JPH05344583

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DESCRIPTION JPH05344583
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to
small electronic devices, and more particularly to small electronic devices such as small portable
radios.
[0002]
2. Description of the Related Art FIG. 4 is a block diagram schematically showing a signal
processing circuit from an amplifier to a speaker in a small-sized portable radio device
conventionally used, and in the figure, 11 denotes an amplifier. The output side of the amplifier
11 is electrically connected to the terminal 15 of the jack 17 via the DC cut circuit 13 formed of
a capacitor, and the oscillation of the amplifier formed of the resistor 12a and the capacitor 12b
between the amplifier 11 and the DC cut circuit 13 The stop circuit 12 is electrically connected.
The terminal 16 of the jack 17 is electrically connected to the small internal speaker 10 having a
diameter of about 30 to 40 mm and the thickness of about 4 mm, and the terminal 14 is
electrically connected to the ground 19 of the small electronic device outer box. The signal
amplified by the amplifier 11 is output only from the internal speaker 10 when an external
speaker (not shown) such as an earphone is not connected to the external speaker output
terminal 20, and when connected, the terminal 18 is It is configured to be turned off and output
only from the external speaker.
[0003]
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SUMMARY OF THE INVENTION In the above-described compact electronic device, the internal
speaker 10 is compact and thin, and its sound quality characteristic is such that the high range is
emphasized and the low range is missing. For this reason, there is a problem that high-pitched
noise becomes unpleasant and the sound is distorted.
[0004]
Moreover, as an external speaker, a large-sized speaker may be connected other than an
earphone, and it is desirable to send a signal from the external speaker output terminal 20 with
the signal frequency characteristic amplified by the amplifier 11 as it is.
[0005]
The present invention has been made in view of such problems, and for a small and thin internal
speaker, a high frequency region is cut or a low frequency region is expanded to transmit a
signal of a frequency characteristic, and an external speaker It is an object of the present
invention to provide a compact electronic device which can send out the signal from the
amplifier as it is, can easily hear the internal speaker sound, and does not narrow the use range
of the external speaker.
[0006]
In order to achieve the above object, a compact electronic device according to the present
invention is a compact electronic device provided with an internal speaker and an external
speaker output terminal, which is disposed between the internal speaker and the amplifier.
Alternatively, it is characterized in that a frequency correction circuit is interposed in a feedback
circuit from the internal speaker side to the amplifier.
[0007]
According to the small electronic device of the present invention, the internal speaker and the
external speaker output terminal are provided, and the frequency correction circuit is interposed
between the internal speaker and the amplifier. By selecting the constant of the capacitor and the
resistor and performing the function of the low pass filter (hereinafter referred to as LPF), it is
possible to output the voice having the frequency characteristic with the high tone area cut off
only from the internal speaker. .
[0008]
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Further, according to the small electronic device of the present invention, since the internal
speaker and the external speaker output terminal are provided, and the feedback circuit from the
internal speaker to the amplifier is interposed with the frequency correction circuit, By selecting
a constant of a capacitor and a resistor and applying feedback to the amplifier to adjust the gain
of the amplifier, a voice having a frequency characteristic in which a high range is cut and a low
range is expanded is output only from the internal speaker It will get.
[0009]
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The preferred embodiments of the
compact electronic device according to the present invention will be described below with
reference to the drawings.
The components having the same functions as those of the conventional example are denoted by
the same reference numerals, and the detailed description is omitted.
[0010]
FIG. 1 is a block diagram schematically showing a signal processing circuit of a small electronic
device according to the present embodiment, and in the figure, 11 indicates an amplifier.
The output side of the amplifier 11 is electrically connected to the terminal 15 of the jack 17 via
the DC cut circuit 13 formed of a capacitor, and the oscillation of the amplifier formed of the
resistor 12a and the capacitor 12b between the amplifier 11 and the DC cut circuit 13 The stop
circuit 12 is electrically connected.
The terminal 16 of the jack 17 is electrically connected to the small internal speaker 10 having a
diameter of about 30 to 40 mm and a thickness of about 4 mm, and is branched at a connection
point 33 to between the small internal speaker 10 and the amplifier 11 A feedback circuit 31 is
formed, and the feedback circuit 31 is provided with a frequency correction circuit 30 for cutting
a high range composed of a capacitor 30a and a resistor 30b.
When the external speaker (not shown) is not connected to the external speaker output terminal
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20, the terminal 18 is connected and the feedback circuit 31 of the amplification system is
activated, and when the external speaker is connected, the terminal 18 is turned off. And the
feedback circuit 31 is configured not to operate.
[0011]
Signal processing in the small electronic device configured in this way is performed as follows.
When an external speaker such as an earphone is not connected, a signal output from the
amplifier 11 after the terminal 18 is turned on is input to the small internal speaker 10 through
the DC cut circuit 13, the terminal 15, the terminal 18, and the terminal 16. Together with the
frequency correction circuit 30. By operating the feedback circuit 31 of the amplification system,
the frequency characteristic of the signal output from the amplifier 11 is adjusted, and the highpitched sound region is cut, and the sound in which the low-pitched sound region is expanded is
outputted only from the internal speaker 10. On the other hand, when an external speaker is
connected, the terminal 18 is turned off and the feedback circuit 31 of the amplification system
does not operate, and an audio signal based on the output characteristic of the amplifier 11
passes through the amplifier 11, the DC cut circuit 13 and the terminal 15. Thus, the signal is
output only from the external speaker output terminal 20.
[0012]
FIG. 2 is a graph schematically showing the frequency characteristics of the signal in the
embodiment, and the solid line shows the case where the frequency correction circuit 30 is not
operating, and the dotted line shows the case where the frequency correction circuit 30 is
operating. As described above, when the external speaker is not connected, the high-pitched area
is cut, and the sound in which the low-pitched area is expanded is output from the internal
speaker 10, and the offensive high-pitched noise is suppressed and sufficient. A low range is
obtained. On the other hand, when the external speaker is connected, the frequency correction
circuit 30 does not operate, and a signal based on the characteristic of the amplifier 11 is output
from the external speaker output terminal 20 as it is, so that the characteristic of the amplifier
11 can be utilized. A desired frequency characteristic can be obtained by variously combining the
capacitor 30a and the resistor 30b in the frequency correction circuit 30. The frequency
correction circuit can also be realized by a resonant circuit using a coil or the like.
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[0013]
FIG. 3 is a block diagram schematically showing a signal processing circuit of a small electronic
device according to another embodiment, and in the figure, 11 indicates an amplifier. The output
side of the amplifier 11 is electrically connected to the terminal 15 of the jack 17 via the DC cut
circuit 13 formed of a capacitor, and the oscillation of the amplifier formed of the resistor 12a
and the capacitor 12b between the amplifier 11 and the DC cut circuit 13 The stop circuit 12 is
electrically connected. Between the terminal 16 of the jack 17 and the small internal speaker 10
having a diameter of about 30 to 40 mm and a thickness of about 4 mm, an L.P.F 32 composed
of a capacitor 32a and a resistor 32b is interposed. When the external speaker (not shown) is not
connected to the external speaker output terminal 20, the terminal 18 is connected and the LPF
32 operates, while when the external speaker is connected, the terminal 18 is turned off and the
LPF 32 Is configured to not work.
[0014]
Signal processing in the small electronic device configured in this way is performed as follows.
When an external speaker such as an earphone is not connected, the signal amplified by the
amplifier 11 is input from the DC cut circuit 13 to the LPF 32 through the terminal 15, the
terminal 18 and the terminal 16 and the LPF 32 operates to generate high-pitched sound The
audio whose area is cut is output only from the internal speaker 10. On the other hand, when an
external speaker is connected, the signal amplified by the amplifier 11 is output via the DC cut
circuit 13, the terminal 15, and the external speaker output terminal 20, and the LPF 32 does not
operate, and the characteristics of the amplifier 11 Is output from only the external speaker.
[0015]
Therefore, when the external speaker is not connected, a signal in which the high sound area is
cut is output from the internal speaker 10, and the noise in the offensive high sound area is
suppressed. On the other hand, when the external speaker is connected, a signal based on the
characteristic of the amplifier 11 is output from the external speaker output terminal 20 as it is,
and the characteristic of the amplifier 11 is not impaired.
[0016]
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As described above in detail, in the compact electronic device according to the present invention,
the frequency correction circuit is interposed between the internal speaker and the amplifier or
from the internal speaker side to the feedback circuit from the internal speaker side to the
amplifier. When the external speaker is not connected, a sound with a high sound area cut or an
expanded low sound area is output from the internal speaker by turning on and off the operation
of the frequency correction circuit by the jack. Therefore, offensive treble noise can be
suppressed, or richer bass range can be reproduced. On the other hand, when the external
speaker is connected, the signal before correction based on the characteristic of the amplifier is
output as it is from the external speaker output terminal, and the characteristic of the amplifier is
not impaired.
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