JPH0477094A - On-vehicle acoustic reproducing device - Google Patents

Abstract

PURPOSE:To emphasize a high frequency of the amplitude characteristic of an amplitude change means by using resistors, capacitors and one amplifier so as to set a value (Q) representing the sharpness of the resonance of a low pass filter to be 1.0 or over. CONSTITUTION:For example, the resistance of a resistor 21 is set to 12.0KOMEGA, the resistance of a resistor 22 is set to 12.0KOMEGA, the capacitance of a capacitor 17 is set to 0.001muF, the capacitance of a capacitor 18 is set to 0.0018muF, the resistance of a resistor 19 is set to 39.0KOMEGA, and the resistance of a resistor 20 is set to 13.0KOMEGA, then a gain of 12dB is obtained for the entire frequency band with a Q set to 2.2. Moreover, the resistance of the resistors 21, 22 is set equal and the capacitance of the capacitors 17, 18 is set equal respectively, since the Q depends on the ratio of the resistance of the resistors 19, 20, the setting of the circuit constants is set simply. Thus, the amplitude characteristic emphasizing a high frequency signal component is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION FIELD OF INDUSTRIAL APPLICATION The present invention relates to an in-vehicle sound reproducing device that improves the acoustic characteristics of a vehicle interior.

2. Description of the Related Art In recent years, in-vehicle sound reproduction devices using loudness circuits and graphic equalizer circuits have been used as a method of correcting vehicle interior acoustic characteristics that lack high-pitched sounds, but little consideration has been given to means of changing amplitude characteristics. The current situation is that this is not the case. A conventional in-vehicle sound reproduction device will be described below. FIG. 7 is a block diagram showing an example of a conventional in-vehicle sound reproduction device. (2) is an audio signal source such as a car radio, car tape deck, or car compact disc player; (2) is an equalizer circuit having a resonant circuit made up of semiconductor inductors; (3) is a power amplifier; and (4) is a speaker.

FIG. 8 shows a semiconductor inductor 5, two amplifiers 6.7, resistors 8.9.10. A circuit diagram of the equalizer circuit 2 configured by the LL capacitor 12, FIG. 9 is the equalizer circuit 2
FIG.

Regarding the in-vehicle sound reproduction device configured as above,
The operation will be explained below.

First, the signal sent from the acoustic signal source 1 is sent to the equalizer circuit 2 shown in FIG. 8, where the high frequency range of the amplitude characteristic is emphasized as shown in FIG. 9, and the signal is amplified by the power amplifier 3. Played by Subinono 4. the result,
Since the high-frequency sound that is insufficient when using a conventional reproducing device without a high-frequency compensator is corrected and reproduced, it is well-balanced with the medium and low mounting platform, and flat acoustic characteristics in the vehicle interior are obtained.

Problems to be Solved by the Invention However, in the above-mentioned conventional configuration, in order to emphasize the high range of the amplitude characteristic in the equalizer circuit 2 which constitutes a resonant circuit with the semiconductor inductor 5, an amplifier 6 is installed as shown in FIG. , 7 are required at least, and the circuit configuration becomes complicated.

The present invention solves the above-mentioned conventional problems, and aims to provide an in-vehicle sound reproducing device with a simple circuit configuration in which an amplitude changing means for emphasizing high frequencies is implemented using a single amplifier. be.

Means for Solving the Problem In order to solve this problem, the in-vehicle sound reproducing device of the present invention uses a resistor, a capacitor, and one amplifier as the amplitude changing means, and sets the Q of the low-pass filter to 1.0 or more. It consists of a low-pass filter that emphasizes the high frequency range of the amplitude characteristic, a power amplifier that amplifies the output of this low-pass filter, and a speaker that reproduces the output of the power amplifier.

Effect: With this configuration, an amplitude characteristic in which high frequencies are emphasized can be achieved with a low-pass filter composed of a single amplifier.

EXAMPLE An example of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of an on-vehicle sound reproduction device according to an embodiment of the present invention. In Figure 1, 13
14 is a positive feedback low-pass filter composed of a resistor, a capacitor, and an operational amplifier; 15 is a power amplifier; and 16 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.

Regarding the in-vehicle sound reproduction device configured as above,
The operation will be explained below.

First, the output of the acoustic signal source 13 is input to a positive feedback low-pass filter 14 . As shown in FIG. 2, the positive feedback low-pass filter 14 has resistors 1.9.20 and 21.2.
2, capacitors 17 and 18, and one operational amplifier 23, and the transfer function is expressed by the following equation.

■.

■.

・・・・・・(1) However, K=1 + RP/R5, S=J・ω, j=J
-1ω: angular frequency, j: imaginary unit The high-frequency cutoff frequency of the positive feedback low-pass filter 14 and Q, which indicates the sharpness of resonance, are expressed by the following equation.

However, ωc=2・π・Fc Here, the resistor 21 is set to 2.7Ω and the resistor 22 is set to 2.7Ω so that Q is 2.4 and the cutoff frequency is 10KHz.
Ω, capacitor 17 to 0.027 μF, capacitor 1
8 is 0.012 μF, and resistor 19 is 0.012 μF. IKΩ, resistance 20
1. When a constant is set for each OKΩ, as shown in FIG. 3, the amplitude characteristics can have a peak near the high-frequency cutoff frequency, and a level difference of about 10 dB with the middle and low frequencies below 5 KHz can be secured. In other words, the amplitude characteristic of the positive feedback low-pass filter 14 emphasizes the high frequency range. When the output that has passed through the positive feedback low-pass filter 14 is reproduced by the speaker 16 in addition to the power amplifier 15, it is equivalent to the conventional in-vehicle sound reproduction device configured with an equalizer circuit that requires two amplifiers, and the lack of high Since the range sound is corrected, it is balanced with the mid-low range and provides a flat interior acoustic characteristic.

As described above, according to this embodiment, the amplitude changing means is constituted by a positive feedback low-pass filter 14 using a resistor, a capacitor, and one operational amplifier, and the constants of the resistor and capacitor are adjusted to create a positive feedback low-pass filter. By setting the Q of 14 to 2.4, amplitude characteristics that emphasize high frequencies can be achieved with a single amplifier.

In addition, in the above embodiment, a positive feedback low-pass filter]
To determine the Q of 4 and the cutoff frequency, other constants may be used for the resistor and capacitor. As shown in FIG. 4, to set Q to 2.3, resistor 21 is set to 15. OKΩ
, resistor 22 to 15. OKΩ, capacitor 17 0.00
12μF, capacitor 18 0.00082μF, resistor 19 10, OKΩ, resistor 20 10. OKΩ.

At this time, high frequencies can be emphasized by about 6 dB at 10 KHz. Similarly, if Q is set to 1.0, the high frequency region can be emphasized by about 1 dB. In addition, as shown in FIG. 5, in order to increase the cutoff frequency without changing Q, the constants of the resistors 21 and 22 must be decreased, and in order to decrease the cutoff frequency,
Increase the constants of resistor 21 and resistor 22.

Further, as shown in FIG. 6, the resistor 21 is connected to 12. OKΩ,
The resistor 22 is 12. OKΩ, capacitor 17 0.001
μF, capacitor 18 is 0.0018μF, resistor 19 is 39. OKΩ, resistor 20 to 13. If OKΩ is set, the gain is 12 dB in all frequency bands with Q set to 2.2.
You can have it. In this case, there is an effect of reducing the load on the voltage amplification circuit of the power amplifier 15 connected later.

Furthermore, if the resistors 21 and 22 and the capacitors 17 and 18 are made equal, Q can be determined by the ratio of the resistors 19 and 20, and therefore the constant can be easily set. Further, in the above embodiment, the low-pass filter is the positive feedback type low-pass filter 14, but the positive feedback type low-pass filter 14 may be composed of a multiple feedback type low-pass filter.

Effects of the Invention As described above, the present invention configures the amplitude changing means with a low-pass filter using a resistor, a capacitor, and one amplifier,
By adjusting the constants of the resistor and capacitor and setting the Q of the low-pass filter to 1.0 or more, it is possible to create an excellent in-vehicle sound reproduction device that can configure amplitude characteristics that emphasize the high frequency range of the signal. It is.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an in-vehicle sound reproducing device according to an embodiment of the present invention, FIG. 2 is a circuit diagram of the low-pass filter shown in FIG. 1, and FIG. 3 is an amplitude characteristic diagram of the low-pass filter shown in FIG. Figure 4 is an amplitude characteristic diagram when the Q of the low-pass filter in Figure 1 is varied, Figure 5 is an amplitude characteristic diagram when the Q of the low-pass filter in Figure 1 is kept constant, and Figure 6 is the diagram shown in Figure 1. Figure 7 is a block diagram of a conventional in-vehicle sound reproduction device, Figure 8 is a circuit diagram of the equalizer circuit in Figure 7, and Figure 9 is a diagram of the equalizer circuit in Figure 7.
FIG. 3 is an amplitude characteristic diagram of the equalizer circuit shown in the figure. 13...Acoustic signal source, 14...Low pass filter, 15...Power amplifier, 16...
...Speaker, 17.18...Capacitor,
19-22... Resistor, 23... Operational amplifier. Name of agent: Patent attorney Shigetaka Awano (1 person) Figure 5 Figure 6 Figure 3 Figure 16...Speaker Figure? 0 Figure 8 9r/I Peripheral number Peripheral speed [H2] Wave number used for 10

Claims (1)

[Claims] The amplitude changing means for changing the amplitude of the signal from the acoustic signal source that generates the acoustic electrical signal uses a resistor, a capacitor, and one amplifier, and the constants of the resistor and capacitor are adjusted to set the Q of the low-pass filter to 1.0 or more. An in-vehicle device consisting of a low-pass filter that is configured to emphasize the high range of the amplitude characteristics of the signal by setting , a power amplifier that amplifies the output of this low-pass filter, and a speaker that reproduces the output of the power amplifier Sound reproduction device.