JP2003318665A - One-bit signal amplifier and control method thereof, and audio equipment mounting the one-bit signal amplifier - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the noise level of a radio reception band by changing a ΔΣmodulation order and a ΔΣ modulation sampling frequency, in a ΔΣ modulation one-bit signal generating circuit so that higher noise will not coincide with the radio reception frequency band in a one-bit signal amplifier that is mounted on audio equipment. <P>SOLUTION: The one-bit signal amplifier 14 has the ΔΣ modulation one-bit signal generating circuit 21, an amplification circuit 22, and a D/A conversion circuit 23. The ΔΣ modulation one-bit signal generating circuit 21 can vary the sampling frequency and the order of ΔΣ modulation and performs the ΔΣmodulation of an input signal, that is inputted from one of a plurality of input sources (AM/SW/FM radios, CD, MD) to generate one-bit signals. The amplification circuit 22 amplifies the one-bit signals. The D/A conversion circuit 23 converts the one-bit signals, after the amplification to analog signals. Additionally, the one-bit signal amplifier 14 has sampling frequency switching equipment 24 for setting the sampling frequency, according to the input source of the input signal, and ΔΣ modulation order switching equipment 26 for setting the ΔΣmodulation order. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a radio and a CD / M.
The present invention relates to a 1-bit signal amplifier for amplifying an audio source such as D, a control method thereof, and an audio device equipped with the same.

[0002]

2. Description of the Related Art Conventionally, audio equipment including a plurality of audio sources such as radio and CD / MD has been used. Some of these audio devices use a so-called 1-bit signal amplifier to amplify the audio signal.

FIG. 4 shows a conventional 1-bit signal amplifier 104.
2 is a block diagram showing an outline of a configuration of an audio device 100 equipped with the.

The audio device 100 has an input unit 10
An audio signal to be amplified is selected from each input source (AM radio, SW radio, FM radio, CD, MD, etc.) input from 1 by the source switching unit 102 under the control of the control microcomputer 105. Next, the volume controller 103 adjusts the volume of the analog output. Next, in the 1-bit signal amplifier 104, the sampling oscillator 1 is driven by the ΔΣ modulation 1-bit signal generation circuit 111.
The audio signal (analog signal) is converted into a 1-bit signal by the sampling signal of 14, and this is converted into an amplifier circuit 11
After being amplified by 2, it is smoothed by the D / A converter 113 and converted into an analog signal.

Here, in the 1-bit signal amplifier 104,
The ΔΣ modulation method is used in order to reduce noise in the audible band and improve S / N in the audible band. That is, Δ
In the Σ-modulation 1-bit signal generation circuit 111, noise in the audible band is lowered by moving the audible band noise on the noise floor to the high frequency side by the noise shaping action at the time of generating the 1-bit signal. Furthermore, the effect of reducing audible band noise can be increased by increasing the ΔΣ modulation order.

Recently, in order to improve the sound quality of high-fidelity audio, it is desired to lower the noise floor in the audible band and make the reproduction band wide in the range of up to 100 KHz. Therefore, in order to move the peak of the noise floor to the high frequency side and widen the noise reduction effect band, ΔΣ
It is required to increase the sampling frequency of modulation.

[0007]

However, in the ΔΣ modulation circuit, when the ΔΣ modulation order is increased and the audible band noise of the noise floor is moved to the high frequency side in order to reduce the noise in the audible band, the high frequency band is increased. (500 kHz to several MH
z) Noise increases. In addition, if the sampling frequency of ΔΣ modulation is increased to widen the noise reduction effect band,
The peak of the noise floor moves to the high frequency side.

This causes a problem in audio equipment equipped with an AM / SW radio as an input source.
That is, the carrier wave of AM radio broadcasting is 535 to 1605.
carrier wave for SW radio broadcasting is 3 to 30 MH
z. Since the AM / SW radio broadcast is an amplitude modulation system, the amplitude corresponds to the signal wave, and it is difficult to eliminate noise after reception. Therefore, when the peak of the noise floor is moved to the high frequency side, the band of the high frequency noise generated by the ΔΣ modulation circuit matches the reception frequency band of the AM / SW radio, which causes interference noise in the AM / SW radio reception. Sound quality deteriorates.

As shown in FIG. 3, due to the noise shaping characteristic of the ΔΣ modulation circuit, the noise level in the audible band (generally, up to 20 KHz) is low even in the case of low-order (third-order) ΔΣ modulation. Reception frequency band (500
The noise level in KHz to several MHz) increases rapidly.
Then, in order to reduce audible band noise as high-fidelity audio, if the ΔΣ modulation order is increased (higher order (7
Next)), noise in the reception band of AM radio is further increased.

Further, as shown in FIG. 2, the sampling frequency of ΔΣ modulation is set to 6 in order to widen the noise reduction effect band.
When it is increased from 4fs to 128fs (fs is 44.1kHz), the peak frequency of the noise floor moves to the high range, and S
Noise in the reception band of W radio increases.

As described above, in the audio equipment equipped with the conventional 1-bit signal amplifier, the band of the high frequency noise generated by the ΔΣ modulation circuit matches the reception band of the AM / SW radio. Interfering noise causes a problem that radio reception becomes difficult.

The present invention has been made to solve the above problems, and an object thereof is to provide a 1-bit signal amplifier capable of reducing noise according to an audio characteristic of an input source and a control method thereof. And to provide an audio device equipped with the same.

[0013]

In order to solve the above problems, a method of controlling a 1-bit signal amplifier according to the present invention performs ΔΣ modulation on an input signal input from any one of a plurality of input sources. A ΔΣ modulation 1-bit signal generation circuit that generates a 1-bit signal, an amplification circuit that amplifies the 1-bit signal generated by this ΔΣ modulation 1-bit signal generation circuit, and a D / A conversion of the 1-bit signal that is amplified by this amplification circuit A D / A conversion circuit for converting into an analog signal by means of a 1-bit signal amplifier control method, comprising: a sampling frequency of the ΔΣ modulation 1-bit signal generation circuit according to an input source of the input signal; Alternatively, it is characterized by setting the ΔΣ modulation order.

In the 1-bit signal amplifier of the present invention, at least one of the sampling frequency and the ΔΣ modulation order is variable, and the input signal input from any one of the plurality of input sources is ΔΣ-modulated. ΔΣ modulation 1-bit signal generating means for generating a 1-bit signal by
Amplifying means for amplifying the 1-bit signal generated by the Σ-modulated 1-bit signal generating means, and D / for converting the 1-bit signal amplified by the amplifying means into an analog signal by D / A conversion.
The sampling frequency and / or ΔΣ that are variable according to the A conversion means and the input source of the input signal.
And a setting means for setting the modulation order.

With the above method and configuration, in the 1-bit signal amplifier of the ΔΣ modulation system, the sampling frequency and / or the ΔΣ modulation order of the ΔΣ modulation circuit can be switched according to the input source.

Therefore, normally, ΔΣ modulation is performed at a high sampling frequency and / or a high ΔΣ modulation order, and with this setting, when noise generated by the ΔΣ modulation circuit is mixed in the input signal, a low sampling frequency and / or a low ΔΣ It is possible to perform ΔΣ modulation with the modulation order.

Therefore, for example, FM radio / MD /
With an input source such as a CD, high sound quality can be realized by a high sampling frequency and / or a high ΔΣ modulation order, and with an input source such as an AM / SW radio,
With a low sampling frequency and / or a low ΔΣ modulation order, the noise of the ΔΣ modulation circuit has a minimal effect on the radio receiver, and a clear audio output without noise can be realized.

As described above, since the ΔΣ modulation circuit can be set to the optimum audio characteristic according to the input source, the 1-bit signal amplifier using the ΔΣ modulation method can be used to set the audio characteristic within the audible band for any input source. It is possible to perform signal amplification with a good S / N.

Further, the control method of the 1-bit signal amplifier of the present invention is characterized in that, when the input source is a radio broadcast, the ΔΣ modulation order is set according to the reception band of the radio broadcast.

Also, in the 1-bit signal amplifier of the present invention, the input source includes radio broadcasting, and the setting means, when the input source is radio broadcasting, the ΔΣ modulation according to the reception band of the radio broadcasting. The feature is that the order is set.

By the above method and configuration, Δ
The ΔΣ modulation order can be set so that the level of noise generated by the Σ modulation circuit does not increase in the reception band of the radio that is the input signal.

Therefore, in the case of an input source (AM / SW radio or the like) in which noise generated by the ΔΣ modulation circuit is mixed in the input signal, ΔΣ modulation is performed at a low ΔΣ modulation order and amplification is performed, while the ΔΣ modulation circuit emits. In the case of an input source in which noise is not mixed in the input signal, the input signal can be ΔΣ modulated with a high ΔΣ modulation order and amplified.

Therefore, for example, in an input source such as an AM / SW radio, the low ΔΣ modulation order minimizes the influence of the noise of the ΔΣ modulation circuit on the radio receiver and realizes a clear audio output without noise. In addition, with other input sources such as FM radio / MD / CD, high sound quality can be realized by a high ΔΣ modulation order.

Further, the control method of the 1-bit signal amplifier of the present invention is characterized in that, when the input source is a radio broadcast, the sampling frequency is set according to the reception band of the radio broadcast.

Also, in the 1-bit signal amplifier of the present invention, the input source includes a radio broadcast, and the setting means, when the input source is a radio broadcast, the sampling frequency according to the reception band of the radio broadcast. It is characterized by setting.

With the above method and configuration, Δ
The sampling frequency can be set so that the level of noise generated by the Σ modulation circuit does not increase in the reception band of the radio that is the input signal.

Therefore, in the case of an input source (SW radio or the like) in which noise generated by the ΔΣ modulation circuit is mixed with the input signal, ΔΣ modulation is performed at a low sampling frequency and amplification is performed, while noise generated by the ΔΣ modulation circuit is input. In the case of an input source that does not mix in the signal, the input signal can be ΔΣ modulated and amplified at a high sampling frequency.

Therefore, for example, in an input source such as a SW radio, a low sampling frequency can minimize the influence of noise of the ΔΣ modulation circuit on the radio receiver, and a clear voice output without noise can be realized. With other input sources such as AM / FM radio / MD / CD, high sound quality can be realized by a high sampling frequency.

The audio equipment of the present invention is characterized by mounting the above-mentioned 1-bit signal amplifier.

With the above configuration, the audio equipment is equipped with the 1-bit signal amplifier to obtain Δ
The Σ modulation circuit can be set to the optimum audio characteristic according to the input source. Therefore, the audio device is provided with a plurality of input sources such as radio (AM, SW, FM) and CD / MD, and for any input source, signal amplification with good S / N in the audible band is performed. It can be carried out.

[0031]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to FIGS. 1 to 3.

1-bit signal amplifier 1 according to the present embodiment
4 is an audio device 10 equipped with a radio (AM, S
W, FM) and CD (compact disc) / MD (mini dis)
The audio device includes a plurality of audio sources such as c), and uses the 1-bit signal amplifier 14 to amplify the audio signal.

FIG. 1 is a block diagram showing an outline of the configuration of the audio device 10. As shown in FIG. 1, the audio device 10 includes an input unit 11, a source switching unit 12, a volume controller 13, a 1-bit signal amplifier 14,
The control microcomputer 15 is provided.

The input section 11 includes an AM receiving section 11a and a SW receiving section 11 which are receivers for receiving radio waves.
b, an FM receiving section 11c, a CD reproducing section 11d for reproducing an audio signal from each recording medium, and an MD reproducing section 11e.

The source selector 12 is a switch or the like, and controls the input source of the audio signal to be amplified from the input source (AM radio, SW radio, FM radio, CD, MD, etc.) of the input section 11 by a control microcomputer. 15
Select according to the control of.

The volume controller 13 adjusts the volume of the analog output which is the final output of the audio device 10.

The control microcomputer 15 sends a control signal designating an input source to be selected to the source switching unit 12. At the same time, the control microcomputer 15 sends a similar control signal, that is, a control signal indicating the input source designated to the source switch 12, to the sampling frequency switch 24 and the ΔΣ modulation order switch 26 of the 1-bit signal amplifier 14. Send.

The 1-bit signal amplifier 14 converts the analog signal input from the volume controller 13 into ΔΣ.
The modulated 1-bit signal generation circuit 21 converts the signal into a 1-bit signal, which is amplified by an amplifier circuit 22 and then the D / A converter 2
The signal is smoothed by 3, converted into an analog signal and output.

Specifically, the 1-bit signal amplifier 14 is
ΔΣ modulation 1-bit signal generation circuit 21, amplification circuit 22, D
/ A converter 23, sampling frequency switch 24, sampling oscillators 25a and 25b, ΔΣ modulation order switch 2
6 and the order setting signal generators 27a and 27b.

The ΔΣ modulation 1-bit signal generation circuit 21
Converts the analog signal (input signal) input from the volume controller 13 into a 1-bit signal by ΔΣ modulation. Here, the ΔΣ modulation 1-bit signal generation circuit 21
The sampling frequency of ΔΣ modulation and the ΔΣ modulation order are variable. Then, the ΔΣ modulation 1-bit signal generation circuit 21
Can set the sampling frequency and the ΔΣ modulation order based on the control signal from the control microcomputer 15 according to the input source (input unit 11) of the analog signal which is the input signal.

Hereinafter, the ΔΣ modulation 1-bit signal generation circuit 21
Setting of the sampling frequency and the ΔΣ modulation order will be described.

(1) Sampling Frequency The 1-bit signal amplifier 14 is provided with two sampling oscillators 25a and 25b having different oscillation frequencies as oscillators for sampling signals. The sampling oscillator 25a is an oscillator that outputs a sampling signal with a high oscillation frequency, and the oscillation frequency is set to 128 fs (fs is 44.1 kHz). The sampling oscillator 25b is an oscillator that outputs a sampling signal with a low oscillation frequency, and the oscillation frequency is set to 64fs.

Then, the sampling oscillators 25a, 25
Which sampling signal b is supplied to the ΔΣ modulation 1-bit signal generation circuit 21 is determined by the control microcomputer 1
The sampling frequency switching unit 24 selects the signal based on the control signal from the control unit 5. Specifically, the sampling frequency switching unit 24 selects the sampling oscillator 25b having a low sampling frequency when the input source is the SW radio broadcast (SW receiving unit 11b). On the other hand, the input source is AM / FM radio broadcast / CD / MD (AM receiver 1
1a, FM receiver 11c, CD playback 11d, MD playback 1
1e), the sampling oscillator 25a having a high sampling frequency is selected.

FIG. 2 is a graph showing the noise shaping characteristics of the ΔΣ modulation circuit for each sampling frequency.

As shown in FIG. 2, in order to widen the noise reduction effect band, the sampling frequency of ΔΣ modulation is set to 64 fs.
To 128 fs (fs is 44.1 kH), the peak frequency of the noise floor moves to the high frequency side. As a result, the noise in the AM radio reception band (535 to 1605 kHz) is reduced, but the noise in the SW radio (3 to 30 MHz) reception band is increased. That is, if ΔΣ modulation is performed with a sampling frequency of 128 fs during SW radio reception, noise generated by the ΔΣ modulation circuit will be mixed into the input signal at a high level. FM radio is
Since the modulation method is different from that of the AM / SW radio and the reception band (76 to 90 MHz) is out of the range, there is no possibility that noise generated by the ΔΣ modulation circuit is mixed. Also, CD / MD
Reproduces the audio signal from the recording medium.
There is no risk of noise generated by the modulation circuit being mixed.

Therefore, in the 1-bit signal amplifier 14, S
At the time of receiving W radio, the high frequency side peak of the noise generated by the ΔΣ modulation 1-bit signal generation circuit 21 which is the ΔΣ modulation circuit is S
A low sampling frequency is set so that it does not match the reception band of W radio broadcasting. On the other hand, AM / FM
A high sampling frequency is set during radio reception or CD / MD playback.

As described above, the ΔΣ modulation 1-bit signal generation circuit 21, the sampling oscillator 25a, and the sampling frequency switching unit 24 are provided in the case where noise generated by the ΔΣ modulation 1-bit signal generation circuit 21 is not likely to be mixed into the input signal. In order to satisfy the low noise level in the audible band and to secure a wide band from the reproduction band to 100 KHz, the ΔΣ modulation circuit with a high sampling frequency is set. As a result, AM / FM radio / MD /
With a CD or the like, high quality sound can be realized as high-fidelity audio.

Further, the ΔΣ modulation 1-bit signal generation circuit 2
1, the sampling oscillator 25b, and the sampling frequency switch 24, the high frequency noise generated by the ΔΣ modulation 1-bit signal generation circuit 21 when the noise generated by the ΔΣ modulation 1-bit signal generation circuit 21 may be mixed in the input signal. Is set so as to realize a ΔΣ modulation circuit having a low ΔΣ modulation order in order to prevent the band of 1 from matching the band of the input signal (for example, the reception band of the SW radio). As a result, the receiver (SW receiver 1
It is possible to realize clear voice output without noise by minimizing the influence on 1b).

(2) ΔΣ Modulation Order The above-mentioned ΔΣ modulation 1-bit signal generation circuit 21 operates in accordance with the order setting signal inputted from the ΔΣ modulation order switch 26.
To function as a next- or third-order ΔΣ modulation circuit,
The ΔΣ modulation order can be switched. ΔΣ modulation 1
The bit signal generation circuit 21 includes, for example, a seventh-order ΔΣ modulation circuit, and when the third-order is designated by the order setting signal,
A part of the ΔΣ modulation may be omitted, or a seventh-order and a third-order ΔΣ modulation circuit may be provided in parallel and one of the ΔΣ modulation circuits may be selected by a switch according to the order setting signal. It may be configured.

Then, the ΔΣ modulation 1-bit signal generation circuit 2
The ΔΣ modulation order of 1 is selected by the ΔΣ modulation order switch 26 based on the control signal from the control microcomputer 15. Specifically, the ΔΣ modulation order switching unit 26 selects either one of the order setting signals input from the two order setting signal generators 27a and 27b based on the control signal from the control microcomputer 15, and ΔΣ The modulated 1-bit signal generation circuit 21 is supplied. Here, the order setting signal generator 27a outputs an order setting signal that specifies a high ΔΣ modulation order (7th order). In addition, the order setting signal generator 27b
Outputs an order setting signal that specifies a low ΔΣ modulation order (third order). In the ΔΣ modulation order switch 26, the input source is AM / SW radio broadcast (AM receiving section 11a, S
When it is the W receiver 11b), the order setting signal from the order setting signal generator 27b is selected so as to specify the low ΔΣ modulation order. On the other hand, the input source is FM radio broadcast / CD / MD (FM receiver 11c, CD playback 11d, M
During the D reproduction 11e), the order setting signal from the order setting signal generator 27a is selected so as to specify a high ΔΣ modulation order.

FIG. 3 is a graph showing the noise shaping characteristics of the ΔΣ modulation circuit for each ΔΣ modulation order.

As shown in FIG. 3, due to the noise shaping characteristic of the ΔΣ modulation circuit, the noise level in the audible band (generally, up to 20 KHz) is low even in the case of low-order (third-order) ΔΣ modulation. Reception frequency band (500
The noise level in KHz to several MHz) increases rapidly.
Then, in order to reduce audible band noise as high-fidelity audio, if the ΔΣ modulation order is increased (higher order (7
Next)), noise in the high band (including the AM / SW radio reception band) is further increased than the AM radio reception band.

Therefore, in the 1-bit signal amplifier 14, A
When the M / SW radio is received, the noise generated by the ΔΣ modulation 1-bit signal generation circuit 21 which is the ΔΣ modulation circuit is detected by AM / SW.
A low ΔΣ modulation order is set so as not to increase in the reception band of radio broadcasting. On the other hand, a high ΔΣ modulation order is set during FM radio reception or CD / MD reproduction.

As described above, in the ΔΣ modulation 1-bit signal generation circuit 21, the order setting signal generator 27a, and the ΔΣ modulation order switching unit 26, noise generated by the ΔΣ modulation 1-bit signal generation circuit 21 may be mixed in the input signal. In the case where there is not, a high ΔΣ is required to satisfy the low noise level in the audible band and to secure a wide band of the reproduction band to 100 KHz.
It is set so as to realize a ΔΣ modulation circuit having a modulation order. As a result, in FM radio / MD / CD and the like, high sound quality as high-fidelity audio can be realized.

Further, the ΔΣ modulation 1-bit signal generation circuit 2
1, order setting signal generator 27b, ΔΣ modulation order switching device 2
6 is Δ when the noise generated by the ΔΣ modulation 1-bit signal generating circuit 21 may be mixed in the input signal.
In order to prevent the level of the high frequency noise generated by the Σ-modulation 1-bit signal generation circuit 21 from increasing in the band of the input signal (for example, the reception band of AM / SW radio), a low Δ
It is set so as to realize a ΔΣ modulation circuit having a Σ modulation order. As a result, a clear audio output without noise can be realized in AM / SW radio or the like.

With the above configuration, the audio device 1 described above
0 is from each input source (AM radio, SW radio, FM radio, CD, MD, etc.) input from the input unit 11.
The source switching unit 12 selects the audio signal to be amplified under the control of the control microcomputer 15. Next, the volume controller 13 adjusts the volume of the analog output. Next, in the 1-bit signal amplifier 14, the ΔΣ modulation 1-bit signal generating circuit 21 converts the audio signal (analog signal) into a 1-bit signal, which is then amplified.
After being amplified by, the signal is smoothed by the D / A converter 23 and converted into an analog signal.

In particular, in the audio device 10, the 1-bit signal amplifier 14 is provided with a plurality of sampling oscillators 25a and 25b having different oscillation frequencies, a sampling frequency switch 24, and a plurality of order setting signals for designating different ΔΣ modulation orders. Generators 27a and 27b and a ΔΣ modulation order switch 26 are provided.

In the audio device 10, the sampling frequency and the ΔΣ modulation order of the ΔΣ modulation 1-bit signal generation circuit 21 are switched according to the input source under the control of the control microcomputer 15. This switching is performed at a high transmission frequency so as to satisfy the low noise level in the audible band, which is a condition of high-fidelity audio, and to secure a wide band from the reproduction band to 100 KHz during FM radio reception or CD / MD reproduction. And high Δ
Select the Σ modulation order. On the other hand, at the time of AM / SW radio reception or the like, a low transmission frequency corresponding to the reception band of the radio broadcast is set so as to enable clear radio reception by minimizing the influence of radio broadcast waves on the receiver. Select a low ΔΣ modulation order.

In order to improve the sound quality of high-fidelity audio, it is desired to lower the noise floor in the audible band and set the reproduction band to a wide range of up to 100 KHz. Generally, reproduction of AM / SW radio is performed. Band is -10KH
Since it is z, when receiving AM / SW radio, it is required that the received voice be heard clearly, rather than higher sound quality than that of other sources (MD / CD / FM radio reception).

The present embodiment does not limit the scope of the present invention, and various modifications can be made within the scope of the present invention.

For example, the case where the sampling frequency is switched between 64 fs and 128 fs and the ΔΣ modulation order is switched between the third-order ΔΣ modulation and the seventh-order ΔΣ modulation has been described in the present embodiment. Not limited. That is, the settable number (three or more) of the sampling frequency and the ΔΣ modulation order and the specific set value are ΔΣ
It can be appropriately selected according to the specifications of the audio device equipped with the modulation circuit. Also, the sampling frequency and / or the ΔΣ modulation order should be switched not by input source, but by
You may perform according to an input signal.

The present invention can also be configured as follows. A method of controlling a 1-bit signal amplifier according to the present invention is a method of switching a sampling frequency and a ΔΣ modulation order of a 1-bit signal amplifier provided with a plurality of input sources so that audio characteristics according to each input source can be obtained. . A method of controlling a radio-equipped 1-bit signal amplifier of the present invention is a method of reducing noise to a radio reception frequency band by switching the radio-equipped 1-bit signal amplifier in a ΔΣ modulation 1-bit signal generation circuit. Is. The method for controlling a radio-equipped 1-bit signal amplifier of the present invention is a radio-equipped 1-bit signal amplifier, in which a plurality of oscillators having different oscillation frequencies are provided in a ΔΣ modulation 1-bit signal generation circuit, and the sampling frequency is switched to perform radio reception. This is a method of reducing noise to the frequency band.

[0063]

As described above, the control method of the 1-bit signal amplifier according to the present invention is the ΔΣ modulation in which the input signal input from any one of the plurality of input sources is ΔΣ-modulated to generate the 1-bit signal. 1-bit signal generation circuit, amplification circuit for amplifying 1-bit signal generated by this ΔΣ modulation 1-bit signal generation circuit, and D / for converting 1-bit signal amplified by this amplification circuit to analog signal by D / A conversion A method for controlling a 1-bit signal amplifier including an A conversion circuit, wherein the sampling frequency and / or the ΔΣ modulation order of the ΔΣ modulation 1-bit signal generation circuit is set according to the input source of the input signal. Is.

In the 1-bit signal amplifier of the present invention, at least one of the sampling frequency and the ΔΣ modulation order is variable, and the input signal input from any one of the plurality of input sources is ΔΣ-modulated. ΔΣ modulation 1-bit signal generating means for generating a 1-bit signal by
Amplifying means for amplifying the 1-bit signal generated by the Σ-modulated 1-bit signal generating means, and D / for converting the 1-bit signal amplified by the amplifying means into an analog signal by D / A conversion.
The sampling frequency and / or ΔΣ that are variable according to the A conversion means and the input source of the input signal.
And a setting means for setting the modulation order.

Therefore, normally, ΔΣ modulation is performed with a high sampling frequency and / or a high ΔΣ modulation order,
With this setting, when noise generated by the ΔΣ modulation circuit is mixed in the input signal, ΔΣ modulation can be performed at a low sampling frequency and / or a low ΔΣ modulation order.

Therefore, for example, FM radio / MD /
With an input source such as a CD, high sound quality can be realized by a high sampling frequency and / or a high ΔΣ modulation order, and with an input source such as an AM / SW radio,
With a low sampling frequency and / or a low ΔΣ modulation order, the effect of noise of the ΔΣ modulation circuit on the radio receiver can be minimized, and a clear audio output without noise can be realized.

As described above, since the ΔΣ modulation circuit can be set to the optimum audio characteristic according to the input source, the 1-bit signal amplifier using the ΔΣ modulation method can be used to set the audio characteristic within the audible band for any input source. This has the effect of enabling signal amplification with a good S / N.

Further, the control method of the 1-bit signal amplifier of the present invention is a method of setting the ΔΣ modulation order according to the reception band of the radio broadcast when the input source is the radio broadcast.

Further, in the 1-bit signal amplifier of the present invention, the input source includes a radio broadcast, and the setting means, when the input source is a radio broadcast, the ΔΣ modulation according to the reception band of the radio broadcast. This is a configuration for setting the order.

Therefore, further, in the case of an input source (AM / SW radio or the like) in which noise generated by the ΔΣ modulation circuit is mixed in the input signal, ΔΣ modulation is performed with a low ΔΣ modulation order for amplification, while ΔΣ modulation is performed. If the input source does not mix the noise generated by the circuit with the input signal, increase the input signal
It can be amplified by ΔΣ modulation with the Σ modulation order.

Therefore, for example, in an input source such as an AM / SW radio, the low ΔΣ modulation order minimizes the influence of the noise of the ΔΣ modulation circuit on the radio receiver and realizes a clear audio output without noise. In addition, the other input sources such as FM radio / MD / CD have an effect that high sound quality can be realized by a high ΔΣ modulation order.

Further, the control method of the 1-bit signal amplifier of the present invention is a method of setting the sampling frequency according to the reception band of the radio broadcast when the input source is the radio broadcast.

Also, in the 1-bit signal amplifier of the present invention, when the input source includes a radio broadcast and the setting means is a radio broadcast, the sampling frequency corresponds to the reception band of the radio broadcast. Is a configuration for setting.

Therefore, in the case of an input source (SW radio or the like) in which the noise generated by the ΔΣ modulation circuit is mixed in the input signal, ΔΣ modulation is performed at a low sampling frequency and amplification is performed.
On the other hand, in the case of an input source in which noise generated by the ΔΣ modulation circuit is not mixed in the input signal, the input signal can be ΔΣ-modulated at a high sampling frequency and amplified.

Therefore, for example, in an input source such as a SW radio, a low sampling frequency minimizes the influence of noise of the ΔΣ modulation circuit on the radio receiver, and a clear voice output without noise can be realized. With other input sources such as AM / FM radio / MD / CD, it is possible to achieve high sound quality with a high sampling frequency.

The audio equipment of the present invention has the above-mentioned 1-bit signal amplifier.

Therefore, the audio equipment is
By mounting the bit signal amplifier, the ΔΣ modulation circuit can be set to the optimum audio characteristic according to the input source. Therefore, the audio device is a radio (AM, S
W, FM), CD / MD, and other input sources are provided, and it is possible to perform signal amplification with good S / N in the audible band for any input source.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of an audio device equipped with a 1-bit signal amplifier according to an embodiment of the present invention.

FIG. 2 is a graph showing noise shaping characteristics of the ΔΣ modulation circuit for each sampling frequency.

FIG. 3 shows a noise shaping characteristic of a ΔΣ modulation circuit as ΔΣ
It is a graph shown according to the modulation order.

FIG. 4 is a block diagram showing a schematic configuration of an audio device equipped with a conventional 1-bit signal amplifier.

[Description of Reference Signs] 10 audio equipment 14 1-bit signal amplifier 21 ΔΣ modulation 1-bit signal generation circuit (ΔΣ modulation 1-bit signal generation means) 22 amplification circuit (amplification means) 23 D / A conversion circuit (D / A conversion means) 24 Sampling frequency switch (setting means) 26 ΔΣ modulation order switch (setting means)

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 5J091 AA02 AA41 CA41 FA18 HA26                       HA38 KA00 KA32 KA33 KA34                       KA53 SA05 TA01 TA03                 5J092 AA02 AA26 AA53 CA41 FA18                       HA38 KA00 KA23 KA32 KA33                       KA34 KA53 MA10 SA05 TA01                       TA03 UM03                 5J500 AA02 AA26 AA41 AA53 AC41                       AF18 AH26 AH38 AK00 AK23                       AK32 AK33 AK34 AK53 AM10                       AS05 AT01 AT03 MU03

Claims (7)

[Claims] 1. A ΔΣ modulation 1-bit signal generation circuit for generating a 1-bit signal by ΔΣ-modulating an input signal input from any one of a plurality of input sources, and this ΔΣ-modulation 1-bit signal generation circuit. The amplification circuit that amplifies the 1-bit signal that has been generated and the 1-bit signal that this amplification circuit has amplified are D / A
A D / A conversion circuit for converting into an analog signal by conversion, and a method for controlling a 1-bit signal amplifier comprising: a sampling frequency of the ΔΣ modulation 1-bit signal generation circuit according to an input source of the input signal; And / or a method of controlling a 1-bit signal amplifier, characterized in that the ΔΣ modulation order is set. 2. When the input source is a radio broadcast,
The method of controlling a 1-bit signal amplifier according to claim 1, wherein the ΔΣ modulation order is set according to a reception band of the radio broadcast. 3. When the input source is a radio broadcast,
The method for controlling a 1-bit signal amplifier according to claim 1 or 2, wherein the sampling frequency is set according to a reception band of the radio broadcast. 4. A ΔΣ modulation in which at least one of a sampling frequency and a ΔΣ modulation order is variable, and an input signal input from any one of a plurality of input sources is ΔΣ modulated to generate a 1-bit signal. 1-bit signal generation means, amplification means for amplifying the 1-bit signal generated by the ΔΣ modulation 1-bit signal generation means, and D / for converting the 1-bit signal amplified by the amplification means into an analog signal by D / A conversion. A 1-bit signal amplifier comprising: A conversion means; and setting means for setting the sampling frequency and / or the ΔΣ modulation order which are variable according to the input source of the input signal. 5. The input source includes a radio broadcast, and the setting means, when the input source is a radio broadcast,
The 1-bit signal amplifier according to claim 4, wherein the ΔΣ modulation order is set according to a reception band of the radio broadcast. 6. The input source includes a radio broadcast, and the setting means, when the input source is a radio broadcast,
5. The sampling frequency is set according to the reception band of the radio broadcast.
Alternatively, the 1-bit signal amplifier according to item 5. 7. The 1 according to claim 4, wherein
An audio device equipped with a bit signal amplifier.