier circuit for amplifying the scanning speed modulation signal which is an output signal of the scanning speed modulation signal processing circuit, An amplifier circuit for amplifying an output signal of the variable gain amplifier circuit, an output circuit for supplying an amplified output from the amplifier circuit to the modulation coil and causing it to flow, and a current detection circuit for detecting an output current of the output circuit. And a comparison circuit for comparing a current detection value by the current detection circuit with a given reference voltage value, and a gain of the variable gain amplification circuit is reduced when the current detection value exceeds the reference voltage value as a result of the comparison. The present invention proposes a scanning speed modulation circuit including the gain control means for controlling the gain control means, and a television receiver provided with a contour enhancement circuit including the scanning speed modulation circuit.

[0011]

According to the present invention, in the scanning speed modulation circuit,
When a video signal having many high frequency components such as noise is input, the current flowing through the output circuit can be suppressed, and the power consumption does not increase significantly.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a scanning speed modulation circuit as an embodiment of the present invention. In the figure, 100S
Is a scanning speed modulation circuit according to the present invention, 10 is an input terminal, 2 is
0 is a scanning speed modulation signal processing circuit, 30 is a variable gain amplification circuit, 40 is an amplification circuit, 50 is an output circuit, 70 is a current detection circuit, 80 is a comparison circuit, 200 is a scanning speed modulation coil,
Is.

Although FIG. 3 has been described above as a signal waveform diagram showing the waveform of each part signal in FIG. 2, a signal useful for explaining the waveform of each part signal in the embodiment of the present invention shown in FIG. Since it is a waveform diagram, the circuit operation will be described below with reference to FIGS. 1 and 3.

A video signal input to the input terminal 10 (see FIG.
3 (a) is subjected to necessary signal processing by the scanning speed modulation signal processing circuit 20 and becomes the signal (b) in FIG. This signal (b) is amplified by the variable gain amplifier circuit 30 and the amplifier circuit 40, and is applied to the scanning speed modulation coil 200 by the output circuit 50. At this time, the scanning velocity modulation coil 2
A current as shown in (c) of FIG. 3 flows through 00, and the luminance change of the image on the cathode ray tube 600 (FIG. 2) is as shown in FIG.
As shown in (d), the contour of the image can be emphasized.

The current detection circuit 70 outputs the output circuit 50.
The average current flowing through the circuit is detected and compared with a reference voltage value (not shown) separately determined by the comparison circuit 80. As a result of this comparison,
When the average current detection value is smaller than the reference voltage value, the gain control of the variable gain amplification circuit 30 is not performed, but when the average current detection value exceeds the reference voltage value, the variable gain amplification circuit 30 is not.
Scanning speed modulation coil 2 by reducing the gain of
The amplitude of the signal applied to 00 is reduced, and the current flowing through the output circuit 50 is suppressed.

The case where the average current detection value exceeds the reference voltage value will be described. In FIG. 1, the input terminal 1
When a signal with many high frequency components such as noise is input to 0,
A current having a waveform as shown in FIG. 4 flows through the scanning velocity modulation coil 200, and the effective value of the current increases. Here, in FIG.
It is a waveform diagram which shows an example of the current waveform which flows into a scanning velocity modulation coil, when the signal with many high frequency components, such as noise, is input into the scanning velocity modulation circuit.

Therefore, in FIG. 1, the current detection circuit 7
The average current detection value detected at 0 also increases and exceeds the reference voltage value. In such a case, by decreasing the gain of the variable gain amplifier circuit 30, the amplitude of the signal applied to the scanning speed modulation coil 200 is decreased and the output circuit 5
The current flowing to 0 is suppressed. In this way, an increase in power consumption can be significantly suppressed.

FIG. 5 is a block diagram showing a specific example of the scanning speed modulation signal processing circuit 20 in FIG. In FIG. 5, 21 is an LC differentiating circuit, and 22 is also an LC differentiating circuit. As shown in FIG. 5, the scanning speed modulation signal processing circuit 20
Can be constructed by a simple second order differentiating circuit.

FIG. 6 is a circuit diagram showing a specific example of the scanning speed modulation circuit as an embodiment of the present invention. This circuit diagram corresponds to the variable gain amplifier circuit 30, the amplifier circuit 40, the output circuit 50, the scanning speed modulation coil 200, the current detection circuit 70, and the comparison circuit 80 in the block diagram shown in FIG. Is. The operation of this circuit example will be described below.

In FIG. 6, the current detection resistor 71 and the smoothing capacitor 72 convert the average value of the collector current of the output transistor 52 into a voltage, and the voltage value (hereinafter referred to as the average current detection value) is converted into a constant voltage. The reference voltage value determined by the source 81 is compared. When the average current detection value is smaller than the reference voltage value, the transistor 33 is in a cutoff state, and the gain of the variable gain amplifier circuit 30 surrounded by the broken line in the figure is determined by the transistors 31 and 32 and the resistors 34 and 35. It

When the average current detection value exceeds the reference voltage value,
The current starts to flow through the transistor 33, the gain of the variable gain amplifier circuit 30 decreases, the amplitude of the signal applied to the scanning speed modulation coil 200 decreases, and the output transistors 51 and 52 are output.
The electric current flowing through is suppressed. In this example, resistors 82,
By changing the resistance value of 83, the variable sensitivity of the variable gain amplifier circuit 30 can be easily adjusted.

The embodiment of the television receiver provided with the contour enhancement circuit including the scanning speed modulation circuit according to the present invention described above is shown in FIG.
Can be easily realized by substituting the scanning speed modulation circuit according to the present invention with, so further explanation will be unnecessary.

[0023]

According to the present invention, in a scanning speed modulation circuit which constitutes an outline emphasis circuit of a television receiver or the like,
When a signal with many high frequency components such as noise is input,
The current flowing through the output circuit can be suppressed and power consumption can be reduced. Therefore, the power loss of the transistor of the output circuit is also reduced, and there is an advantage that an inexpensive element can be used for the transistor of the output circuit.

[Brief description of drawings]

FIG. 1 is a block diagram showing a scanning speed modulation circuit as an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration example of a television receiver including a video contour enhancement circuit including a scanning speed modulation circuit.

3 is a signal waveform diagram showing operation waveforms of respective parts of the scanning speed modulation circuit shown in FIG. 1 or FIG.

FIG. 4 is a waveform diagram showing an example of a current waveform of the scanning velocity modulation coil when a signal having many high frequency components is input.

5 is a block diagram showing a specific example of a scanning speed modulation signal processing circuit in FIG.

FIG. 6 is a circuit diagram showing a specific example of a scanning speed modulation circuit as an embodiment of the present invention.

[Explanation of symbols]

20 ... Scan speed modulation signal processing circuit, 21, 22 ... LC differentiating circuit, 30 ... Variable gain amplifying circuit, 31, 32, 33,
51, 52 ... Transistors, 34, 35, 71, 82,
83 ... Resistor, 40 ... Amplifying circuit, 50 ... Output circuit, 72
... Capacitor, 81 ... Constant voltage source, 70 ... Current detection circuit,
80 ... Comparison circuit, 100 ... Scanning speed modulation circuit, 100S
... scan speed modulation circuit according to the present invention, 200 ... scan speed modulation coil, 300 ... video signal processing circuit, 400 ... video circuit, 500 ... cathode, 600 ... cathode ray tube

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuhiro Umizaki 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Hitachi, Ltd. Information & Video Media Division (72) Akira Ueno Yoshida, Totsuka-ku, Yokohama-shi, Kanagawa 292, Machi Incorporated company Hitachi Image Information System

Claims (3)

[Claims] 1. A cathode-ray tube display device is provided with a modulation coil for modulating the scanning speed of an electron beam, and when an image is displayed on the cathode-ray tube display device, a scanning speed created by the scanning speed modulation circuit thereat. The scanning speed modulation circuit in a contour enhancement circuit for enhancing a contour portion of an image displayed on the cathode ray tube display device by supplying a modulation signal to the modulation coil and causing the modulation signal to flow. A scanning speed modulation signal processing circuit for generating the scanning speed modulation signal from the scanning speed modulation signal processing circuit, a variable gain amplification circuit for amplifying the scanning speed modulation signal which is an output signal of the scanning speed modulation signal processing circuit, and an output signal of the variable gain amplification circuit. An amplifying circuit for amplifying, and an output circuit for supplying the amplified output from the amplifying circuit to the modulation coil and letting it flow.
A current detection circuit that detects the output current of the output circuit, a comparison circuit that compares the current detection value of the current detection circuit with a given reference voltage value, and the comparison result shows that the current detection value exceeds the reference voltage value. In this case, the scanning speed modulation circuit comprises: a gain control means for reducing the gain of the variable gain amplification circuit. 2. The scanning speed modulation circuit according to claim 1, wherein the current detection circuit includes a circuit that detects a current flowing through a collector of an output transistor that constitutes the output circuit. circuit. 3. A television receiver comprising an edge enhancement circuit including the scanning speed modulation circuit according to claim 1. Description: