JP3857154B2 - Pulse code modulation signal regeneration device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pulse code modulation signal reproducing apparatus that performs pulse density modulation (PDM modulation) on a pulse code modulation signal (PCM signal) and then amplifies the power by switching to reproduce it as an analog signal.
[0002]
[Prior art]
The switching output type PCM signal reproducing apparatus is excellent in that a device such as a speaker can be driven while D / A converting a PCM (Pulse Code Modulation) signal without using a normal analog circuit.
[0003]
In the switching output type PCM signal reproducing apparatus, the PCM signal is input to the PDM modulator 51 as shown in FIG. This PCM signal is an analog signal having a maximum value 62 as shown in FIG.
[0004]
The PDM modulator 51 converts the input PCM signal into a PDM (Pulse Density Modulator) signal that is expressed by a signal that rapidly changes to a HIGH / LOW binary value, and outputs it to the switching output stage 52. The switching output stage 52 performs power switching based on the input PDM signal. At this time, the constant voltage power supply 53 supplies a constant and constant voltage indicated by the constant voltages 63 and 63 to the switching output stage 52 as shown in FIGS. 6B shows the relationship between the constant voltage 63 output from the switching output stage 52 and the output signal component from the switching output stage 52, while FIG. 6C shows the relationship from the switching output stage 52. The relationship between the output constant voltage 63 and the output noise component from the switching output stage 52 is shown.
[0005]
Here, when the PDM modulator 51 and the switching output stage 52 are viewed as one system 55, it is assumed that the input signal maximum value 62 of the PCM signal does not have a full amplitude with respect to the constant voltage 63. Further, the output signal component when the gain G of the system 55 is 0.5 is represented as having an output signal maximum value 64 as shown in FIG. Furthermore, the noise component generated with the magnitude of the power supply voltage is represented as having a maximum noise value 66 as shown in FIG.
[0006]
On the other hand, as shown in FIG. 5, a low-pass filter (hereinafter referred to as “LPF”) 54 removes a high-frequency component of the switching signal output from the switching output stage 52. Further, the audio signal that has passed through the LPF 54 is output as sound by a device such as a speaker (not shown).
[0007]
[Problems to be solved by the invention]
However, the switching output type power amplifier in the conventional dynamic range control circuit generally has a problem that the dynamic range is smaller and the efficiency is lower than that of the analog amplifier.
[0008]
In order to solve this problem, in order to increase the efficiency by improving the PDM modulator 51, it is necessary to use expensive components as the elements used. Therefore, it is very difficult to obtain an analog-like dynamic range at low cost.
[0009]
In order to increase efficiency digitally, for example, as shown in FIGS. 7 and 8A, 8B, and 8C, input signals are input from a predetermined period or a predetermined signal unit stored in the buffer 71. The signal maximum value 80 is detected by the maximum value detector 72, and the PCM signal is multiplied by the coefficient α by the multiplier 73 according to the output of the maximum value detector 72, thereby increasing the signal 81 after multiplication by a predetermined amount. Can be input to the PDM modulator 51. As a result, as shown in FIGS. 8B and 8C, the output of the switching output stage 52 is the maximum output signal having a larger amplitude than the output signal maximum value 64 at the same voltage 82 as the constant voltage 63. It seems that the signal-to-noise ratio (hereinafter referred to as “S / N ratio”) can be improved by obtaining an output signal of value 83.
[0010]
However, this method merely raises the level of the input PCM signal, which is the original signal, to be higher than the level of the signal to be originally reproduced, and cannot be said to faithfully represent the original signal.
[0011]
Of course, simply increasing the supply voltage from the constant voltage power supply 53 also increases the noise maximum value 85 shown in FIG. 8C at the same time, increasing the noise level and improving the S / N ratio.
[0012]
Another problem is that the above-described switching output type power amplifier that supplies a constant voltage 63 from a constant voltage power supply 53 and performs high-speed and high-speed switching consumes a large amount of power.
[0013]
The present invention has been made in view of the above-described conventional problems. The object of the present invention is to improve the S / N ratio while faithfully reproducing the pulse code modulation signal by using the maximum dynamic range. Another object of the present invention is to provide a switching output type pulse code modulation signal reproducing apparatus capable of reducing power consumption.
[0014]
[Means for Solving the Problems]
In order to solve the above problems, a pulse code modulation signal reproducing apparatus of the present invention performs switching based on pulse density modulation means for pulse density modulation of an input pulse code modulation signal and an output signal from the pulse density modulation means. And a switching output means for amplifying the power of the pulse code modulation signal reproducing apparatus for reproducing the output from the switching output means as an analog signal, from a predetermined period unit or a predetermined signal unit of the input pulse code modulation signal. The maximum value detection means for obtaining the maximum value and the maximum value obtained by the maximum value detection means Multiplication factor The above pulse density modulation Means input range The Outputs the maximum value after multiplication that can be used as much as possible. do it , The maximum value after multiplication above Dynamic range variable means for inputting to the pulse density modulation means, and the dynamic range variable means Above coefficient Variable voltage power supply means for changing the supply voltage to the switching output means according to The It is a feature.
[0015]
According to the above invention, the dynamic range variable means is set to the maximum value obtained by the maximum value detecting means. Multiplication factor Pulse density modulation Means input range The Outputs the maximum value after multiplication that can be used as much as possible. do it , The maximum value after multiplication Input to the pulse density modulation means. Also, with this dynamic range variable means coefficient In response, the variable voltage power supply means changes the supply voltage to the switching output means.
[0016]
Therefore, for example, the dynamic range varying means can change the pulse code modulation signal by a predetermined amount so as to be the maximum of the range of the dynamic range varying means, according to the maximum value obtained by the maximum value detecting means. Then, a supply voltage inversely proportional to the magnification at the maximum signal value expanded by the dynamic range variable means is supplied from the variable voltage power supply means to the switching output means. Thereby, the signal of the same maximum value as before can be output from the switching output means.
[0017]
On the other hand, at this time, since the supply voltage supplied from the variable voltage power supply means to the switching output means is smaller than that of the conventional one, the noise accompanying this supply voltage is also reduced. This indicates that the ratio of noise to the inputted pulse code modulation signal, that is, the S / N ratio becomes small.
[0018]
As a result, the conventional dynamic range can be used to the maximum even with a low-volume signal, and the S / N ratio can be improved. Further, the pulse code modulation signal can be faithfully reproduced by changing the supply voltage to the switching output means in accordance with the amount of change in the dynamic range variable means. Furthermore, since the supply voltage to the switching output means can be low as a whole, it is possible to keep power consumption low.
[0019]
Accordingly, there is provided a switching output type pulse code modulation signal reproducing apparatus that can maximize the dynamic range, faithfully reproduce the pulse code modulation signal, improve the S / N ratio, and reduce power consumption. be able to.
[0020]
Further, the pulse code modulation signal reproducing device of the present invention is the above pulse code modulation signal reproducing device in which the switching is performed with respect to the variable voltage power source means according to the amount of change in the dynamic range variable means during reproduction. While the supply voltage to the output means is changed, a regeneration / stop control means for making the supply voltage to the switching output means zero is provided for the variable voltage power supply means when the regeneration is stopped. .
[0021]
According to the above invention, the reproduction / stop control means causes the variable voltage power supply means to change the supply voltage to the switching output means in accordance with the amount of change in the dynamic range variable means during reproduction. . As a result, at the time of reproduction, the same operation / function as the above-described invention can be obtained.
[0022]
On the other hand, the regeneration / stop control means causes the variable voltage power supply means to set the supply voltage to the switching output means to 0 when the regeneration is stopped. Therefore, the output of the switching output means is 0, and the final analog signal is also 0.
[0023]
As a result, it is possible to reduce power consumption when playback is stopped, and it is also effective as a means for muting noise generated when the apparatus is powered on.
[0024]
Further, the pulse code modulation signal reproducing apparatus of the present invention is An output from the switching output means, comprising: pulse density modulation means for pulse density modulating the input pulse code modulation signal; and switching output means for performing power amplification by switching based on an output signal from the pulse density modulation means. As an analog signal In the pulse code modulation signal reproducing device, Maximum value detection means for obtaining a maximum value from a predetermined period unit or a predetermined signal unit of the input pulse code modulation signal, and a predetermined amount of the pulse code modulation signal according to the maximum value obtained by the maximum value detection means Dynamic range variable means that changes and inputs the pulse density modulation means, and variable voltage power supply means that changes the supply voltage to the switching output means according to the amount of change in the dynamic range variable means. With When it is detected that the pulse code modulation signal is silent based on the level of the input pulse code modulation signal, and when it is detected that the pulse code modulation signal is silent, the voltage supplied to the switching output means is set to 0. It is characterized by including silent detection adjusting means.
[0025]
According to the above invention, the silence detection means detects that the pulse code modulation signal is silent based on the level of the input pulse code modulation signal, and detects that the pulse code modulation signal is silent. Sometimes, the supply voltage to the switching output means is made zero. Therefore, the output of the switching output means is 0, and the final analog signal is also 0.
[0026]
As a result, power consumption can be reduced when playback is stopped or when the playback signal is silent.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
[Embodiment 1]
An embodiment of the present invention will be described with reference to FIGS. 1 and 2 as follows.
[0028]
A switching output type pulse code modulation signal (hereinafter referred to as “PCM (Pulse Code Modulation) signal”) reproducing apparatus used in the digital amplifier or the like of the present embodiment reproduces a PCM signal without using a normal analog circuit. It is excellent that a playback device such as a speaker can be driven while performing A / A conversion.
[0029]
As shown in FIG. 1, a switching output type PCM signal reproducing apparatus 10 according to the present embodiment includes a buffer 1, a maximum value detector 2 as a maximum value detecting means, and a multiplier 3 as a dynamic range variable means. , A pulse density modulator (hereinafter referred to as “PDM (Pulse Density Modulator) modulator”) 4 as a pulse density modulation means, a switching output stage 5 as a switching output means, and a variable voltage power supply as a variable voltage power supply means And a low-pass filter (hereinafter referred to as “LPF (Low-Pass filter)”) 7.
[0030]
The buffer 1 temporarily stores a predetermined period unit or a predetermined signal unit of the input PCM signal and holds the input PCM signal until the output of the maximum value detector 2 is obtained. The predetermined period unit is, for example, several clock units. The predetermined signal unit is, for example, several cycles of the input PCM signal.
[0031]
The maximum value detector 2 obtains the input signal maximum value 12 of the input PCM signal from the predetermined period unit or the predetermined signal unit of the input PCM signal accumulated in the buffer 1 as shown in FIG. The input PCM signal is a digital signal, but is described as an analog signal for easy understanding.
[0032]
The multiplier 3 multiplies the input PCM signal by a predetermined coefficient α according to the output of the maximum value detector 2. Accordingly, the output is represented as an expanded input PCM signal having a maximum value 13 after multiplication, as shown in FIG. The coefficient α multiplied by the multiplier 3 is set so that the maximum value 13 after multiplication fully uses the input range of the PDM modulator 4.
[0033]
The PDM modulator 4 converts the output signal of the multiplier 3 having the post-multiplication maximum value 13 into a high / low binary value at a high speed, thereby converting it into a PDM signal representing the original signal.
[0034]
The switching output stage 5 is made of, for example, a transistor. The output of the PDM modulator 4 is applied to the base side, while the supply power supply voltage 14 supplied from the variable voltage power supply unit 6 is applied to the collector side. Is applied. Accordingly, the switching output stage 5 performs class D amplification based on the switching function by the power conversion circuit such as the half bridge circuit as described above. In the present embodiment, the supply power supply voltage 14 is a predetermined multiple of a constant power supply voltage supplied from a constant voltage power supply (not shown) provided in the variable voltage power supply section 6 as will be described later. Yes. Therefore, in the variable voltage power supply unit 6, the constant power supply voltage is variable.
[0035]
On the other hand, the variable voltage power supply unit 6 applies a predetermined coefficient (1 / α) to a constant power supply voltage supplied from a constant voltage power supply (not shown) according to the output of the maximum value detector 2 (FIG. 2A). Supply power supply voltages 14 and 14 shown in b) are supplied to the switching output stage 5.
[0036]
Here, as described above, the multiplied maximum value 13 is a signal having a full amplitude with respect to the input range of the PDM modulator 4, and the output of the PDM modulator 4 is switched by the variable voltage power supply unit 6. Is. Therefore, when the gain when the configuration of the PDM modulator 4 + switching output stage 5 is viewed as one system 8 is G = 0.5, the maximum output signal value 15 in the system 8 is shown in FIG. It becomes like this. This has the same amplitude as the output signal maximum value 64 shown in FIG. 6B which is the output signal of the switching output stage 52 shown in FIG.
[0037]
Further, as shown in FIG. 2C, the noise component 17 generated with the magnitude of the power supply voltage 16 is compared with the power supply voltage 63 shown in FIG. And small. For this reason, the noise maximum value 17 of the noise component is smaller than the noise maximum value 66 of the noise component shown in FIG.
[0038]
That is, in the prior art, the S / N ratio obtained from FIGS. 6B and 6C = (maximum output signal value 64 / maximum noise value 66) and the S / N ratio of this embodiment = (maximum output signal value 15 / When comparing with the maximum noise value 17), it can be seen that the S / N ratio is improved in the present embodiment. At this time, the signal component is exactly the same between the conventional technique and the present embodiment.
[0039]
Finally, the LPF 7 removes the high frequency component of the switching signal output from the switching output stage 5. The audio signal that has passed through the LPF 7 is output as sound by a device such as a speaker (not shown).
[0040]
As described above, in the PCM signal reproduction apparatus 10 according to the present embodiment, the multiplier 3 has the maximum dynamic range of the multiplier 3 in accordance with the input signal maximum value 12 obtained by the maximum value detector 2. Thus, the input PCM signal can be changed by a predetermined amount. The changed PCM signal is input to the PDM modulator 4. Further, the variable voltage power supply unit 6 changes the supply voltage to the switching output stage 5 according to the change amount in the multiplier 3.
[0041]
Therefore, for example, a 1 / α supply power voltage 14 that is inversely proportional to the enlargement magnification α at the maximum value 13 after multiplication multiplied by α by the multiplier 3 is supplied from the variable voltage power supply unit 6 to the switching output stage 5. As a result, the switching output stage 5 can output a signal having the same maximum output signal value 15 as the conventional one.
[0042]
On the other hand, at this time, the supply power supply voltage 14 supplied from the variable voltage power supply unit 6 to the switching output stage 5 is smaller than the conventional one, so that the noise maximum value 17 associated with the supply power supply voltage 14 is also reduced. This indicates that the noise ratio with respect to the input PCM signal, that is, the S / N ratio becomes small.
[0043]
As a result, the conventional dynamic range can be used to the maximum even with a low-volume signal, and the S / N ratio can be improved. Further, the PCM signal can be reproduced faithfully by changing the power supply voltage 14 supplied to the switching output stage 5 in accordance with the amount of change in the multiplier 3. Further, since the power supply voltage 14 to the switching output stage 5 is generally low, the power consumption can be kept low.
[0044]
Therefore, it is possible to provide a switching output type PCM signal reproducing apparatus 10 that can maximize the dynamic range, faithfully reproduce the PCM signal, improve the S / N ratio, and reduce power consumption. .
[0045]
[Embodiment 2]
The following will describe another embodiment of the present invention with reference to FIG. For convenience of explanation, members having the same functions as those shown in the drawings of the first embodiment are given the same reference numerals and explanation thereof is omitted.
[0046]
As shown in FIG. 3, the PCM signal reproduction apparatus 20 of the present embodiment includes a reproduction / stop control unit 21 as reproduction / stop control means. The reproduction / stop control unit 21 is a maximum value detector. 2, a playback / stop control signal, which is information indicating whether or not the system is currently playing back a PCM signal, is sent. When the playback / stop control signal indicates that playback is in progress, the buffers 1 to LPF 7 perform the same functions as those described in the first embodiment.
[0047]
On the other hand, when the reproduction / stop control signal from the reproduction / stop control unit 21 indicates that the signal is being stopped, the maximum value detector 2 has a coefficient 1 / α = 0, that is, the power supply is stopped, Give a signal. At this time, the coefficient α output to the multiplier 3 does not make sense, and therefore the coefficient α may be an arbitrary value.
[0048]
The variable voltage power supply unit 6 that has received the power supply stop signal cuts off the power supply to the switching output stage 5. As a result, the output of the switching output stage 5 is completely zero immediately after the power is turned on or during the reproduction stop of the PCM signal. Therefore, the sound that passes through the LPF 7 and is output from a device such as a speaker (not shown) is completely silent.
[0049]
As described above, in the PCM signal reproduction apparatus 20 according to the present embodiment, the reproduction / stop control unit 21 performs the switching output stage with respect to the variable voltage power supply unit 6 according to the change amount in the multiplier 3 during reproduction. The power supply voltage 14 to 5 is changed. As a result, at the time of reproduction, the same operation / function as in the first embodiment can be obtained.
[0050]
On the other hand, the regeneration / stop control unit 21 causes the variable voltage power supply unit 6 to set the supply power supply voltage 14 to the switching output stage 5 to 0 when the regeneration is stopped. Therefore, the output of the switching output stage 5 is 0, and the final analog signal is also 0.
[0051]
As a result, it is possible to reduce power consumption when reproduction is stopped, and it is also effective as a means for muting noise generated when the PCM signal reproduction apparatus 20 is powered on.
[0052]
[Embodiment 3]
The following will describe another embodiment of the present invention with reference to FIG. For convenience of explanation, members having the same functions as those shown in the drawings of Embodiment 1 and Embodiment 2 are given the same reference numerals, and the description thereof is omitted.
[0053]
As shown in FIG. 4, the PCM signal reproducing apparatus 30 of the present embodiment includes a silence detector 31 as silence detection means, and the silence detector 31 has a level of an input PCM signal equal to or lower than a predetermined value. When no sound is detected, a silence detection signal is sent to the maximum value detector 2 as silence.
[0054]
When the silence detector 31 does not detect silence, the buffers 1 to LPF 7 operate in exactly the same manner as described in the first embodiment. On the other hand, when the silence detector 31 detects silence, the maximum value detector 2 issues a coefficient 1 / α = 0, that is, a power supply stop signal, to the variable voltage power supply unit 6. At this time, the coefficient α output to the multiplier 3 does not make sense, and therefore the coefficient α may be an arbitrary value.
[0055]
The variable voltage power supply unit 6 that has received the power supply stop signal cuts off the power supply to the switching output stage 5. Thereby, the output of the switching output stage 5 at the time of silence becomes completely zero. Therefore, the sound that passes through the LPF 7 and is output from a device such as a speaker (not shown) is completely silent.
[0056]
As described above, in the PCM signal reproduction apparatus 30 of the present embodiment, the silence detector 31 detects that the input PCM signal is silent based on the level of the input PCM signal, and the input PCM signal is silent. Is detected, the supply power supply voltage 14 to the switching output stage 5 is set to zero. Therefore, the output of the switching output stage 5 is 0, and the final analog signal is also 0.
[0057]
As a result, power consumption can be reduced when playback is stopped or when the playback signal is silent.
[0058]
【The invention's effect】
As described above, the pulse code modulated signal reproducing apparatus of the present invention includes the maximum value detecting means for obtaining the maximum value from the predetermined period unit or the predetermined signal unit of the input pulse code modulated signal, and the maximum value detecting means. To the maximum value Multiplication factor The above pulse density modulation Means input range The Outputs the maximum value after multiplication that can be used as much as possible. do it , The maximum value after multiplication above Dynamic range variable means for inputting to the pulse density modulation means, and the dynamic range variable means Above coefficient And a variable voltage power supply means for changing the supply voltage to the switching output means.
[0059]
Therefore, for example, a supply voltage inversely proportional to the signal maximum value expanded by the dynamic range variable means is supplied from the variable voltage power supply means to the switching output means. Thereby, the signal of the same maximum value as before can be output from the switching output means.
[0060]
On the other hand, at this time, since the supply voltage supplied from the variable voltage power supply means to the switching output means is smaller than that of the conventional one, the noise accompanying this supply voltage is also reduced. This indicates that the ratio of noise to the inputted pulse code modulation signal, that is, the S / N ratio becomes small.
[0061]
As a result, the conventional dynamic range can be used to the maximum even with a low-volume signal, and the S / N ratio can be improved. Further, the pulse code modulation signal can be faithfully reproduced by changing the supply voltage to the switching output means in accordance with the amount of change in the dynamic range variable means. Furthermore, since the supply voltage to the switching output means can be low as a whole, it is possible to keep power consumption low.
[0062]
Accordingly, there is provided a switching output type pulse code modulation signal reproducing apparatus that can maximize the dynamic range, faithfully reproduce the pulse code modulation signal, improve the S / N ratio, and reduce power consumption. There is an effect that can be.
[0063]
Further, the pulse code modulation signal reproducing apparatus of the present invention is the above pulse code modulation signal reproducing apparatus in which the switching is performed with respect to the variable voltage power source means according to the change amount in the dynamic range variable means during reproduction. While changing the supply voltage to the output means, the regeneration / stop control means for making the variable voltage power supply means zero the supply voltage to the switching output means when the regeneration is stopped.
[0064]
Therefore, at the time of reproduction, the reproduction / stop control means causes the variable voltage power supply means to change the supply voltage to the switching output means according to the amount of change in the dynamic range variable means. As a result, at the time of reproduction, the same operation / function as the above-described invention can be obtained.
[0065]
On the other hand, the regeneration / stop control means causes the variable voltage power supply means to set the supply voltage to the switching output means to 0 when the regeneration is stopped. Therefore, the output of the switching output means is 0, and the final analog signal is also 0.
[0066]
As a result, it is possible to reduce the power consumption when playback is stopped, and to produce an effect that it is effective as a means for muting noise generated when the apparatus is powered on.
[0067]
Further, the pulse code modulation signal reproducing apparatus of the present invention is Maximum value detection means for obtaining a maximum value from a predetermined period unit or a predetermined signal unit of the input pulse code modulation signal, and a predetermined amount of the pulse code modulation signal according to the maximum value obtained by the maximum value detection means Dynamic range variable means that changes and inputs the pulse density modulation means, and variable voltage power supply means that changes the supply voltage to the switching output means according to the amount of change in the dynamic range variable means. With When it is detected that the pulse code modulation signal is silent based on the level of the input pulse code modulation signal, and when it is detected that the pulse code modulation signal is silent, the voltage supplied to the switching output means is set to 0. It is provided with silent detection adjustment means for making it.
[0068]
Therefore, the silence detection means detects that the pulse code modulation signal is silent based on the level of the input pulse code modulation signal, and when detecting that the pulse code modulation signal is silent, the switching output The supply voltage to the means is made zero. Therefore, the output of the switching output means is 0, and the final analog signal is also 0.
[0069]
As a result, it is possible to reduce power consumption when playback is stopped or when the playback signal is silent.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an embodiment of a PCM signal reproducing apparatus according to the present invention.
2A is a comparison diagram showing a relationship between a maximum input signal value and a maximum value after multiplication of a multiplier in the PCM signal reproduction apparatus, and FIG. 2B is a supply power voltage and a switching output from a variable voltage power supply unit; FIG. 4C is a comparison diagram showing the relationship between the maximum output signal value of the stage and FIG. 4C is a comparison diagram showing the relationship between the power supply voltage supplied from the variable voltage power supply unit and the maximum noise value.
FIG. 3 is a block diagram showing another embodiment of the PCM signal reproducing apparatus according to the present invention.
FIG. 4 is a block diagram showing still another embodiment of the PCM signal reproducing apparatus according to the present invention.
FIG. 5 is a block diagram showing a conventional PCM signal reproducing apparatus.
6A is a waveform diagram showing the maximum input signal value in the PCM signal reproducing apparatus, and FIG. 6B is a comparison showing the relationship between the supply power voltage from the constant voltage power supply and the output signal maximum value of the switching output stage. FIG. 4C is a comparison diagram showing the relationship between the power supply voltage supplied from the constant voltage power supply and the maximum noise value.
FIG. 7 is a block diagram showing a PCM signal reproducing apparatus of a comparative example.
FIG. 8A is a comparison diagram showing the relationship between the maximum value of an input signal and the maximum value after multiplication of the multiplier in the PCM signal reproduction apparatus, and FIG. 8B is a supply power voltage from a constant voltage power supply and a switching output stage. FIG. 6C is a comparison diagram showing the relationship between the power supply voltage supplied from the constant voltage power supply and the maximum noise value.
[Explanation of symbols]
1 buffer
2 Maximum value detector (maximum value detection means)
3 Multiplier (dynamic range variable means)
4 PDM modulator (pulse density modulation means)
5 Switching output stage (switching output means)
6 Variable voltage power supply (variable voltage power supply means)
7 LPF
10 PCM signal regeneration device (pulse code modulation signal regeneration device)
12 Maximum input signal
13 Maximum value after multiplication
14 Supply voltage
15 Maximum output signal
17 Noise component

Claims (3)

An output from the switching output means, comprising: pulse density modulation means for pulse density modulating the input pulse code modulation signal; and switching output means for performing power amplification by switching based on an output signal from the pulse density modulation means. In a pulse code modulation signal reproducing apparatus for reproducing the signal as an analog signal,
A maximum value detecting means for obtaining a maximum value from a predetermined period unit or a predetermined signal unit of the input pulse code modulation signal;
The maximum value obtained by the maximum value detection means is multiplied by a coefficient to output a maximum value after multiplication that makes full use of the input range of the pulse density modulation means, and the maximum value after multiplication is set to the pulse Dynamic range variable means for input to the density modulation means;
Depending on the coefficient of the above dynamic range changing means, pulse code modulation signal reproducing apparatus characterized by comprising a variable voltage supply means for changing the supply voltage to the switching output means. During reproduction, the variable voltage power supply means changes the supply voltage to the switching output means according to the change amount in the dynamic range variable means,
2. A pulse code modulation signal reproducing apparatus according to claim 1, further comprising a reproduction / stop control means for causing said variable voltage power supply means to make a supply voltage to said switching output means zero when reproduction is stopped. . An output from the switching output means, comprising: pulse density modulation means for pulse density modulating the input pulse code modulation signal; and switching output means for performing power amplification by switching based on an output signal from the pulse density modulation means. In a pulse code modulation signal reproducing apparatus for reproducing the signal as an analog signal,
A maximum value detecting means for obtaining a maximum value from a predetermined period unit or a predetermined signal unit of the input pulse code modulation signal;
Dynamic range variable means for changing the pulse code modulation signal by a predetermined amount and inputting it to the pulse density modulation means according to the maximum value obtained by the maximum value detection means,
A variable voltage power supply means for changing the supply voltage to the switching output means according to the amount of change in the dynamic range variable means;
When it is detected that the pulse code modulation signal is silent based on the level of the input pulse code modulation signal, and when it is detected that the pulse code modulation signal is silent, the voltage supplied to the switching output means is set to 0. A pulse code modulated signal reproducing apparatus comprising a silent detection adjusting means for making

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