JPH0690409A - Television reception circuit - Google Patents

Abstract

PURPOSE:To provide the television reception circuit which outputs a sound signal after such correction that the high frequency component of the sound signal is reduced in the case of the weak electric field reception state. CONSTITUTION:In a range correction block 18, a tone control block 21 outputs a 'Low' signal to a transistor TR Q3 when judging it by detection information inputted to a detection information input terminal that the PLL lock state is not released, and the block 21 outputs a 'Hi' signal to the TR Q3 when judging it by detection information that the PLL lock state is released. When the 'Low' signal is outputted, a TR Q1 is turned on by an input sound signal, and the sound signal is outputted from a sound output terminal through the emitter electrode of the TR Q1 and an output resistance RO; and when the 'Hi' signal is outputted, the TR Q3 is turned on, and the signal pass band characteristic is changed by the connection capacity in the TR Q3 to reduce the high frequency component of the sound signal, and the sound signal is outputted to a sound amplifier through the sound output terminal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a television receiving circuit, and more particularly to a television receiving circuit which corrects sound in a weak electric field.

[0002]

2. Description of the Related Art Conventionally, a television receiver has been owned by one person from one person in a family, has become more personalized, and is a small liquid crystal panel which can be moved from a room to a room by a battery drive. Television receivers using the TV are becoming popular.

As such a conventional television receiver,
For example, there is a block configuration as shown in FIG.
In FIG. 3, the television receiver 1 selects a designated channel, converts a reception radio wave supplied from the antenna 2 into an intermediate frequency signal, and outputs the intermediate frequency signal to the IF block 4.
And an IF block 4 that performs video detection of the intermediate frequency signal input from the tuner 3 and extracts the video signal and outputs it to the chroma block 5, and extracts the audio signal from this video signal and outputs it to the audio amplifier 8. , IF block 4
A chroma block 5 that performs Y / C separation, image correction, and other processing on a video signal input from the device, and then converts the video signal into R, G, and B signals for display, and outputs the signals to a display block 6, and a chroma block 5. A display block 6 for displaying a received image in accordance with a display signal input from the device, an audio amplifier 7 for amplifying the audio signal input from the IF block 4 and outputting the amplified audio signal to the speaker 8, and a control signal output to each of the above parts. And a control block 9 for controlling the channel change and volume.

In such a small-sized television receiver, the receiving place is constantly changed and the receiving situation is constantly changing. Therefore, in a place where the receiving situation is bad, such as in a valley of a building or in a tunnel, that is, in a weak electric field, an image and a sound are received. It will be disturbed. It is good if you don't see the distortion of the image, but the distortion of the sound is unbearable to hear. Therefore, in such a case, the television receiver 1
Then, the control block 9 detects the reception state of the synchronization signal during reception of broadcast radio waves by the audio mute function and outputs a control signal for muting the audio to the audio amplifier 8 to cut the audio output.

[0005]

However, in such a conventional television receiver, the audio output is cut by the audio mute function when the audio detection is not normally performed in the weak electric field. However, when the voice mute function does not operate and voice detection is not normally performed, there is a problem that the user hears a noisy voice that is noisy.

Therefore, an object of the present invention is to provide a television receiving circuit that corrects and outputs a high frequency component of an audio signal when the reception state is a weak electric field.

[0007]

According to the present invention, in a television receiving circuit for receiving a television radio wave and outputting a video signal and an audio signal, a receiving state detecting means for detecting the receiving state of the television radio wave, and the receiving state. Audio correction means for correcting so that the high frequency component of the audio signal decreases when the received electric field is detected as a weak electric field by the detection means.

[0008]

According to the present invention, when the reception electric field is detected as the weak electric field by the reception state detecting means, the high frequency component of the voice signal is corrected by the voice correcting means so as to be reduced.

Therefore, even in a weak electric field where voice detection is not normally performed, it is possible to output a voice with less high frequency components and which is not offensive to the ears.

[0010]

EXAMPLES Examples will be described below with reference to FIGS.

FIG. 1 is a diagram showing an embodiment of a television receiver to which the television receiving circuit of the present invention is applied.

First, the structure will be described. FIG. 1 is a block diagram of the television receiver 11. In this figure, the television receiver 11 includes an antenna 12, a tuner 13 and an I
F block 14, chroma block 15, display block 1
6, control block 17, range correction block 1
8, audio amplifier 19, speaker 20 and the like.

The antenna 12 receives the radio wave received by the tuner 13.
The tuner 13 is supplied to the control block 1
The designated channel is selected according to the band switching control signal input from the antenna 7, the reception radio wave supplied from the antenna 12 is converted into an intermediate frequency signal, and the intermediate frequency signal is output to the IF block 14.

The IF block 14 is composed of a video detection circuit, a video amplification circuit, etc., and the intermediate frequency signal input from the tuner 13 is subjected to video detection by the video detection circuit to extract the video signal and output it to the chroma block 15. At the same time, an audio signal is extracted from this video signal and output to the range correction block 18, and the detection information is output to the range correction block 18 by the video detection circuit. Here, the detection information indicates whether or not the audio signal is normally detected in the IF block 14, and generally, the detection PLL (Phase Locked Loop) of the video signal is locked. It is what outputs as a signal. That is, in the case of television received radio waves, if the lock of the detection PLL of the video signal is released, the reception state of the audio signal deteriorates, so the lock state of the detection PLL is used as detection information. As the detection information, in addition to the locked state of the PLL for detecting the video signal, the locked state of the PLL for the audio signal can be extracted and used as a signal. There are many other methods of extracting detection information depending on the detection method of the IF block 14,
In this embodiment, the information obtained by these detection methods can be used as the detection information.

The chroma block 15 is the IF block 14
The video signal input from the above is subjected to Y / C separation, image correction, etc., and then converted into R, G, B signals for display and the like and output to the display block 16. The display block 16 is composed of a liquid crystal display panel or the like, and displays a received image according to a display signal input from the chroma block 5. The control block 17 is composed of a microcomputer or the like, and outputs various control signals for controlling the tuner 13, the IF block 14, the chroma block 15 and the audio amplifier, and controls the channel change and volume of the tuner 13.

As shown in FIG. 2, the range correction block 18 is connected to the input stage transistor Q1, the input side coupling capacitor CCI connected to the base electrode of the transistor Q1, the base resistor RB1, and the emitter electrode of the transistor Q1. Emitter resistor RE1, output resistor RO connected between the emitter electrode and the audio output terminal, output stage protection resistor RL, noise elimination transistor Q2, and collector resistor RC connected to the collector electrode of transistor Q2.
2. Output side coupling capacitor CCO and transistor Q2
Delay capacitor CCB connected between the base and collector electrodes of the transistor Q2, a base resistor RB2 connected to the base electrode of the transistor Q2, an emitter resistor RE2 connected to the emitter electrode of the transistor Q2, and a bypass capacitor CB.
2, a voltage dividing resistor RB that divides the power supply voltage Vcc with the base resistor RB2, a bypass capacitor CB1 that bypasses a noise component of the power supply voltage Vcc, and operates according to a control signal input from the tone control block 21 to the base electrode. Then, the tone control block 21 outputs a control signal to the base electrode of the transistor Q3 according to the detection information input from the detection block input transistor Q3 and IF block 14 for reducing the high frequency component of the audio output. Composed of and.

In the tone range correction block 18, when the tone control block 21 determines from the detection information input to the detection information input terminal that the detection PLL is not out of lock, a control signal is sent to the base electrode of the transistor Q3. Is output as a “Low” signal, and when it is determined from the detection information that the detection PLL is out of lock, a control signal “H” is output to the base electrode of the transistor Q3.
When the "Low" signal is output, the transistor Q1 is turned on by the audio signal input from the IF block 14 through the audio input terminal, and the audio output is performed through the emitter electrode of the transistor Q1 and the output resistor RO. An audio signal is output from the terminal, at which time noise pulses and the like contained in the input audio signal are transmitted to the collector electrode side (point A in the figure) of the transistor Q2 and transmitted through the coupling capacitor CCO on the output side. The noise pulse contained in the output audio signal is canceled, and when the “Hi” signal is input to the transistor Q3, that is, when the lock state of the detection PLL of the video signal is released, the transistor Q3 is turned on. , The high-pass characteristic on the output side is changed by the connection capacitance in the transistor Q3, that is, the high-frequency component of the audio signal. Change the signal pass-band characteristics to reduce, and outputs to the audio amplifier 19 via the audio output terminal to reduce the high frequency component of the audio signal.

The voice amplifier 19 has a range correction block 18
The audio signal input from the speaker is amplified to drive the speaker 20, and the amplification factor is changed according to the control signal input from the control block 17 to adjust the output volume of the speaker.

Next, the operation of this embodiment will be described.

First, referring to FIG. 1, in the television receiver 11, the antenna 12 receives television radio waves, and the tuner 1
3, the tuner 13 selects a designated channel according to the band switching control signal input from the control block 17, converts the received radio wave supplied from the antenna 12 into an intermediate frequency signal, and outputs the IF block 14 to the IF block 14. Output to. In the IF block 14, the intermediate frequency signal input from the tuner 13 is subjected to video detection by the video detection circuit to extract the video signal and output it to the chroma block 15. At the same time, the audio signal is extracted from this video signal to correct the range. The signal is output to the block 18, and the lock state of the PLL for detecting the video signal by the video detection circuit is output to the range correction block 18 as detection information. The chroma block 15 performs Y / C separation, image correction, and other processing on the video signal input from the IF block 14, and then converts the video signal into R, G, B signals for display, and outputs the signals to the display block 16. The display block 16 displays the received image according to the chroma block 5 and the display signal input from the chroma block 5.

Next, in the tone range correction block 18 of FIG. 2, the tone control block 21 monitors the detection information input from the IF block 14 to the detection information input terminal, and this detection information indicates that the lock state of the detection PLL is normal. When determined, the control signal is output as a "Low" signal to the base electrode of the transistor Q3, and the transistor Q3
3 is cut off. At this time, the audio signal input from the IF block 14 through the audio input terminal turns on the transistor Q1, and the audio signal is output from the audio output terminal to the audio amplifier 19 through the emitter electrode of the transistor Q1 and the output resistor RO. . Also, noise pulses and the like included in the input audio signal are
2 is transmitted to the collector electrode side (point A in the figure) and is canceled out by the noise pulse contained in the output audio signal transmitted through the output side coupling capacitor CCO.

When the tone control block 21 determines that the detection PLL is out of lock, the tone range correction block 18 outputs a control signal as a "Hi" signal to the base electrode of the transistor Q3, and the transistor Q3 is turned on. Turn it on. At this time, the audio signal input from the IF block 14 through the audio input terminal is turned on by the transistor Q1, and this audio signal is transmitted by the transistor Q1.
Is input to the collector side of the transistor Q3 through the emitter electrode of the transistor Q3, but the high-pass characteristic on the output side is changed by the connection capacitance in the transistor Q3, that is, the signal pass band characteristic is reduced so as to reduce the high-frequency component of the audio signal. Is changed, and the audio signal in which the high frequency component of the audio signal is reduced by the transistor Q3 is output to the audio amplifier 19 through the audio output terminal.

Therefore, in the television receiver 11, the IF
Based on the detection information output from the block 14 to the range correction block 18, it is surely detected that the video detection is not normally performed, and the high frequency component of the audio signal detected by the range correction block 18 is detected according to the detection result. It is possible to reliably prevent the annoying sound from being output from the speaker 20 by reducing the noise, and to prevent the user from hearing the noisy audio that is noisy when the electric field is weak. it can.

As a result, by using the television receiver of this embodiment for an application such as an in-vehicle liquid crystal television whose electric field state is apt to change, it is possible to make it easy to hear the sound even in a situation where the image is easily disturbed. Therefore, the operability of tuning adjustment in a weak electric field can be improved.

[0025]

According to the present invention, the reception state detecting means for detecting the reception state of the television radio wave is provided, and when the reception state detecting means detects that the reception electric field is a weak electric field, the sound correcting means is used. Since the correction is performed so as to reduce the high-frequency component of the audio signal, it is possible to prevent the user from hearing a noisy and annoying sound when the electric field is weak. As a result, by utilizing the television image receiving circuit of the present invention in an application such as an in-vehicle liquid crystal television whose electric field state is likely to change, it is possible to make it easy to hear sound even in a situation where the image is easily disturbed, It is possible to improve the operability and the like of tuning adjustment in.

[Brief description of drawings]

FIG. 1 is a block diagram of a television receiver to which a television receiving circuit of the present invention is applied.

FIG. 2 is a circuit configuration diagram of a range correction block in FIG.

FIG. 3 is a block diagram of a conventional television receiver.

[Explanation of symbols]

 11 TV receiver 12 Antenna 13 Tuner 14 IF block 15 Chroma block 16 Display block 17 Control block 18 Range correction block 19 Audio amplifier 20 Speaker 21 Tone control block Q1, Q2, Q3 Transistor CCI, CCO Coupling capacitor

Claims (1)

[Claims] 1. In a television receiving circuit for receiving television radio waves and outputting a video signal and an audio signal, a reception state detecting means for detecting a reception state of the television radio waves, and a reception electric field of a weak electric field by the reception state detecting means. And a sound correcting unit that corrects the high frequency component of the sound signal so as to decrease.