JPH0641399Y2 - Portable broadcast receiver - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to an audio output circuit of a portable broadcast receiver for driving an external speaker incorporating an amplifier.

[Conventional technology]

In recent years, demand for portable television receivers such as liquid crystal television receivers and portable radio receivers such as card radios has been rapidly increasing.

A portable broadcast receiver cannot use a large speaker because of its overall size and weight, and it has a small speaker with a diameter of 25 mm to 40 mm. In addition, a portable broadcast receiver that has a multiplex audio broadcast reception function and an FM stereo broadcast reception function requires two speakers that are separated by a certain distance, but this is also achieved in terms of overall size, weight, and power consumption. It is difficult, and the reality is that only the earphones are stereo and the built-in speakers are monaural.

Therefore, an audio output signal is supplied from the earphone terminal of the portable broadcast receiver using an external speaker with a built-in amplifier.
It is used to make loud noises and reproduce stereo sound. This amplifier is a power switch ON / OF
In order to avoid the complication of F and to prevent forgetting to turn off the power, the method in which the power is turned on / off according to the level of the input audio signal is the mainstream.

[Problems to be solved by the device]

In this case, broadcast software often turns the power on and off to cause audio discontinuity, and to prevent a so-called POP sound being generated each time the power is turned on and off, making it difficult to hear.
The time constant of N is set to be short and the time constant of OFF is set to be long.However, the power is turned off when there is a long period of silence, such as in drama programs, and there are variations in threshold and temperature changes. Therefore, there is a problem that the signal level that turns on and off changes.

Therefore, in the present invention, the audio output signal of the portable broadcast receiver is weighted with a signal of a frequency other than the audible frequency band having a level sufficient to turn on the power of the amplifier incorporated in the external speaker, and the portable type As long as the power of the broadcast receiver is turned on, the amplifier power is not turned off so that the sound will not be discontinuous regardless of the broadcast software, or POP sound will not occur.

[Means for Solving the Problems]

The present invention is, firstly, in a portable broadcast receiver capable of connecting and using an external speaker having an amplifier whose power is turned on or off according to the level of an input audio signal. ON or OF
An output unit for outputting a frequency signal other than the audible frequency band having a level that enables F, and an external speaker drive terminal that is connected to the external speaker and supplies the input audio signal to the external speaker, A portable broadcast receiver, wherein a frequency signal other than the audible frequency band is superimposed on an audio signal and output from an external speaker drive terminal.

Secondly, the frequency signal other than the audible frequency band is obtained from the drive circuit of the light source of the liquid crystal panel.

〔Example〕

FIG. 1 is a circuit diagram showing a first embodiment of an audio output circuit of a portable broadcast receiver of the present invention.

In FIG. 1, the audio output signal (3) output from the audio signal amplifier (2) of the portable broadcast receiver (1) is replaced by a signal (of a frequency other than the audible frequency band generated by the oscillator (4) ( 5) is superimposed. The level of this signal (5) is sufficient to turn on the power source of the amplifier (8) in the external speaker (7) connected to the external speaker driving terminal (6).

FIG. 2 is a circuit diagram showing a second embodiment of the audio output circuit of the portable broadcast receiver of the present invention. FIG. 2 shows a case where the present invention is applied to a liquid crystal television receiver. In FIG. 2, the television broadcast radio wave received by the antenna (9) is selectively amplified by the tuner (10), frequency-converted, and sent to the IF amplifier (11), where it is amplified and video and audio detection is performed.
The video-detected signal is amplified by the video signal amplifier (12),
An image is displayed on the liquid crystal panel (14) through the panel drive circuit (13). Since the liquid crystal panel (14) does not emit light by itself, the backlight (1
5) is equipped. The backlight (15) is driven by the backlight drive circuit (16). This backlight drive circuit (16) is composed of an inverter, and its oscillation frequency is about 30 KHz other than the audible frequency. Therefore, a part (17) of this oscillation signal is superimposed on the audio output signal (3). There is. As a result, the power of the amplifier (8) in the external speaker (7) is turned on.

[Effect of device]

As described in detail above, when an external speaker having an amplifier for turning the power on and off according to the level of an input audio signal is connected to a portable broadcast receiver for operation, the portable broadcast receiver is used in the present invention. A portable broadcast receiver that employs an extremely simple circuit that superimposes a signal of a frequency other than the audible frequency band that has a level sufficient to turn on the power of the amplifier built into the external speaker to the audio output signal of the device. As long as the power is turned on, the power of the amplifier is not turned off so that the discontinuity of the sound or the pop noise does not occur regardless of the broadcasting software.

Therefore, it is possible to enjoy a powerful voice and stereo sound extremely comfortably with the external speaker.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a first embodiment of an audio output circuit of a portable broadcasting receiver of the present invention, and FIG. 2 is a second embodiment of an audio output circuit of a portable broadcasting receiver of the present invention. It is a circuit diagram showing. 1 ... Portable broadcasting receiver 2 ... Audio signal amplification section 3 ... Audio output signal 4 ... Oscillation section 5 ... Frequency signal other than audible frequency band 6 ... External speaker driving terminal 7 ... External speaker 8 …… Amplifier 9 …… Antenna 10 …… Tuner 11 …… IF amplifier 12 …… Video signal amplifier 13 …… Panel drive circuit 14 …… Liquid crystal panel 15 …… Backlight 16 …… Backlight drive circuit 17… … Part of the oscillation signal

Claims (2)

[Scope of utility model registration request] 1. A portable broadcast receiver capable of connecting and using an external speaker having a built-in amplifier that turns on or off according to the level of an input audio signal, wherein the amplifier built in the external speaker is turned on or off.
An output unit for outputting a frequency signal other than the audible frequency band having a level that enables F, and an external speaker drive terminal that is connected to the external speaker and supplies the input audio signal to the external speaker, A portable broadcast receiver, wherein a frequency signal other than the audible frequency band is superimposed on an audio signal and output from an external speaker drive terminal. 2. The portable broadcast receiver according to claim 1, wherein the frequency signal other than the audible frequency band is obtained from a drive circuit of a light source of a liquid crystal panel.