JPH0662416A - Color television receiver - Google Patents

Abstract

PURPOSE:To eliminate the addition of a mechanical PAL/NTSC changeover switch by changing the chroma mode via a transistor TR turned on/off in response to a mode switching signal. CONSTITUTION:A mode switch signal output terminals 13 and 14 of a microcomputer 5 are set at L and H levels respectively with the input of the video signal of the PAL mode. Then an analog switch 2 is switched toward an input terminal 2a to select the video signal 1 of the PAL system supplied from an external equipment. Meanwhile the TR 19 and 29' are turned on together with the TR 21 and 24 turned off respectively and the image of the video signals of the PAL system is displayed. When the video signal of the NTSC mode is inputted from the external equipment, both terminals 13 and 14 are set at L levels. Thus the switch 2 is changed over to the side of the terminal 2a to select the video signal of the NTSC system. At the same time, the TR 19 and 29' are turned off with the TR 21 and 24 turned on respectively. Then the image of the video signals of the NTSC mode is displayed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color television receiver, and more particularly to a color television receiver capable of displaying a color image according to video signals of different chroma modes inputted from an external device. is there.

[0002]

2. Description of the Related Art For color television broadcasting, for example, the PAL system and the NTSC system are adopted in each country. Therefore, the color television receiver is manufactured so as to conform to the broadcasting system of the color television broadcasting in the viewing area (country). Further, the color television receiver is provided with a terminal capable of inputting a video signal from an external device, such as a CD player or a video tape recorder, so that an image based on the video signal from the external device can be displayed.

However, for example, in a PAL-type color television receiver, an external device different from the PAL-type NTSC is used.
When it becomes necessary to input the video signal of the system, the color image by the video signal is not displayed.
In order to eliminate such inconvenience, PA
A switch that can switch between L format and NTSC format is provided, and it is modified to support video signals with different chroma modes.

FIG. 1 is a block diagram showing the essential structure of a conventional color television receiver modified by adding a mechanical switch for switching between the PAL system and the NTSC system. The video signal 1 input to the external signal input terminal CN from an external device (not shown) such as a CD player or a video tape recorder is given to the input terminal 2a of the analog switch 2,
The video detection output signal 7 received from the broadcast and output from the video intermediate frequency amplifier circuit is given to the input terminal 2b. The video signal or the video detection output signal 7 selected by the analog switch 2 is input to the composite circuit 3 including a delay line, a 4.43 MHz trap and a bandpass filter.

The luminance signal S _B and the chroma signal S _C separated into the luminance signal and the chroma signal by the composite circuit 3 are input to the IC 4 including the video circuit and the chroma circuit, and the IC
The chroma demodulation signal S _D is output from the chroma demodulation output terminal 12 of FIG. The mode switching signal output terminal 13 of the microcomputer 5 for controlling the signal of each part is a resistor 16
Is connected to the power supply + B via the resistor 17, and is connected to the switching signal terminal 2c of the analog switch 2 via the resistor 17.

The circuit for transmitting the brightness signal S _B from the composite circuit 3 is connected to the collector of the grounded-emitter transistor 21 via a 3.58 MHz trap. IC4 PAL / NT
Between the SC switching terminal 8 and the vertical circuit 50Hz / 60Hz switching terminal 9, a series circuit of a resistor 25 and a resistor 26 is provided.
The connecting portion between 25 and 26 is connected to the output terminal 32 of the PAL / NTSC changeover switch 31 and is connected to the base of the transistor 21 via the resistor 22. The other end of the 3.58MHz crystal oscillator 10 whose one end is connected to the oscillator connection terminal 4a of the IC4 is connected to the collector of the transistor 24 whose emitter is grounded, and its base is connected to the output terminal 32 via the resistor 23. ing.

The other end of the 4.43 MHz crystal oscillator 11, one end of which is connected to the oscillator connection terminal 4b of the IC 4, is connected to the emitter of the transistor 29 whose collector is grounded, and the base of which is the output terminal via the resistor 30. Connected with 32. The collector of the transistor 24 is connected via the resistor 27, and the emitter of the transistor 29 is connected via the resistor 28 to the power source + B. The power supply connection terminal 33, which is selectively connected to the output terminal 32 of the PAL / NTSC selector switch 31, is connected to the power supply + B via the resistor 35.
And the ground terminal 34 is grounded.

Next, the operation of this color television receiver will be described. The video signal 1 from the external device input to the external signal input terminal CN and the video detection output signal 7 output from the video intermediate frequency amplifier circuit into which the signal received the broadcast is input are the mode switching of the microcomputer 5. It is selected and amplified by the analog switch 2 which is switch-controlled by the control signal output from the signal output terminal 13. The amplified signal is input to the composite circuit 3, separated into the luminance signal S _B and the chroma signal S _C , input to the IC 4, and subjected to signal processing, and then output from the chroma demodulation output terminal 12 Are supplied to a cathode ray tube (not shown).

If the PAL / NTSC selector switch 31 is switched to the ground terminal 34 side, the transistors 21 and 24 are turned off and the transistor 29 is turned on. Therefore 4.43MHz
The crystal oscillator 11 is grounded. Also, PAL / NTSC switching terminal 8
The vertical circuit 50Hz / 60Hz switching terminal 9 is grounded through the resistors 25 and 26, so that the IC 4 operates in the 50Hz PAL mode.

Next, if the PAL / NTSC selector switch 31 is switched to the power supply connection terminal 33 side, the transistors 21 and 24
Both turn on and the transistor 29 turns off. As a result, the 3.58 MHz crystal oscillator 10 and the 3.58 MHz trap 6 are grounded. Also, the PAL / NTSC switching terminal 8 of IC4 is connected to the resistor 35.
The vertical circuit 50Hz / 60Hz switching terminal 9 is pulled up by the power source + B via the series circuit of 25 and the series circuit of the resistors 35 and 26, respectively, and the IC 4 operates in the 60Hz NTSC mode.

[0011]

However, since the conventional color television receiver is remodeled by using a mechanical switch for the PAL / NTSC changeover switch, it is necessary to select its mounting location and perform mechanical processing. Therefore, the remodeling cost is high. There is also a problem that the aesthetic appearance of the color television receiver may be impaired depending on the mounting location.

In view of the above problems, the present invention is based on the PAL system or
An object of the present invention is to provide a color television receiver capable of changing to a chroma mode according to a video signal input from an external device without adding a mechanical switch for switching the NTSC system.

[0013]

A color television receiver according to the present invention is turned on or off by a mode switching signal output from a microcomputer when a video signal in a predetermined chroma mode is input from an external device. A transistor is provided which is turned off to selectively operate an oscillator for changing to a chroma mode according to a video signal from an external device.

[0014]

When the video signal in the predetermined chroma mode is input from the external device, the microcomputer outputs the mode switching signal according to the predetermined chroma mode. The transistor is turned on or off according to the mode switching signal, and the oscillator for changing to the predetermined chroma mode is selectively operated. Therefore, when the video signal in the predetermined chroma mode is input from the external device, the chroma mode of the video signal input from the external device is automatically changed.

[0015]

The present invention will be described in detail below with reference to the drawings showing the embodiments thereof. FIG. 2 is a block diagram showing a main configuration of a color television receiver according to the present invention. Video signal 1 input to the external signal input terminal CN from an external device (not shown) such as a CD player or a video tape recorder is applied to the input terminal 2a of the analog switch 2, and the video signal to which the broadcast is received is input. The video detection output signal 7 output from the intermediate frequency amplifier circuit is given to the input terminal 2b.

The video signal or video detection output signal 7 selected by the analog switch 2 is input to a composite circuit 3 including a delay line, a 4.43 MHz trap and a bandpass filter. Is separated into a chroma signal S _C luminance signals S _B by the composite circuit 3, the luminance signal S _B and the chroma signal S _C is
It is input to the IC4 equipped with the video circuit and the chroma circuit, and the chroma demodulation signal S is output from the chroma demodulation output terminal 12 of the IC4.
_D is output.

The mode switching signal output terminal 13 of the microcomputer 5 is connected to the power source + B via the resistor 16, and
It is connected to the switching signal terminal 2c of the analog switch 2 via 17. The mode switching signal output terminal 14 of the microcomputer 5 is connected to the power source + B via the resistor 15, is connected to the base of the transistor 19 described later via the resistor 18, and is connected to the base of the transistor 29 'described later via the resistor 30. It is connected to the base. Luminance signal S _B from composite circuit 3
Is connected to the collector of the transistor 21 having a grounded emitter through the 3.58 MHz trap 6.

PAL / NTSC switching terminal 8 of IC4 and vertical circuit
A series circuit of a resistor 25 and a resistor 26 is interposed between the 50Hz / 60Hz switching terminal 9, and a connection portion between the resistors 25 and 26 is connected to the base of the transistor 21 via the resistor 22, It is also directly connected to the collector of the transistor 19. The collector of the transistor 19 is connected to the power source + B via the resistor 20. The other end of the 3.58MHz crystal oscillator 10 whose one end is connected to the oscillator connection terminal 4a of the IC4 is connected to the collector of the transistor 24 whose emitter is grounded, and its base is the resistor 23.
Is connected to the collector of the transistor 19 through.

The other end of the 4.43 MHz crystal oscillator 11 whose one end is connected to the oscillator connection terminal 4b of the IC 4 is connected to the collector of the grounded emitter transistor 29 ', and its base is connected via the resistor 30 to the micro. It is connected to the mode switching signal output terminal 14 of the computer 5. The collector of the transistor 24 is connected via the resistor 27, and the collector of the transistor 29 'is connected via the resistor 28 to the power source + B. The mode switching signal output terminal of the microcomputer 5
When the PAL system broadcast is received, both 13 and the mode switching signal output terminal 14 become "H" level.

On the other hand, when a PAL video signal is input from an external device, the mode switching signal output terminal 13 becomes "L" level and the mode switching signal output terminal 14 becomes "H" level. When an NTSC video signal is input from an external device, both the mode switching signal output terminal 13 and the mode switching signal output terminal 14 become "L" level.

Next, the operation of the color television receiver thus constructed will be described. The video signal 1 from the external device input to the external signal input terminal CN and the video detection output signal 7 output from the video intermediate frequency amplifier circuit into which the signal received the broadcast is input are the mode switching of the microcomputer 5. It is selected and amplified by the analog switch 2 that performs a switching operation by the switching signal output from the signal output terminal 13. The amplified signal is input to the composite circuit 3, separated into the luminance signal S _B and the chroma signal S _C , input to the IC 4 including the video circuit and the chroma circuit, and subjected to signal processing and then chroma demodulation. A chroma demodulation signal is given from the output terminal 12 to a cathode ray tube (not shown).

Now, for example, when a remote control device (not shown) is operated to receive a broadcast, both the mode switching signal output terminal 13 and the mode switching signal output terminal 14 become "H" level, and the analog switch 2 Is the input terminal 2b side Switch to. Also transistor 19,
Both 29 'are turned on and both transistors 21 and 24 are turned off. As a result, the PAL system video detection output signal is selected and amplified by the analog switch 2, separated by the composite circuit 3 into the luminance signal S _B and the chroma signal S _C, and input to the IC 4, where the signal is processed as the 50 Hz PAL system. The demodulated chroma signal S _D is applied to a cathode ray tube (not shown), and a color image of the received PAL system broadcast is displayed on the cathode ray tube.

Next, when the remote control device is operated to input the PAL system video signal from the external device, the mode switching signal output terminal 13 becomes "L" level,
The mode switching signal output terminal 14 becomes "H" level. Then, the analog switch 2 is switched to the input terminal 2a side, and the PAL video signal 1 from the external device is selected by the analog switch 2 and amplified. Further, the transistors 19 and 29 'are turned on, and the transistors 21 and 24 are turned off. Then, as described above, the IC4 processes the signal in the 50Hz PAL system, and the demodulation chroma signal output terminal 12 outputs the demodulation chroma signal in the chroma mode according to the video signal from the external device. Display a color image of the signal.

Next, when the remote control device is operated to input the video signal of the NTSC system from the external device, both the mode switching signal output terminal 13 and the mode switching signal output terminal 14 become "L" level. Therefore, the analog switch 2 is switched to the input terminal 2a side to select and amplify the NTSC video signal from the external device. Also, transistors 19 and 29 'are both turned off, and transistors 21 and 24'
Both turn on. The amplified signal is selected is separated into a chroma signal S _C brightness signal S _B in the composite circuit 3, the luminance signal S _B and the chroma signal S _C is signal processed in the input 60HzNTSC scheme IC 4, A demodulation chroma signal output terminal 12 outputs a chroma mode demodulation chroma signal in accordance with a video signal from an external device, which is given to a Braun tube, and an image of an NTSC video signal from the external device is displayed on the Braun tube.

That is, the transistor 19 is turned on or off in accordance with the mode switching signal output from the microcomputer 5 without using a mechanical PAL / NTSC switch for switching between the PAL system and the NTSC system. , PAL system or NTSC system can be switched to the chroma mode of the video signal input from the external device.
Therefore, there is no need to add a mechanical PAL / NTSC changeover switch for modification, so that mechanical processing for mounting the changeover switch is not necessary and the modification cost can be reduced. Further, the appearance of the color television receiver is not spoiled by the mounting of the changeover switch.

In this embodiment, the video signal is PAL system and NTSC.
Although the case of the method has been described, the same effect can be obtained in the case of the PAL method and the SECAM method, or in the case of the SECAM method and the NTSC method.

[0027]

As described above in detail, according to the present invention, the chroma mode is changed by the transistor which is turned on or off according to the mode switching signal output from the microcomputer with respect to the video signal from the external device having the different chroma mode. Since it was decided to do so, mechanical PAL / NT as in the past
There is no need to add an SC changeover switch, and there is no need for mechanical processing, which can reduce remodeling costs. Further, it has excellent effects such as not impairing the aesthetic appearance of the color television receiver.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a main part of a conventional color television receiver.

FIG. 2 is a block diagram showing a main configuration of a color television receiver according to the present invention.

[Explanation of symbols]

 2 Analog switch 3 Composite circuit 4 IC 5 Microcomputer 6 3.58MHz trap 10 3.58MHz crystal oscillator 11 4.43MHZ crystal oscillator 13,14 Mode switching signal output terminal 19,21,24, 29 'transistor

Claims (1)

[Claims] 1. A video signal from an external device and a video detection signal of a broadcast being received can be selected by a mode switching signal output by a microcomputer controlling signals of respective parts. In a color television receiver provided with an oscillator having different oscillation frequencies for changing to a chroma mode according to the video signal, the oscillator is turned on or off in response to the mode switching signal. A color television receiver including a transistor for performing a selective operation, and being configured to change to a chroma mode according to a video signal by turning on or off the transistor.