JP2008193159A - Signal processor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide one bit amplifier capable of controlling the switching frequency of a switching circuit by setting the two thresholds of a quantizer based on various information corresponding to the specifications or state of equipment on which one bit amplifier is loaded. <P>SOLUTION: The one bit amplifier 1 of this signal processor is provided with: an integrator group 11 for integrating a first electric signal; a quantizer 12 for quantizing the signal from the integrator group 11 with two thresholds, and for outputting a ternary digital signal; a switching circuit 20 for amplifying and outputting the power of the ternary digital signal from the quantizer 12; and a threshold changing circuit 40 for changing the two thresholds of the quantizer. The threshold changing circuit 40 sets the two thresholds of the quantizer 12 based on the original signal for setting two thresholds from the outside. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a signal processing apparatus that modulates an inputted external electric signal into a ternary digital signal using ΔΣ modulation, amplifies the power of the ternary digital signal, and outputs an analog signal. It is.

  In recent years, switching amplifiers employing a ΔΣ modulation method, called 1-bit amplifiers, have been widely used because of their excellent conversion efficiency and feasibility in integrated circuits.

  In the 1-bit amplifier, a method is used in which a digital signal is generated by ΔΣ modulation of an electrical signal that is an analog audio signal or a digital audio signal, and the digital signal is amplified to a predetermined amplitude by a switching circuit. ing.

Here, a 1-bit amplifier using ΔΣ modulation will be described with reference to FIG.
FIG. 15 is a block diagram illustrating an example of a configuration of a 1-bit amplifier including a ΔΣ modulation circuit and a switching circuit.

  As shown in the figure, the 1-bit amplifier 100 includes a ΔΣ modulation circuit 110 and a switching circuit 120, and the ΔΣ modulation circuit 110 includes an integrator group 111 and a quantizer 112. Is done.

  Hereinafter, control in the 1-bit amplifier 100 will be described. An electrical signal that is an analog audio signal or a digital audio signal from an input unit (not shown) is input to the ΔΣ modulation circuit 110. The electric signal input to the ΔΣ modulation circuit 110 is integrated by the integrator group 111, and the quantized data is quantized by the quantizer 112 and modulated into a ternary digital signal. Next, the ternary digital signal generated by the ΔΣ modulation circuit 110 is input to the switching circuit 120. The switching circuit 120 switches ON / OFF of a switch provided inside based on the value of the input ternary digital signal, amplifies the power of the ternary digital signal, and outputs it to the speaker 130.

  Note that the quantizer 112 has two thresholds, a high threshold (hereinafter referred to as threshold A) and a low threshold (hereinafter referred to as threshold B), and an integrator group 111. Is quantized with the two threshold values A and B to generate a ternary digital signal.

Here, an audio signal input from the outside to the ΔΣ modulation circuit 110 is S (t), and an output signal from the integrator group 111 to the quantizer 112 is X (t). Furthermore, when S (t) is a full swing audio signal and the signal output from X (t) is “−2 <X (t) <2”, for example,
In the case of X (t) ≦ − (2/3), the value of the ternary digital signal output from the quantizer 112 is “−1”.
When − (2/3) <X (t) <(2/3), the value of the ternary digital signal output from the quantizer 112 is “0”.
When (2/3) ≦ X (t), the value of the ternary digital signal output from the quantizer 112 is “+1”. At this time, of the two threshold values in the quantizer 112, the threshold value A is (2/3) and the threshold value B is-(2/3).

  Here, when the difference between the threshold A and the threshold B is increased, for example, when the threshold A is set to (4/3) and the threshold B is set to − (4/3), the quantizer 112 determines “0”. Will be widened. At this time, even when a signal having a large amplitude is input to the ΔΣ modulation circuit 110, the output from the quantizer 112 tends to be “0”. As a result, by increasing the difference between the two threshold values in the quantizer 112, the value of the ternary digital signal is less likely to switch from “0” to “−1” or “+1”, based on the ternary digital signal. The switching frequency of the switching circuit 120 that switches ON / OFF of the switch is lowered.

  On the other hand, when the difference between the threshold A and the threshold B is reduced, for example, when the threshold A is set to (1/3) and the threshold B is set to-(1/3), a signal with a small amplitude is sent to the ΔΣ modulation circuit 110. Even when is input, the output value from the quantizer 112 is easily switched to “+1” or “−1”. As a result, by reducing the difference between the two threshold values in the quantizer 112, the value of the ternary digital signal is easily switched, and the switching frequency of the switching circuit 120 that switches the switch ON / OFF based on the ternary digital signal is reduced. Get higher.

  Here, in the 1-bit amplifier 100, as the difference between the two threshold values in the quantizer 112 is reduced and the switching frequency is increased, the time resolution for the output signal from the integrator group 111 is increased and the audio performance is improved. It will be.

  However, contrary to the improvement in audio performance, when the switching frequency increases, THD (Total Harmonic Distortion) of the signal output from the switching circuit 120, heat generation in the switching circuit 120, unnecessary radiation, and power consumption become problems. . The THD is a numerical value of the degree of distortion of the signal waveform.

  Specifically, when the switching frequency is increased, the influence per one switching pulse of the nonlinear component generated in the switching circuit 120 and the waveform collapse such as overshoot becomes relatively large and THD is deteriorated. become.

  Further, when the switch in the switching circuit 120 is switched from ON to OFF or from OFF to ON, power loss of the switch occurs. This power loss is converted into heat, and as the switching frequency increases, the number of times the switch is switched increases, which causes a problem that the power consumed and the heat generated by the switch increase.

  Furthermore, as another adverse effect of an increase in switching frequency, there is a problem that electromagnetic noise such as unnecessary radiation that causes EMI (Electromagnetic Interference) increases. The electromagnetic noise such as unnecessary radiation is determined to be suppressed to a certain level by an international standard. Therefore, in order to prevent electromagnetic noise such as unnecessary radiation, new parts and the like are required for the audio equipment, resulting in a problem of further cost increase.

  As described above, the audio performance of the 1-bit amplifier 100 and the THD, heat generation, unnecessary radiation, and power consumption are in a contradictory relationship.

Patent Document 1 discloses a method for setting a threshold value of a quantizer based on a peak value of an audio signal input to a ΔΣ modulation circuit.
JP 7-131881 A (published on May 19, 1995)

  Since the 1-bit amplifier 100 is mounted on various types of devices, it is necessary to control the switching frequency of the switching circuit 120 based on various information according to specifications and states of the mounted devices.

  However, in Patent Document 1, since the information input to the ΔΣ modulation circuit 110 is only the peak value of the audio signal, the switching of the switching circuit 120 is performed according to the specification and state of the device in which the 1-bit amplifier 100 is mounted. Can't control the frequency.

  The present invention has been made to solve the above-described problems, and its object is to provide two threshold values for a quantizer based on various information in accordance with specifications and states of a device on which a signal processing device is mounted. Is to provide a signal processing device capable of controlling the switching frequency of the switching circuit.

In order to solve the above problems, a signal processing apparatus according to the present invention provides
An integration circuit for integrating the first electrical signal; a quantizer for quantizing the signal from the integration circuit with two threshold values; and outputting a ternary digital signal; and a ternary digital signal from the quantizer. A signal processing apparatus comprising a switching circuit for amplifying and outputting power and a threshold value changing circuit for changing two threshold values of the quantizer, wherein the threshold value changing circuit is configured to output the two threshold values from the outside. It is characterized in that two threshold values of the quantizer are set based on an original signal for setting.

  According to said structure, a signal processing apparatus integrates the input 1st electric signal by an integration circuit. Next, the data integrated by the integrating circuit is quantized by the quantizer with two threshold values in the quantizer and modulated into a ternary digital signal. Next, the switching circuit switches the switches in the switching circuit based on the value of the ternary digital signal modulated by the quantizer and amplifies and outputs the power of the ternary digital signal.

  Furthermore, the signal processing apparatus includes a threshold value changing circuit that changes two threshold values in the quantizer. The threshold value changing circuit sets the two threshold values of the quantizer based on the original signal for setting the two threshold values from the outside.

  Here, the threshold value changing circuit changes the two threshold values in the quantizer based on the original signal input from the outside, thereby changing the frequency of the ternary digital signal output from the quantizer. The switching frequency in the switching circuit is changed. The threshold value changing circuit sets the two threshold values in the quantizer to such a value that the difference between the two threshold values becomes small, thereby increasing the switching frequency of the switching circuit. Furthermore, by setting the two threshold values of the threshold value changing circuit to such a value that the difference between the two threshold values becomes small, the frequency of the ternary digital signal output from the quantizer becomes higher and is generated by the quantizer. Quantization noise can be reduced. As a result, the theoretical SNR value of the signal output from the quantizer increases, and the signal processing apparatus can output a high-performance signal having a large theoretical SNR value.

  On the other hand, the threshold value changing circuit sets the two threshold values in the quantizer to a value that increases the difference between the two threshold values, thereby lowering the switching frequency of the switching circuit. As a result, when the switching frequency is lowered, power loss caused by switching on and off of the switch in the switching circuit is suppressed, and heat generation and power consumption in the switching circuit are suppressed. Furthermore, by lowering the switching frequency of the switching circuit, THD, which is a distortion of the waveform of the signal output from the switching circuit, is reduced, and unnecessary radiation is also reduced.

  As described above, the signal processing device can control the switching frequency in the switching circuit based on the original signal for setting the two threshold values of the quantizer from the outside. Here, by changing the original signal input from the outside to the signal processing device according to the specification and state of the device on which the signal processing device is mounted, the original signal input to the signal processing device can be In addition, there is an effect that the switching frequency of the switching circuit can be controlled based on various information.

  For example, when the device on which the signal processing device is mounted is a portable device, the specification is aimed at low power consumption. In such a case, by inputting a signal that increases the difference between the two threshold values in the quantizer to the signal processing device as an original signal input from the outside to the signal processing device, the threshold value changing circuit performs quantization. Increase the difference between the two thresholds in the unit and lower the switching frequency. As a result, the power consumption of the signal processing device can be reduced.

  In addition, for example, when the device including the signal processing device is an audio device, and the user replaces the speaker that is the output destination of the signal processing device with a speaker of a different model, the impedance of the speaker that is the output destination of the signal processing device, etc. Changes its characteristics. Along with this, the optimum values of the two threshold values in the quantizer also change. Even in such a case, by inputting two threshold values according to the model of the replaced speaker as an original signal input to the signal processing device from the outside, the two threshold values in the quantizer are An optimum value can be set.

  As described above, the signal processing apparatus of the present invention includes the threshold value changing circuit, and the threshold value changing circuit sets the two threshold values of the quantizer based on the original signal for setting the two threshold values from the outside. Set and control the switching frequency of the switching circuit. Furthermore, by changing the original signal in accordance with the specification and state of the device on which the signal processing device is mounted, the signal processing device can convert various information according to the specification and state of the device on which the signal processing device is mounted. Based on this, the switching frequency of the switching circuit can be controlled.

The signal processing apparatus according to the present invention is
It has a ΔΣ modulation circuit composed of at least the integration circuit and the quantizer,
The first electric signal is obtained by subtracting the second electric signal input from the outside of the ΔΣ modulation circuit and the output signal from the quantizer or the switching circuit. As an original signal for changing the threshold value, the attenuation value or amplification factor of the second electric signal for attenuating or amplifying the second electric signal is input to the threshold value changing circuit. And recording means in which a plurality of sets of two threshold values corresponding to each value of the attenuation factor or amplification factor are recorded, and the threshold value changing circuit records the two threshold values of the quantizer in the recording means. Of the plurality of sets of two threshold values, two threshold values corresponding to the input attenuation factor or amplification factor are set.

  The device equipped with the signal processing device multiplies the second electrical signal input to the signal processing device by an attenuation factor or an amplification factor, and a signal to be output by adjusting the attenuation factor or the amplification factor. The volume is adjusted. That is, when a device on which a signal processing device is mounted receives an instruction to reduce the volume from the user, the device on which the signal processing device is mounted increases the attenuation factor applied to the second electrical signal and causes the signal processing device to The amplitude of the input second electric signal is reduced. On the other hand, when the device equipped with the signal processing device receives an instruction to increase the volume from the user, the device equipped with the signal processing device increases the amplification factor applied to the second electric signal and The amplitude of the input second electric signal is increased.

  Here, the threshold value changing circuit inputs an attenuation factor or an amplification factor for attenuating or amplifying the second electrical signal. Furthermore, the threshold value changing circuit includes recording means in which a plurality of sets of two threshold values corresponding to respective values of the attenuation factor or the amplification factor applied to the second electric signal are recorded. The threshold value changing circuit acquires two threshold values corresponding to the input attenuation factor or amplification factor from the recording means. Next, the threshold value changing circuit sets the two threshold values of the quantizer by outputting the two threshold values acquired from the recording means to the quantizer.

  As described above, the signal processing device can change the two threshold values of the quantizer based on the attenuation factor or amplification factor for attenuating or amplifying the second electrical signal. The frequency can be adjusted. Therefore, the signal processing apparatus has an effect that the two threshold values of the quantizer can be set to optimum values according to the attenuation factor or the amplification factor.

  Furthermore, in the signal processing apparatus according to the present invention, the plurality of sets of two threshold values recorded in the recording means has a value in which the difference between the two threshold values of the quantizer becomes smaller as the attenuation factor increases. The larger the amplification factor, the larger the difference between the two threshold values of the quantizer.

  Here, when the attenuation rate for attenuating the second electrical signal is large, in other words, when the amplitude of the second electrical signal input to the signal processing device is small, the signal output from the quantizer The theoretical SNR is reduced, resulting in poor audio performance. This is because the frequency of the ternary digital signal output from the quantizer decreases when the amplitude of the second electric signal input to the signal processing device is small. In order to solve this problem, when the amplitude of the second electric signal input to the signal processing device is small, the difference between the two threshold values in the quantizer is changed to a small value, and the quantizer It is necessary to prevent a decrease in the frequency of the ternary digital signal output from the terminal, in other words, a decrease in the switching frequency of the switching circuit.

  Here, the plurality of sets of two threshold values recorded in the recording means are such that the larger the attenuation factor, the smaller the difference between the two threshold values of the quantizer, and the larger the amplification factor. The difference between the two threshold values of the quantizer becomes larger.

  Therefore, when the attenuation rate for attenuating the second electrical signal is large, the threshold value changing circuit sets the two threshold values of the quantizer to a value such that the difference between the two threshold values of the quantizer becomes small. The switching frequency of the switching circuit can be prevented from decreasing. As a result, the signal processing apparatus has an effect that it is possible to prevent a decrease in audio performance by preventing a decrease in switching frequency.

  In addition, when the amplification factor for amplifying the second electric signal is large, the threshold value changing circuit sets the two threshold values of the quantizer so that the difference between the two threshold values of the quantizer becomes large. The switching frequency of the switching circuit can be increased. As a result, the signal processing device has an effect of reducing heat generation, power consumption, and unnecessary radiation in the switching circuit by increasing the switching frequency.

The signal processing apparatus according to the present invention is
As an original signal for changing the two threshold values from the outside, the threshold value changing circuit is supplied with a signal indicating the remaining battery level of a device in which the signal processing device is mounted. The threshold value changing circuit has recorded the two threshold values of the quantizer in the recording means, each of which includes a plurality of sets of two threshold values corresponding to each value of the signal indicating the remaining amount. Of the two threshold values of the plurality of sets, the threshold value is set to two threshold values corresponding to the signal value indicating the input remaining battery level.

  According to said structure, the threshold value change circuit has input the signal which shows the battery remaining charge of the apparatus in which the signal processing apparatus is mounted. Furthermore, the threshold value changing circuit acquires two threshold values corresponding to the input remaining battery level from the recording means. Next, the threshold value changing circuit sets the two threshold values of the quantizer by outputting the two threshold values acquired from the recording means to the quantizer.

  As described above, the signal processing device can set the two threshold values of the quantizer and control the switching frequency of the switching circuit based on the information on the remaining battery level of the device in which the signal processing device is mounted. . Therefore, the signal processing apparatus has an effect that the two threshold values of the quantizer can be set to optimum values according to the remaining battery level of the mounted device.

Furthermore, the signal processing device according to the present invention provides:
The plurality of sets of two threshold values recorded in the recording means are characterized in that the smaller the remaining amount of the battery, the larger the difference between the two threshold values of the quantizer.

  With the above configuration, when the battery level of the device on which the signal processing device is mounted is low, the threshold value changing circuit increases the difference between the two threshold values in the quantizer and reduces the switching frequency. Can do. As a result, the signal processing device has an effect that it is possible to reduce power consumption in the switching circuit by reducing the switching frequency.

  Further, when the battery level of the device on which the signal processing device is mounted is large, the threshold value changing circuit can reduce the difference between the two threshold values in the quantizer and increase the switching frequency. As a result, the signal processing apparatus has an effect that the audio performance can be improved by increasing the switching frequency.

The signal processing apparatus according to the present invention is
An integration circuit for integrating the first electrical signal; a quantizer for quantizing the signal from the integration circuit with two threshold values; and outputting a ternary digital signal; and a ternary digital signal from the quantizer. A signal processing apparatus comprising a switching circuit that amplifies and outputs power and a threshold value changing circuit that changes two threshold values of the quantizer, wherein the threshold value changing circuit reflects an operating state of the switching circuit The above-described signal is input, and two threshold values of the quantizer are set based on the received signal.

  With the above configuration, the signal processing device sets the two threshold values of the quantizer based on information from the switching circuit. Here, by changing the information from the switching circuit in accordance with the specifications and state of the device in which the signal processing device is mounted, the signal processing device can perform the quantization of the quantizer based on various information from the switching circuit. Two threshold values can be set, and the switching frequency of the switching circuit can be controlled.

The signal processing apparatus according to the present invention is
As a signal reflecting the operating state of the switching circuit, it corresponds to each value of a switching frequency measuring circuit for measuring the switching frequency in the switching circuit and a signal indicating the switching frequency measured by the switching frequency measuring circuit. And a recording means in which a plurality of sets of two threshold values are recorded, and the threshold value changing circuit receives a signal indicating the number of switching times from the switching number measuring circuit. Set the two threshold values of the quantizer to two threshold values corresponding to the value of the input signal indicating the number of times of switching among a plurality of two threshold values recorded in the recording means. It is characterized by.

  According to said structure, the signal processing apparatus is provided with the switching frequency measurement circuit which measures the switching frequency in a switching circuit. Here, the threshold value changing circuit receives a signal indicating the switching frequency of the switching circuit as information from the switching circuit from the switching frequency measurement circuit. Furthermore, the threshold value changing circuit includes a recording unit in which a plurality of sets of two threshold values corresponding to each value of the signal indicating the number of times of switching are recorded. Therefore, the threshold value changing circuit obtains two threshold values corresponding to the inputted switching frequency from the recording means. Next, the threshold value changing circuit changes the two threshold values of the quantizer by outputting the two threshold values acquired from the recording means to the quantizer.

  As described above, the signal processing device can change the two threshold values of the quantizer based on the information on the number of times of switching in the switching circuit and control the number of times of switching in the switching circuit. Therefore, the signal processing device has an effect that the two threshold values of the quantizer can be set to optimum values according to the number of times of switching in the switching circuit.

Furthermore, the signal processing device according to the present invention provides:
The plurality of sets of two threshold values recorded in the recording means are characterized in that the smaller the number of switching times, the smaller the difference between the two threshold values of the quantizer.

  By providing the above configuration, the signal processing device can reduce the number of switchings by increasing the difference between the two threshold values in the quantizer by the threshold value changing circuit when the switching number in the switching circuit is large. As a result, the signal processing device has an effect that heat generation, power consumption, and unnecessary radiation in the switching circuit can be suppressed.

  Further, when the number of times of switching in the switching circuit is small, the signal processing device can reduce the difference between the two threshold values in the quantizer and increase the number of times of switching by the threshold value changing circuit. As a result, the signal processing apparatus has an effect that the noise level of the signal output from the switching circuit can be reduced.

The signal processing apparatus according to the present invention is
As a signal reflecting the operating state of the switching circuit, there are a plurality of two threshold values corresponding to the temperature sensor for measuring the temperature in the switching circuit and the temperature values in the switching circuit measured by the temperature sensor. A recording means for recording the set; a signal indicating the temperature of the switching circuit is input from the temperature sensor to the threshold value changing circuit, and the threshold value changing circuit includes the quantizer These two threshold values are set to two threshold values corresponding to the input temperature of the switching circuit among a plurality of sets of two threshold values recorded in the recording means.

  According to said structure, the signal processing apparatus is provided with the temperature sensor which measures the temperature in a switching circuit. Here, the threshold value changing circuit inputs temperature information in the switching circuit as information from the switching circuit from the temperature sensor. Further, the threshold value changing circuit includes recording means in which a plurality of sets of two threshold values corresponding to respective values of the temperature of the switching circuit are recorded. Here, the threshold value changing circuit acquires two threshold values corresponding to the input temperature of the switching circuit from the recording means. Next, the threshold value changing circuit sets the two threshold values of the quantizer by outputting the two threshold values acquired from the recording means to the quantizer.

  As described above, the signal processing device sets the two threshold values of the quantizer based on the temperature of the switching circuit by inputting the temperature information of the switching circuit from the temperature sensor to the threshold value changing circuit. The switching frequency of the switching circuit can be controlled. Therefore, the signal processing apparatus has an effect that the two threshold values of the quantizer can be set to optimum values according to the temperature of the switching circuit.

Furthermore, the signal processing device of the present invention provides:
The plurality of sets of two threshold values recorded in the recording means are characterized in that the higher the temperature of the switching circuit, the larger the difference between the two threshold values of the quantizer.

  With the above configuration, when the temperature in the switching circuit is high, the signal processing device sets the two threshold values of the quantizer so that the difference between the two threshold values in the quantizer becomes large by the threshold value changing circuit. Can be set to reduce the number of times of switching in the switching circuit.

  Since the temperature of the switching circuit increases as the number of times of switching increases, the temperature of the switching circuit decreases by decreasing the number of times of switching.

  Therefore, when the temperature in the switching circuit is high, the signal processing device can reduce the switching frequency in the switching circuit by increasing the difference between the two threshold values of the quantizer. As a result, the signal processing device has an effect of lowering the temperature in the switching circuit by reducing the switching frequency.

  In addition, when the temperature in the switching circuit is low, the signal processing device can reduce the difference between the two threshold values of the quantizer and increase the switching frequency in the switching circuit. As a result, the signal processing apparatus has an effect that the audio performance can be improved by increasing the switching frequency.

  Furthermore, the circuit components that make up the switching circuit may be destroyed by their own heat generation. Even in such a case, the threshold value changing circuit can set the two threshold values of the quantizer based on the temperature of the switching circuit and adjust the temperature of the switching circuit. There is also an effect to prevent.

The signal processing apparatus according to the present invention is
As a signal reflecting the operating state of the switching circuit, it corresponds to a noise measurement circuit that measures the noise level of the signal output from the switching circuit, and the noise level measured by the noise measurement circuit. A recording means in which a plurality of sets of two threshold values are recorded,
The threshold value changing circuit receives a signal indicating the noise level from the noise measuring circuit, and the threshold value changing circuit records two threshold values of the quantizer in the recording means. Of the plurality of sets of two threshold values, two threshold values corresponding to the inputted noise level value are set.

  According to said structure, the signal processing apparatus is provided with the noise measurement circuit which measures the noise level of the signal output from a switching circuit. The threshold value changing circuit inputs the value of the noise level measured by the noise measuring circuit. Furthermore, the threshold value changing circuit includes recording means in which a plurality of sets of two threshold values corresponding to each value of the noise level are recorded. Here, the threshold value changing circuit acquires two threshold values corresponding to the input noise level value from the recording means. The threshold value changing circuit changes the two threshold values of the quantizer by outputting the two threshold values acquired from the recording means to the quantizer.

  As described above, the signal processing device can control the switching frequency in the switching circuit by changing the two threshold values of the quantizer based on the noise level that is the noise level of the signal output from the switching circuit. Therefore, the signal processing apparatus has an effect that the two threshold values of the quantizer can be set to optimum values according to the noise level.

Furthermore, the signal processing device according to the present invention provides:
The plurality of sets of two threshold values recorded in the recording means is characterized in that the higher the noise level, the smaller the difference between the two threshold values of the quantizer.

  With the above configuration, when the noise level of the signal output from the switching circuit is high, the signal processing device reduces the difference between the two threshold values of the quantizer by using the threshold value changing circuit, and sets the switching frequency. Can be increased. As a result, the noise level output from the switching circuit can be reduced.

  Further, when the noise level of the signal output from the switching circuit is low, the signal processing device can reduce the switching frequency by increasing the difference between the two threshold values of the quantizer by the threshold value changing circuit. As a result, the signal processing device has an effect of reducing heat generation, power consumption, and unnecessary radiation in the switching circuit by reducing the switching frequency.

The signal processing apparatus according to the present invention is
A ΔΣ modulation circuit including at least the integration circuit and the quantizer; and the first electric signal is a second electric signal input from the outside of the ΔΣ modulation circuit and a quantizer or a switching device. It is obtained by subtracting the output signal from the circuit, and the second electric signal or the reference signal can be selected as a reference signal generation circuit for generating a reference signal and a signal input to the ΔΣ modulation circuit It is preferable to provide a simple selector.

  With the above configuration, when the noise level of the signal output from the switching circuit is measured by the noise measurement circuit, the reference signal can be input to the ΔΣ modulation circuit.

  Here, when the noise level of the output signal output from the switching circuit is measured by the noise measurement circuit, the noise measurement circuit measures the noise level of the output signal by measuring using the reference signal from the reference signal measurement circuit. Can be measured accurately. This is not an indeterminate signal like the normal second electrical signal, but the noise measurement circuit discriminates between the noise component and the reference signal by inputting a predetermined reference signal to the ΔΣ modulation circuit. This is because it can be easily performed.

  Therefore, the signal processing apparatus can accurately set the two threshold values of the quantizer to optimum values by changing the two threshold values of the quantizer based on the accurately measured noise level. There is a possible effect.

The signal processing apparatus according to the present invention is
Each of a distortion measuring circuit that measures distortion of a waveform of a signal output from the switching circuit, and a signal that indicates distortion of the waveform measured by the distortion measuring circuit, as signals reflecting the operating state of the switching circuit. Recording means for recording a plurality of threshold values corresponding to the values, and the threshold value changing circuit is configured to receive a signal indicating distortion of the waveform from the distortion measuring circuit, and the threshold value changing circuit. Sets the two threshold values of the quantizer to two threshold values corresponding to the value of the signal indicating the distortion of the input waveform among the plurality of two threshold values recorded in the recording means. It is characterized by that.

  According to said structure, the signal processing apparatus is provided with the distortion measurement circuit which measures distortion of the waveform of the signal output from a switching circuit. The threshold value changing circuit receives a signal indicating the distortion of the waveform measured by the distortion measuring circuit. Further, the threshold value changing circuit includes recording means in which a plurality of sets of two threshold values corresponding to respective values of the signal indicating the waveform distortion are recorded. Here, the threshold value changing circuit acquires two threshold values corresponding to the input waveform distortion value from the recording means. The threshold value changing circuit changes the two threshold values of the quantizer by outputting the two threshold values acquired from the recording means to the quantizer.

  As described above, the signal processing device can control the switching frequency in the switching circuit by changing the two threshold values of the quantizer based on the distortion of the waveform of the signal output from the switching circuit. Therefore, the signal processing apparatus has an effect that the two threshold values of the quantizer can be set to optimum values according to waveform distortion.

Furthermore, the signal processing device according to the present invention provides:
The plurality of sets of two threshold values recorded in the recording means are characterized in that the larger the distortion of the waveform, the larger the difference between the two threshold values of the quantizer.

  By providing the above configuration, the signal processing apparatus increases the difference between the two threshold values of the quantizer by using the threshold value changing circuit when the distortion of the waveform of the signal output from the switching circuit is large. Can be reduced. As a result, the signal processing apparatus has an effect of reducing distortion of the waveform of the signal output from the switching circuit.

  Moreover, when the distortion of the waveform of the signal output from the switching circuit is small, the signal processing device can reduce the difference between the two threshold values of the quantizer and increase the switching frequency by the threshold value changing circuit. As a result, the signal processing apparatus can improve audio performance by increasing the switching frequency.

The signal processing apparatus according to the present invention is
A ΔΣ modulation circuit including at least the integration circuit and the quantizer; and the first electric signal is a second electric signal input from the outside of the ΔΣ modulation circuit and a quantizer or a switching device. It is obtained by subtracting the output signal from the circuit, and the second electric signal or the reference signal can be selected as a reference signal generation circuit for generating a reference signal and a signal input to the ΔΣ modulation circuit It is preferable to provide a simple selector.

  With the above configuration, the reference signal can be input to the ΔΣ modulation circuit when the noise measurement circuit measures the distortion of the waveform of the signal output from the switching circuit.

  Here, when the distortion of the waveform of the output signal output from the switching circuit is measured by the distortion measurement circuit, the distortion measurement circuit can measure the waveform of the output signal by measuring using the reference signal from the reference signal measurement circuit. Can be measured accurately.

  Therefore, the signal processing apparatus accurately sets the two threshold values of the quantizer to the optimum values by changing the two threshold values of the quantizer based on the accurately measured waveform distortion information. The effect which becomes possible is produced.

The signal processing apparatus according to the present invention is
An integration circuit that integrates a digital signal, a signal from the integration circuit is quantized with two threshold values, a quantizer that outputs a ternary digital signal, and the power of the ternary digital signal from the quantizer is amplified. A switching circuit that outputs, a threshold value changing circuit that changes two threshold values of the quantizer, a bit accuracy measuring circuit that measures the bit accuracy of the digital signal, and a value corresponding to each value of the bit accuracy, A signal processing device including a recording unit in which a plurality of sets of two threshold values are recorded, wherein the threshold value changing circuit receives a signal indicating the bit accuracy from the bit accuracy measuring circuit, The threshold value changing circuit includes two threshold values corresponding to two input threshold values of the quantizer, the two threshold values recorded in the recording means, and corresponding to the value of the signal indicating the input bit accuracy. It is characterized by setting to.

  According to the above configuration, the signal processing apparatus includes the bit accuracy reading circuit that reads the bit accuracy of the input digital signal. Here, the threshold value changing circuit receives the bit accuracy information of the digital signal from the bit accuracy reading circuit. Furthermore, the threshold value changing circuit includes a recording unit in which a plurality of sets of two threshold values corresponding to respective values of bit precision are recorded. Here, the threshold value changing circuit acquires two threshold values corresponding to the input bit precision from the recording means. Next, the threshold value changing circuit sets the two threshold values of the quantizer by outputting the two threshold values acquired from the recording means to the quantizer.

  As described above, the signal processing device can set the two threshold values of the quantizer and control the switching frequency of the switching circuit based on the bit accuracy of the digital signal input to the integrating circuit. Therefore, the signal processing apparatus has an effect that the two threshold values of the quantizer can be set to optimum values according to the bit accuracy.

Furthermore, the signal processing device according to the present invention provides:
The plurality of sets of two threshold values recorded in the recording means is characterized in that the higher the bit accuracy, the smaller the difference between the two threshold values of the quantizer.

  Here, when the input digital signal has high bit accuracy, it is preferable to reduce the noise level of the signal output from the signal processing device and output a high-performance signal commensurate with high bit accuracy. On the other hand, if the input digital signal has low bit accuracy, the bit level of the original digital signal is low even if the noise level of the signal output from the switching circuit is reduced. The noise level of the signal cannot be reduced.

  As described above, when the bit accuracy of the digital signal input to the signal processing device is high, the threshold value changing circuit can reduce the difference between the two threshold values in the quantizer and increase the switching frequency in the switching circuit. As a result, the signal processing apparatus has an effect of being able to output a signal with a reduced noise level commensurate with high bit accuracy.

  On the other hand, when the bit accuracy of the input digital signal is low, the threshold value changing circuit can suppress the reduction of the switching frequency in the switching circuit more than necessary by increasing the difference between the two threshold values in the quantizer. . As a result, the signal processing device has an effect of reducing heat generation, power consumption, and unnecessary radiation in the switching circuit.

  In the signal processing device of the present invention, as described above, the threshold value changing circuit sets the two threshold values of the quantizer based on the original signal for setting the two threshold values of the quantizer from the outside. ing.

  In the signal processing apparatus of the present invention, as described above, the threshold value changing circuit inputs a signal reflecting the operation state of the switching circuit, and sets two threshold values of the quantizer based on the signal. is doing.

  In the signal processing device of the present invention, as described above, the threshold value changing circuit receives the two threshold values of the quantizer out of a plurality of sets of two threshold values recorded in the recording means. Two threshold values corresponding to the signal value indicating the bit precision are set.

  Therefore, the signal processing device of the present invention sets two threshold values of the quantizer based on various information according to the specification and state of the device on which the signal processing device is mounted, and sets the switching frequency of the switching circuit. Can be controlled.

Embodiment 1
A first embodiment of the present invention will be described below with reference to FIGS.

(Configuration of 1-bit amplifier)
First, the configuration of the 1-bit amplifier according to the present embodiment will be described below with reference to FIG. FIG. 1 is a block diagram showing a basic configuration of a 1-bit amplifier 1 according to an embodiment of the present invention.

  As shown in the figure, a 1-bit amplifier 1 (corresponding to a signal processing device described in the claims) can be used, for example, in an audio device or a large-sized liquid crystal television, and includes a ΔΣ modulation circuit 10 and a switching circuit 20 and a threshold value changing circuit 40. Further, the ΔΣ modulation circuit 10 includes a subtractor, an integrator group 11 (corresponding to an integration circuit described in claims), and a quantizer 12.

  The signal input to the ΔΣ modulation circuit 10 is the second electrical signal described in the claims, and the signal from the subtractor input to the integration circuit is the first electrical signal described in the claims. However, in this embodiment, for convenience of explanation, both are referred to as electrical signals.

(Control operation of 1-bit amplifier 1)
Hereinafter, operation control in the 1-bit amplifier 1 will be described. An electrical signal that is an analog audio signal or a digital audio signal from an input unit (not shown) is subtracted by a subtracter and input to the ΔΣ modulation circuit 10. The electric signal input to the ΔΣ modulation circuit 10 is integrated by the integrator group 11, and the quantized data is quantized by the quantizer 12 and modulated into a ternary digital signal. Next, the ternary digital signal generated by the ΔΣ modulation circuit 10 is input to the switching circuit 20. The switching circuit 20 switches ON / OFF of a switch provided inside based on the input ternary digital signal, amplifies the power of the ternary digital signal, and outputs it to the speaker 30.

  In the 1-bit amplifier 1, the ternary digital signal output from the quantizer 12 is fed back to the integrator group 11 via a subtractor. This means that a ternary digital signal including quantization noise generated in the integrator group 11 and the quantizer 12 is fed back to the integrator group 11. The integrator group 11 extracts the quantization noise component from the ternary digital signal including quantization noise, and outputs a signal for canceling the quantization noise component to the quantizer 12 in accordance with the electric signal from the input unit. To do. In this way, by feeding back the ternary digital signal from the quantizer 12 to the integrator group 11, the 1-bit amplifier 1 reduces the quantization noise of the ternary digital signal.

  1 feeds back the ternary digital signal output from the quantizer 12 to the integrator group 11. However, the 1-bit amplifier according to the present invention is not limited to this. Instead, the output signal from the switching circuit 20 may be fed back to the integrator group 11.

(Threshold change of the quantizer 12)
Next, the quantizer 12 has a high-side threshold (hereinafter referred to as threshold A) and a low-side threshold (hereinafter referred to as threshold B), which are two threshold values, and an integrator group. 11 is quantized with the two threshold values A and B to generate a ternary digital signal. Furthermore, the threshold value changing circuit 40 can change the values of the threshold value A and the threshold value B.

  The threshold value changing circuit 40 inputs an original signal for setting two threshold values from the outside as information according to the specification and state of the device on which the 1-bit amplifier 1 is mounted. Here, the threshold value changing circuit 40 sets the threshold value A and the threshold value B in the quantizer 12 based on the original signal input from the outside.

(Relationship between threshold and switching frequency)
Below, the relationship between the values of the threshold A and threshold B in the quantizer 12 and the switching frequency in the switching circuit 20 will be described.

Here, an externally input audio signal to the ΔΣ modulation circuit 10 is S (t), and an output signal from the integrator group 11 to the quantizer 12 is X (t). Furthermore, when S (t) is a full swing audio signal and the signal output from X (t) is “−2 <X (t) <2”, for example,
When X (t) ≦ − (2/3), the value of the ternary digital signal output from the quantizer 12 is “−1”.
When − (2/3) <X (t) <(2/3), the value of the ternary digital signal output from the quantizer 12 is “0”.
When (2/3) ≦ X (t), the value of the ternary digital signal output from the quantizer 12 is “+1”. At this time, of the two threshold values in the quantizer 12, the threshold value A is (2/3) and the threshold value B is-(2/3).

  Here, when the difference between the threshold A and the threshold B is increased, for example, when the threshold A is set to (4/3) and the threshold B is set to − (4/3), the quantizer 12 determines “0”. Will be widened. At this time, even when a signal having a large amplitude is input to the ΔΣ modulation circuit 10, the output from the quantizer 12 tends to be “0”. That is, by increasing the difference between the threshold value A and the threshold value B of the quantizer 12, the value of the ternary digital signal is not easily switched from “0” to “−1” or “+1”. As a result, when the frequency of the ternary digital signal is lowered, the switching frequency of the switching circuit 20 that switches ON / OFF of the switch based on the ternary digital signal is lowered.

  On the other hand, when the difference between the threshold A and the threshold B is reduced, for example, when the threshold A is set to (1/3) and the threshold B is set to-(1/3), a signal with a small amplitude is sent to the ΔΣ modulation circuit 10. Even when is input, the output value from the quantizer 112 is easily switched to “+1” or “−1”. That is, by reducing the difference between the two threshold values of the quantizer 12, the value of the ternary digital signal is easily switched from “0” to “−1” or “+1”. As a result, when the frequency of the ternary digital signal is increased, the switching frequency of the switching circuit 20 that switches the switch ON / OFF based on the ternary digital signal is increased.

  The specific relationship between the threshold A and threshold B values in the quantizer 12, the switching frequency, and the theoretical SNR (Signal to Noise Ratio) of the signal output from the ΔΣ modulation circuit 10 will be described below with reference to FIG. Will be described with reference to FIG. Here, for simplification of explanation, noise factors other than the theoretical SNR appearing in the output signal from the switching circuit 20 are eliminated, and the value of the theoretical SNR of the signal output from the ΔΣ modulation circuit 10 is increased. If so, it is assumed that the actual SNR value of the signal output from the switching circuit 20 also increases. Furthermore, the theoretical SNR indicates the ratio of the audio signal input to the ΔΣ modulation circuit 10 to the quantization noise generated in the ΔΣ modulation circuit.

  FIG. 2 shows the relationship between the switching frequency of the switching circuit 20 and the theoretical SNR of the signal output from the ΔΣ modulation circuit 10 when the threshold A and threshold B in the quantizer 12 are set to a plurality of different values. It is explanatory drawing.

  In the figure, the number of switching times and the theoretical SNR corresponding to each threshold when an audio signal having a constant frequency is input to the ΔΣ modulation circuit 10 are shown. Note that there are two cases where the magnitude of the audio signal input to the ΔΣ modulation circuit 10 is −0.9 dB and −20.0 dB. Further, the thresholds in the figure indicate the values of the threshold A and the threshold B, and a positive value corresponds to the threshold A and a negative value corresponds to the threshold B. Also, the larger the theoretical SNR value, the smaller the noise value for the signal, in other words, the less the noise of the output signal from the ΔΣ modulation circuit 10, and the audio performance is improved as a result. Indicates.

  As shown in the figure, the smaller the threshold difference, the greater the number of switchings in the switching circuit 20 per unit time. That is, the switching frequency in the switching circuit 20 is high. Further, the smaller the threshold difference, the higher the frequency of the ternary digital signal output from the quantizer, in other words, the higher the switching frequency in the switching circuit, and the higher the theoretical SNR value. Specifically, when the absolute value of the threshold is 0.33 and the size of the input audio signal is −0.9 dB, the number of switching times per unit time is 669 times, and the theoretical SNR is It is 115.4 dB. Here, when the absolute value of the threshold is 1.50 and the magnitude of the input audio signal is −0.9 dB, the number of switching per unit time is 347, and the theoretical SNR is 107. It is 1 dB.

  Furthermore, when the magnitude of the audio signal input to the ΔΣ modulation circuit 10 is decreased from −0.9 dB to −20.0 dB, the number of switching times decreases and the theoretical SNR value decreases. Specifically, when the value of the audio signal input to the ΔΣ modulation circuit 10 is −0.9 dB when the values of the threshold A and the threshold B are ± 0.33, −20.0 dB When the value of the audio signal is −0.9 dB, the theoretical SNR value is −115.4 dB, and when it is −20.0 dB, the theoretical SNR value is −113.1 dB. It has become. In other words, it can be seen that the smaller the value of the audio signal input to the ΔΣ modulation circuit 10, the smaller the theoretical SNR value and the lower the audio performance.

Next, simulation results showing the frequency characteristics of the output signal of the ΔΣ modulation circuit 10 in the 1-bit amplifier 1 are shown in FIGS.
FIG. 3A shows a case where the threshold A of the quantizer 12 is set to +0.2, the threshold B is set to −0.2, and a 1 kHz audio signal is input to the ΔΣ modulation circuit 10 from the ΔΣ modulation circuit 10. It is explanatory drawing which shows the frequency component of an output signal, The same figure (b) makes the threshold value A +1.0, threshold value B -1.0, and others at the same conditions as FIG. FIG. 6 is an explanatory diagram showing frequency components of an output signal from the ΔΣ modulation circuit 10.

  First, in FIG. 6A, the threshold value A and threshold value B of the quantizer 12 are set to ± 0.2, and the switching frequency in the switching circuit 20 at this time is 722 k times / sec. On the other hand, in FIG. 5B, the threshold value A and threshold value B of the quantizer 12 are set to ± 1.0, and the switching frequency in the switching circuit 20 at this time is 120 k times / sec. .

  Comparing (a) and (b) of the figure, in FIG. (A), the noise floor level in the vicinity of 1 kHz indicated by the arrow in the figure is about -130 dB. On the other hand, in FIG. 5B, the noise floor level in the vicinity of 1 kHz indicated by the arrow in the figure is about −120 dB. This indicates that the noise floor level has increased by changing the threshold A and threshold B of the quantizer 12 from ± 0.2 to ± 1.0. That is, it can be seen that increasing the difference between the threshold value A and the threshold value B of the quantizer decreases the switching frequency in the output signal of the ΔΣ modulation circuit 10, resulting in a decrease in audio performance.

  As described above, the threshold value changing circuit 40 can control the output signal of the ΔΣ modulation circuit 10 and thus the switching frequency per unit time in the switching circuit 20 by changing the threshold value A and the threshold value B. The value of the theoretical SNR, which is a standard for performance, will be affected.

(Relationship between switching frequency and factors affecting 1-bit amplifier)
Next, the relationship between the switching frequency and each element affecting the 1-bit amplifier 1 will be described with reference to FIG.
FIG. 4 is an explanatory diagram showing a relationship for each element affecting the 1-bit amplifier when the difference between the threshold A and the threshold B is increased and when the difference is decreased.

  In the figure, when the threshold A and threshold B are changed and the switching frequency in the switching circuit 20 is changed, the theoretical SNR of the signal output from the ΔΣ modulation circuit 10, THD (Total Harmonic Distortion), and switching The relationship between the calorific value in the circuit 20, power consumption, and unnecessary radiation is shown. The shaded portions in the figure indicate that the 1-bit amplifier 1 has a negative effect. The THD is a value obtained by quantifying the degree of signal distortion.

In the same figure,
When the difference between the threshold A and the threshold B is reduced, the difference between the thresholds is indicated by the lower right arrow indicating the decrease, and when the difference between the threshold A and the threshold B is increased, the difference is indicated by the upper right arrow indicating the increase And
The switching frequency is indicated by an upper right arrow indicating an increase when the frequency is increased, and is indicated by an lower right arrow indicating a decrease when the frequency is decreased.
The theoretical SNR is indicated by an upper right arrow indicating an increase when the value is increased, and by a lower right arrow indicating a decrease when the value is decreased.
THD is indicated by an upper right arrow indicating an increase when the value is increased, and is indicated by a lower right arrow indicating a decrease when the value is decreased.
The amount of heat generation is indicated by an upper right arrow indicating an increase when the heat generation is large, and a lower right arrow indicating a decrease when the heat generation is small,
The power consumption is indicated by an upper right arrow indicating an increase when the power consumption is increased, and a lower right arrow indicating a decrease when the power consumption is decreased.
Unwanted radiation is indicated by an upper right arrow indicating rising when the unnecessary radiation is increased, and is indicated by a lower right arrow indicating lowering when it is reduced.

  As shown in the figure, by reducing the difference between the threshold A and the threshold B, the switching frequency is increased, the theoretical SNR is increased, and the audio performance is improved. However, as the switching frequency increases, the value of THD indicating the distortion of the waveform of the signal output from the switching circuit 20 increases. Furthermore, since the switching frequency is increased, the amount of heat generation and power consumption in the switching circuit 20 are increased, and unnecessary radiation is also increased.

  On the other hand, by increasing the difference between the threshold A and the threshold B, the switching frequency is lowered, and further, the theoretical SNR is reduced and the audio performance is lowered. However, as the switching frequency is lowered, the value of THD indicating the distortion of the waveform of the signal output from the switching circuit 20 is reduced. Furthermore, since the switching frequency is lowered, the heat generation amount and power consumption in the switching circuit 20 are reduced, and unnecessary radiation is also reduced.

  As described above, in the change of the threshold A and the threshold B, the theoretical SNR indicating the audio performance and the THD, the heat generation amount, the power consumption, and the unnecessary radiation have a contradictory relationship. Therefore, it is necessary to change the threshold value A and the threshold value B according to the specification and state of the device on which the 1-bit amplifier 1 is mounted.

  Specifically, if the device in which the 1-bit amplifier 1 is mounted requires high audio performance, it is necessary to set the threshold A and the threshold B so that the theoretical SNR and THD are the best.

  On the other hand, when the device including the 1-bit amplifier 1 is intended to be manufactured at a lower cost than high audio performance, it is necessary to set the threshold A and the threshold B so as to suppress heat generation and unnecessary radiation. is there. As a result, it is possible to suppress as much as possible additional components that take measures against heat generation and unnecessary radiation.

  The above is the basic configuration of the 1-bit amplifier 1 according to the first embodiment.

  Furthermore, the 1-bit amplifier 1 according to the first embodiment preferably includes a recording unit.

  As shown in FIG. 5, the 1-bit amplifier 1 according to the first embodiment is provided with a recording unit 42 inside the threshold value changing circuit 40.

Hereinafter, the 1-bit amplifier 1 according to the first embodiment provided with the recording means will be described with reference to FIG.
As shown in the figure, the threshold value changing circuit inputs an original signal for changing the threshold value A and the threshold value B from the outside, which is information according to the specification and state of the device in which the 1-bit amplifier 1 is mounted. . Further, the threshold value changing circuit 40 includes a recording unit 42.

  The recording means 42 records a plurality of sets of threshold A and threshold B corresponding to respective values of the original signal for changing the threshold A and threshold B from the outside. Here, the threshold value changing circuit 40 corresponds to the threshold value A and threshold value B of the quantizer 12 corresponding to the value of the input original signal among the plurality of sets of threshold values A and B recorded in the recording means 42. Threshold value A and threshold value B are set. Specifically, the threshold value changing circuit 40 reads the threshold value A and the threshold value B corresponding to the value of the input original signal from the recording unit 42. Further, the threshold changing circuit 40 outputs the threshold A and threshold B read from the recording means 42 to the quantizer 12 and changes the threshold A and threshold B in the quantizer 12.

  As described above, the threshold value A and the threshold value B corresponding to the input original signal are recorded in the recording means 42 in advance even if the original signal input from the outside is a signal other than the signal representing the threshold value. Thus, the threshold value changing circuit 40 can set the threshold value A and the threshold value B in the quantizer 12 based on the input information.

  That is, by rewriting the information recorded in the recording means 42, the threshold value changing circuit 40 can set the threshold value A and the threshold value B in the quantizer 12 based on various information.

  Here, in the present embodiment, a microcomputer 50 is connected to the threshold changing circuit 40 as means for inputting the original signal for setting the two thresholds of the quantizer 12 from the outside. The threshold change circuit 40 inputs an instruction from the user as a signal from the microcomputer 50. Further, the threshold value changing circuit 40 can set the threshold value A and the threshold value B of the quantizer 12 based on a signal from the microcomputer 50.

  For example, the speaker 30 provided at the output destination of the switching circuit 20 may be replaced by a speaker 30 of a different model. At this time, when the model of the speaker 30 is exchanged, the characteristics such as the impedance of the output destination in the switching circuit 20 change. In such a case, the balance of each element affecting the 1-bit amplifier shown in FIG. 4 also changes, and as a result, the optimum threshold value in the quantizer 12 also changes. Accordingly, even in such a case, it is necessary to change the threshold A and the threshold B in the quantizer 12.

  At this time, when the user inputs two threshold values corresponding to the newly replaced speaker 30 to the threshold value changing circuit 40 via the microcomputer 50, the threshold value changing circuit 40 has the threshold value A and the threshold value of the quantizer 12. B can be set to an optimum value.

  Further, the threshold value changing circuit 40 includes a recording unit 42. Here, the threshold values A and B corresponding to the model names or model numbers of various models of the speaker 30 are recorded in the recording means 42 in advance. Thus, when the speaker 30 provided at the output destination of the 1-bit amplifier 1 is replaced with a different model, the threshold value changing circuit 40 can be simply input to the threshold value changing circuit 40 by inputting the model name or model number of the speaker 30. The threshold value A and the threshold value B in the quantizer 12 can be changed to optimum values.

  The recording unit 42 is not limited to being provided inside the threshold value changing circuit 40, and may be provided outside the threshold value changing circuit 40.

  An arithmetic circuit may be provided in place of the recording means 42. Specifically, in the present embodiment, the threshold value changing circuit 40 reads out a plurality of sets of threshold values A and B corresponding to each value of the signal input to the threshold value changing circuit 40 from the recording means 42. The threshold value A and threshold value B of the quantizer 12 are set, but the configuration of the present embodiment is not limited to this. That is, the threshold value A and the threshold value B corresponding to each value of the signal input to the threshold value changing circuit 40 are calculated by the arithmetic circuit, and the threshold value changing circuit 40 sets the threshold value A and the threshold value B calculated by the arithmetic circuit. The threshold value A and the threshold value B of the quantizer 12 may be set by inputting and outputting to the quantizer 12.

  Furthermore, in this embodiment, the signal input to the integrator group 11 is an audio signal. However, the present invention is not limited to this, and may be an analog or digital electric signal other than the audio signal.

  Hereinafter, the configuration shown in the second to tenth embodiments is a modification of the first embodiment. Specifically, in the first embodiment, information from the microcomputer input to the threshold value changing circuit is changed to various information according to the specification and state of the device on which the 1-bit amplifier is mounted.

  In the following second to tenth embodiments, portions that are different from the above-described first embodiment will be described, and descriptions of overlapping portions will be omitted.

[Embodiment 2]
A specific configuration of the 1-bit amplifier 2 according to the second embodiment of the present invention will be described below with reference to FIG.

  In the present embodiment, information on the volume of the sound of the mounted device is used as a source signal for setting two external thresholds according to the specifications of the mounted device.

  As shown in the figure, a device on which the 1-bit amplifier 2 is mounted includes a volume adjusting unit 250 that adjusts the volume of the sound output from the speaker 30.

  The volume adjusting unit 250 multiplies the audio signal by an attenuation factor or amplification factor for attenuating or amplifying the audio signal input to the ΔΣ modulation circuit 10 and adjusts the attenuation factor or amplification factor. Thus, the magnitude of the sound output from the speaker 30 is adjusted.

  Specifically, when the user adjusts the volume of the sound output from the speaker 30, the user gives an instruction to the volume adjusting unit 250. At this time, when the volume adjustment unit 250 receives an instruction to increase the volume from the user, the volume adjustment unit 250 increases the amplification factor to be applied to the audio signal, and the audio signal input to the ΔΣ modulation circuit 10 is increased. Increase the amplitude. On the other hand, when the volume adjustment unit 250 receives an instruction to reduce the volume from the user, the volume adjustment unit 250 increases the attenuation rate applied to the audio signal, and the audio signal input to the ΔΣ modulation circuit 10 is increased. Reduce the amplitude. In this way, the volume of the audio output from the speaker 30 is adjusted by the volume adjusting unit 250 changing the amplitude of the audio signal input to the ΔΣ modulation circuit 10 in accordance with an instruction from the user.

  As described above, when the user sets the volume to be small by adjusting the amplitude of the audio signal input to the ΔΣ modulation circuit 10 by adjusting the magnitude of the sound output from the speaker 30, the ΔΣ modulation circuit The value of the audio signal input to 10 is reduced. Here, as shown in FIG. 2, by reducing the audio signal input to the ΔΣ modulation circuit 10, the theoretical SNR of the signal output from the ΔΣ modulation circuit 10 decreases.

  Here, the threshold changing circuit 240 inputs the attenuation factor or amplification factor output from the volume adjusting unit 250 as an original signal for setting the threshold A and threshold B from the outside. The recording unit 242 records a plurality of sets of threshold values A and B corresponding to the values of the attenuation factor or amplification factor output from the volume adjusting unit 250. At this time, the threshold value changing circuit 240 corresponds to the threshold value A and threshold value B of the quantizer 12 corresponding to the input attenuation factor or amplification factor among the plurality of threshold values A and threshold values B recorded in the recording means 242. , Threshold A and threshold B are set.

  Specifically, the threshold value changing circuit 240 reads out the threshold value A and the threshold value B corresponding to the attenuation factor or the amplification factor from the recording unit 242. Next, the threshold value changing circuit 240 outputs the threshold value A and the threshold value B read from the recording unit 242 to the quantizer 12 and sets the threshold value A and the threshold value B of the quantizer 12.

  The recording means 242 has a value such that the larger the attenuation rate, the smaller the difference between the threshold value A and the threshold value B in the quantizer 12, and the larger the amplification rate, the more the quantizer 12 has. A plurality of sets of threshold values A and B, which are values that increase the difference between the threshold value A and the threshold value B, are recorded.

  Therefore, when the user reduces the volume, in other words, when the amplitude of the audio signal input to the ΔΣ modulation circuit 10 is reduced via the volume adjustment unit 250, the threshold value changing circuit 240 uses the threshold value in the quantizer 12. By reducing the difference between A and the threshold B, the theoretical SNR of the signal output from the ΔΣ modulation circuit 10 is prevented from decreasing.

  When the user increases the volume, in other words, when the audio signal input to the ΔΣ modulation circuit 10 is increased by the volume adjusting unit 250, the threshold changing circuit 240 sets the threshold A and threshold B of the quantizer 12. By increasing the difference, the switching frequency in the switching circuit 20 is prevented from becoming higher than necessary. That is, if the theoretical SNR of the signal output from the ΔΣ modulation circuit 10 is a value greater than the specified value, it is not necessary to increase the switching frequency more than necessary. Therefore, the switching circuit 20 is generated by keeping the switching frequency low. Heat and power consumption are suppressed.

[Embodiment 3]
A third embodiment according to the present invention will be described below with reference to FIG. In addition, about the member which is common in 1st Embodiment mentioned above, the same code | symbol is attached | subjected and detailed description is abbreviate | omitted.

  As shown in the figure, the 1-bit amplifier 4 includes a ΔΣ modulation circuit 10, a switching circuit 20, a threshold value changing circuit 440, and a battery remaining amount measuring circuit 450. Further, the ΔΣ modulation circuit 10 includes an integrator group 11 and a quantizer 12, and the threshold value changing circuit 440 includes a recording unit 442. In addition, a device on which the 1-bit amplifier 4 is mounted includes a battery 460 that supplies power to the device.

  Here, when the remaining amount of the battery 460 is low, it is necessary to reduce the power consumption of the device in which the 1-bit amplifier 4 is mounted. At this time, as shown in FIG. 4, the power consumption in the 1-bit amplifier 4 increases as the switching frequency in the switching circuit 20 increases. Therefore, the power consumption in the 1-bit amplifier 4 is suppressed by increasing the difference between the threshold A and the threshold B in the quantizer 12 and lowering the switching frequency in the switching circuit 20. On the other hand, when the battery 460 has a large remaining battery capacity, the difference between the threshold value A and the threshold value B in the quantizer 12 is reduced, and the theoretical SNR of the signal output from the ΔΣ modulation circuit 10 is increased, thereby improving the audio performance. Will be improved.

  Here, the voltage output from the battery 460 varies depending on the remaining battery level of the battery 460. The 1-bit amplifier 4 inputs the power supply voltage output from the battery 460 to the threshold value changing circuit 440 as a signal indicating the remaining battery level. The recording unit 442 records a plurality of sets of threshold values A and B corresponding to the signal value indicating the remaining battery level. At this time, the threshold value changing circuit 440 sets the threshold value A and the threshold value B of the quantizer 12 corresponding to the input remaining battery power among the plurality of sets of threshold values A and B recorded in the recording unit 442. A and threshold B are set.

  Specifically, the threshold value changing circuit 440 reads the threshold value A and the threshold value B corresponding to the remaining battery level of the battery 460 from the recording unit 442. Next, the threshold value changing circuit 440 outputs the threshold value A and the threshold value B read from the storage unit 442 to the quantizer 12 and sets the threshold value A and the threshold value B of the quantizer 12.

  Further, the plurality of sets of threshold values A and B recorded in the recording unit 442 are values such that the difference between the threshold value A and the threshold value B in the quantizer 12 increases as the remaining battery level of the battery 460 decreases. Thus, the larger the remaining battery level is, the smaller the difference between the threshold value A and the threshold value B in the quantizer 12 is.

  As described above, when the battery remaining amount is low by changing the values of the threshold value A and the threshold value B in the quantizer 12 according to the battery remaining amount of the battery 460, the threshold value changing circuit 440 causes the quantizer 12 to The switching frequency of the switching circuit 20 is lowered by reducing the difference between the threshold value A and the threshold value B in FIG. As a result, the power consumption in the 1-bit amplifier 5 can be reduced by lowering the switching frequency in the switching circuit 20.

  On the other hand, when the remaining battery level of battery 460 is large, threshold change circuit 440 reduces the difference between threshold A and threshold B in quantizer 12 and increases the theoretical SNR of the signal output from ΔΣ modulation circuit 10. High audio performance can be realized.

[Embodiment 4]
A fourth embodiment according to the present invention will be described below with reference to FIG. In addition, about the member which is common in 1st Embodiment mentioned above, the same code | symbol is attached | subjected and detailed description is abbreviate | omitted.

  As shown in the figure, the 1-bit amplifier 3 includes a ΔΣ modulation circuit 10, a switching circuit 20, a threshold value changing circuit 340, and a switching times measuring circuit 350. Further, the ΔΣ modulation circuit 10 includes an integrator group 11 and a quantizer 12, and the threshold value changing circuit 340 includes a recording unit 342.

  The switch in the switching circuit 20 performs ON / OFF switching based on the value of the ternary digital signal output from the quantizer 12. Therefore, the number of changes in the value of the ternary digital signal is the number of times of switching in the switching circuit 20.

  The switching frequency measuring circuit 350 receives the ternary digital signal output from the quantizer 12 and measures the switching frequency per unit time in the switching circuit 20 by detecting a change in the value of the ternary digital signal. is doing.

  Here, the switching frequency measuring circuit 350 outputs a signal representing the measured switching frequency per unit time to the threshold control circuit 340. The threshold value changing circuit 340 receives a signal that is information on the number of switching times from the switching number measuring circuit 350. The recording means 342 records a plurality of sets of threshold values A and B corresponding to the respective values of the switching frequency output from the switching frequency measuring circuit 350. At this time, the threshold value changing circuit 340 sets the threshold value A and the threshold value B of the quantizer 12 to the threshold value A corresponding to the input number of times of switching among the plural threshold values A and B recorded in the recording unit 342. And the threshold value B is set.

  Specifically, the threshold value changing circuit 340 reads the threshold value A and the threshold value B corresponding to the switching number from the switching number measuring circuit 350 from the recording unit 342. Next, the threshold changing circuit 340 outputs the threshold A and threshold B read from the recording unit 342 to the quantizer 12 and sets the threshold A and threshold B of the quantizer 12.

  Further, the plurality of sets of threshold values A and B recorded in the recording unit 342 become values such that the larger the number of switching times, the larger the difference between the threshold value A and the threshold value B of the quantizer 12. The smaller the value, the smaller the difference between the threshold value A and the threshold value B of the quantizer 12.

  Therefore, the threshold value changing circuit 340 can suppress the power consumption and heat generation in the switching circuit 20 by increasing the difference between the threshold value A and the threshold value B in the quantizer 12 when the number of times of switching is large. On the other hand, the threshold value changing circuit 340 reduces the threshold value A and threshold value B in the quantizer 12 and increases the theoretical SNR of the signal output from the ΔΣ modulation circuit 10 when the number of times of switching is small. Performance can be improved.

  As described above, the 1-bit amplifier 3 can change the threshold value A and the threshold value B in the quantizer 12 based on the information on the number of switching times measured by the switching number measuring circuit 350.

  As described above, the number of times of switching in the switching circuit 20 is measured, and the values of the threshold value A and the threshold value B of the quantizer 12 are changed according to the number of times of switching. An increase in power and an increase in heat generation can be reduced.

[Embodiment 5]
A fifth embodiment according to the present invention will be described below with reference to FIG. In addition, about the member which is common in 1st Embodiment mentioned above, the same code | symbol is attached | subjected and detailed description is abbreviate | omitted.

  As shown in the figure, the 1-bit amplifier 6 includes a ΔΣ modulation circuit 10, a switching circuit 20, a threshold value changing circuit 640, and a temperature sensor 650. Further, the ΔΣ modulation circuit 10 includes an integrator group 11 and a quantizer 12, and the threshold value changing circuit 640 includes a recording unit 642.

  As the switching frequency in the switching circuit 20 increases, heat generation due to switching loss increases in the switching circuit 20.

  Here, the 1-bit amplifier 6 includes a temperature sensor 650 that measures the temperature in the switching circuit 20. The temperature sensor 650 outputs the measured temperature information in the switching circuit 20 to the threshold value changing circuit 640. Next, the threshold value changing circuit 640 receives an input signal representing the temperature in the switching circuit 20 from the temperature sensor 650. The recording unit 642 records a plurality of sets of threshold values A and B corresponding to each value of the temperature of the switching circuit 20 output from the temperature sensor 650. At this time, the threshold changing circuit 640 corresponds to the temperature of the input switching circuit 20 among the plurality of sets of threshold A and threshold B recorded in the recording unit 642. , Threshold A and threshold B are set.

  Specifically, the threshold change circuit 640 reads the threshold A and the threshold B corresponding to the temperature in the switching circuit 20 from the recording unit 642. Next, the threshold change circuit 640 outputs the threshold A and threshold B read from the recording unit 642 to the quantizer 12 and sets the threshold A and threshold B in the quantizer 12.

  Further, the plurality of sets of threshold values A and B recorded in the recording unit 642 are values such that the lower the temperature of the switching circuit 20, the smaller the difference between the threshold value A and the threshold value B in the quantizer 12. The higher the temperature of the switching circuit 20, the larger the difference between the threshold A and the threshold B in the quantizer 12.

  Thus, by changing the values of the threshold A and the threshold B in the quantizer 12 according to the temperature in the switching circuit 20, when the temperature in the switching circuit 20 is high, the threshold A in the quantizer 12 and The difference in the threshold value B is increased to lower the switching frequency in the switching circuit 20. As a result, the temperature in the switching circuit 20 can be lowered by lowering the switching frequency.

  On the other hand, when the temperature in the switching circuit 20 is low, the difference between the threshold value A and the threshold value B is reduced, the theoretical SNR of the signal output from the ΔΣ modulation circuit 10 is increased, and high audio performance is realized. it can.

  In addition, the electronic components constituting the switching circuit 20 may be destroyed by the heat generated by itself. Even in such a case, the 1-bit amplifier 6 measures the temperature of the switching circuit 20 with the temperature sensor 650 and controls the switching frequency of the switching circuit 20, thereby preventing the electronic components constituting the switching circuit 20 from being destroyed. It is also possible.

[Embodiment 6]
A sixth embodiment according to the present invention will be described below with reference to FIG. In addition, about the member which is common in 1st Embodiment mentioned above, the same code | symbol is attached | subjected and detailed description is abbreviate | omitted.

  As shown in the figure, the 1-bit amplifier 7a includes a ΔΣ modulation circuit 10, a switching circuit 20, a threshold value changing circuit 740, and a noise measuring circuit 750. Further, the ΔΣ modulation circuit 10 includes an integrator group 11 and a quantizer 12, and includes a threshold value changing circuit 740 recording unit 742.

  Here, the 1-bit amplifier 7 a includes a noise measurement circuit 750 that measures an SNR that is a noise level of a signal output from the switching circuit 20. Furthermore, the threshold value changing circuit 740 receives a signal indicating the noise level or the SNR calculated from the noise level from the noise measuring circuit 750. The recording unit 742 records a plurality of sets of threshold values A and B corresponding to each value of the noise level or SNR output from the noise measurement circuit 750. At this time, the threshold value changing circuit 740 corresponds to the input noise level or SNR of the threshold value A and the threshold value B of the quantizer 12 among the plurality of sets of threshold values A and B recorded in the recording unit 742. , Threshold A and threshold B are set.

  Specifically, the threshold value changing circuit 740 reads the threshold value A and the threshold value B corresponding to the noise level or SNR input from the noise measuring circuit from the recording unit 742. Next, the threshold value changing circuit 740 outputs the read threshold value A and threshold value B to the quantizer 12, and sets the values of the threshold value A and the threshold value B in the quantizer 12.

  Further, the plurality of sets of threshold values A and B recorded in the recording unit 742 have a smaller noise level, that is, the larger the SNR value, the larger the difference between the threshold value A and the threshold value B in the quantizer 12. The value is such that the difference between the threshold value A and the threshold value B in the quantizer 12 decreases as the noise level increases, that is, as the SNR decreases.

  Thus, by changing the threshold A and threshold B in the quantizer 12 according to the noise level or SNR of the signal output from the switching circuit 20, the noise level is high, that is, the SNR value is small. In this case, the difference between the threshold value A and the threshold value B in the quantizer 12 can be reduced, the noise level can be reduced, that is, the SNR can be increased, and the audio performance can be improved. On the other hand, when the noise level is low, that is, when the SNR is high, the difference between the threshold value A and the threshold value B in the quantizer 12 can be increased to reduce heat generation and power consumption in the switching circuit 20.

[Embodiment 7]
A seventh embodiment according to the present invention will be described below with reference to FIG. In addition, about the member which is common in 1st Embodiment mentioned above, the same code | symbol is attached | subjected and detailed description is abbreviate | omitted.

  As shown in the figure, the 1-bit amplifier 7b includes a ΔΣ modulation circuit 10, a switching circuit 20, a threshold change circuit 740, a noise measurement circuit 750, a reference signal generation circuit 760, and a selector 770. . Further, the ΔΣ modulation circuit 10 includes an integrator group 11 and a quantizer 12, and the threshold value changing circuit 740 includes a recording unit 742.

  The reference signal generated by the reference signal generation circuit 760 preferably has a constant frequency such as a sine wave of 1 kHz and 0 dB.

  Here, the 1-bit amplifier 7 b inputs the reference signal generated by the reference signal generation circuit 760 to the ΔΣ modulation circuit 10 when measuring the SNR of the signal output from the switching circuit 20. Further, the signal input to the ΔΣ modulation circuit 10 is switched by the selector 770 from an external electric signal to a reference signal from the reference signal generation circuit 760.

  Next, the noise measurement circuit 750 measures the SNR of the signal output from the switching circuit 20 when the reference signal is input to the ΔΣ modulation circuit 10. Information on the SNR measured by the noise measurement circuit 750 is output to the threshold change circuit 740. Furthermore, the threshold value changing circuit 740 changes the threshold value A and the threshold value B in the quantizer 12 based on the input SNR information.

  As described above, when a reference signal that is a simple signal and has a constant frequency is input to the ΔΣ modulation circuit 10, the noise measurement circuit 750 can accurately measure the SNR. Therefore, the audio performance in the 1-bit amplifier 7b is accurately measured. As a result, it is possible to set the optimum threshold A and threshold B by changing the threshold A and threshold B in the quantizer 12 based on the accurately measured SNR information.

  Further, it is possible to measure the SNR with a single 1-bit amplifier. Therefore, it is possible to measure the SNR at the user's hand without using a special device.

[Embodiment 8]
An eighth embodiment according to the present invention will be described below with reference to FIG. In addition, about the member which is common in 1st Embodiment mentioned above, the same code | symbol is attached | subjected and detailed description is abbreviate | omitted.

  As shown in the figure, the 1-bit amplifier 8 a includes a ΔΣ modulation circuit 10, a switching circuit 20, a threshold change circuit 840, and a distortion measurement circuit 850. Further, the ΔΣ modulation circuit 10 includes an integrator group 11 and a quantizer 12, and the threshold value changing circuit 840 includes a recording unit 842.

  Here, the 1-bit amplifier 8a includes a distortion measurement circuit 850 that measures THD indicating waveform distortion of a signal output from the switching circuit 20. Information on the THD measured by the distortion measuring circuit 850 is output to the threshold value changing circuit 840. The recording unit 842 records a plurality of sets of threshold A and threshold B corresponding to each value of THD output from the distortion measurement circuit 850. At this time, the threshold value changing circuit 840 sets the threshold value A and the threshold value B of the quantizer 12 to the threshold value A and the threshold value A corresponding to the input THD among the plurality of sets of threshold values A and B recorded in the recording unit 842. The threshold value B is set.

  Specifically, the threshold value changing circuit 840 reads the threshold value A and the threshold value B corresponding to THD from the recording unit 842. Next, the threshold change circuit 840 outputs the read threshold A and threshold B to the quantizer 12 and sets the threshold A and threshold B in the quantizer 12.

  Further, the plurality of sets of threshold values A and B recorded in the recording unit 842 become values such that the higher the THD value, the larger the difference between the threshold value A and the threshold value B in the quantizer 12. The lower the value, the smaller the difference between the threshold A and the threshold B in the quantizer 12.

  In this way, by setting the threshold value A and threshold value B in the quantizer 12 according to the THD of the signal output from the switching circuit 20, when the THD value is high, the threshold value A and A signal output from the ΔΣ modulation circuit 10 by increasing the difference between the threshold values B and decreasing the THD while increasing the difference between the threshold values A and B in the quantizer 12 when the THD value is low. Increase the theoretical SNR value. Thus, by changing the values of the threshold A and the threshold B in the quantizer 12 so as to balance the THD and the theoretical SNR, it is possible to realize optimum audio performance.

[Embodiment 9]
A ninth embodiment according to the present invention will be described below with reference to FIG. In addition, about the member which is common in 1st Embodiment mentioned above, the same code | symbol is attached | subjected and detailed description is abbreviate | omitted.

  As shown in the figure, the 1-bit amplifier 8b includes a ΔΣ modulation circuit 10, a switching circuit 20, a threshold value changing circuit 840, a distortion measurement circuit 850, a reference signal generation circuit 860, and a selector 870. . Further, the ΔΣ modulation circuit 10 includes an integrator group 11 and a quantizer 12, and the threshold value changing circuit 840 includes a recording unit 842.

  The reference signal generated by the reference signal generation circuit 860 preferably has a constant frequency such as a sine wave of 1 kHz and 0 dB.

  Here, the 1-bit amplifier 8 b inputs the reference signal generated by the reference signal generation circuit 860 to the ΔΣ modulation circuit 10 when measuring the THD of the signal output from the switching circuit 20. Further, the signal input to the ΔΣ modulation circuit 10 is switched by the selector 870 from an external electric signal to a reference signal from the reference signal generation circuit 860.

  Next, the noise measurement circuit 850 measures the THD of the signal output from the switching circuit 20 when the reference signal is input to the ΔΣ modulation circuit 10. Information on the THD measured by the distortion measuring circuit 850 is output to the threshold value changing circuit 840. Further, the threshold value changing circuit 840 receives an input signal that is information on the THD from the distortion measuring circuit 850. The threshold change circuit 840 changes the values of the threshold A and the threshold B in the quantizer 12 based on the THD information input from the noise measurement circuit 850.

  In this way, when a reference signal that is a simple signal at a constant frequency is input to the ΔΣ modulation circuit 10, it is possible to accurately measure the THD in the distortion measurement circuit. Therefore, the audio performance in the 1-bit amplifier 8b is accurately measured, and the optimum threshold value is changed by changing the threshold value A and the threshold value B in the quantizer 12 based on the information of the THD measured accurately. A and threshold value B can be set.

  Further, it is possible to measure THD with a single 1-bit amplifier, and therefore THD measurement can be performed at the user's hand without using a special device.

[Embodiment 10]
A tenth embodiment according to the present invention will be described below with reference to FIG. In addition, about the member which is common in 1st Embodiment mentioned above, the same code | symbol is attached | subjected and detailed description is abbreviate | omitted.

  As shown in the figure, the 1-bit amplifier 5 includes a ΔΣ modulation circuit 10, a switching circuit 20, a threshold value changing circuit 540, and a bit precision reading circuit 550. Further, the ΔΣ modulation circuit 10 includes an integrator group 11 and a quantizer 12, and the threshold value changing circuit 540 includes a recording unit 542.

  If the audio signal input to the 1-bit amplifier 5 is a digital audio signal, this digital audio signal may be a fine representation of the audio signal with high bit accuracy, or a rough representation of the audio signal with low bit accuracy. There are also things.

  Here, when the digital audio signal input to the 1-bit amplifier 5 has high bit accuracy, it is preferable to realize high audio performance commensurate with the high bit accuracy of the input digital audio signal. Therefore, it is necessary to increase the theoretical SNR of the signal output from the ΔΣ modulation circuit 10. For this purpose, the difference between the threshold value A and the threshold value B in the quantizer 12 is reduced, and the noise floor of the signal output from the switching circuit 20 shown in FIGS. 3A and 3B is kept low. Necessary.

  On the other hand, when the digital audio signal input to the 1-bit amplifier 5 has low bit accuracy, it is not necessary to increase the theoretical SNR of the signal output from the ΔΣ modulation circuit 10 more than necessary. This is because when the bit accuracy of the digital audio signal input to the 1-bit amplifier 5 is low, the noise floor of the signal output from the ΔΣ modulation circuit 10 is not the quantization noise generated by the quantizer 12 but digital. This is because it is determined by the quantization noise included in the audio signal itself, and the theoretical SNR becomes small. Therefore, even if the difference between the threshold value A and the threshold value B in the quantizer 12 is made small, high audio performance cannot be realized. .

  Here, the 1-bit amplifier 5 includes a bit accuracy reading circuit 550 that reads the bit accuracy of the input digital audio signal. Further, the threshold value changing circuit 540 receives a signal indicating the bit accuracy from the bit accuracy reading circuit 550. The recording unit 542 records a plurality of sets of threshold values A and B corresponding to the respective bit accuracy values output from the bit accuracy measurement circuit 550. At this time, the threshold value changing circuit 540 sets the threshold value A and threshold value B of the quantizer 12 to the threshold value A corresponding to the input bit precision among the plurality of sets of threshold values A and B recorded in the recording unit 542. And the threshold value B is set.

  Specifically, the threshold change circuit 540 reads the threshold A and threshold B corresponding to the bit accuracy from the recording unit 542. Next, the threshold changing circuit 540 sets the threshold A and threshold B in the quantizer 12 by outputting the read threshold A and threshold B to the quantizer 12.

  Further, the plurality of sets of threshold values A and B recorded in the recording unit 542 become values such that the higher the bit accuracy, the smaller the difference between the threshold value A and the threshold value B in the quantizer 12. The lower the value, the larger the difference between the threshold A and the threshold B in the quantizer 12.

  As described above, when the bit accuracy is high by changing the values of the threshold value A and the threshold value B in the quantizer 12 according to the bit accuracy of the digital audio signal input to the 1-bit amplifier 5, The difference between the threshold A and the threshold B is reduced to increase the theoretical SNR of the signal output from the ΔΣ modulation circuit 10. As a result, by increasing the theoretical SNR of the signal output from the ΔΣ modulation circuit 10, it is possible to realize high audio performance commensurate with the digital audio signal input to the 1-bit amplifier 5.

  On the other hand, when the bit precision is low, the difference between the threshold value A and the threshold value B is increased to lower the switching frequency in the switching circuit 20. As a result, by reducing the switching frequency, heat generation and power consumption in the switching circuit 20 can be reduced.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

  In the 1-bit amplifier, the two threshold values in the quantizer are changed according to the specifications of the device in which the 1-bit amplifier is mounted, thereby placing importance on the theoretical SNR of the output signal from the 1-bit amplifier. Can provide 1-bit amplifiers according to various specifications such as low power consumption and low cost, especially for audio equipment equipped with 1-bit amplifiers, mobile phones, large LCD TVs, etc. It can be used in a device that outputs sound.

It is a block diagram which shows the structure of 1 bit amplifier based on one Embodiment of this invention. It is explanatory drawing which shows the relationship between the threshold value in a quantizer and the switching frequency of a switching circuit based on one Embodiment of this invention. (A) And (b) is explanatory drawing which shows the spectrum distribution of the signal output from a switching circuit at the time of changing the difference of the threshold value in a quantizer based on one Embodiment of this invention. It is explanatory drawing which shows the relationship between the threshold value in a quantizer and the various performance in 1 bit amplifier based on one Embodiment of this invention. It is a block diagram which shows the structure of 1 bit amplifier provided with the recording means in the threshold value change circuit based on one Embodiment of this invention. It is a block diagram which shows the structure of 1 bit amplifier which changes the threshold value in a quantizer based on the information from the volume adjustment means based on one Embodiment of this invention. It is a block diagram which shows the structure of 1 bit amplifier which changes the threshold value in a quantizer based on the information of the battery remaining amount of a battery based on one Embodiment of this invention. It is a block diagram which shows the structure of 1 bit amplifier which changes the threshold value in a quantizer based on the frequency | count of switching in a switching circuit based on one Embodiment of this invention. It is a block diagram which shows the structure of 1 bit amplifier which changes the threshold value in a quantizer based on the information of the temperature of the switching circuit based on one Embodiment of this invention. It is a block diagram which shows the structure of 1 bit amplifier which changes the threshold value in a quantizer based on the noise level of the output signal from a switching circuit based on one Embodiment of this invention. The block which shows the structure of 1 bit amplifier which changes the threshold value in a quantizer based on the noise level of the output signal from a switching circuit when a reference signal is input into the delta-sigma modulation circuit based on one Embodiment of this invention FIG. It is a block diagram which shows the structure of 1 bit amplifier which changes the threshold value in a quantizer based on distortion of the waveform of the output signal from a switching circuit based on one Embodiment of this invention. 1 shows a configuration of a 1-bit amplifier that changes a threshold value in a quantizer based on waveform distortion of an output signal from a switching circuit when a reference signal is input to a ΔΣ modulation circuit according to an embodiment of the present invention. It is a block diagram. It is a block diagram which shows the structure of 1 bit amplifier which changes the threshold value in a quantizer based on the bit precision of the digital audio signal input into the delta-sigma modulation circuit based on one Embodiment of this invention. It is a block diagram which shows the structure of 1 bit amplifier in a prior art example.

Explanation of symbols

1 1-bit amplifier (signal processing device)
2 1-bit amplifier (signal processing device)
3 1-bit amplifier (signal processing device)
4 1-bit amplifier (signal processor)
5 1-bit amplifier (signal processing device)
6 1-bit amplifier (signal processor)
7a 1-bit amplifier (signal processing device)
7b 1-bit amplifier (signal processing device)
8a 1-bit amplifier (signal processor)
8b 1-bit amplifier (signal processing device)
9 1-bit amplifier (signal processor)
10 ΔΣ modulation circuit 11 Integrator group (integrator)
DESCRIPTION OF SYMBOLS 12 Quantizer 20 Switching circuit 40 Threshold change circuit 42 Recording means 240 Threshold change circuit 242 Recording means 250 Volume adjustment means 340 Threshold change circuit 342 Recording means 350 Switching circuit measurement circuit 440 Threshold change circuit 442 Recording means 450 Battery remaining amount measurement circuit 540 Threshold change circuit 542 Recording means 550 Bit precision reading circuit 640 Threshold change circuit 642 Recording means 650 Temperature sensor 740 Threshold change circuit 742 Recording means 750 Noise measurement circuit 760 Reference signal generation circuit 770 Selector 840 Threshold change circuit 842 Recording means 850 Distortion measurement Circuit 860 Reference signal generation circuit 870 Selector 940 Threshold change circuit 942 Recording means

Claims (18)

An integrating circuit for integrating the first electrical signal;
A quantizer for quantizing the signal from the integration circuit with two threshold values and outputting a ternary digital signal;
A switching circuit for amplifying and outputting the power of the ternary digital signal from the quantizer;
A signal processing apparatus comprising a threshold value changing circuit for changing two threshold values of the quantizer,
The signal processing device, wherein the threshold value changing circuit sets the two threshold values of the quantizer based on an original signal for setting the two threshold values from the outside. It has a ΔΣ modulation circuit composed of at least the integration circuit and the quantizer,
The first electric signal is obtained by subtracting the second electric signal input from the outside of the ΔΣ modulation circuit and the output signal from the quantizer or the switching circuit,
As the original signal for changing the two threshold values from the outside, the threshold value changing circuit receives the attenuation factor or amplification factor of the second electric signal that attenuates or amplifies the second electric signal. It is supposed to
A recording unit in which a plurality of sets of two threshold values corresponding to each value of the attenuation factor or amplification factor are recorded;
The threshold value changing circuit sets the two threshold values of the quantizer to two threshold values corresponding to an input attenuation factor or amplification factor among a plurality of two threshold values recorded in the recording unit. The signal processing apparatus according to claim 1, wherein: A plurality of sets of two threshold values recorded in the recording means are:
The greater the attenuation factor, the smaller the difference between the two threshold values of the quantizer.
The signal processing apparatus according to claim 2, wherein the larger the amplification factor, the larger the difference between the two threshold values of the quantizer. As an original signal for changing the two threshold values from the outside, a signal indicating the remaining battery level of the device on which the signal processing device is mounted is input to the threshold value changing circuit,
A recording means in which a plurality of sets of two threshold values corresponding to each value of the signal indicating the remaining battery capacity are recorded;
The threshold value changing circuit corresponds to two threshold values corresponding to a value of a signal indicating the input remaining battery power among a plurality of two threshold values recorded in the recording unit. The signal processing device according to claim 1, wherein the signal processing device is set as follows. A plurality of sets of two threshold values recorded in the recording means are:
The signal processing apparatus according to claim 4, wherein the smaller the remaining amount of the battery, the larger the difference between the two threshold values of the quantizer. An integrating circuit for integrating the first electrical signal;
A quantizer for quantizing the signal from the integration circuit with two threshold values and outputting a ternary digital signal;
A switching circuit for amplifying and outputting the power of the ternary digital signal from the quantizer;
A signal processing apparatus comprising a threshold value changing circuit for changing two threshold values of the quantizer,
The signal processing apparatus, wherein the threshold value changing circuit receives a signal reflecting an operating state of the switching circuit and sets two threshold values of the quantizer based on the signal. As a signal reflecting the operating state of the switching circuit, a switching frequency measuring circuit for measuring the switching frequency in the switching circuit,
Recording means in which a plurality of sets of two threshold values corresponding to each value of a signal indicating the number of switching times measured by the switching number measuring circuit is recorded,
A signal indicating the number of switching times is input to the threshold value changing circuit from the switching number measuring circuit.
The threshold value changing circuit includes two threshold values corresponding to the input signal value indicating the number of times of switching among the two threshold values recorded in the recording unit. The signal processing apparatus according to claim 6, wherein the signal processing apparatus is set as follows. A plurality of sets of two threshold values recorded in the recording means are:
The signal processing apparatus according to claim 7, wherein the smaller the number of times of switching, the smaller the difference between the two threshold values of the quantizer. As a signal reflecting the operating state of the switching circuit, a temperature sensor that measures the temperature in the switching circuit;
Recording means in which a plurality of sets of two threshold values corresponding to respective values of the temperature in the switching circuit measured by the temperature sensor are recorded,
A signal indicating the temperature of the switching circuit is input to the threshold change circuit from the temperature sensor.
The threshold value changing circuit sets the two threshold values of the quantizer to two threshold values corresponding to the input temperature of the switching circuit among a plurality of two threshold values recorded in the recording means. The signal processing apparatus according to claim 6, wherein: A plurality of sets of two threshold values recorded in the recording means are:
The signal processing device according to claim 9, wherein the higher the temperature of the switching circuit, the larger the difference between the two threshold values of the quantizer. As a signal reflecting the operating state of the switching circuit, a noise measurement circuit that measures the noise level of the signal output from the switching circuit;
Recording means for recording a plurality of sets of two threshold values corresponding to each value of the noise level measured by the noise measurement circuit,
A signal indicating the noise level is input to the threshold change circuit from the noise measurement circuit,
The threshold value changing circuit sets the two threshold values of the quantizer to two threshold values corresponding to the input noise level value among a plurality of sets of two threshold values recorded in the recording means. The signal processing apparatus according to claim 6, wherein: A plurality of sets of two threshold values recorded in the recording means are:
The signal processing apparatus according to claim 11, wherein the higher the noise level, the smaller the difference between the two threshold values of the quantizer. It has a ΔΣ modulation circuit composed of at least the integration circuit and the quantizer,
The first electric signal is obtained by subtracting the second electric signal input from the outside of the ΔΣ modulation circuit and the output signal from the quantizer or the switching circuit,
A reference signal generation circuit for generating a reference signal;
13. The signal processing apparatus according to claim 11, further comprising a selector capable of selecting the second electric signal or the reference signal as a signal input to the ΔΣ modulation circuit. As a signal reflecting the operating state of the switching circuit, a distortion measuring circuit that measures distortion of a waveform of a signal output from the switching circuit,
Recording means for recording a plurality of threshold values corresponding to each value of the signal indicating the distortion of the waveform measured by the distortion measuring circuit;
The threshold value changing circuit is configured to receive a signal indicating distortion of the waveform from the distortion measuring circuit,
The threshold value changing circuit includes two threshold values corresponding to a value of a signal indicating distortion of the input waveform among a plurality of two threshold values recorded in the recording unit. The signal processing device according to claim 6, wherein the signal processing device is set to a threshold value. A plurality of sets of two threshold values recorded in the recording means are:
15. The signal processing apparatus according to claim 14, wherein the larger the distortion of the waveform, the larger the difference between the two threshold values of the quantizer. It has a ΔΣ modulation circuit composed of at least the integration circuit and the quantizer,
The first electric signal is obtained by subtracting the second electric signal input from the outside of the ΔΣ modulation circuit and the output signal from the quantizer or the switching circuit,
A reference signal generation circuit for generating a reference signal;
16. The signal processing apparatus according to claim 14, further comprising a selector capable of selecting the second electric signal or the reference signal as a signal input to the ΔΣ modulation circuit. An integration circuit for integrating the digital signal;
A quantizer for quantizing the signal from the integration circuit with two threshold values and outputting a ternary digital signal;
A switching circuit for amplifying and outputting the power of the ternary digital signal from the quantizer;
A threshold value changing circuit for changing two threshold values of the quantizer;
A bit accuracy measuring circuit for measuring the bit accuracy of the digital signal;
A plurality of sets of two threshold values corresponding to the respective values of the bit precision, and recording means,
The threshold change circuit is configured to receive a signal indicating the bit accuracy from the bit accuracy measurement circuit,
The threshold value changing circuit converts the two threshold values of the quantizer into two threshold values corresponding to the input signal value indicating the bit precision among a plurality of two threshold values recorded in the recording means. A signal processing device, wherein the signal processing device is set. A plurality of sets of two threshold values recorded in the recording means are:
18. The signal processing apparatus according to claim 17, wherein the higher the bit accuracy, the smaller the difference between the two threshold values of the quantizer.

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