JP2008306491A - Audio reproducing system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To eliminate the need for monitoring a power supply voltage and an audio signal of an output section, as well as, to prevent adjustment noises from mixing in with the audio signal. <P>SOLUTION: The gain of an audio signal V<SB>i</SB>, input to an audio input terminal 11, is adjusted in a gain adjusting section 15 to input the signal adjusted to an audio amplifying section 16. Then, a speaker 17 is driven by the output voltage V<SB>L</SB>of the audio amplifying section 16. A voltage V<SB>C</SB>is supplied from power supply terminals 12, 13 and a power supply capacitor 14 to the audio amplifying section 16. A gain adjustment section 15 calculates and predicts a voltage V<SB>C</SB>required, based on an input voltage V<SB>L</SB>(=V<SB>i</SB>×G<SB>1</SB>×G<SB>2</SB>) of the speaker 17, which is determined from the audio signal V<SB>i</SB>to be input, the gain G<SB>1</SB>of the gain adjustment section 15 and the gain G<SB>2</SB>of the audio-amplifying section 16, to adjust the gain G<SB>1</SB>so as to hold the value of the voltage V<SB>C</SB>to be under the condition V<SB>C</SB>≥V<SB>L</SB>. Furthermore, the gain adjusting section 15 makes a change in the gain G<SB>1</SB>resulting from the adjustment goes out of the audible frequency range. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an audio reproduction apparatus that inputs an audio signal, adjusts gain, amplifies power, and drives a speaker.

In this type of audio reproduction device, when the power supply capacity is insufficient, the audio reproduced by the speaker may be distorted depending on the gain adjustment. For example, as shown in FIG. 7, when the audio signal V _in input to the audio input terminal 51 is set to an audio signal V _i whose volume is adjusted by a volume 52 and amplified by an amplifier 53 and reproduced by a speaker 54, As shown in FIG. 8, when the supplied power supply voltage Vdd is consumed and lowered, the signal _VL input to the speaker 54 is clipped, and the reproduced sound is distorted.

Therefore, conventionally, as shown in FIG. 9, insert the level adjusting circuit 55 between the volume 52 and the amplifier 53, to reduce the level of the audio signal V _i at the higher the level adjusting circuit 55 power supply voltage Vdd drops Thus, the signal _VL input to the amplifier 53 and input to the speaker 54 is prevented from being clipped (see, for example, Patent Document 1). In addition, there is also one that detects a potential fluctuation of the power supply voltage, A / D converts this, and fetches it into the CPU, adjusts the gain of the audio signal by this CPU, and prevents the reproduction signal from being distorted (for example, Patent Documents). 2). Furthermore, the audio signals on all the output sides of a plurality of channels are measured, A / D converted, and the output power is calculated. When the calculated value exceeds the power capacity, the input signal amplitude is limited by a limiter. In some cases, the reproduction signal is prevented from being distorted (see, for example, Patent Document 3).

From the above, paying attention to the fact that the average power is statistically about 11% with respect to the peak power characteristic of the audio signal, the power supply capacity is designed at about 12.5% considering the margin. Applied when Since the audio signal is distorted at peak power, a large capacity capacitor 56 is connected to the line of the power supply Vdd as shown by the broken line in FIG. 7 to charge the power required at peak time at times other than peak time. There is also a technique to keep.
JP 61-096807 A JP 2002-299961 A JP 2002-198756 A

  However, in any of the methods, it is necessary to monitor the fluctuation of the power supply voltage or the audio signal. In Patent Document 1, the analog circuit is used for monitoring, but in Patent Documents 2 and 3, an A / D converter is required. It was.

  In each method described above, the gain varies when the power supply is insufficient. Since this fluctuation is caused by the audio signal, it becomes a fluctuation in the audible range, and there is a problem that noise in the audible range is mixed in the audio signal during gain adjustment and the sound quality is deteriorated.

  An object of the present invention is to provide an audio reproduction device that does not require monitoring of a power supply voltage or an output-side audio signal and prevents adjustment noise from being mixed into the audio signal.

In order to achieve the above object, an audio reproduction device according to a first aspect of the present invention includes a gain adjusting unit that adjusts the gain of an audio signal input to the audio input terminal, a power supply capacitor connected in parallel to the power supply terminal, A sound amplification unit that inputs a sound signal gain-adjusted by the gain adjustment unit and amplifies the sound using a voltage supplied from the power supply terminal and the power supply capacitor as a power supply voltage, and a signal amplified by the sound amplification unit An audio reproduction device including an input speaker, wherein the gain adjustment unit is based on an input voltage of the speaker obtained from a value of the input audio signal, a gain of the gain adjustment unit, and a gain of the audio amplification unit. Predicting the required value of the power supply voltage, and when the predicted power supply voltage value is lower than the input voltage value of the speaker, reducing the gain of the input audio signal; When the value of the predicted power supply voltage is higher than the value of the input voltage of the speaker to increase the gain of the audio signal to said input, characterized in that.
According to a second aspect of the present invention, there is provided an audio reproduction device in which a gain adjustment unit for adjusting a gain of an audio signal input to an audio input terminal, a power supply capacitor connected in parallel to a power supply terminal, and gain adjustment by the gain adjustment unit. A plurality of audio amplifying units that input audio signals and amplify audio using voltages supplied from the power supply terminal and the power supply capacitor as power supply voltages, and signals amplified by the audio amplifying units are individually input. An audio reproduction device including a plurality of speakers, wherein the gain adjustment unit is configured to input each input voltage of each speaker obtained from a value of the input audio signal, a gain of the gain adjustment unit, and a gain of each of the audio amplification units. The power supply voltage value required is predicted based on the input power, and when there is a speaker having an input voltage higher than the predicted power supply voltage value among the plurality of speakers, the input is performed. The gain of a voice signal is reduced, and when all the input voltage values of the plurality of speakers are lower than the predicted power supply voltage, the gain of the input voice signal is increased. The invention according to No. 3 is characterized in that, in the audio reproduction device according to claim 1 or 2, the change of the gain adjustment in the gain adjustment unit is performed outside the frequency range of the audible range.
According to a fourth aspect of the present invention, in the audio reproduction device according to the third aspect, the amount of gain adjustment per time in the gain adjusting unit is increased when the gain is reduced, and is decreased when the gain is increased. It is characterized by doing.
According to a fifth aspect of the present invention, in the audio reproduction device according to any one of the first to fourth aspects, the audio reproduction device includes a storage device that stores an audio signal that has been gain-adjusted in the gain adjustment unit, and is read from the storage device. A voice signal is input to the voice amplifier.

  According to the present invention, the required power supply voltage value is predicted based on the input audio signal value, the gain of the gain adjustment unit, and the input voltage of the speaker obtained from the gain of the audio amplification unit, and according to the prediction result. Since the gain of the input audio signal is adjusted, it is not necessary to monitor the power supply voltage or the output audio signal, and an A / D converter or the like is unnecessary. Further, by performing the gain change in the gain adjustment unit so that it is outside the frequency range of the audible band, it is possible to prevent adjustment noise from being mixed into the audio signal.

<First embodiment>
FIG. 1 is a block diagram showing the configuration of an audio playback device 10A according to the first embodiment of the present invention. 11 is an audio input terminal for inputting a digital audio signal, 12 is a high potential (Vdd) power supply terminal, 13 is a low potential (GND) power supply terminal, 14 is a large-capacity power capacitor, and 15 is an input audio signal. A gain adjusting unit 16 for adjusting the gain of the audio signal, 16 an audio amplifying unit for amplifying the power of the audio signal whose gain has been adjusted, and 17 a speaker.

  The power supply capacitor 14, the sound amplifying unit 15, and the speaker 17 are driven by the voltage Vdd applied between the power supply terminals 12 and 13. When the power supply capability from the power supply terminals 12 and 13 becomes insufficient due to the large output, the shortage of supply is compensated by the electric charge accumulated in the power supply capacitor 14.

(1)式のカッコ内は、音声増幅部１６とスピーカ１７に要求される消費電流を最大入力電流Ｉ_ＩＮから減算する式（電荷減少量）である。Ｖ_Ｃ’は、電源コンデンサ１４の両端の初期値電圧であり、前回演算時の演算結果の電圧Ｖ_Ｃである。電圧Ｖ_Ｌは利得調整部１５に入力する音声信号の電圧値Ｖ_ｉと全体の利得Ｇに応じて決まる値であり、Ｖ_Ｌ＝Ｇ・Ｖ_ｉである。利得調整部１５の現在の利得をＧ_１、音声増幅部１６の利得をＧ_２（一定）とすると、Ｇ＝Ｇ_１×Ｇ_２で求められる。 The gain adjusting unit 15 stores the maximum input current I _IN (constant) of the apparatus, the capacity C (constant) of the power supply capacitor 14, the efficiency η ₁ (constant) of the audio amplifying unit 16, and the impedance of the speaker 17. On the basis of R _L (constant) and voltage V _L (variable) applied to the speaker 17, a built-in DSP (digital signal processor) is used for every sampling period Δt (sampling frequency is 44.1 kHz, for example) of the audio signal. , a voltage V _C across the power supply capacitor 14 is calculated predicted by the following equation (1), so as to satisfy the expression (2), to adjust the gain of the gain adjustment unit 15.

(1) in parentheses is an expression of subtracting the current consumption required for the audio amplifier 16 and speaker 17 from the maximum input current I _IN (charge reduction). V _C ′ is an initial value voltage at both ends of the power supply capacitor 14, and is a voltage V _C as a calculation result at the previous calculation. The voltage V _L is a value determined according to the voltage value V _i of the audio signal input to the gain adjusting unit 15 and the overall gain G, and V _L = G · V _i . When the current gain of the gain adjusting unit 15 is G ₁ and the gain of the audio amplifying unit 16 is G ₂ (constant), G = G ₁ × G ₂ is obtained.

At the time of processing, the voltage V _L is obtained based on the voltage value V _i and the gain G of the input audio signal at a certain sample, and the obtained voltage V _L is calculated by substituting it into the equation (1) to obtain a new voltage V _C. Ask for. When the relationship of V C _{<V L} is established is when the voltage V _C is insufficient, to prevent the output waveform is clipped, reduces the gain G ₁ of the gain adjustment section 15.

In this case, one sample per reduction step number of the gain G ₁ (low loss), the case may but as the number of steps corresponding to the difference between V _C and V _L, there is a concern that lead to sudden volume change ( When emphasizing the prevention of volume change more rapidly than the prevention of audio signal clipping), the number of steps is set in advance. In the latter case, the change in gain G ₁ is, the frequency range of the audio band, for example, it is preferable to be a 20Hz about whether frequency slightly lower. The frequency increases as the number of reduction steps increases, and decreases as the number of reduction steps decreases. Then, at the next sample after the lapse of Δt, as V _C → V _C ′, the voltage V V obtained based on the voltage value V _i and the gain G (G ₁ is the previously adjusted value) of the new input audio signal _The same calculation is performed by substituting _L into equation (1).

On the other hand, when the relationship of V _C > V _L is established as a result of the calculation of the equation (1), there is a margin in the voltage V _C of the power supply capacitor 14 and the gain G ₁ of the gain adjusting unit 15 is set. Increase. Per sample of increasing the number of steps of the gain G ₁ (increase amount) is also good as a number of steps corresponding to the difference between V _C and V _L, this case leads to rapid volume change, in order to prevent it Is a predetermined number of steps. In the latter case, the change in gain G ₁ is, it is preferable that a frequency of about 2 Hz. The frequency increases as the number of steps increases and decreases as the number of steps decreases. Then, at the next sample after the lapse of Δt, as V _C → V _C ′, the voltage V obtained based on the voltage value V _i of the new input audio signal and the gain G (G ₁ is the previously adjusted value) _The same calculation is performed by substituting _L into equation (1).

As described above, every time the sampling period Δt elapses, the voltage V _C is obtained according to the voltage value V _i of the input audio signal, and the gain in the gain adjustment unit 15 is reduced or increased, and the audio signal V _S adjusted in gain. Is input to the audio amplifying unit 16, the relationship of V _C ≧ V _{L in} the above-described equation (2) can be maintained, and the waveform of the voltage V _L input to the speaker 17 is prevented from being clipped and output. It is possible to prevent distortion from occurring in the sound (see FIG. 2). Gain frequency of the change in G ₁ may, when the gain reduction slightly lower than 20Hz approximately as described above, by approximately 2Hz when the gain increases, avoiding the problem of audible frequency noise due to gain change Can do.

<Second embodiment>
FIG. 3 is a block diagram showing the configuration of the audio reproduction device 10B of the second embodiment. Here, n speakers 17 _{1 to} 17 _n for multi-channels and n audio amplifying units 16 _{1 to} 16 _n (gains G _{21 to} G _2n ) corresponding thereto are provided, and gain adjustment by the gain adjustment unit 15 The audio signal V _S is input to each of the audio amplifiers 16 _{1 to} 16 _n .

(3)式のカッコ内は、各スピーカ１７_ｋ毎に要求される電流の総計を最大入力電流Ｉ_ＩＮから減算する式（電荷減少量）である。η_ｋは各音声増幅部１６_ｋの効率である。 In this embodiment, since the input voltage V _Lk of the speaker 17 _k (k = 1 to n) is obtained by V _Lk = V _i · G ₁ · G _2k , the voltage V _C is _calculated by the following equation (3). determined, (4) expression to be retained, to adjust the gain G ₁ of the gain adjustment section 15.

In parentheses (3) is an equation (charge reduction) for subtracting the total current required for each speaker 17 _k from the maximum input current I _IN. η _k is the efficiency of each audio amplifying unit 16 _k .

The gain adjustment unit 15, among the plurality of voltages V _Lk, reduce the gain G ₁ when a voltage higher than the value of the voltage V _C is also one, all values of the plurality of voltage V _Lk is the predicted is lower than the value of the voltage V _C increases the gain G _1. Change in gain G ₁ is performed in the same manner as the first embodiment described above.

<Third embodiment>
FIG. 4 is a block diagram showing the configuration of an audio playback device 10C according to the third embodiment. Here, a DC / DC converter 18 is provided on the input side of the power supply terminals 12 and 13. When the voltage supplied between the power supply terminals 19 and 20 does not match the standard voltage Vdd supplied to the power supply terminals 12 and 13, voltage conversion is performed by the DC / DC converter 18. For example, when the built-in battery 21 is connected between the power supply terminals 19 and 20 and the voltage does not match, the DC / DC converter 18 boosts the voltage. When the input voltage between the power supply terminals 19 and 20 is V _DD , the input current is I _DD , and the conversion efficiency of the DC / DC converter 18 is η ₂ , its input / output characteristics are expressed by the following equation (5). .

<Fourth embodiment>
FIG. 5 is a block diagram showing the configuration of an audio playback device 10D of the fourth embodiment. When the built-in battery 21 is used as in the audio playback device 10C shown in FIG. 4, it is preferable to eliminate the need for an external connection cable. Therefore, the audio reproduction device 10D of the present embodiment includes the wireless signal receiving device 22, and is configured to receive the audio signal by the wireless signal receiving device 22 and input the audio signal from the audio input terminal 11 to the gain adjusting unit 15. . As a result, the entire configuration can be accommodated in the apparatus of the speaker 17 which is wireless.

<Fifth embodiment>
FIG. 6 is a block diagram showing the configuration of the audio reproducing device 10E of the fourth embodiment. Here, the audio signal V _S whose gain has been adjusted by the gain adjusting unit 15 is stored in a storage device 23 such as a CD, MD, DVD, flash memory, hard disk, or the like, read from there, and then the audio amplifying unit 16. To output an audio signal. When the storage device 23 is provided in this way, when the same piece of music is played back repeatedly, the same calculation can be omitted, power consumption for the calculation can be reduced, and it is advantageous when the built-in battery is used. .

<Other examples>
Note that the gain adjustment in the gain adjusting unit 15 is not limited to using a DSP, and a personal computer can be used. The audio signal input to the audio input terminal 11 is not limited to a digital signal, and is an analog signal. There may be. In this case, the gain adjustment is performed after conversion to a digital signal. The gain-adjusted audio signal output from the gain adjusting unit 15 may be either a digital signal or an analog signal.

It is a block diagram which shows the structure of the audio | voice reproduction apparatus of a 1st Example. It is a wave form diagram for operation | movement description of the audio | voice reproduction apparatus of FIG. It is a block diagram which shows the structure of the audio | voice reproduction apparatus of a 2nd Example. It is a block diagram which shows the structure of the audio | voice reproduction apparatus of a 3rd Example. It is a block diagram which shows the structure of the audio | voice reproduction apparatus of a 4th Example. It is a block diagram which shows the structure of the audio | voice reproduction apparatus of a 5th Example. It is a block diagram which shows the structure of the conventional audio | voice reproduction apparatus. FIG. 8 is a waveform diagram for explaining the operation of the audio reproduction device of FIG. 7. It is a block diagram which shows the structure of another conventional audio | voice reproduction apparatus.

Explanation of symbols

10A, 10B, 10C, 10D, 10E: Audio playback device 11: Audio input terminal, 12: High potential power supply terminal, 13: Low potential power supply terminal, 14: Power supply capacitor, 15: Gain adjustment unit, 16, 16 ₁ ˜16 _n : audio amplifier, 17, 17 ₁ ˜17 _n : speaker, 18: DC / DC converter, 19: high potential power supply terminal, 20: low potential power supply terminal, 21: battery, 22: wireless signal reception Device, 23: storage device

Claims (5)

A gain adjusting unit that adjusts a gain of an audio signal input to the audio input terminal; a power supply capacitor connected in parallel to the power supply terminal; and the power supply terminal that inputs the audio signal gain-adjusted by the gain adjusting unit; An audio reproducing device comprising: an audio amplifying unit for amplifying audio using the voltage supplied from the power supply capacitor as a power supply voltage; and a speaker for inputting a signal amplified by the audio amplifying unit,
The gain adjustment unit predicts a value of the power supply voltage required based on the input voltage of the speaker obtained from the value of the input audio signal, the gain of the gain adjustment unit, and the gain of the audio amplification unit, When the predicted power supply voltage value is lower than the input voltage value of the speaker, the gain of the input audio signal is reduced, and when the predicted power supply voltage value is higher than the input voltage value of the speaker, the Increase the gain of the input audio signal,
An audio reproducing apparatus characterized by the above. A gain adjusting unit that adjusts a gain of an audio signal input to the audio input terminal; a power supply capacitor connected in parallel to the power supply terminal; and the power supply terminal that inputs the audio signal gain-adjusted by the gain adjusting unit; An audio reproduction apparatus comprising: a plurality of audio amplifying units that amplify audio using the voltage supplied from the power supply capacitor as a power supply voltage; and a plurality of speakers that individually input signals amplified by the audio amplifying units. ,
The gain adjustment unit determines a value of the power supply voltage required based on each input voltage of each speaker obtained from the value of the input audio signal, the gain of the gain adjustment unit, and the gain of each audio amplification unit. Predicting, when there is a speaker having an input voltage higher than the predicted power supply voltage value among the plurality of speakers, the gain of the input audio signal is reduced, and the values of all the input voltages of the plurality of speakers are reduced. Increases the gain of the input audio signal when the predicted power supply voltage value is lower,
Sound reproducing apparatus The sound reproducing device according to claim 1 or 2,
An audio reproducing apparatus, wherein the gain adjustment in the gain adjusting unit is performed so that the change of the gain adjustment is outside an audible frequency range. The audio playback device according to claim 3,
An audio reproducing apparatus characterized in that an adjustment amount of gain adjustment per time in the gain adjusting unit is increased when the gain is reduced, and is decreased when the gain is increased. The sound reproducing device according to any one of claims 1 to 4,
An audio reproduction apparatus comprising: a storage device that stores an audio signal that has been gain-adjusted in the gain adjustment unit, and an audio signal read from the storage device is input to the audio amplification unit.

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