JPH0272723A - Sound circuit for pocketable television - Google Patents

Abstract

PURPOSE:To automatically switch an operation to a monaural receiving operation at the time of using a built-in speaker by connecting the output terminal of a low frequency amplifier in a pocketable television sound circuit to the input terminal of a stereo-monaural mode switching signal generation circuit intermittently by loading/unloading a stereo earphone to a stereo jack. CONSTITUTION:When the stereo earphone is connected to the stereo jack 108, the terminals (c) and (d) are disconnected from the output terminal of the low frequency amplifier circuit 107. Therefore, a transistor in the stereo-monaural mode switching signal generation circuit is turned off, and a signal is inputted to the stereo-monaural operation switching terminal (e) of a stereo demodulation circuit 104. Thereby, stereo reproduction can be performed and heard by the stereo earphone. When the stereo earphone is not connected to the stereo jack 108, an AC signal centering DC potential VDD/2 is inputted to the input terminal of the stereo-monaural mode switching signal generation circuit 109, which energizes the transistor. Therefore, the stereo demodulation circuit 104 can perform a monaural operation.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field 1] The present invention relates to a technology for switching between stereo and monaural reception operations when receiving radio and stereo broadcasts on a pocket television equipped with an FM radio broadcast reception function.

[Prior Art 1] Pocket televisions, especially composite type pocket televisions in which a radio reception function is added to a liquid crystal display type pocket television, have come to be seen here and there on the market. If you classify radios by reception function, there are FM monaural only types, FM
There are also types that can receive stereo broadcasts and even AM broadcasts at the same time.

However, in these pocket TVs with radio broadcast reception function, the product concept is that the TV is the main component and the radio is only a secondary feature. For example, pocket TVs are limited in size and space, so they are limited to only one built-in speaker. Even if the radio can receive FM stereo broadcasts, it only has one built-in speaker.
It is possible to receive FM stereo broadcasts only when using stereo earphones.

[Problems to be Solved by the Invention] The problems to be solved by the present invention arise because pocket TVs in particular are required to be small, thin, and low cost, and are as follows. The content is

As an audio output device for a pocket TV with FM radio broadcast reception function, it is equipped with only one built-in speaker inside the main body.
Pocket TVs with an FM radio broadcast receiving function that use a stereo mini-phon as an earphone by attaching and detaching it to a stereo jack have the following problems.

There is no problem if the broadcast you are receiving is a TV broadcast, but if you are receiving an FM stereo broadcast and are using stereo earphones attached to the stereo jack, both the left audio signal and the right audio signal will be affected. It plays without any problems, but
When using the built-in speakers without wearing stereo earphones, only the left audio signal or the right audio signal can be played. Which one can be played depends on which output signal is connected to the only built-in speaker. Therefore, viewers will listen to FM stereo broadcasts in an abnormal manner, and once they notice an abnormality in sound quality, they will have to manually switch the external switch from stereo to monaural6.Furthermore, if the external switch is During operation, even if stereo earphones are used, the FM stereo demodulation circuit is in a monaural operating state, so stereo broadcasting cannot be heard, and it is necessary to similarly switch from monaural to stereo using an external changeover switch.

The present invention has been made in view of the above-mentioned problems, and its purpose is to provide one built-in speaker in the main body as an audio output device, and a speaker for connection from the outside.
For pocket TVs with FM radio broadcast reception function that have stereo earphones, the reception mode automatically switches to monaural operation when using the built-in speaker and to stereo operation when using stereo earphones. An object of the present invention is to provide an audio circuit for a boget television with a radio broadcast receiving function.

[Means to solve the problem 1 In order to solve the problems of the conventional technology as mentioned above.

The audio circuit of the pocket TV with FM radio broadcast receiving function which uses only one built-in speaker and stereo earphones as audio output devices according to the present invention is a stereo system that generates a stereo/monaural mode switching signal consisting of a diode, a capacitance, a transistor, and a resistor.・It has a monaural mode switching signal generation circuit, and the stereo/monaural mode switching signal generation circuit allows the output terminal of the audio circuit for the pocket TV with FM radio broadcast reception function to switch to the stereo mode by attaching and detaching the stereo earphones to the stereo jack.・Monaural mode switching It is intermittent with the input terminal of the large signal generation circuit, and a switching signal is generated according to the intermittent operation, and the receiving mode is switched to monaural when using the built-in speaker and to stereo when using stereo earphones. do.

[Example] Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of an audio circuit for a pocket television with an F, M radio reception function having a stereo/monaural reception mode switching signal generation circuit according to the present invention.

In Fig. 1, 101 is a TV FM detection circuit, 102
TV day emphasis circuit 5103 is a radio FM detection circuit, 104 is a stereo demodulation circuit, 105 and 106 are radio day emphasis circuits, 107 is a low frequency amplification circuit, 108 is a stereo jack, 109 is a stereo/monaural mode switching signal The generating circuit 110 is a built-in speaker.

FIG. 2 shows an example of a stereo/monaural mode switching circuit, which is composed of a rectifier circuit consisting of a diode, a resistor, and a capacitance, and a switching transistor and a resistor.

First, a case will be described in which a TV broadcast wave is received and an audio signal is listened to. Naturally, when watching TV, the radio FM detection circuit 103, the stereo demodulation circuit 104, and the stereo/monaural mode switching signal generation circuit 109 do not operate, so the output terminals of the stereo demodulation circuit The output becomes Low. TV FM detection circuit 1
The TV audio signal detected by 01 is de-emphasized by a TV day emphasis circuit 102, and then input to a low frequency amplification circuit 107, and the amplified signal is
, Rout.

At this time, regardless of whether the built-in speaker 11O or a stereo miniphon (not shown) is used as the audio output device, since the TV audio itself is monaural audio, there is no abnormality in the reproduced audio.

Next, a case will be described in which the user is listening to a stereo broadcast of FM radio. Naturally, at this time, the television FM detection circuit 101 does not operate, and the detection output is LOW.

The stereo composite signal detected by the radio FM detection circuit 103 is demodulated by the next stage stereo demodulation circuit 104, and then
The signal is de-emphasized by radio de-emphasis circuits 105 and 106 and input to a low frequency amplification circuit 107, and the amplified signal is output to LOut and Rout terminals.

At this time, consider the case where stereo earphones are connected to the stereo jack to listen to audio. Assuming that stereo earphones (not shown) are connected to the stereo jack 108, the terminals ■ and @ are connected to the low frequency amplifier circuit 10.
It is separated from the output terminal of 7. Therefore, the pace potential of the transistor in the stereo/monaural mode switching signal generation circuit shown in FIG. 2 becomes Low, and the transistor is turned off.

Therefore, the collector potential becomes High and is input to the stereo/monaural operation switching terminal (2) of the stereo demodulation circuit 104 in FIG.

When the stereo demodulation circuit 104 switches between stereo and monaural operation, if the terminal ■ is High and the operation is stereo, an L signal and an R signal are output to the output terminals ■ and ■ of the stereo demodulation circuit 104, respectively, and the low frequency amplification is performed. circuit 10
After being amplified in step 7, it can be played back in stereo and listened to with stereo earphones.

(2) When the terminal is Low and stereo operation is performed, it is natural that the same result can be obtained by replacing the stereo/monaural switching signal generation circuit shown in FIG. 2 with an emitter follower.

Next, consider a case where a stereo miniphone (not shown) is not connected to the stereo jack 108.

The low frequency amplification circuit 107 is a hybrid IC for boat fishing.
, and the DC potential of the output terminals Lout and Rout is normally two times the power supply voltage vDD (not shown immediately). At the input terminal, the potential at point 2 of the DC amount becomes High due to the rectifying action of the diode, capacitor, and resistor, causing the transistor to conduct.

Therefore, the collector potential in FIG. 2 becomes Low, and this signal is input to the stereo/monaural mode switching terminal (2) of the stereo demodulation circuit 104 in FIG. 1, so the stereo demodulation circuit 104 operates in monaural mode. Therefore, the output terminals ■, ■, and furthermore, the output terminal Lo of the low frequency amplifier circuit 107
monaural audio will be played in the ut, Rou-car.

[Effects of the Invention] As described above, the audio circuit of the pocket TV with FM radio broadcast reception function according to the present invention has a stereo/monaural mode switching signal generation circuit consisting of a diode, a capacitance, a transistor, and a resistor, and further includes: , the stereo/monaural mode switching signal generation circuit can be used by attaching and detaching stereo earphones to the stereo jack.
The output terminal of the low-frequency amplifier circuit of the pocket TV audio circuit and the input terminal of the stereo/monaural mode switching signal generation circuit are intermittent, and depending on the intermittent operation, the receiving mode changes to stereo mode or switches to monaural mode. It is characterized by having the ability to change.

Therefore, in the audio circuit of the pocket television with FM radio broadcast reception function of the present invention, the number of parts is relatively small.
In addition, without changing the structure of the pocket TV, it is an inexpensive method that automatically switches to stereo broadcasting when using a stereo mini phone when listening to FM stereo broadcasts, and automatically switches to monaural reception when using the built-in speakers. In addition, the present invention is effective in increasing the attractiveness and marketability of the additional functions of pocket TVs with FM radio broadcast reception functions, and is very meaningful in expanding the market for pocket TVs. I can say that.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the audio circuit of a pocket television according to the present invention. FIG. 2 is an example diagram of a stereo/monaural mode switching signal generation circuit according to the present invention. Applicant: Seiko Epson Corporation

Claims (1)

[Claims] In an audio circuit for a pocket TV with an FM radio broadcast receiving function that uses one built-in speaker and stereo earphones as audio output devices, the audio circuit has a stereo/monaural mode switching signal composed of at least a diode, a capacitance, a transistor, and a resistor. The stereo/monaural mode switching signal generation circuit generates a stereo/monaural mode switching signal generation circuit that enables the stereo/monaural mode switching signal generation circuit to switch the audio circuit of the pocket TV with FM radio broadcast reception function by attaching and detaching the stereo earphones to the stereo jack. The output terminal of the frequency amplification circuit is intermittent with the input terminal of the stereo/monaural mode switching circuit, and due to this intermittent operation, a stereo/monaural mode switching signal is generated in the stereo/monaural mode switching signal generation circuit, and the built-in speaker is used. An audio circuit for pocket televisions that has a function of switching the reception mode to monaural at times and to stereo when using stereo earphones.