JP2003173612A - Volume controller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a volume controller in which degradation in signals is suppressed and the volume of binary signals is controlled using a simple constitution. <P>SOLUTION: The volume controller controls the volume of analog audio signals represented by inputted binary signals S1 that are provided by pulse density modulating the analog audio signals. The controller is provided with a volume setting section 5 which is used to set the volume of the analog audio signals being represented by output binary signals S3, a switching circuit 1 which generates new binary signals by conducting a switching of a reference voltage V using the signals S1 as control signals and outputs the new signals as output binary signals S3 and a variable voltage source 2 which supplies the voltage V to the circuit 1. The voltage V is varied by the voltage source 2 in accordance with the volume set by the section 5 so that a wave height value V of the signals S3 is varied in accordance with the volume. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a binary signal representing the signal level of an analog audio signal and the volume (signal level) of the analog audio signal represented by the binary signal.
The present invention relates to a volume control device for controlling.

[0002]

2. Description of the Related Art Conventionally, as a volume control device for controlling volume information of analog information contained in a digital audio signal (representing the signal level of the original analog audio signal), a volume using an arithmetic unit such as a digital attenuator is used. Controllers are known.

In this volume control device, arithmetic processing is performed on a digital audio signal according to a set volume.

For example, a switching output type pulse code modulation signal reproducing device used for a digital amplifier or the like is known to include a volume key for setting a volume and a digital attenuator. In the digital attenuator, a digital code (a code represented by a combination of 0 and 1) representing a sound volume included in the pulse code modulated signal is multiplied by a coefficient 1 / k (k is 1 or more). I am supposed to do it. In the digital attenuator, the coefficient 1 / k is changed according to the volume set by the volume key,
The pulse code modulation signal is attenuated according to the volume.

When reproducing an audio recording medium such as a CD,
When handling a multi-bit digital audio signal (pulse code modulation signal), it is possible to control the volume using the conventional volume control device described above.

However, recently, an audio recording medium in which a 1-bit digital audio signal (binary digital signal corresponding to the original analog audio signal) obtained by ΣΔ modulation is directly recorded has appeared. Also, A / D
As converters and D / A converters, those using ΣΔ modulation have become common. Also, an increasing number of audio amplifiers reproduce a voice by switching a constant voltage by using a binary digital signal of 1-bit digital audio signal as a control signal. For these reasons, it has become common to handle the 1-bit digital audio signal itself.

In such a situation, for example, an audio recording medium in which a 1-bit digital audio signal obtained by ΣΔ modulation is directly recorded is reproduced, and the reproduced signal is directly reproduced as 1
When a voice is reproduced by sending it to a device that can handle a 1-bit digital audio signal (1-bit D / A converter, 1-bit digital audio signal as an control signal, audio amplifier, etc.)
There is a demand for controlling the volume of reproduced voice by controlling a bit digital audio signal.

Conventionally, no method has been established for increasing or decreasing the amplitude of analog information contained in the 1-bit digital audio signal.

As a method of increasing / decreasing the amplitude of analog information contained in a 1-bit audio signal, a method of using a volume control device having a computing unit such as the conventional digital attenuator can be considered.

[0010]

However, in the volume control device provided with the arithmetic unit such as the conventional digital attenuator, the digital audio signal in which the amplitude value of the analog information is represented by a digital code is used for performing the arithmetic processing. Is required. Therefore, the conventional volume control device can apply only a multi-bit digital audio signal (pulse code modulation signal) and cannot control the volume of a 1-bit digital audio signal.

Therefore, when the amplitude of the analog information included in the 1-bit digital audio signal is increased or decreased by using the conventional volume control device, the 1-bit digital audio signal obtained by reproducing the audio recording medium is It must be down-converted to a multi-bit digital audio signal and then input to a digital attenuator. In addition, the multi-bit digital audio signal whose volume is controlled by the digital attenuator must be up-converted in order to return to the 1-bit digital audio signal.

Therefore, when the conventional volume control device is used, a down converter and an up converter are required, which increases the cost. Also, since requantization noise is generated during up-conversion, the S / N ratio becomes worse.

Further, in the digital attenuator, waveform distortion occurs due to a calculation error. In the calculation process of the digital attenuator, the calculation error increases as the volume (signal level) of the input signal decreases, so that the waveform distortion increases as the signal level of the output signal decreases. Therefore,
When the volume of a digital signal is controlled using a digital attenuator, a large waveform distortion occurs especially at a low volume, and S /
There is a problem that the N ratio (signal to noise ratio) becomes worse. Further, when a digital arithmetic circuit having a large number of bits is used to reduce the arithmetic error of the digital attenuator, the circuit scale becomes very large, which leads to an increase in power consumption and cost.

The present invention has been made in view of the above conventional problems, and an object thereof is to suppress deterioration of a signal and
It is to provide a volume control device capable of controlling the volume of a binary signal with a simple configuration.

[0015]

In order to solve the above-mentioned problems, a volume control device of the present invention is designed to solve the above-mentioned problems by inputting binary signals representing an analog audio signal by pulse width modulation or pulse density modulation. In a volume control device for controlling the volume of an analog audio signal represented by a value signal, a volume setting means for setting the volume of an analog audio signal represented by an output binary signal, and the input binary signal as a control signal. The variable voltage source is provided with a switching means for generating a new binary signal by performing voltage switching and outputting it as an output binary signal, and a variable voltage source for supplying a variable reference voltage to the switching means. The reference voltage is changed according to the volume set by the volume setting means so that the peak value of the binary signal changes according to the volume. It is characterized by a door.

According to the above configuration, the reference binary voltage is switched using the input binary signal representing the analog audio signal as the control signal, and the peak value of the binary signal is changed by changing the reference voltage according to the set volume. It can be changed according to the set volume. Accordingly, the volume of the analog audio signal represented by the binary signal can be controlled with the binary signal in the state of the binary signal with respect to the binary signal subjected to the pulse width modulation or the pulse density modulation.

Therefore, the process of down-converting a binary signal into a multi-bit signal and the multi-bit signal processed by the digital attenuator, which are required for the volume control using the conventional digital attenuator, are binary signals. The process of up-converting to return to is unnecessary. As a result, it is possible to prevent deterioration of sound quality due to the down-conversion processing and the up-conversion processing, for example, generation of requantization noise due to the up-conversion processing. Further, since the down converter and the up converter can be omitted, the configuration can be simplified, and power consumption and cost can be reduced.

Further, in the above configuration, since the digital operation processing is not required unlike the case where the signal level of the multi-bit signal is processed by the digital attenuator, the occurrence of the waveform distortion due to the digital operation processing can be suppressed. Further, since it is not necessary to provide an arithmetic circuit having a large circuit scale for digital arithmetic processing, it can be realized with a simple circuit configuration, and power consumption and cost can be suppressed low.

Therefore, according to the above structure, the deterioration of the signal is suppressed, and the volume of the binary signal (2
It is possible to provide a volume control device capable of controlling the volume of the analog audio signal represented by the value signal.

Further, in order to solve the above-mentioned problems, the volume control device of the present invention is directed to an input binary signal representing an analog audio signal by pulse density modulation, and an analog audio signal represented by the input binary signal. In a volume control device for controlling the volume, a volume setting means for setting the volume of an analog audio signal represented by an output binary signal and a rising edge of the input binary signal are detected, and an elapsed time from the detection time point. Timing signal generating means for generating a timing signal indicating the falling timing of the output binary signal when the time reaches the set time, and by switching the reference voltage using the input binary signal and the timing signal as control signals. And a switching means for generating a new binary signal and outputting it as an output binary signal. The signal generation means changes the set time according to the volume set by the volume setting means so that the pulse width of the output binary signal changes according to the volume set by the volume setting means. It is characterized by being.

According to the above configuration, the reference voltage is switched using the input binary signal representing the analog audio signal and the timing signal generated after the elapse of the set time from the rising of the input binary signal as the control signals, and By changing the set time according to the set volume, the pulse width of the binary signal can be changed according to the set volume. Therefore, the pulse duty ratio of the binary signal can be changed according to the set volume. This makes it possible to control the volume of the analog audio signal represented by the binary signal with respect to the pulse density modulated binary signal in the state of the binary signal.

Therefore, the process of down-converting a binary signal into a multi-bit signal, which is necessary for volume control using a conventional digital attenuator, and the multi-bit signal processed by the digital attenuator are binary signals. The process of up-converting to return to is unnecessary. As a result, it is possible to prevent deterioration of sound quality due to the down-conversion processing and the up-conversion processing, for example, generation of requantization noise due to the up-conversion processing. Further, since the down converter and the up converter can be omitted, the configuration can be simplified, and power consumption and cost can be reduced.

Further, in the above configuration, since the digital operation processing is not required unlike the case where the signal level of the multi-bit signal is processed by the digital attenuator, the occurrence of waveform distortion due to the digital operation processing can be suppressed. Further, since it is not necessary to provide an arithmetic circuit having a large circuit scale for digital arithmetic processing, it can be realized with a simple circuit configuration, and power consumption and cost can be suppressed low.

Therefore, according to the above configuration, the deterioration of the signal is suppressed and the volume of the binary signal (2
It is possible to provide a volume control device capable of controlling the volume of the analog audio signal represented by the value signal.

The volume control device of the present invention further comprises a variable voltage source for supplying a variable reference voltage to the switching means, and the variable voltage source is arranged so that the peak value of the output binary signal changes according to the volume. Alternatively, the reference voltage may be changed according to the volume set by the volume setting means.

According to the above configuration, both the crest value of the binary signal and the pulse duty ratio are changed according to the set volume, so that the volume control can be performed with higher accuracy.

In the volume control device of the present invention, a plurality of the switching means are provided corresponding to each of the plurality of input binary signals in order to control the volume of the analog audio signal represented by the plurality of input binary signals. On the other hand, the variable voltage source may supply the same reference voltage to a plurality of switching means in common.

According to the above configuration, the reference voltage supplied to each switch circuit is supplied from the common variable voltage source,
When controlling the volume of multi-channel binary signal,
The volume of each channel can be adjusted accurately.

In the volume control device of the present invention, the input binary signal is sampled at a constant sampling frequency, and is input together with a clock signal representing information on the sampling frequency, and the clock signal is input. Demodulation means for demodulating a sampling clock signal representing the sampling frequency of the input binary signal based on the signal, and waveform shaping means for shaping the waveform of the input binary signal based on the sampling clock signal are further provided. May be.

According to the above configuration, the waveform of the input binary signal is shaped by using the demodulated clock signal,
The input binary signal can be supplied to the switching means after removing the jitter component and the waveform rounding. By controlling the volume with the input binary signal from which the jitter component and the waveform rounding have been removed in this way, an input including the jitter component and the waveform rounding can be input like an input binary signal transmitted over a long transmission distance. It is possible to perform accurate volume control even for a binary signal.

[0031]

BEST MODE FOR CARRYING OUT THE INVENTION [First Embodiment] The following will describe one embodiment of the present invention in reference to FIG. 1 and FIG.

As shown in FIG. 1, the volume control device 10 according to the present embodiment increases or decreases the amplitude of analog information contained in the input binary signal S1 (the signal level of the analog audio signal represented by the input binary signal S1). And a plurality of contact points A and B and an input 2
A switch circuit (switching means) 1 for opening and closing the connection to the contacts A and B according to the value signal S1, and an output binary signal S3
And a variable voltage source 2 that supplies a variable voltage V corresponding to the volume control signal S2 to the contact A. .

The switch circuit 1 has a contact A and a contact B, and connects the output end C to either the contact A or the contact B. The contact A is connected to the variable voltage source 2 and has a variable potential V (output voltage of the variable voltage source 2). The contact B is grounded and its potential is always kept at zero.

The input binary signal S1 is input to the switch circuit 1 as a control signal. This input binary signal S
Reference numeral 1 is a binary signal corresponding to the original analog information by the pulse density, that is, a binary signal representing the signal level of the analog audio signal by the pulse density modulation. As shown in FIG. 2A, the input binary signal S1 is a pulse density modulated binary signal whose signal level changes between “H” (High) and “L” (Low).

The input binary signal S1 representing the signal level of the analog audio signal by pulse width modulation is Σ
Obtained by Δ modulation. The input binary signal S1 is
It can also be obtained by up-converting a multi-bit digital audio signal (pulse code modulation signal). Further, here, the input binary signal S1 is a binary signal representing the signal level of the analog audio signal by pulse density modulation (pulse number modulation), but it represents the signal level of the analog audio signal by pulse width modulation. It may be a binary signal (pulse width modulation signal). The binary signal representing the signal level of the analog audio signal by the pulse width modulation at a constant sampling frequency is, for example, a pulse width corresponding to the sample value (amplitude) obtained by sampling the analog audio signal. It can be obtained by an analog-to-digital converter that performs the modulation. The pulse width modulation includes one in which the pulse width (time width) is an analog component and one in which the pulse width is increased or decreased with a constant high frequency clock.

The switch circuit 1 has the input binary signal S1.
The contact point A and the contact point B are switched based on the above. That is, the switch circuit 1 connects the output end C to the contact A when the signal level of the input binary signal S1 is “H”, and contacts the output end C when the signal level of the input binary signal S1 is “L”. Connect to B. Therefore, the switch circuit 1 outputs the voltage V supplied from the variable voltage source 2 when the input binary signal S1 is “H”, and the input binary signal S1 is output.
Is "L", the voltage 0 is output. As a result, the switch circuit 1 outputs the output binary signal S3 having the peak value V synchronized with the input binary signal S1. The switch circuit 1 can be realized by a transistor or the like.

The volume setting unit 5 includes an operation unit such as a volume key that can be operated by the user, and represents the set volume (volume of the analog audio signal represented by the output binary signal) according to the state of the operation unit. That is, the set signal level (output 2
A volume control signal S2 representing the analog audio signal represented by the value signal) is output to the variable voltage source 2.

The variable voltage source 2 outputs a variable voltage V to the contact A of the switch circuit 1. The variable voltage source 2 changes the voltage V from 0 to Vmax (maximum voltage) based on the set volume of the volume control signal S2 input from the volume setting unit 5. For example, if the volume control signal S2 is an analog signal having an amplitude value equal to the set signal level, the voltage V is changed so as to be proportional to the amplitude value of this analog signal. Further, the variable voltage source 2 keeps the voltage V constant when the volume control signal S2 does not change.

Therefore, the variable voltage source 2 sets the voltage V to the maximum voltage Vmax when the set volume of the volume control signal S2 is the maximum volume, and when the set volume of the volume control signal S2 is larger than 0 and smaller than the maximum volume. The voltage V is set to a voltage higher than 0 and lower than the maximum voltage Vmax, and when the set sound volume is 0, the voltage V is set to 0. When the set volume of the volume control signal S2 is larger than 0 and smaller than the maximum volume, the voltage V is set to the voltage V ₁ when the set volume of the volume control signal S2 is relatively small, and the volume control signal S2 When the set volume is relatively high, the voltage V is set to a voltage V ₂ higher than the voltage V ₁ .

In this way, the voltage V is set to the volume control signal S2.
The peak value of the output binary signal S3 output from the switch circuit 1 changes according to the set volume of the volume control signal S2. For example, the volume control signal S2
When the set volume of is relatively low, the output binary signal S3
2 is a signal having a relatively low peak value V ₁ and synchronized with the input binary signal S ₁ , as shown in FIG. 2B. on the other hand,
When the set volume of the volume control signal S2 is relatively high,
Output binary signal S3, as shown in FIG. 2 (c), has a relatively high peak value V _2, the signal synchronized with the input binary signal S1.

Since the crest value (pulse amplitude) of the output binary signal S3 changes according to the set volume of the volume control signal S2, if it is converted into an analog audio signal, the output binary signal S3 will have a waveform corresponding to the set volume of the volume control signal S2. It becomes an analog audio signal whose high value (pulse amplitude) changes. Therefore, the output binary signal S3 can be regarded as a signal in which the amplitude of the analog information of the input binary signal S1 is controlled. The conversion from the output binary signal S3 to the analog audio signal is
For example, it can be performed by removing a high frequency component with a low pass filter.

The output binary signal S3 may be converted into an analog audio signal or may be sent as it is to an external device capable of handling a 1-bit digital audio signal. However, when an attempt is made to reproduce the output binary signal S3 whose volume is controlled by the volume control device 10 with a 1-bit amplifier which switches a constant voltage using a 1-bit signal as a control signal and reproduces sound, when the volume control device 10 reproduces the output binary signal S3, the voltage is restricted. The output binary signal S3 having a low peak value cannot be used in the signal system in the 1-bit amplifier.

Therefore, in the case of FIG. 1, the output binary signal S3 is converted into a 1-bit signal by the ΣΔ modulation circuit 3 to obtain a 1-bit signal in which the amplitude of the analog information of the input binary signal S1 is controlled. There is. As a result, a 1-bit signal that does not affect the voltage can be obtained, and the obtained 1-bit signal can be used in the signal system in the 1-bit amplifier.
The ΣΔ modulation circuit 3 includes an adder 24a, an integrator 3b, a quantizer 3c, and a one-sample delay circuit 3d. Further, a capacitor 4 for cutting a direct current component (low frequency component) from the output binary signal S3 is interposed between the volume control device 10 and the ΣΔ modulation circuit 3.

The 1-bit signal output from the ΣΔ modulation circuit 3 can be converted into an analog audio signal by removing a high frequency component with a low pass filter. Further, a 1-bit signal is generated by switching a constant voltage using the 1-bit signal as a control signal, and a high-pass component is removed from the 1-bit signal by a low-pass filter to generate an analog audio signal. You can also Then, a voice can be generated by converting the obtained analog audio signal into voice by a voice output device such as a speaker (not shown).

In the volume control device 10 of this embodiment, the variable voltage V is supplied to the contact A of the switch circuit 1,
The contact B of the switch circuit 1 is designed to be grounded, but the potentials of the contact A and the contact B of the switch circuit 1 are such that their difference changes according to the set volume of the volume control signal S2. However, it is not particularly limited.
For example, the potential of the contact B of the switch circuit 1 may be changed from 0 to -V.

As described above, the volume control device 10 of the present embodiment is different from the input binary signal S1 representing the analog audio signal by the pulse density modulation, with respect to the input binary signal S1.
Which is a device for controlling the volume of the analog audio signal represented by, the volume setting unit 5 for setting the volume of the analog audio signal represented by the output binary signal S3, and the input binary signal S1 as a control signal. A switch circuit 1 that generates a new binary signal by switching the voltage V and outputs it as an output binary signal S3, and a variable voltage source 2 that supplies a variable reference voltage V to the switch circuit 1 are provided. The voltage source 2 changes the reference voltage V according to the volume set by the volume setting unit 5 so that the peak value V of the output binary signal S3 changes according to the volume.

According to the above configuration, the reference voltage V is switched by using the input binary signal S1 as a control signal, and the reference voltage V is changed according to the set sound volume to output the output 2
The peak value V of the value signal S3 can be changed according to the set volume. As a result, the volume of the analog audio signal represented by the input binary signal S1 can be controlled in the state of the binary signal.

Therefore, the down-conversion processing and up-conversion processing required for the volume control using the conventional digital attenuator are unnecessary, and the deterioration of the sound quality such as the generation of requantization noise can be prevented. Further, since the down converter and the up converter can be omitted, the configuration can be simplified, and power consumption and cost can be reduced.

Further, in the above configuration, since the digital operation processing is not required unlike the case where the signal level of the multi-bit signal is processed by the digital attenuator, the occurrence of the waveform distortion due to the digital operation processing can be suppressed. Further, since it is not necessary to provide an arithmetic circuit having a large circuit scale for digital arithmetic processing, it can be realized with a simple circuit configuration, and power consumption and cost can be suppressed low.

[Second Embodiment] The following will describe another embodiment of the present invention with reference to FIG. For convenience of description, members having the same functions as the members shown in the first embodiment will be designated by the same reference numerals, and the description thereof will be omitted.

By the way, when a binary signal is transmitted over a long transmission distance, noise components increase due to the effects of waveform distortion and jitter. When the binary signal is a binary signal sampled using a sampling clock signal having a constant sampling frequency, if the sampling clock signal can be restored,
The original binary signal with high accuracy can be obtained.

Therefore, in the present embodiment, a volume control device will be described which restores the sampling clock signal and removes the waveform rounding and jitter of the input binary signal and then controls the volume.

As shown in FIG. 3, the sound volume control device 20 according to the present embodiment, in addition to the switch circuit 1, the variable voltage source 2, and the sound volume setting section 5, eliminates waveform rounding and jitter of the input binary signal S1. In order to remove, a PLL (phase-locked loop) circuit (demodulation means) 11 for demodulating (restoring) the sampling clock signal, and a flip-flop (waveform shaping means) for shaping the waveform of the input binary signal S1. ) 12 and.

The volume control device 20 has an input binary signal S1.
As a binary signal sampled at a fixed sampling frequency is input as a clock signal CK (sampling clock signal or word clock signal) indicating the sampling period of the input binary signal S1. ing.

When the PLL circuit 11 receives the input binary signal S1 including the waveform rounding and the jitter and the clock signal CK, the PLL circuit 11 restores the clock signal CK to the original accurate sampling clock signal. .

In the flip-flop 12, the PLL circuit 1 receives the input binary signal S1 containing the rounded waveform and the jitter.
Waveform shaping is performed using the sampling clock signal restored in 1. As a result, waveform rounding and jitter are removed.
Then, the binary signal from which the waveform rounding and the jitter are removed is input to the switch circuit 1.

In the sound volume control device 20 of this embodiment, the binary signal from which the waveform rounding and the jitter are removed can be input to the switch circuit 1 as described above. As a result, it is possible to obtain the output binary signal S3 in which the waveform rounding and the jitter are removed and the amplitude of the analog information is controlled.

The volume control device 20 of the present embodiment uses the input 2
This is effective, for example, when the value signal S1 is one in which audio information (music source) recorded as a 1-bit signal is reproduced and the reproduced 1-bit signal is transmitted over a long transmission distance. Further, it is particularly effective when applied to an audio amplifier which switches a constant voltage and reproduces sound by using a 1-bit signal as a control signal.

In this embodiment, the pulse density modulation signal is used as the input binary signal S1, but the pulse density modulation signal is used as the input binary signal S1. However, a pulse whose pulse width is increased or decreased by a constant high frequency clock is used. It is also possible to use a pulse width modulation signal obtained by density modulation.

The output binary signal S3 may be converted into an analog audio signal or may be directly sent to an external device capable of handling a 1-bit digital audio signal. In the case of FIG. 3, the input binary signal S3 is converted by converting the output binary signal S3 into a 1-bit signal by the ΣΔ modulation circuit 3.
A 1-bit signal whose amplitude of analog information of 1 is controlled is obtained.

Further, the volume control device 20 and the ΣΔ modulation circuit 3
A capacitor 4 for cutting a direct current component (low frequency component) from the output binary signal S3 is interposed between and.

The 1-bit signal output from the ΣΔ modulation circuit 3 can be converted into an analog audio signal by removing high frequency components with a low pass filter. Further, a 1-bit signal is generated by switching a constant voltage using the 1-bit signal as a control signal, and a high-pass component is removed from the 1-bit signal by a low-pass filter to generate an analog audio signal. You can also Then, a voice can be generated by converting the obtained analog audio signal into voice by a voice output device such as a speaker (not shown).

[Third Embodiment] The following will describe still another embodiment of the present invention with reference to FIGS. 4 and 5. For convenience of description, members having the same functions as the members shown in the first embodiment will be designated by the same reference numerals, and the description thereof will be omitted.

As shown in FIG. 4, the volume control device 30 according to the present embodiment is for performing signal processing for increasing or decreasing the amplitude of analog information included in the binary signals S4A and S4B (input binary signal). Of the input binary signal S1 and the timing signal S5A.
Switch circuits (switching means) 23A and 23B for opening and closing the connection to the contacts A and B according to S5B, and a volume control signal S for setting the volume of the output binary signals S3A and S3B.
A volume setting section (volume setting means) 5 for outputting 2 and timer circuits (timing signal generating means) 22A, 22B for outputting timing signals S5A, S5B corresponding to the volume control signal S2 to the switch circuits 23A, 23B are provided. ing.

The binary signals S4A and S4B input to the volume control device 30 of this embodiment are binary signals having a constant sampling period, that is, a binary signal having a constant pulse width, and depending on the pulse density. It is a binary signal corresponding to the original analog information, that is, a binary signal representing the signal level (volume) of the analog audio signal by pulse density modulation. The binary signals S4A and S4B are shown in FIG.
As shown in (b) and (c), it is a binary signal whose signal level changes between "H" (High) and "L" (Low).

The binary signals S4A and S4B are obtained by processing the input binary signal S1 by the return-to-zero circuit 21. This input binary signal S1 is a binary signal corresponding to the original analog information according to the pulse density,
That is, it is a binary signal representing the signal level (volume) of the analog audio signal by pulse density modulation. As shown in FIG. 5A, the input binary signal S1 is a binary signal whose signal level changes between “H” (High) and “L” (Low). Here, the input binary signal S
An example using a 1-bit signal obtained by ΣΔ modulation, which is a general pulse density modulation signal, will be treated as 1.

The pulse density modulation signal is a pulse density modulation signal in which the amplitude of the analog signal is indicated by the density of the pulse. The larger the positive amplitude of the analog signal, the larger the number of positive pulses (density). The larger the negative amplitude of the analog signal, the larger the number (density) of negative pulses. Further, these pulses are always present at a constant sampling period. Since the pulse density modulation signal is sampled at a constant sampling period, it can be treated as a return-to-zero signal.

The return-to-zero circuit 21 generates a pulse signal (return-to-zero signal) with a duty ratio of 50% having a constant pulse width sufficiently shorter than the pulse width of the input binary signal S1 and inputs the pulse signal. While the binary signal S1 is "H", this pulse signal is output as a positive binary signal S4A (+1 bit signal). Therefore, if the input binary signal S1 is "H", the positive binary signal S4A always has a rising edge every pulse period (one sampling period) of the pulse signal. Also, return to
In the zero circuit 21, while the input binary signal S1 is "H", the pulse signal having the duty ratio of 50% is inverted,
The binary signal S4B (-1 bit signal) is output. Therefore, if the input binary signal S1 is "L", the binary signal S4B always has a rising edge every pulse cycle (one sampling cycle) of the pulse signal.

As a result, the input binary signal S1 which is a pulse density modulated signal has a positive binary signal S4A and a negative binary signal which are pulse density modulated signals having a pulse duty of 50% of the input binary signal S1. Converted to S4B.

Each of the switch circuits 23A and 23B has a contact point A and a contact point B, and connects the output end C to either the contact point A or the contact point B. Switch circuit 23A / 2
The contacts A and A of 3B are commonly connected to the constant voltage source 25,
The potential is kept at a constant potential V (output voltage of the variable voltage source 2). Switch circuit 23A and 23B contact B
B is grounded and its potential is always kept at zero. The binary signals S4A and S4B are input from the return-to-zero circuit 21 to the switch circuits 23A and 23B, respectively. Further, the timing signals S5A and S5B are input to the switch circuits 23A and 23B, respectively.

The volume setting section 5 includes an operation section such as a volume key which can be operated by the user, and represents the set volume (volume of the analog audio signal represented by the output binary signal) according to the state of this operation section. That is, the set signal level (output 2
A volume control signal S2 representing the analog audio signal represented by the value signal) is output to the variable voltage source 2.

The timer circuits 22A and 22B are respectively
Output 2 when the rising edges of the binary signals S4A and S4B are detected and the elapsed time from the detection time reaches the set time T
Timing signals S5A and S5B representing the falling timings of the value signals S3A and S3B are output to the switch circuit 23A.

The switch circuit 23A switches between the contact A and the contact B based on the binary signal S4A and the timing signal S5A. Switch circuit 23
In A, the signal level of the binary signal S4A is from "L" to "H".
When it changes to, that is, in synchronization with the rising of the binary signal S4A, the connection destination of the output end C is switched from the contact B to the contact A. In addition, the switch circuit 23A switches the connection destination of the output end C from the contact B to the contact A when receiving the timing signal S5A. Therefore, the switch circuit 23
A will switch the connection destination of the output terminal C from the contact A to the contact B after the set time T has elapsed from the rising of the binary signal S4A. As a result, the switch circuit 23A
Outputs the voltage V supplied from the constant voltage source 25 from the rising time of the binary signal S4A to the time of receiving the timing signal S5A, and outputs the voltage 0 at other times. As a result, the switch circuit 23A outputs the output binary signal S3A whose rising edge is synchronized with the binary signal S4A and whose pulse width is equal to the set time T.

Similarly, the switch circuit 23B switches between the contact A and the contact B based on the binary signal S4B and the timing signal S5B. The switch circuit 23B changes the connection destination of the output terminal C from the contact B to the contact A when the signal level of the binary signal S4B changes from "L" to "H", that is, in synchronization with the rising of the binary signal S4B. Switch. Further, the switch circuit 23B switches the connection destination of the output end C from the contact B to the contact A when receiving the timing signal S5B. Therefore, the switch circuit 23B switches the connection destination of the output end C from the contact A to the contact B after the set time T elapses from the rising of the binary signal S4B. As a result, the switch circuit 23B outputs the voltage V supplied from the constant voltage source 25 from the rising time of the binary signal S4B to the time of receiving the timing signal S5B, and otherwise outputs the voltage 0. As a result, the rising edge of the switch circuit 1 is 2
An output binary signal S3B whose pulse width is equal to the set time T is output in synchronization with the value signal S4B.

In the timer circuits 22A and 22B, the set time T is set to be equal to or less than the sampling period of the binary signals S4A and S4B. At this time, when the volume is lowered, the set time T is shortened, and when the volume is raised, the set time T is lengthened. That is, the timer circuits 22A and 22B change the set time T from 0 to Tmax (maximum pulse width) based on the set volume of the volume control signal S2 input from the volume setting unit 5. For example, if the volume control signal S2 is an analog signal having an amplitude value equal to the setting signal level, the setting time T is changed so as to be proportional to the amplitude value of this analog signal. Further, the timer circuits 22A and 22B keep the set time T constant when the volume control signal S2 does not change.

By changing the set time T in accordance with the volume control signal S2 in this manner, the switch circuit 23A.
The pulse width of the output binary signals S3A and S3B output from 23B changes according to the set volume of the volume control signal S2. For example, when the set volume of the volume control signal S2 is relatively low, the output binary signals S3A and S3B are as shown in FIG.
As shown in (d) and (e), the signal has a relatively small pulse width. On the other hand, when the set volume of the volume control signal S2 is relatively high, the output binary signals S3A and S3B are as shown in FIG.
As shown in (f) and (g), the signal has a relatively large pulse width. When the set volume of the volume control signal S2 is 0, the set time T becomes 0, and the switch circuits 23A and 23A
B is always connected to contact B.

Output binary signal S3A and output binary signal S
The pulse width of 3B changes according to the set volume of the volume control signal S2. Therefore, if a high-frequency component is removed by a low-pass filter and converted into an analog audio signal, the crest value according to the set volume of the volume control signal S2 is changed. It becomes an analog audio signal whose (pulse amplitude) changes. Therefore, the output binary signal S3A and the output binary signal S3 are
B can be regarded as a signal in which the amplitude of the analog information of the input binary signal S1 is controlled. Also, the output binary signal S
3A and the output binary signal S3B can be treated as a pair of signals of a pair of +1 bit signal and −1 bit signal.

The output binary signal S3A and the output binary signal S3B may be converted into analog audio signals or may be sent as they are to an external device capable of handling a 1-bit digital audio signal. However, a 1-bit signal is used as a control signal to switch a constant voltage to reproduce voice.
The output binary signals S3A and S3B whose pulse duty is controlled by the volume control device 30 in the bit amplifier can be used in the signal system in the 1-bit amplifier if there is no problem in voltage, but depending on the pulse duty, high-speed switching is possible. You need speed. At present, the volume control device 30
There is no device that can handle all the pulse duties output from.

Therefore, in the case of FIG. 4, the output binary signal S3A
By converting the output binary signal S3B into a 1-bit signal by the ΣΔ modulation circuit 24, a 1-bit signal in which the amplitude of the analog information of the input binary signal S1 is controlled is obtained. This will not affect the switching speed.
A bit signal can be obtained, and the obtained 1-bit signal can be used in the signal system in the 1-bit amplifier. The ΣΔ modulation circuit 24 includes an adder 24a, an integrator 24b, a quantizer 24c, and a one-sample delay circuit 24d, like the ΣΔ modulation circuit 3 described above.

In addition, 1 output from the ΣΔ modulation circuit 24
The bit signal can be converted into an analog audio signal by removing a high frequency component with a low pass filter.
Further, a 1-bit signal is generated by switching a constant voltage using the 1-bit signal as a control signal, and a high-pass component is removed from the 1-bit signal by a low-pass filter to generate an analog audio signal. You can also Then, a voice can be generated by converting the obtained analog audio signal into voice by a voice output device such as a speaker (not shown).

Further, in the present embodiment, when the input binary signal S1 input to the return-to-zero circuit 21 is a signal sent by a long transmission distance, the volume control of the second embodiment shown in FIG. 3 is performed. Similar to the device 20, first, the input binary signal S1 may be shaped into a waveform so as to remove the waveform rounding and the jitter, and then the obtained binary signal may be input to the return-to-zero circuit 21. .

As described above, the volume control device 30 of the present embodiment is different from the binary signal S4A / S4B representing the analog audio signal by the pulse density modulation, in contrast to the binary signal S4.
A device for controlling the volume of an analog audio signal represented by A / S4B, which is an output binary signal S3A / S3B
The volume setting unit 5 for setting the volume of the analog audio signal represented by and the rising edges of the binary signals S4A and S4B are detected, and the output binary signal of the output binary signal is detected when the elapsed time from the detection time reaches the set time T. By switching the reference voltage using the timer circuits 22A and 22B that generate the timing signals S5A and S5B representing the falling timing, the binary signals S4A and S4B, and the timing signals S5A and S5B as control signals, a new binary value is obtained. A timer circuit 22A is provided with switch circuits 23A and 23B for generating signals and outputting them as output binary signals S3A and S3B.
22B is a set time T according to the volume set by the volume setting unit 5 so that the pulse width of the output binary signals S3A and S3B changes according to the volume set by the volume setting unit 5.
According to the above configuration that changes the reference voltage, the binary signals S4A and S4B and the timing signals S5A and S5B generated after the set time T has elapsed from the rising of the binary signals S4A and S4B are used as control signals. By performing switching and changing the set time T according to the set volume, the pulse width of the output binary signals S3A and S3B can be changed according to the set volume. Therefore, the output binary signal S3A · S
The pulse duty ratio of 3B can be changed according to the set volume. Thereby, the binary signals S4A and S4B
It is possible to control the volume of the analog audio signal represented by the symbol while maintaining the state of the binary signal.

Therefore, the down-conversion processing and the up-conversion processing required for the volume control using the conventional digital attenuator are unnecessary, and the deterioration of the sound quality such as the generation of requantization noise can be prevented. Further, since the down converter and the up converter can be omitted, the configuration can be simplified, and power consumption and cost can be reduced.

Furthermore, in the above configuration, since the digital operation processing is not required unlike the case where the signal level of the multi-bit signal is processed by the digital attenuator, the occurrence of waveform distortion due to the digital operation processing can be suppressed. Further, since it is not necessary to provide an arithmetic circuit having a large circuit scale for digital arithmetic processing, it can be realized with a simple circuit configuration, and power consumption and cost can be suppressed low.

[Fourth Embodiment] The following description will explain still another embodiment of the present invention with reference to FIGS. 6 and 7. For convenience of description, members having the same functions as those of the members described in the first or third embodiment will be designated by the same reference numerals, and the description thereof will be omitted.

The volume control device 40 according to the present embodiment has a constant voltage source 2 for the contact A of the switch circuits 23A and 23B in the volume control device 30 described in the third embodiment.
The volume control device 30 has the same configuration as the volume control device 30 except that a variable voltage source 32 is connected instead of the variable voltage source 5.

The variable voltage source 32 supplies a variable voltage V to the switch circuits 23A and 23B in common. Variable voltage source 3
2 changes the voltage V from 0 to Vmax (maximum voltage) based on the set volume of the volume control signal S2 input from the volume setting unit 5, and when the volume control signal S2 does not change, the voltage V is Keep constant. When the volume is 0, the reference voltage V of the variable voltage source 32 may be always 0, and the contacts of the switch circuits 23A and 23B may be always B.

At this time, for example, if the volume control signal S2 is an analog signal having an amplitude value equal to the setting signal level, the product of the voltage V and the setting time T is proportional to the amplitude value of the analog signal. The voltage V and the set time T are changed.

Thus, as shown in FIGS. 7D to 7I, both the pulse duty and the peak value of the output binary signals S3A and S3B can be changed according to the set volume. As a result, it is possible to control the volume with higher accuracy.

The output binary signal S3 may be converted into an analog audio signal or may be sent as it is to an external device capable of handling a 1-bit digital audio signal. In the case of FIG. 6, the output binary signal S3 is transferred to the ΣΔ modulation circuit 24.
By converting into a 1-bit signal, the 1-bit signal in which the amplitude of the analog information of the input binary signal S1 is controlled is obtained. The 1-bit signal output from the ΣΔ modulation circuit 24 may be converted into an analog audio signal or may be sent as it is to an external device that can handle a 1-bit digital audio signal.

In addition, 1 output from the ΣΔ modulation circuit 24
The bit signal can be converted into an analog audio signal by removing a high frequency component with a low pass filter.
Further, a 1-bit signal is generated by switching the constant voltage using the 1-bit signal as a control signal, and an analog audio signal is generated by subjecting the 1-bit signal to a process of removing high-frequency components with a low-pass filter. You can also Then, a voice can be generated by converting the obtained analog audio signal into voice by a voice output device such as a speaker (not shown).

Also in this embodiment, the return
When the input binary signal S1 input to the to-zero circuit 21 is a signal sent by a long transmission distance, first, like the volume control device 20 of the second embodiment shown in FIG. After performing the waveform shaping of S1 to remove the waveform rounding and the jitter, the obtained binary signal may be input to the return-to-zero circuit 21.

In the volume control device of each of the above embodiments, when processing a plurality of input binary signals corresponding to a plurality of analog audio signals as in the case of multi-channel reproduction, the actual switch circuit (and the timer circuit). )
Should be provided by the number of input binary signals so as to correspond to each input binary signal.

At that time, in the volume control devices of the first, second, and fourth embodiments, the voltage supplied to the contacts (contacts A) of the plurality of switch circuits may be supplied from a common variable voltage source. As a result, the peak value of the volume-controlled output signal can be changed at the same rate in common for each channel. As a result, it is possible to suppress the volume difference between the channels.

[0095]

As described above, the volume control device of the present invention has a volume setting means for setting the volume of an analog audio signal represented by an output binary signal, and a pulse width modulated or pulse density modulated input 2. A switching means for generating a new binary signal by performing switching of the reference voltage using the value signal as a control signal and outputting it as an output binary signal; and a variable voltage source for supplying a variable reference voltage to the switching means, The variable voltage source changes the reference voltage according to the volume set by the volume setting means so that the peak value of the output binary signal changes according to the volume.

According to the above configuration, by changing the peak value of the pulse-width-modulated or pulse-density-modulated binary signal in accordance with the set volume, the analog audio represented by the binary signal in the state of the binary signal is maintained. It is possible to control the volume of the signal.

Therefore, the down conversion processing and the up conversion processing are unnecessary. As a result, it is possible to prevent deterioration of sound quality due to the down conversion processing and the up conversion processing, simplify the configuration, and reduce power consumption and cost.

Further, in the above configuration, since the digital operation processing is not required unlike the case where the signal level of the multi-bit signal is processed by the digital attenuator, the generation of the waveform distortion due to the digital operation processing can be suppressed and a simple operation can be performed. It can be realized with a circuit configuration, and power consumption and cost can be suppressed low.

Therefore, the above configuration has an effect that it is possible to provide a volume control device capable of suppressing the signal deterioration and controlling the volume of a binary signal with a simple configuration.

Further, as described above, the volume control device of the present invention has the volume setting means for setting the volume of the analog audio signal represented by the output binary signal, and the rise of the pulse density modulated input binary signal. Of the input binary signal and the timing signal generating means for generating a timing signal indicating the falling timing of the output binary signal when the elapsed time from the detection time reaches the set time. Switching means for generating a new binary signal by performing switching of the reference voltage as a control signal and outputting it as an output binary signal,
The timing signal generating means changes the set time according to the volume set by the volume setting means so that the pulse width of the output binary signal changes according to the volume set by the volume setting means. It is a thing.

According to the above configuration, the pulse width of the binary signal whose pulse density is modulated is changed in accordance with the set volume, so that the volume of the analog audio signal represented by the binary signal remains unchanged. Control can be performed.

Therefore, the down conversion processing and the up conversion processing are unnecessary. As a result, it is possible to prevent deterioration of sound quality due to the down conversion processing and the up conversion processing, simplify the configuration, and reduce power consumption and cost.

Further, in the above configuration, since the digital operation processing is not required unlike the case where the signal level of the multi-bit signal is processed by the digital attenuator, the generation of the waveform distortion due to the digital operation processing can be suppressed and the simple operation is possible. It can be realized with a circuit configuration, and power consumption and cost can be suppressed low.

Therefore, the above-described structure has an effect that it is possible to provide a volume control device capable of suppressing the signal deterioration and controlling the volume of a binary signal with a simple structure.

The volume control device of the present invention further comprises a variable voltage source for supplying a variable reference voltage to the switching means, and the variable voltage source is arranged so that the peak value of the output binary signal changes according to the volume. Alternatively, the reference voltage may be changed according to the volume set by the volume setting means.

According to the above configuration, both the crest value of the binary signal and the pulse duty ratio are changed according to the set volume, so that it is possible to obtain a further accurate volume control.

In the volume control device of the present invention, the switching means is provided in plural corresponding to each of the plurality of input binary signals in order to control the volume of the analog audio signal represented by the plurality of input binary signals. On the other hand, the variable voltage source may supply the same reference voltage to a plurality of switching means in common.

According to the above configuration, since the same reference voltage is supplied to each switch circuit, the volume of each channel can be adjusted accurately when controlling the volume of a multi-channel binary signal. Is further obtained.

In the volume control device of the present invention, the input binary signal is sampled at a constant sampling frequency, and is input together with a clock signal representing information on the sampling frequency, and the clock signal Demodulation means for demodulating a sampling clock signal representing the sampling frequency of the input binary signal based on the signal, and waveform shaping means for shaping the waveform of the input binary signal based on the sampling clock signal are further provided. May be.

According to the above configuration, the input binary signal can be supplied to the switching means after removing the jitter component and the waveform rounding. Therefore, the above configuration can perform accurate volume control even for an input binary signal including a jitter component and a waveform rounding, such as an input binary signal transmitted over a long transmission distance. Has the effect.

[Brief description of drawings]

FIG. 1 is a diagram showing a circuit configuration of a volume control device according to an embodiment of the present invention.

2A and 2B are waveform diagrams showing waveforms of an input binary signal and an output binary signal in the volume control device of FIG. 1, where FIG. 2A is a waveform of the input binary signal, and FIG. 2B is an output 2 at a low volume. The waveform of the value signal, (c) shows the waveform of the output binary signal at high volume.

FIG. 3 is a diagram showing a circuit configuration of a volume control device according to another embodiment of the present invention.

FIG. 4 is a diagram showing a circuit configuration of a volume control device according to still another embodiment of the present invention.

5 is a waveform diagram showing waveforms of an input binary signal and an output binary signal in the volume control device of FIG. 4, (a).
(B) and (c) are waveforms of an input binary signal, (d) and (e) are waveforms of an output binary signal at a low volume, and (f) and (g) are waveforms of an output binary signal at a high volume. Show.

FIG. 6 is a diagram showing a circuit configuration of a volume control device according to still another embodiment of the present invention.

7 is a waveform diagram showing waveforms of an input binary signal and an output binary signal in the volume control device of FIG. 6, FIG.
(B) and (c) are waveforms of input binary signals, (d) and (e) are waveforms of output binary signals at low volume, (f) and (g) are waveforms of output binary signals at medium volume, (H) and (i) show the waveform of the output binary signal at a low volume.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 switch circuit (switching means) 2 variable voltage source 5 volume setting unit (volume setting means) 10 volume control device 11 PLL circuit (demodulation means) 12 flip-flop (waveform shaping means) 20 volume control devices 22A and 22B timer circuit (timing) 23A / 23B switch circuit (switching means) 25 constant voltage source 30 volume control device 32 variable voltage source 40 volume control device CK clock signal S1 input binary signal S2 volume control signal S3 output binary signal S3A / S3B output Binary signal S4A / S4B Binary signal (input binary signal) S5A / S5B Timing signal

Claims (5)

[Claims] 1. An input binary signal representing an analog audio signal by pulse width modulation or pulse density modulation,
In a volume control device for controlling the volume of an analog audio signal represented by the input binary signal, volume control means for setting the volume of the analog audio signal represented by the output binary signal, and controlling the input binary signal. A variable voltage source for generating a new binary signal by switching a reference voltage as a signal and outputting it as an output binary signal; and a variable voltage source for supplying a variable reference voltage to the switching means. Is a volume control device, wherein the reference voltage is changed according to the volume set by the volume setting means so that the peak value of the output binary signal changes according to the volume. 2. A volume control device for controlling the volume of an analog audio signal represented by the input binary signal with respect to the input binary signal representing the analog audio signal by pulse density modulation, and the output binary signal represents the volume. Volume setting means for setting the volume of the analog audio signal, and a rising timing of the input binary signal is detected, and when the elapsed time from the detection time reaches a set time, it represents the falling timing of the output binary signal. To generate a new binary signal and output it as an output binary signal by switching a reference voltage using the timing signal generating means for generating a timing signal and the input binary signal and the timing signal as control signals. Switching means, and the timing signal generating means responds to the volume set by the volume setting means. The volume control device is characterized in that the set time is varied according to the volume set by the volume setting means so that the pulse width of the output binary signal changes. 3. A variable voltage source for supplying a variable reference voltage to the switching means, wherein the variable voltage source is set by the volume setting means so that the peak value of the output binary signal changes according to the volume. 3. The volume control device according to claim 2, wherein the reference voltage is changed according to the generated volume. 4. A plurality of the switching means are provided corresponding to each of the plurality of input binary signals in order to control the volume of an analog audio signal represented by the plurality of input binary signals. The volume control device according to claim 1 or 3, wherein the variable voltage source is adapted to commonly supply the same reference voltage to the plurality of switching means. 5. The input binary signal is sampled at a constant sampling frequency, and is input together with a clock signal representing information on the sampling frequency, and the input binary signal is input based on the clock signal. Demodulation means for demodulating a sampling clock signal representing the sampling frequency of the value signal, and waveform shaping means for shaping the waveform of the input binary signal based on the sampling clock signal are further provided. The volume control device according to any one of claims 1 to 4.