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JPH0477094

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DESCRIPTION JPH0477094
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
on-vehicle acoustic reproduction device with improved in-vehicle acoustic characteristics. 2.
Related Art In recent years, as a method of correcting an in-vehicle acoustic characteristic lacking
a high-pitched sound, a vehicle-mounted audio reproduction apparatus using a loudness circuit
and a graphic equalizer circuit is used. It is not the current situation. Hereinafter, a conventional
on-vehicle acoustic reproduction apparatus will be described. FIG. 7 is a block diagram showing
an example of a conventional on-vehicle acoustic reproducing apparatus. 1 is an acoustic signal
source such as a car radio, a car tape, a car compact disc player, 2 is an equalizer circuit in which
a resonant circuit is constituted by a semiconductor inductor, 3 is a power amplifier, and 4 is a
speaker. Fig. 8 shows a semiconductor inductor 5, two amplifiers 6.7, and a resistor 8.9.10. FIG.
9 is a circuit diagram of the equalizer circuit 2 configured by the LL capacitor 12, and FIG. 9 is an
amplitude characteristic diagram of the equalizer circuit 2. The operation of the on-vehicle
acoustic playback device configured as described above will be described below. First, in the
equalizer circuit 2 shown in FIG. 8, the high-frequency characteristic of the amplitude
characteristic is emphasized by the equalizer circuit 2 shown in FIG. 8, the signal sent from the
acoustic signal source 1 is amplified by the power amplifier 3 Played by Subino 4. As a result,
since the insufficient high-frequency sound is corrected and reproduced only by the conventional
reproduction device without the high-frequency pressure compensating device, the vehicle
interior acoustic characteristics of a flat interior can be obtained, being balanced with the low-tomedium range. . SUMMARY OF THE INVENTION However, in the above-described conventional
configuration, in order to emphasize the high region of the amplitude characteristic with the
equalizer circuit 2 in which the resonant circuit is constituted by the semiconductor inductor 5,
the amplifier 6 is shown in FIG. , 7 are required at least two, and there is a pressure point that the
circuit configuration becomes complicated. The present invention is intended to solve the above-
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mentioned conventional problems, and it is an object of the present invention to provide an onvehicle audio reproducing apparatus having a simple circuit configuration in which an amplitude
changing unit emphasizing high frequency is realized by one amplifier. is there. Means for
Solving the Problem In order to solve this task, the on-vehicle acoustic reproducing apparatus of
the present invention sets the Q of the low-pass filter to 1.0 or more using a resistor, a capacitor
and one amplifier as the amplitude changing means. By doing this, the low-pass filter that
emphasizes the high region of the amplitude characteristic, the power amplifier that amplifies the
output of the low-pass filter, and the speaker that reproduces the output of the power amplifier.
Operation With this configuration, it is possible to realize an amplitude characteristic in which
high frequencies are emphasized by a low pass filter configured of one amplifier. Embodiment An
embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a
block diagram showing the structure of a vehicle-mounted sound reproduction apparatus
according to an embodiment of the present invention. In FIG. 1, 13 is an acoustic signal source
such as a car radio, a car tape, a car compact disc player, 14 is a positive feedback low pass filter
comprising a resistor and a capacitor and one operational amplifier, 15 is a power amplifier, 16
is It is a speaker. FIG. 2 is a circuit diagram of the positive feedback low pass filter 14. FIG. 3 is
an amplitude characteristic diagram of the positive feedback low pass filter 14. The operation of
the on-vehicle acoustic playback device configured as described above will be described below.
First, the output of the acoustic signal source 13 is input to the positive feedback low pass filter
14. As shown in FIG. 2, the positive feedback low pass filter 14 is composed of a resistor 1.9.20,
21.22, a capacitor 17.18, and one operational amplifier 23, and the transfer function is
expressed by the following equation . ?? ?? иииииииииииииииииииииииииииииииииииииииии (1) where K = 1 + RP / R5, S
= J и ?, j = J?1?: angular frequency, j: imaginary unit High frequency cutoff of this positive
feedback low pass filter 14 The frequency and Q indicating the sharpness of resonance are given
by the following equations. However, ?c = 2 и ? и Fc, where Q is 2.4, cutoff frequency is 10 KHz,
resistor 21 is 2.7 ?, resistor 22 is 2.7 ?, and capacitor 17 is 0 .027 ?F, 0.012 ?F for the
capacitor 18, 0. IK ?, resistance 20 1. When each constant is set to OK?, as shown in FIG. 3, it
is possible to give a peak to the amplitude characteristic in the vicinity of the high frequency
cutoff frequency, and to secure a level difference of about 10 dB from the middle low frequency
band of 5 KHz or less. In other words, the amplitude characteristic of the positive feedback low
pass filter 14 is such that the high region is emphasized. When the output passing through this
positive feedback low pass filter 14 is added to the power amplifier 15 and reproduced by the
speaker 16, it is equal to the on-vehicle river sound reproduction device configured with an
equalizer circuit that requires two conventional amplifiers. Since the range sound is corrected, it
is balanced with the low and mid range, and a flat cabin interior acoustic characteristic is
obtained. As described above, according to the present embodiment, the amplitude changing
means is constituted by the positive feedback low pass filter 14 using the resistor and the
capacitor and one operational amplifier, and the constant of the resistor and the capacitor is
adjusted to adjust the positive feedback low pass filter. By setting the Q of 14 to 2.4, an
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amplitude characteristic in which the high frequency band is emphasized can be realized with
one amplifier.
In the above embodiment, in order to determine the Q and the cutoff frequency of the positive
feedback type low pass filter 4, other constants may be used for the resistor and the capacitor. As
shown in FIG. 4, to set Q to 2.3, the resistance 21 is set to 15.2. OK ?, resistance 22 15. OK ?,
capacitor 17 is 0.0012 ?F, capacitor 18 is 0.00082 ?F, resistor 19 is 10, OK ?, resistor 20 is
10. Let's say OK ?. At this time, the high range of about 6 dB can be emphasized at 10 KHz.
Similarly, setting Q to 1.0 can enhance the high band by about 1 dB. Also, as shown in FIG. 5, in
order to increase the cutoff frequency without changing Q, the constants of the resistors 21 and
22 are made smaller (and the cutoff frequency is made smaller (to Increase the constant of
resistor 22. Also, as shown in FIG. OK ?, resistance 22 12. OK .OMEGA., 0.001 .mu.F for
capacitor 17, 0.0018 .mu.F for capacitor 18, 39. OK ?, resistance 20 13. Assuming that it is
OK?, it is possible to have a gain of 12 dB in the entire frequency band with Q set at 2.2. In this
case, the load on the voltage amplification circuit of the power amplifier 15 connected behind is
reduced. Furthermore, when the resistors 21 and 22 and the capacitors 17 and 18 are equal, Q
can be determined by the ratio of the resistors 19 and 20, so that the setting of the constant can
be easily performed. Further, although the low pass filter is a positive feedback low pass filter 14
in the above embodiment, the positive feedback low pass filter 14 may be a multiple feedback
low pass filter. Effect of the Invention As described above, according to the present invention, the
amplitude changing means is constituted by the low pass filter using the resistor and the
capacitor and one amplifier, and the constant of the resistor and the capacitor is adjusted to
make the Q of the low pass filter 1.0 or more. By setting, it is possible to realize an excellent onvehicle acoustic reproducing apparatus capable of configuring an amplitude characteristic that
emphasizes a high band of a signal.
[0002]
Brief description of the drawings
[0003]
1 is a block diagram of an on-vehicle acoustic reproducing apparatus according to an
embodiment of the present invention, FIG. 2 is a circuit diagram of the low pass filter of FIG. 1,
FIG. 3 is an amplitude characteristic diagram of the low pass filter of FIG. 4 is an amplitude
characteristic diagram when Q of the low pass filter of FIG. 1 is changed, FIG. 5 is an amplitude
characteristic diagram when Q of the low pass filter of FIG. 1 is fixed, and FIG. 6 is FIG. Fig. 7 is a
block diagram of a conventional on-vehicle acoustic reproduction apparatus, Fig. 8 is a circuit
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diagram of the equalizer circuit of Fig. 7, and Fig. 9 is It is an amplitude characteristic view of the
equalizer circuit of a figure.
13 и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и
и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и capacitor , 19-22 и и и и и и и и и и и и и и и и и и и и и и
Operational amplifier. Name of Agent Attorney Attorney Shigetaka Hakano Figure 1 Figure 5
Figure 6 O Figure 3 16 ... Speaker Figure? 0 Fig. 8 Fig. 9r / I number of waves around the skin
number of revolution speed [H2] 10 wave number
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