JP2006238256A - Amplifying apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide amplifying apparatus for improving sound quality and image quality, by reducing the distortions of the waveform of the output signal, when amplifying and outputting low-level signals. <P>SOLUTION: When input signal level is lowered, based on the signal level of the detected input signal, a level adjuster is controlled to raise the coefficient obtained, by dividing the input signal level before adjustment from the input signal level after adjustment, and the power supply is controlled so as to lower the supply voltage. When the input signal level rises, the level adjuster is controlled to lower the coefficient, and the power supply is controlled so as to raise the supply voltage. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present application relates to a technical field such as an amplifying apparatus that amplifies and outputs an input signal.

  As a conventional amplifying apparatus (hereinafter also referred to as an amplifier as appropriate) for amplifying an input signal such as an audio signal or an image signal, a digital amplifier typified by a class D amplifying apparatus is used in terms of power efficiency and heat generation. It is known that it is superior to analog amplifiers typified by class class amplifiers, class B amplifiers and the like. Also, as in the case of CD (Compact Disc), MD (Mini Disk), etc., since the audio signal source has been digitized, the development of a digital amplifier that can be processed in full digital to improve sound quality has been developed. It has become active.

  The case where a digital amplifier is applied as an example of a conventional amplifying device will be described below with reference to FIGS. FIG. 1 is a block diagram showing an example of a schematic configuration of a conventional digital amplifier.

  As shown in FIG. 1, a conventional digital amplifier includes, as an example, an input terminal 1, an A / D (Analog / Digital) converter 2, a modulation unit 3, an amplification unit 4, a power supply unit 5, and an LPF. (Low Pass Filter) 6 and an output terminal 7.

  An analog input signal Sin input from the input terminal 1 is converted into a digital input signal Sdi such as a PCM (Pulse Code Modulation) signal by the A / D converter 2 and further, for example, a PDM (Pulse Density Modulation) by the modulation unit 3. The modulated signal Smo is modulated and input to the amplifying unit 4. The amplifying unit 4 performs ON / OFF control on the power signal Spw of the constant voltage Vcc supplied from the power supply unit 5 corresponding to the input modulation signal, and outputs it as an amplified signal Sam. The output amplified signal is demodulated into an analog signal from which high-frequency components have been removed by the LPF 6 and output to an external device such as a speaker (not shown) through the output terminal 7 as an output signal Sou.

  FIG. 2 is a diagram illustrating an example of a waveform image of a signal of each part in a conventional digital amplifier. FIG. 2A is a diagram illustrating a waveform of an input signal Sin when the signal level is high, and FIG. (C) is a diagram showing a waveform of the output signal Sou corresponding to the input signal Sin shown in (a), and (d) is a diagram showing a waveform of the amplified signal Sam corresponding to the input signal Sin shown in (a). ) Is a diagram showing the waveform of the input signal Sin when the signal level is low, (e) is a diagram showing the waveform of the amplified signal Sam corresponding to the input signal Sin shown in (d), and (f) is a diagram. It is a figure which shows the waveform of the output signal Sou corresponding to the input signal Sin shown by (d).

  2B and 2E show the waveforms of the amplified signals when the PDM method is adopted as the modulation method of the modulation unit 3. FIG.

  The modulation unit 3 outputs the modulation signal Smo by changing the density at which pulses are generated corresponding to the level of the input signal Sin shown in FIG. 2A or 2D, and the amplification unit 4 outputs the modulation signal Smo. ) Or the amplified signal Sam having the amplitude Vcc indicated by (e) is output. The LPF 6 integrates the amplified signal Sam to form the output signal Sou shown in FIG. 2 (c) or (f).

  However, according to the configuration of the above-described conventional amplification device, the resolution of the signal level expressed by the modulation signal decreases as the signal level of the input signal decreases (FIG. 2D) (FIG. 2E). The quantization noise increases, the waveform of the signal output from the LPF 6 is distorted (FIG. 2 (f)), and the sound quality, image quality, and the like deteriorate.

One way to solve this problem is to improve the performance of the A / D converter, the modulation unit, and the amplification unit to increase the resolution of the signal level. For example, in order to obtain 24-bit resolution, the operation must be performed at 2 ²⁴ Hz, that is, 16.78 MHz.

  On the other hand, A / D converters having a resolution of about 24 bits have been developed. On the other hand, it is technically difficult to develop an amplifying unit that performs a switching operation at a high frequency. There is a problem that the resolution of the signal level is limited as a whole digital amplifier. Therefore, the present application has been made in view of the above problems, and an example of the purpose thereof is to amplify an output signal having a low signal level and output the signal level without operating the amplification unit at a high frequency. It is an object of the present invention to provide an amplifying apparatus that improves the sound quality, image quality, and the like by reducing the distortion of the waveform of the output signal.

  In order to solve the above-mentioned problem, the invention according to claim 1 is characterized in that a modulation unit that modulates an input signal to generate a modulation signal, an amplification unit that amplifies the modulation signal to generate an amplification signal, A power supply means for supplying power to the amplification means; and a detection means for detecting either the signal level of the input signal or information indicating the signal level; and the input to the modulation means Based on the level detection means for adjusting the signal level of the input signal and the detection result of the detection means, when the signal level of the input signal is lowered, the signal level of the input signal after the adjustment by the level adjustment means is set. The level adjusting means is controlled to increase the coefficient obtained by dividing by the signal level of the input signal before adjustment, and the supply voltage by the power supply means is lowered. When the signal level of the input signal increases, the level adjustment unit is controlled to decrease the coefficient, and the power supply unit is controlled to increase the supply voltage. And a control means.

  Next, the best mode for carrying out the present application will be described with reference to the drawings. In addition, the embodiment described below is an embodiment in the case where the present application is applied to a digital amplifier that digitally converts an input analog signal and amplifies the signal after modulating it by the PDM method.

(I) First Embodiment First, a first embodiment according to the present application will be described with reference to FIGS.

  FIG. 3 is a block diagram illustrating an example of a schematic configuration of the digital amplifier according to the first embodiment.

  As shown in FIG. 3, the digital amplifier according to the present embodiment includes an input terminal 51, an A / D converter 52 as digitizing means, a level adjusting section 53 as level adjusting means, and a modulating section as modulating means. 54, an amplifying unit 55 as an amplifying unit, a power source unit 56 as a power supplying unit, an LPF 57 as an analogizing unit, an output terminal 58, and a controller 59 as a detecting unit and a controlling unit. Yes.

  The analog input signal Sin input from the input terminal 51 is converted into a digital input signal Sdi such as a PCM signal by the A / D converter 52 and input to the level adjusting unit 53 and the controller 59. The level adjustment unit 53 outputs a digital signal Sad whose signal level is adjusted by multiplying the signal level of the input digital input signal Sdi by a coefficient set in a level control signal Slc transmitted from the controller 59 described later. To do.

  The modulation unit 54 modulates the input signal into a modulation signal Smo such as a PDM signal and inputs the modulated signal to the amplification unit 55. The modulation unit 54 is not limited to one that modulates to a PDM signal, and one that modulates to a PWM (Pulse Width Modulation) signal or the like can also be applied.

  The power supply unit 56 is a variable voltage power supply, and supplies a power signal Spw of the voltage Vcc set in the voltage control signal Svc transmitted from the controller 59 described later to the amplification unit 55.

  The amplifying unit 55 performs ON / OFF control of the power signal Spw of the supplied voltage Vcc corresponding to the input modulation signal Smo, and outputs an amplified signal Sam having the amplitude Vcc.

  The LPF 57 integrates the amplified signal Sam, removes a high frequency component, and outputs it as an analog output signal Sou to a device such as a speaker (not shown) through the output terminal 58.

  The controller 59 includes a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), and the like, and the CPU reads and executes a control program stored in the RAM, ROM, and the like. The controller 59 functions as detection means and control means. The control program may be recorded in advance in a ROM or the like, or may be read from a recording medium such as a CD-ROM into a RAM or the like. In the present embodiment, the controller 59 is configured to read out and execute the control program. However, the controller 59 is not limited to this, and may be configured by a hard logic circuit.

  Specifically, the controller 59 detects the signal level of the digital input signal Sdi converted by the A / D converter 52. When the detected signal level falls to a low range, the level adjustment unit 53 is controlled to increase the coefficient, and the power supply unit 56 is controlled to decrease the supply voltage. On the other hand, when the detected signal level rises to a high signal level range, the level adjustment unit 53 is controlled to decrease the coefficient, and the power supply unit 56 is controlled to decrease the supply voltage. As an example, it is assumed that the maximum signal level of the digital signal Sad modulated by the modulation unit 54 is m, and the maximum voltage value of the power signal Spw supplied by the power supply unit 56 is n.

  In this case, the controller 59 divides the signal level of the digital input signal Sdi into two ranges in advance, and each of the case where the signal level is in the range of 0 to m / 2 and the case where the signal level is in the range of m / 2 to m. The coefficient and voltage value to be set are determined. For example, when the signal level of the digital input signal Sdi is in the range of 0 to m / 2, the coefficient is 2 and the voltage value is n / 2. On the other hand, when the signal level of the digital input signal Sdi is in the range of m / 2 to m, the coefficient is 1 and the voltage value is n. In this way, the coefficient and the voltage value are changed based on the signal level so as to have an inversely proportional relationship. In this way, the controller 59 sets the coefficient determined based on the signal level of the digital input signal Sdi to the level control signal Slc and transmits it to the level adjustment unit 53, sets the voltage value to the voltage control signal Svc, and supplies power. It transmits to the part 56.

  In the present embodiment, the controller 59 determines the coefficient and the voltage value based on the signal level of the input signal, but the present invention is not limited to this. For example, since the signal level of the signal input to the modulation unit 54 is controlled by the volume position, the attenuation rate by the attenuator, and the like, the coefficient and the voltage value are set based on the information indicating the signal level such as the volume position and the attenuation rate. It is also possible to decide.

  Next, the operation when the signal level is in the range of m / 2 to m, that is, when the signal level of the input signal is high will be described. FIG. 4 is a diagram showing an example of a waveform image of signals at various parts in the digital amplifier according to the first embodiment. FIG. 4A shows an input signal Sin when the signal level is in the range of m / 2 to m. (B) is a figure which shows the waveform of amplified signal Sam corresponding to the input signal Sin shown by (a), (c) is the figure which shows the input signal Sin shown by (a) (D) is a diagram showing an example of the waveform of the input signal Sin when the signal level is in the range of 0 to m / 2, and (e) is a diagram showing the waveform of the output signal Sou corresponding to (e). It is a figure which shows the waveform of the amplified signal Sam corresponding to the input signal Sin shown by d), (f) is a figure which shows the waveform of the output signal Sou corresponding to the said input signal Sin shown by (d).

  The input signal Sin having the waveform shown in FIG. 4A is digitally converted by the A / D converter 52, the signal level is detected by the controller 59, and is input to the level adjusting unit 53. Since the detected signal level is in the range of m / 2 to m higher than the range of 0 to m / 2, the controller 59 transmits the level control signal Slc set with the coefficient lowered to 1 to the level adjustment unit 53. The voltage control signal Svc set by raising the voltage value to n is transmitted to the power supply unit 56.

  The level adjustment unit 53 outputs a digital signal Sad adjusted by multiplying the input digital input signal Sdi by a coefficient of 1. As a result, the signal input to the level adjustment unit 53 is output without changing its signal level, modulated by the modulation unit 54 and input to the amplification unit 55.

  The amplifying unit 55 that has received the power signal Spw having the voltage n from the power supply unit 56 outputs an amplified signal Sam having an amplitude n corresponding to the modulation signal Smo. FIG. 4B shows a waveform of the amplified signal Sam.

  The waveform of the output signal Sou demodulated by the LPF 57 is as shown in FIG.

  Next, the operation when the signal level is in the range of 0 to m / 2, that is, when the signal level of the input signal is low will be described.

  The input signal Sin having the waveform shown in FIG. 4D is digitally converted by the A / D converter, the signal level is detected by the controller 59, and is input to the level adjusting unit 53. Since the detected signal level is in the range of 0 to m / 2, which is lower than the range of m / 2 to m, the controller 59 transmits the level control signal Slc set with the coefficient increased to 2 to the level adjustment unit 53. The voltage control signal Svc set with the voltage value lowered to n / 2 is transmitted to the power supply unit 56.

  The level adjustment unit 53 outputs a digital signal Sad adjusted by multiplying the input digital signal Sdi by a coefficient of 2. As a result, the signal input to the level adjustment unit 53 is output with the signal level adjusted to double. Then, since the signal level of the digital signal Sad input to the modulation unit 54 is in the range from 0 to m, the resolution of the signal level of the modulation signal Smo output from the modulation unit 54 is doubled.

  The amplifying unit 55 that has received the power signal Spw having the voltage n / 2 from the power supply unit 56 outputs the amplified signal Sam having the amplitude n / 2 corresponding to the modulation signal Smo. FIG. 4E shows the waveform of this amplified signal. As described above, the waveform of FIG. 4E has a signal level resolution twice that of the waveform of FIG. 4B and a half amplitude.

  The waveform of the output signal Sou demodulated by the LPF 57 is as shown in FIG.

  Thus, the amplified signal Sam of the digital amplifier according to the present embodiment has a higher signal level resolution than the amplified signal Sam of the conventional digital amplifier (FIG. 2 (e)), so that the waveform of the output signal Sou Distortion is reduced.

  As described above, according to the digital amplifier of the first embodiment, the coefficient to be multiplied by the signal level is controlled by the level adjustment unit 53 based on the signal level of the digital input signal Sdi and input to the modulation unit 54. Since the signal level of the digital signal Sad is adjusted, the resolution of the signal level of the modulation signal Smo output by the modulation unit 54 can be increased when the signal level of the input signal is low. Further, since the voltage supplied by the power supply unit 56 is controlled based on the signal level of the digital input signal Sdi, the signal level of the output signal Sou can be adjusted in accordance with the resolution of the signal level of the modulation signal Smo. As a result, when a signal having a low signal level is amplified and output, the resolution of the signal level can be increased without operating the amplifier 55 at a high frequency, and the waveform distortion of the output signal can be reduced. It is possible to improve sound quality, image quality, and the like.

  When the amplifying unit 55 is operated at a high frequency, an increase in emitted electromagnetic waves or the like is caused, and power loss in the circuit due to energy emission increases. In addition, an increase in the emitted electromagnetic wave means an increase in unnecessary radiation, and there is a concern about the influence on the human body and equipment.

  On the other hand, according to the digital amplifier of the first embodiment, as described above, there is no need to drive the amplifying unit 55 at a high frequency, so that high power efficiency is obtained and the influence on the human body and the like is suppressed. be able to.

  Further, the signal level of the input signal Sdi is divided into a plurality of ranges, and the coefficient and the voltage value set for the control signal are determined for each range, so that the signal level and the supply voltage are controlled stepwise. This makes it possible to perform simpler control than continuous control.

  Further, since the level adjustment unit 53 controls the coefficient multiplied by the signal level and the voltage value of the supply voltage by the power supply unit 56 so as to have an inversely proportional relationship based on the signal level of the digital input signal Sdi, The change level of the signal level can be reproduced in the output signal.

  In addition, since the signal level is adjusted by multiplying the digital input signal Sdi by a coefficient, this is particularly effective when the resolution of the signal level of the A / D converter 52 is higher than that of the modulation unit 54 and the amplification unit 55. That is, in the case of the conventional digital amplifier, the quality of the output signal is limited by the low resolution of the modulation unit 54 and the amplification unit 55, but according to the digital amplifier according to the first embodiment, the A / A Since the high-resolution digital input signal Sdi output from the D converter 52 is adjusted, the amplified signal Sam having a high resolution can be output while effectively using the high resolution of the A / D converter 52. In the above embodiment, the amplifying device according to the present application is applied to an analog input digital amplifier. However, the present invention is not limited to this, and can be applied to a digital input digital amplifier.

(II) Second Embodiment Next, a second embodiment which is another embodiment according to the present application will be described with reference to FIG.

  FIG. 5 is a block diagram illustrating an example of a schematic configuration of the digital amplifier according to the second embodiment.

  Further, in the configuration of the digital amplifier according to the second embodiment described below, only the level adjustment unit and the part related to the controller are different from the case of the digital amplifier according to the first embodiment. Following the configuration of the digital amplifier according to the first embodiment, the same member numbers are assigned, and the detailed description is omitted.

  In the first embodiment described above, the case where the signal level of the digital signal is adjusted has been described. In the second embodiment described below, the case where the signal level of the analog signal is adjusted will be described.

  As shown in FIG. 5, in the digital amplifier according to the first embodiment, the input signal Sin input from the input terminal 51 is input to the level adjustment unit 53 and the controller 59, and the level adjustment unit 53 performs the analog signal after the level adjustment. Saa is supplied to the A / D converter 52.

  The level adjustment unit 53 adjusts the attenuation amount based on the level control signal Slc transmitted from the controller 59, and outputs the analog signal Saa whose signal level is adjusted by attenuating the input analog signal Sin. The level-adjusted analog signal Saa is converted into a digital signal Sdi whose level is adjusted by the A / D converter 52 and input to the modulation unit 54.

  The controller 59 detects the signal level of the analog input signal Sin, and controls the coefficient set in the level control signal Slc and the voltage value set in the voltage control signal Svc based on this signal level.

  As an example, it is assumed that the maximum signal level of the analog signal Saa converted into a digital signal by the A / D conversion unit 52 and the maximum signal level of the digital signal Sdi modulated by the modulation unit 54 are both m and input from the input terminal 51. Assume that the maximum signal level of the input signal Sin is 2 m, and the maximum voltage value of the power signal Spw supplied by the power supply unit 56 is n.

  In this case, when the signal level of the input signal Sin is in the range of 0 to m, the coefficient is 1 and the voltage value is n / 2. When the signal level of the input signal Sin is in the range of m to 2 m, the coefficient is ½ and the voltage value is n.

  Next, the operation when the signal level is in the range of m to 2 m will be described.

  The controller 59 that has detected the signal level of the input signal Sin has a level control signal Slc that is set by reducing the coefficient to 1/2 because the detected signal level is in the range of m to 2 m, which is higher than the range of 0 to m. The voltage control signal Svc set by increasing the voltage value to n is transmitted to the power supply unit 56.

  On the other hand, the level adjusting unit 53 adjusts the attenuation amount so that the signal level becomes 1/2 based on the set coefficient 1/2, and adjusts the signal level of the input signal Sin input to 1/2. An analog signal Saa is output.

  The analog signal Saa is digitally converted by the A / D converter 52, modulated by the modulator 54, and input to the amplifier 55.

  The amplifying unit 55 that has received the power signal Spw having the voltage n from the power supply unit 56 outputs an amplified signal Sam having an amplitude n corresponding to the modulation signal Smo. Then, the LPF 57 outputs an output signal Sou.

  The waveforms of the input signal Sin, the amplified signal Sam, and the output signal Sou in this case are the same as those in FIGS. 4A, 4B, and 4C in the first embodiment.

  Next, the operation when the signal level is in the range of 0 to m will be described.

  The controller 59 that has detected the signal level of the input signal Sin adjusts the level of the level control signal Slc set by increasing the coefficient to 1 because the detected signal level is in the range of 0 to m, which is lower than the range of m to 2 m The voltage control signal Svc set by reducing the voltage value to n / 2 is transmitted to the power supply unit 56.

  On the other hand, the level adjustment unit 53 adjusts the attenuation amount based on the set coefficient 1 so that the signal level does not attenuate, and outputs the analog signal Saa without changing the signal level of the input signal Sin.

  Then, since the signal level of the digital signal Sdi converted by the A / D converter 52 and input to the modulation unit 54 is in the range from 0 to m, the resolution of the signal level of the modulation signal Smo output by the modulation unit 54 Is doubled.

  The amplifying unit 55 that has received the power signal Spw having the voltage n / 2 from the power supply unit 56 outputs the amplified signal Sam having the amplitude n / 2 corresponding to the modulation signal Smo. Then, an output signal Sou is output by the LPF 57.

  The waveforms of the input signal Sin, the amplified signal Sam, and the output signal Sou in this case are the same as those in FIGS. 4D, 4E, and 4F in the first embodiment.

  As described above, according to the digital amplifier according to the second embodiment, the signal level of the analog input signal Sin is adjusted in addition to the effect of the operation of the digital amplifier according to the first embodiment. Since the signal Saa is digitally converted by the A / D converter 52, the signal level can be adjusted so that the dynamic range of the A / D converter 52 can be used effectively.

  Further, as described above, since the signal level of the analog input signal is adjusted and then converted into a digital signal, the resolution of the signal level in the A / D converter 52 is lower than the resolution of the modulation unit 54 and the amplification unit 55. Is also effective. In other words, when the signal level is adjusted by multiplying the digitally converted low resolution signal by a coefficient, the signal level resolution further decreases. However, the digital amplifier according to the second embodiment has such inconvenience. There is no.

(III) Third Embodiment Next, a third embodiment which is another embodiment according to the present application will be described with reference to FIG.

  FIG. 6 is a block diagram illustrating an example of a schematic configuration of the digital amplifier according to the third embodiment.

  Further, in the configuration of the digital amplifier according to the third embodiment described below, only the part related to the A / D converter and the level adjustment unit according to the present application is different from the case of the digital amplifier according to the second embodiment. The other members follow the configuration of the digital amplifier according to the second embodiment and are given the same member numbers, and the detailed description is omitted.

  In the second embodiment described above, the case where the level adjustment unit 53 directly adjusts the signal level has been described. However, in the third embodiment described below, the level adjustment unit 53 supplies the signal to the A / D converter 52. A case where the signal level is adjusted by changing the reference voltage will be described.

  As shown in FIG. 5, in the digital amplifier according to the third embodiment, the input signal Sin input from the input terminal 51 is input to the A / D converter 52 and the controller 59, and the level adjustment unit 53 converts the reference voltage Srf to A. / D converter 52 is configured to be supplied.

  The level adjustment unit 53 is a variable voltage power supply, and supplies a reference voltage signal Srf having a voltage value set in the level control signal Slc transmitted from the controller 59 to the A / D converter 52.

  The full scale voltage of the A / D converter 52 is determined by the voltage value of the reference voltage signal Srf. That is, by raising and lowering the voltage value of the reference voltage signal Srf, the signal level of the input signal Sin is adjusted with the voltage value as the maximum signal level and converted to the digital signal Sdi.

  Thus, the signal level of the input signal can be adjusted also by changing the reference voltage supplied to the A / D converter.

  Then, the controller 59 that has detected the signal level of the analog input signal Sin controls the signal level adjustment by the level adjustment unit 53 and the supply voltage by the power supply unit 56 based on this signal level, thereby adjusting the signal level. It is possible to increase the signal level resolution when a low input signal is amplified.

  As described above, in the digital amplifier according to the third embodiment, the same effect as that obtained by the operation of the digital amplifier according to the second embodiment can be obtained.

  The control means in each of the embodiments described above controls the level adjustment coefficient and the supply voltage value in two stages. However, the control means is not limited to this, and is multistage or continuous according to the signal level. It is desirable to control. Thereby, the distortion of the waveform of the output signal can be further reduced.

  In each of the above embodiments, the amplifying apparatus according to the present application is applied to a digital amplifier. However, the present invention is not limited to this and can be applied to an analog amplifier.

It is a block diagram which shows an example of schematic structure of the conventional digital amplifier. It is a figure which shows an example of the waveform image of the signal of each part in the conventional digital amplifier, (a) is a figure which shows the waveform of the input signal Sin in case a signal level is high, (b) is shown by (a). It is a figure which shows the waveform of the amplified signal Sam corresponding to the input signal Sin, (c) is a figure which shows the waveform of the output signal Sou corresponding to the input signal Sin shown in (a), (d) is a signal level. (E) is a figure which shows the waveform of amplified signal Sam corresponding to the input signal Sin shown by (d), (f) is a figure which shows (d). It is a figure which shows the waveform of the output signal Sou corresponding to the input signal Sin shown. It is a block diagram which shows an example of schematic structure of the digital amplifier which concerns on 1st Embodiment. It is a figure which shows an example of the waveform image of the signal of each part in the digital amplifier which concerns on 1st Embodiment, (a) shows an example of the waveform of the input signal Sin in case a signal level exists in the range of m / 2 to m. (B) is a figure which shows the waveform of the amplified signal Sam corresponding to the input signal Sin shown to (a), (c) is the output signal Sou corresponding to the input signal Sin shown to (a). (D) is a diagram showing an example of the waveform of the input signal Sin when the signal level is in the range of 0 to m / 2, and (e) is an input shown in (d). It is a figure which shows the waveform of the amplified signal Sam corresponding to the signal Sin, (f) is a figure which shows the waveform of the output signal Sou corresponding to the said input signal Sin shown by (d). It is a block diagram which shows an example of schematic structure of the digital amplifier which concerns on 2nd Embodiment. It is a block diagram which shows an example of schematic structure of the digital amplifier which concerns on 3rd Embodiment.

Explanation of symbols

1, 51 Input terminal 2, 52 A / D converter 3, 54 Modulation unit 4, 55 Amplification unit 5, 56 Power supply unit 6, 57 LPF
7, 58 Output terminal 53 Level adjustment unit 59 Control unit

Claims (7)

In an amplifying apparatus comprising: a modulating unit that modulates an input signal to generate a modulated signal; an amplifying unit that amplifies the modulated signal to generate an amplified signal; and a power supply unit that supplies power to the amplifying unit.
Detecting means for detecting either the signal level of the input signal or information indicating the signal level;
Level adjusting means for adjusting the signal level of the input signal input to the modulating means;
When the signal level of the input signal decreases based on the result detected by the detection unit, the signal level of the input signal after the adjustment by the level adjustment unit is divided by the signal level of the input signal before the adjustment. When the level adjustment means is controlled to increase the required coefficient and the power supply means is controlled to decrease the supply voltage by the power supply means, and the signal level of the input signal increases, the coefficient Control means for controlling the power supply means to increase the supply voltage;
An amplifying device further comprising: The amplification device according to claim 1,
The control means adjusts the level so as to increase the coefficient when the signal level falls from the one of a plurality of pre-divided ranges to the range having a signal level lower than the range. And controlling the power supply means to lower the supply voltage, and lowering the coefficient when the signal level rises from the one range to the range where the signal level is higher than the range. And a power supply means for controlling the level adjusting means and raising the supply voltage. The amplification device according to claim 1 or 2,
The amplifying apparatus characterized in that the control means controls the level adjusting means and the power supply means so that the coefficient and the supply voltage are in an inversely proportional relationship. In the amplification device according to any one of claims 1 to 3,
The amplification device characterized in that the level adjustment means adjusts the signal level of the input signal which is a digital signal and inputs the signal to the modulation means. In the amplification device according to any one of claims 1 to 3,
Further comprising digitizing means for digitizing an analog signal and inputting it to the modulating means;
The amplification device characterized in that the level adjustment means adjusts the signal level of the input signal which is an analog signal and inputs the signal to the digitization means. In the amplification device according to any one of claims 1 to 3,
Further comprising digitizing means for digitizing the input signal which is an analog signal and inputting the digitized signal to the modulating means;
The level adjusting means supplies a reference voltage to the digitizing means, and adjusts the signal level of the input signal by changing the reference voltage supplied to the digitizing means. In the amplification device according to any one of claims 1 to 3,
Further comprising digitizing means for digitizing the input signal which is an analog signal and inputting the digitized signal to the modulating means;
The modulation means modulates the digitized input signal to generate either a PDM (Pulse Density Modulation) signal or a PWM (Pulse Width Modulation) signal as the digitized modulation signal,
The amplification means amplifies the digitized modulated signal to generate the digitized amplified signal,
Furthermore, an amplifying apparatus comprising analog means for analogizing the digitized amplified signal.

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