JP4739765B2 - Electroacoustic transducer drive system - Google Patents

Description

  The present invention relates to a driving system for an electroacoustic conversion system that converts a high-power random noise electric signal into an acoustic signal.

  An electroacoustic conversion system for generating a high-output random noise acoustic signal in water uniformly outputs a required frequency spectrum signal from several tens Hz to several kHz. The drive amplifier used for this has a large output of several kW. Such a technique is disclosed in Patent Document 1 and Non-Patent Document 1.

Japanese Patent No. 2648067 The Ocean Acoustics Society "Basics and Applications of Ocean Acoustics" Naruyamado Shoten

The drive amplifier used in the electroacoustic conversion system has a large output of several kW, but has a problem that the output transformer becomes huge because a low frequency of several Hz is passed.
As a countermeasure, there is a method in which the underwater speaker is directly driven without passing through the output transformer. However, since the output voltage of the drive amplifier is a high voltage of, for example, a peak value of 750 V and an effective value of 250 V, the resistance of the power output element is reduced. It is difficult to realize from the viewpoint of voltage. The specification that the margin of the withstand voltage of the output element cannot be taken should be avoided, but the random noise electrical signal has a maximum voltage about 3 times the effective voltage due to its characteristics, and in order to take the margin twice. It is necessary to expect a withstand voltage 3 × 2 = 6 times the effective voltage.

  This is a withstand voltage specification that is impossible in view of the currently available device standards. For example, the maximum withstand voltage of a power field effect transistor, which is a general power device as an output device, is about 1200 V, but it gives the required transmission level. Requires a withstand voltage of 250V x 6 times = 1500V or more.

  The same argument holds for current, and the maximum current is about 3 times the effective current. Therefore, in order to double the margin, it is necessary to expect a withstand current of 3 × 2 = 6 times the effective current. . In addition, there is a problem in realization that the instantaneous power is 3 times effective voltage x 3 times effective current = 9 times.

  The problem to be solved by the present invention is that, in an electroacoustic conversion system that converts a random noise electric signal into an acoustic signal, the output power of the electroacoustic conversion system drive amplifier and the output power of the electroacoustic conversion system drive amplifier are maintained while maintaining the required transmission spectrum characteristics within the required band. By providing a drive system that can minimize the output voltage, it is possible to reduce the withstand voltage standards and power withstand standards of power output elements of drive amplifiers required for electroacoustic conversion systems, and to meet the currently available element standards To lower.

The present invention is required transmitting random noise electrical signal based on the frequency characteristics corresponding to spectral characteristics data were generated by random noise generator, transmitting in this the random noise electrical signal amplified by driving amplifier electroacoustic transducer A drive system for an electroacoustic conversion system that converts and outputs an acoustic signal,
A voltage limit circuit for limiting the absolute value of the output voltage of the drive amplifier, a current limit circuit for limiting the absolute value of the output current, and a control unit,
The control unit calculates and sets a frequency characteristic of the random noise signal generator, and a frequency characteristic setting unit;
The transmission spectrum level in the required band of the transmitted acoustic signal is the required transmission spectrum characteristic data, where the limited voltage is the drive limit voltage (Vlim) and the limited current is the drive limit current (Ilim). And a drive limit setting unit for calculating and setting the drive limit voltage and the drive limit current at which drive power = drive limit voltage × drive limit current (Wlim = Vlim × Ilim) is within the allowable square mean error ,
The transmission spectrum level of the transmitted acoustic signal is measured and compared with the required transmission spectrum characteristic data, and the drive limit voltage of the drive amplifier is set so that the transmitted acoustic signal is within the allowable mean square error. A fine adjustment unit for performing fine adjustment is provided.

  According to the present invention, it is easy to realize the drive amplifier because the power output element of the drive amplifier having a low withstand voltage standard and low withstand voltage standard can be adopted while maintaining the required transmission spectrum characteristic within the required band. . In addition, the output power, output voltage, and output current of the entire drive amplifier can be reduced, which contributes to reducing the size and weight of the drive amplifier and reducing power consumption.

  Hereinafter, an embodiment according to the present invention will be described with reference to the accompanying drawings.

  FIG. 1 shows an electroacoustic conversion system drive system according to an embodiment of the present invention. Reference numeral 102 denotes a control unit constituted by a calculator, which calculates a spectrum level of random noise to be generated, a drive limit voltage and a drive limit current based on a required transmission spectrum characteristic 101 inputted from the outside, and generates random noise. The generator 103 is instructed of the generated spectrum level. Further, the control unit 102 instructs the limit voltage circuit 104 and the limit current circuit 105 about the drive limit voltage and the drive limit current of the drive amplifier 106. The drive amplifier 106 has a power semiconductor output element, amplifies a random noise electric signal, and inputs it to the electroacoustic transducer 107.

  The control unit 102 includes a frequency characteristic setting unit 102A, a drive limit setting unit 102B, and a fine adjustment unit 102C that are realized by a program loaded on the memory and executed.

  The frequency characteristic setting unit 102A uses the limited voltage as the drive limit voltage and the limited current as the drive limit current, so that the transmission spectrum level in the required band is within the allowable mean square error compared to the required transmission spectrum characteristic. As shown, the frequency characteristic of the random noise generator 103 is calculated and set.

  The drive limit setting unit 102B calculates and sets the minimum values of the drive limit voltage and the drive limit current, and calculates and sets the drive limit voltage so as to be within the allowable root mean square error.

  The fine adjustment unit 102C measures the spectral level of the transmitted acoustic signal, compares it with the required transmission spectral characteristic, and finely adjusts the spectral level of the random noise generator and the drive amplifier so as to be within the allowable mean square error. Make fine adjustments to the drive limit voltage.

  The control unit 102 calculates the spectrum level of the generated random noise, the drive limit voltage and the drive limit current based on the required transmission spectrum characteristic 101 input from the outside, and simultaneously instructs the generated noise level to the random noise generator 103. Then, the limit voltage circuit 104 and the limit current circuit 105 are instructed about the drive limit voltage and the drive limit current of the drive amplifier 106. The output of the drive amplifier 106 is converted into a transmitted acoustic signal 108 by an electroacoustic transducer 107, and a part of the transmitted acoustic signal 108 is converted into a monitor electrical signal 110 by an acoustic monitor 109. The control unit 102 calculates the spectrum level from the monitor signal 110 and compares it with the required transmission spectrum characteristic 101 to instruct the random noise generator to determine the spectrum level of the generated random signal so as to enter the allowable mean square error. Make fine adjustments.

FIG. 2 shows a frequency spectrum level and a waveform in each processing. (1) is a required transmission spectrum characteristic P _r (f) given from the outside, for example, by a user. The ideal drive voltage v _r (kΔt) corresponding to this required transmission spectrum characteristic is shown in (2). (3) shows the limit transmission spectrum level P _C (nΔf), and the outputs of the low frequency region and the high frequency region are clipped corresponding to the required transmission spectrum characteristic P _r (f). (4) shows the drive limit voltage v _C (kΔt) obtained by performing the voltage limit process on the ideal drive voltage v _r (kΔt) based on the characteristic of (3).

  Next, the operation of the electroacoustic conversion system will be described according to an example of an electrodynamic electroacoustic conversion system. As described above, the control unit 102 of the drive system includes the frequency characteristic setting unit 102A, the drive limit setting unit 102B, and the fine adjustment unit 102C, and each process is executed by the control unit.

  FIG. 3 shows a flowchart of the calculation process of the optimum limit drive voltage corresponding to the equations (3) to (14) described below.

The output power w is set in advance by the user.
In the electrodynamic electroacoustic transducer system, the required transmit spectral characteristic P _{r (f)} an ideal drive current spectrum level for obtaining the I _{r (f),} as the formula (1).

The ideal drive voltage spectrum level V _r (f) is given by

Therefore, I _r (f) is eliminated, and the relational expression (3) between the required transmission spectrum characteristic P _r (f) and the ideal drive voltage spectrum level V _r (f) is obtained (step 301).

Thereby, a relational expression between the required transmission spectrum characteristic P _r (f) and the ideal drive voltage V _r (f) is obtained.
However,
f: Frequency
B: Magnetic flux density
l: Coil length
z ₀ : Radiation impedance
z ₁ : Diaphragm mechanical impedance
Z ₀ : Power supply impedance
Z ₁ : Coil impedance
a: Diaphragm radius
ρ ₀ : Density of water Next, an ideal drive voltage v _r (t) on the time axis corresponding to this is obtained (step 302). The ideal drive voltage v _r (t) can be calculated as the following equation (4) as an inverse Fourier transform of the frequency f = nΔf included in the interval T = NΔt of the ideal drive voltage spectrum level V _r (f). .

Next, the ideal drive voltage v _r (kΔt) is subjected to a voltage limit process of v _lim , and this is used as the drive limit voltage v _C (kΔt) by Fourier transform to obtain the drive limit voltage spectrum level V _C (nΔt) as Calculation is performed as in (5) and (6) (steps 303 and 304).

  That is,

And

Next, a drive limit current spectrum level I _C (nΔf) is obtained (step 305). The drive limit current spectrum level I _C (nΔf) based on the drive limit voltage spectrum level V _C (nΔf) is expressed by the following equation (2).

The drive limit current i _C (kΔt) on the time axis corresponding to this is obtained by Fourier transformation (step 306),

The drive limit current i _C (kΔt) is subjected to a current limit process i _lim , and this is used as the drive relimit current i _CC (kΔt) (step 307), and the drive relimit current spectrum level I _CC (nΔf) is obtained by Fourier transform. ) Is calculated (step 308).

  That is,

And

Next, the drive re-limit voltage spectrum level _VCC is obtained (step 309). Driving again limit current spectrum level _I CC _(nΔf) by the drive re-limit voltage spectrum level _V CC _(nΔf), from equation (2),

The limit transmission spectrum level P _C (nΔf) based on the drive re-limit voltage spectrum level V _CC (nΔf) is obtained from the equation (3) (step 310),

  from now on,

In-band mean square error Err of the re-limit drive voltage spectrum level V _CC (nΔf) under the condition

(Step 311), a limit drive voltage v _lim that minimizes this is obtained, w _lim in equation (13) is sequentially increased, and equations (5) to (14) are repeated (step 312), and in-band square is calculated. In w _lim where the average error Err satisfies the allowable error, v _lim that minimizes the in-band mean square error is the optimum limit drive voltage (step 313).

From FIG. 4, it can be seen that w _lim = 25 kW and the limit drive voltage v _lim = 400 V is the optimum limit drive voltage in order to keep the in-band mean square error Err within 1 dB.

  That is, according to the method of the present invention, the output voltage of the electrodynamic electroacoustic conversion drive amplifier can be suppressed to a maximum of ± 400 V and the output current can be suppressed to a maximum of ± 62.5 A.

  According to the present embodiment, the drive amplifier is driven with the limit drive voltage and the limit drive current, so that the drive amplifier power output element has a withstand voltage standard and a withstand voltage while maintaining the required transmission spectrum characteristics within the required band. A low standard can be adopted. Therefore, it is easy to realize a drive amplifier, and the output power, output voltage, and output current of the entire drive amplifier can be reduced, which contributes to a reduction in size and weight of the drive amplifier and a reduction in power.

  When the power output element of the drive amplifier is formed of a semiconductor element, the current value can be suppressed to a low current value by arranging the semiconductor elements in parallel. However, regarding the voltage value, it is difficult to reduce the voltage applied to the semiconductor element only by the circuit configuration, and it is effective to adopt the method of the present invention.

  Any of the drive systems of the present invention can be configured with known general-purpose devices as elements, and detailed description thereof will be omitted. The calculator 101 is obtained by adding an input / output device to a general-purpose computer. The random noise generator 103 can be realized by inputting the random noise waveform calculated by the calculator 101 to a general-purpose signal generator. The voltage limiter circuit 104 controls the power supply voltage of the power output element of the drive amplifier 106 by the calculator 102, and the current limiter 105 controls the power supply current of the power output element of the drive amplifier 106 by the calculator 102. Both can be realized with a general-purpose power supply. The drive amplifier 106 is a general-purpose power amplification amplifier, and is of a type in which the power source of the output power element is separated from other power sources. The electroacoustic transducer 107 includes an electrodynamic type using a magnet and a voice coil, a piezoelectric type using a piezoelectric effect, and the like. The acoustic monitor is a general-purpose microphone. Although a method for directly monitoring the voltage or current of the drive amplifier output without using an acoustic monitor can be easily devised from this embodiment, there is a drawback that the characteristics of the electroacoustic transducer cannot be corrected, and a description thereof will be omitted.

  If the required transmission spectrum characteristics or electroacoustic conversion method changes, the drive voltage and drive current will change. However, according to the method of the present invention, the optimum limit drive voltage and optimum limit drive current can be obtained, and random noise is output. In the electro-acoustic conversion system, the maximum voltage and maximum current of the drive amplifier are limited by the clip circuit, and it is possible to exert the maximum capability even if the power withstand voltage, withstand voltage, and withstand current of the power output element are marginal. Become.

  In the first embodiment, a system including both a voltage limit circuit that limits the absolute value of the output voltage of the drive amplifier and a current limit circuit that limits the absolute value of the output current has been described. For the output output, a limit circuit based on the present invention that clips the maximum or minimum value of either current or voltage, for example, only a voltage limit circuit may be employed.

  By measuring the impulse response due to the generation of high output random Gaussian noise by the method of the present invention, it can be used for grasping the acoustic propagation characteristic peculiar to the sea area. Moreover, it can be used for a device that explodes mine by simulating ship's navigation noise, a device that obstructs detection by an acoustic sensor by generating high output noise, and the like.

1 is an explanatory diagram of an electroacoustic conversion system according to a first embodiment of the present invention. FIG. FIG. 3 is an explanatory diagram showing a frequency spectrum and a waveform in the first embodiment. 3 is a flowchart of processing for calculating an optimum drive limit voltage in the first embodiment. FIG. 6 is an explanatory diagram showing the relationship between the limit drive voltage of the electroacoustic conversion system and the mean square error of the transmission spectrum in the first example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 ... Required transmission spectrum characteristic, 102 ... Calculator, 103 ... Random noise generator, 104 ... Voltage limiter circuit, 105 ... Current limiter circuit, 106 ... Drive amplifier, 107 ... Electroacoustic transducer, 108 ... Transmission acoustic signal 109: Acoustic monitor, 110: Monitor electrical signal.

Claims (3)

The random noise electrical signal based on the frequency characteristics corresponding to the required transmit spectral characteristic data generated by the random noise generator, converted into a transmit audio signal to those said random noise electrical signal amplified electro-acoustic transducer with driving amplifier Drive system of the electroacoustic conversion system that outputs
A voltage limit circuit for limiting the absolute value of the output voltage of the drive amplifier, a current limit circuit for limiting the absolute value of the output current, and a control unit,
The control unit calculates and sets a frequency characteristic of the random noise signal generator, and a frequency characteristic setting unit;
The transmission spectrum level in the required band of the transmitted acoustic signal is the required transmission spectrum characteristic data, where the limited voltage is the drive limit voltage (Vlim) and the limited current is the drive limit current (Ilim). And a drive limit setting unit for calculating and setting the drive limit voltage and the drive limit current at which drive power = drive limit voltage × drive limit current (Wlim = Vlim × Ilim) is within the allowable square mean error ,
The transmission spectrum level of the transmitted acoustic signal is measured and compared with the required transmission spectrum characteristic data, and the drive limit voltage of the drive amplifier is set so that the transmitted acoustic signal is within the allowable mean square error. An electroacoustic conversion system drive system comprising a fine adjustment unit for performing fine adjustment. 2. The frequency characteristic setting unit according to claim 1, wherein the frequency characteristic setting unit calculates the frequency characteristic of the random noise generator so that a transmission spectrum level outside the required band of the transmitted acoustic signal is equal to or less than required transmission spectrum characteristic data. The drive system of the electroacoustic conversion system characterized by setting. The random noise electrical signal based on the frequency characteristics corresponding to the required transmit spectral characteristic data generated by the random noise generator, converted into a transmit audio signal to those said random noise electrical signal amplified electro-acoustic transducer with driving amplifier Drive system of the electroacoustic conversion system that outputs
A limit circuit that limits at least one of an absolute value of an output voltage or an output current of the drive amplifier, and a control unit,
The control unit calculates and sets a frequency characteristic of the random noise signal generator, and a frequency characteristic setting unit;
The transmission spectrum level in the required band of the transmitted acoustic signal is the required transmission spectrum characteristic data, where the limited voltage is the drive limit voltage (Vlim) and the limited current is the drive limit current (Ilim). A drive limit setting unit that calculates and sets the drive limit value at which drive power = drive limit voltage × drive limit current (Wlim = Vlim × Ilim) is within the allowable mean square error ;
The transmission spectrum level of the transmission acoustic signal is measured and compared with the required transmission spectrum characteristic data, and the drive limit value of the drive amplifier is set so that the transmission acoustic signal is within the allowable mean square error. An electroacoustic conversion system drive system comprising a fine adjustment unit for performing fine adjustment.

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