JPH09148851A - Switching power source for audio - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a switching power source in which the responsiveness to rapid load fluctuation like an audio signal is excellent, the audio signal can be taken out without increasing distortion and a power source part is miniaturized. SOLUTION: Based on the amplitude values of digital input signals which are successively inputted, the pulse modulation signal for determining the DC output voltage value of an AC-DC conversion part 5 is determined by a pulse control part 6. By outputting the audio signal for which the power amplification is performed by a digital power amplifier part 1 after the digital input signals are delayed, DC output voltage is corrected by the same timing as the increase of the amplitude of the digital input signal.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a PCM (Pulse
The present invention relates to a switching power supply suitable for an audio amplifier that power-amplifies a digital input signal such as a code modulation wave.

[0002]

2. Description of the Related Art Generally, a dropper type having a structure of a transformer, a rectifying diode, and a smoothing capacitor has been conventionally used as an audio power supply. In recent years, digital power amplification by pulse modulation has been performed with the digitization of audio signals. Class amplifiers have come to be used, and accordingly switching type is being used for the purpose of downsizing and thinning of power supply.

A conventional audio switching power supply will be described below. FIG. 5 is a block diagram of a conventional audio switching power supply. In FIG. 5, reference numeral 1 denotes a digital power amplifier that outputs sequentially input digital signals after pulse power amplification and then outputs the converted analog signals. Reference numeral 2 denotes a clock signal for instructing the operation timing of the digital power amplifier 1. A clock generating unit for outputting 3, a triangular wave generating unit for outputting a triangular wave clock signal, 4 a AC-DC converting unit 5 to a digital power amplifying unit 1
To a predetermined threshold value and a triangular wave clock signal sequentially output from the triangular wave generating section 3, the level comparing section 6 compares the amplitude values with each other.
A pulse controller 5 for sequentially outputting an ON or OFF control signal based on a comparison signal output from a digital power converter after converting an AC voltage sequentially input from an AC power supply into a DC voltage according to a sequentially input control signal. An AC-DC converter that sequentially outputs to the amplifier 1, a power source 7 including a triangular wave generator 3, a level comparator 4, a pulse controller 6, and an AD-DC converter 5, and an output 8 of the digital power amplifier 1. It is a speaker connected to the end.

The operation of the switching power supply configured as above will be described below.

First, when digital input signals are sequentially input, the digital power amplifier 1 performs pulse modulation at a timing according to the clock signal sequentially output from the clock generator 2, and the resulting modulated signal is output by a switch element. After the power is amplified by turning it on and off, unnecessary frequency band components are removed by the LPF, and analog signals are sequentially output, and converted into acoustic signals by the speaker 8. Here, as the pulse modulation method, PWM for performing pulse width modulation, PDM for performing pulse density modulation, or the like is known. In any method, a 1-bit digital signal is used in terms of circuit scale and cost. Is preferred.

On the other hand, the power supply unit 7 has a DC voltage value sequentially output from the AC-DC conversion unit 5 by the level comparison unit 4,
The amplitudes of a predetermined threshold value and a clock signal sequentially output from the triangular wave generator 3 are compared, and the result is sequentially output as a comparison signal. Next, the pulse control unit 6 sequentially outputs a high-level or low-level pulse modulation signal for turning on or off the switch element as a control signal based on the sequentially output comparison signals. Furthermore, the AC-DC converter 5
Is electrically insulated from an AC power source having a voltage value of 100 V, 60 Hz and a DC voltage to be output sequentially, and turns on or off a switching element in accordance with a control signal sequentially output from the pulse control unit 6 for several tens. A DC voltage obtained by converting to a pulse voltage of several hundred Hz and then rectifying the pulse voltage is sequentially output to the digital power amplifier 1.

[0007]

However, in the above-mentioned audio switching power supply, fluctuations in the DC voltage value once output from the AC-DC converter 5 are fed back to the level comparator 4 to correct the DC voltage value. Poor response to sudden load changes such as signals,
As a result, the distortion rate of the power-amplified audio output signal decreases. As a countermeasure therefor, a method of increasing the capacity of the capacitor in the output stage of the AC-DC converter 5 to suppress the fluctuation of the DC voltage value is generally considered, but generally the capacity of the capacitor and the shape are in a proportional relationship, and the capacity is increased. Inevitably, the size of the power supply unit 7 cannot be reduced. Furthermore, the analog circuit for feeding back the once output DC voltage to correct the output voltage value and the digital circuit for converting into the pulse modulation signal are mixed, and the DC voltage output from the secondary side of the transformer is mixed. Since it is necessary to electrically insulate the system from the system on the primary side for inputting the returned DC voltage, the circuits cannot be integrated in the same IC or the like, so that the circuit cannot be integrated, and therefore the power supply unit 7 is downsized. There was a problem that could not be achieved.

The present invention solves the above-mentioned problems of the prior art, realizes miniaturization by integration of a power supply unit, improves the response of correction of a DC voltage value to be output, and deteriorates the sound quality of an audio signal. It is an object of the present invention to provide a switching power supply that can supply a DC voltage without causing it.

[0009]

In order to achieve this object, the present invention provides a digital AC-DC conversion unit of a power supply unit that supplies a DC voltage to a digital power amplification unit that outputs a digital input signal as an analog audio signal. It is controlled by the amplitude of the input signal, and after the digital input signals that are sequentially input are delayed by the delay unit once, the audio signal is taken out from the digital power amplification unit and synchronized with the timing of power amplification in the digital power amplification unit. Since the DC voltage value is increased or decreased in advance, it is possible to control the DC voltage value with respect to the change in the amplitude of the audio signal, that is, the load variation without a time delay, and the DC voltage is controlled by the digital signal processing based on the digital input signal. Therefore, the circuits around the control can be housed in the same IC, and the power supply unit can be made smaller by integration. Achieved.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention is a delay section for delaying sequentially input digital input signals such as audio signals according to a clock signal sequentially output from a clock generation section and then sequentially outputting the delayed signals. And a digital power amplifier that sequentially pulse-modulates the delayed digital signal and sequentially amplifies the resulting pulse-modulated signal,
An absolute value extraction unit that sequentially outputs inverted absolute value data in which bits are inverted after extracting the absolute value of the digital input signal, a clock that is sequentially output from the inverted absolute value data, a predetermined threshold value, and a clock generation unit. A level comparison unit that sequentially outputs a pulse modulation signal obtained by comparing the amplitude value of the signal as a comparison signal; and a pulse control unit that sequentially outputs a high or low level control signal at a timing according to the comparison signal. An AC-DC converter that insulates sequentially input AC power and converts the voltage value of the AC power to a DC voltage value based on the control signal, and then sequentially outputs the DC voltage to the digital power amplifier. The audio switching power supply is configured by, and the digital input signal that is sequentially input is delayed by the delay unit and then output by the digital power amplification unit. After being pulse-modulated Te, it is sequentially outputted as an audio signal is power-amplified by the switching element.

On the other hand, the digital input signals that are sequentially input are subjected to absolute value extraction by the absolute value extraction unit, and the results are compared in amplitude with a predetermined threshold, and compared with the clock signal that is sequentially output from the clock generation unit. The results obtained by performing the amplitude comparison are sequentially output as a comparison signal. next,
Based on the comparison signals sequentially output, the pulse control unit sequentially outputs a high or low level pulse modulation signal for turning on or off the switch element as a control signal. A
The C-DC converter rectifies the pulse-modulated signal obtained by power amplification by turning on or off the switch element according to the sequentially output control signal, converts the pulse-modulated signal into a DC voltage, and sequentially outputs it as an operating voltage of the digital power amplifier 1. To do. The control of the DC voltage value sequentially output from the AC-DC converter is performed by the amplitude of the digital input signals that are sequentially input, and the digital input signals that are sequentially input are temporarily delayed by the delay unit, and then the audio is output from the digital power amplification unit. This has the effect of increasing or decreasing the DC voltage value in advance in synchronization with the timing of extracting a signal and performing power amplification in the digital power amplification unit.

According to a fifth aspect of the present invention, a pulse modulator for sequentially pulse-modulating a digital signal such as audio that is sequentially input and sequentially outputting a resulting pulse-modulated signal, and a timing according to the pulse-modulated signal. And a driver unit that sequentially outputs high or low level drive signals,
A switch unit that sequentially turns on and off switch elements according to the drive signal to perform power amplification, and compares data corresponding to a cycle of the pulse modulation signal with a timing corresponding to the pulse modulation signal and a predetermined threshold value. A pulse period comparison unit that sequentially outputs the pulse-modulated signal obtained as a comparison signal, a driver unit that sequentially outputs a high or low level drive signal based on the comparison signal, and an AC power source that is sequentially input are isolated. An AC- that converts the voltage of the AC power supply into a DC voltage value based on the drive signal and then sequentially outputs the DC voltage to the digital power amplifier.
A switching power supply for audio configured by a DC converter, a digital input signal that is sequentially input is converted into a pulse modulated signal by a pulse modulator of a digital amplifier, and then a switch unit is turned on by a driver.
Alternatively, the result of being converted into a drive signal for turning off and power-amplified by the switch unit is sequentially output as an audio signal.

On the other hand, the pulse modulation signals sequentially output from the pulse modulation unit are compared with a threshold value by the pulse period comparison unit of the power supply unit, and then high or low level comparison signals are sequentially output, and then based on the comparison signals. The driver unit sequentially outputs drive signals for turning on and off the switch elements. The AC-DC converter turns on and off the switch element at a timing according to the drive signal, power-amplifies the pulse-modulated signal, and then rectifies the pulse-modulated signal to sequentially output a DC voltage to the switch section.

An operation of controlling the DC voltage value output from the AC-DC converter based on the pulse modulation signal sequentially output from the pulse modulator to increase or decrease the DC voltage value at the timing when the switch unit turns on and off the switch element. Have.

The embodiment of the present invention will be described below with reference to FIG.
This will be described with reference to FIG. (Embodiment 1) FIG. 1 is a block diagram of an audio switching power supply, and FIG. 2 is a diagram showing operation timings and operation waveforms of respective parts in FIG.

In FIG. 1, as characteristic components, 9 is a clock generator, 10 is a delay unit that delays sequentially input digital input signals, and 11 is an absolute value that extracts absolute value data of sequentially input digital input signals. Value extractor, 12
Is a predetermined threshold value, sequentially input absolute value data, and the amplitude value of the clock signal sequentially output from the clock generator 9 at a cycle sufficiently faster than the sampling frequency of the digital input signal. Are sequentially output as comparison signals. Others are the same as the conventional configuration, and the same reference numerals as those of the conventional example shown in FIG.

The operation of the audio switching power supply in the first embodiment configured as described above will be described below.

First, the delay unit 10 delays the digital input signals sequentially input at the timing according to the clock signals sequentially output from the clock generation unit 9 and then sequentially outputs them to the digital power amplification unit 1. The digital power amplification unit 1 pulse-modulates sequentially input digital input signals at a timing according to a clock signal sequentially output from the clock generation unit 9 at a cycle that is sufficiently faster than the sampling frequency of the digital input signal, and outputs high level signals. The pulse-modulated signal is power-amplified by turning on or off the switch element after converting into the low-level pulse-modulated signal. Furthermore, the digital power amplifier 1 sequentially outputs the result of removing unnecessary frequency band components from the pulse-modulated signal power-amplified by the LPF as an audio signal, and is converted into an acoustic signal by the speaker 8. Here, the digital input signal is, for example, 16
Pulse Code Modulation of bits
This is data (hereinafter referred to as PCM), and the digital power amplifier 1 limits the band by a digital filter or the like, and then 1
Converted to bit digitally modulated signal. As a method of this 1-bit conversion, Pulse Width Modul is used.
application (hereinafter referred to as PWM) or Pulse
Density Modulation (hereinafter PDM
Is called) and any method may be used, but in order to improve the audio characteristics such as the distortion rate, the PD is used.
The M method is preferable.

On the other hand, when the digital input signals are sequentially input, the absolute value extraction unit 11 holds, for example, 16 bits of digital data, converts the data into absolute value data, and then reverses the bit data to obtain the inverted absolute value data. Are sequentially output as. As a conversion method to an absolute value, when the digital data is negative, for example, all bits are inverted and then 1 is added. Next, when the inverted absolute value data is sequentially input, the level comparison unit 12 compares the value of the clock signal sequentially output from the clock generation unit 9 with the value of the inverted absolute value data, and as a result, when the amplitude of the clock signal is equal to or larger than the threshold value. And during the period when the inverted absolute value data exceeds the threshold value, or when the amplitude of the clock signal is greater than or equal to the threshold value and the inverted absolute value data is less than or equal to the threshold value, a high level signal is output while the clock signal exceeds the threshold value.
Otherwise, low-level signals are sequentially output as comparison signals. The waveform of the comparison signal is, for example, the waveform shown in FIG. 2C, and the absolute value data and the inverted absolute value data are the waveforms shown in FIGS. 2E and 2D, respectively, and the threshold value is as shown in FIG. The waveform is as shown in 2 (b). It is necessary to set the threshold value when the amplitude value of the inverted absolute value data (d) is large, that is, when the amplitude of the digital input signal is large. / 8 Output value. here,
The clock signal sequentially output from the clock generation unit 9 to the level comparison unit 12 is converted from a rectangular wave clock signal into a triangular wave clock signal by an integrating circuit such as an LPF of the clock generation unit 9 and is shown in FIG. The waveform is as shown. Further, the pulse control unit 6 sequentially outputs a control signal for turning on or off the switch elements based on the sequentially input comparison signals. This control signal is tens to hundreds of KHz
Then, the AC-DC converter 5 turns on or off the switch element at a timing according to the control signal to power-amplify the pulse-modulated signal and further rectify it with a diode to obtain a direct current. The voltage is sequentially output to the digital power amplifier 1. Incidentally, the constitution of the power supply used for the AC-DC converter 5 is only one for turning on or off the control signal, that is, the one-stone type using one switching element is used in the present embodiment, but the multi-stone type is also used. It does not particularly limit as long as it is a separately excited type in which a clock is externally applied.

Further, the digital power amplifier 1 and AC-
A MOS-FET is preferable as the switch element used in the DC converter 5 because it needs to perform switching at a relatively high speed.

As described above, according to the first embodiment of the present invention, the pulse modulation for determining the DC voltage value output from the AC-DC converter 5 based on the amplitude value of the sequentially input digital input signals. The signal is determined by the pulse control unit 6, the digital input signal is further delayed by the delay unit 10, and then the audio signal power-amplified by the digital power amplification unit 1 is output to output the digital power amplification unit 1.
Since the DC voltage value output from the AC-DC conversion unit 5 is corrected at the same timing as the increase in the amplitude of the digital input signal to be power-amplified by, the audio signal is taken out without increasing the distortion during the power amplification of the digital input signal. be able to.

Further, although the DC voltage has been conventionally fed back through insulation by a photocoupler or the like, transmission of digital input / output signals generally uses an optical fiber in order to suppress radiation noise, and is electrically insulated. Therefore, it is not necessary to insulate the input line to the absolute value extraction unit 11.

(Second Embodiment) FIG. 3 is a block diagram of a switching power supply, and FIG. 4 is a diagram showing operation timings and operation waveforms of respective parts.

In FIG. 3, 13 is a characteristic component.
Is a pulse modulation unit that sequentially converts digital input signals that are sequentially input into a pulse modulation signal, 14 is a driver unit that outputs a drive signal for turning on and off the switch element according to the pulse modulation signal, and 15 is a switch unit that turns on and off the switch element according to the drive signal A switch section for power-amplifying the pulse-modulated signal, 16 a clock generator, 17 a cycle of the pulse-modulated signal sequentially output from the pulse modulator 13 at a cycle sufficiently faster than the sampling frequency of the digital input signal, The pulse period comparison unit that sequentially outputs a high or low level comparison signal after comparing with a threshold value related to the determined period, 18 is a drive for turning on / off the switch element according to the comparison signal sequentially output from the pulse period comparison unit 17. It is a driver unit that outputs a signal. Others are the same as the conventional configuration, and the same reference numerals as those of the conventional example shown in FIG.

The operation of the audio switching power supply according to the second embodiment having the above configuration will be described below.

First, the pulse modulator 13 performs band modulation on the sequentially input digital input signals by a digital filter or the like, and then pulse-modulates them according to the clock signals sequentially output from the clock generator 16 to convert them into 1-bit pulse data. . Here, the digital input signal is, for example, 16-bit Pulse Code Modulation (hereinafter, referred to as PCM) data, and is a digital power amplifier unit 1.
After being converted into a pulse-modulated signal of 1-bit, it becomes 1-bit data.
dth Modulation (hereinafter referred to as PWM)
Or Pulse Density Modulati
on (hereinafter referred to as PDM) and the like are known, and any method may be used, but the PDM method is preferable in order to improve audio characteristics such as distortion. Next, when the 1-bit pulse-modulated signals are sequentially output, the driver unit 1
Reference numeral 8 converts into a drive signal for turning on / off the switch element according to the high or low level of the value of the pulse modulation signal, and sequentially outputs the drive signal. The switch unit 15 turns on or off the switch elements according to the drive signals sequentially sent to power-amplify the pulse-modulated signal and then outputs a signal obtained by removing unnecessary frequency band components by the LPF as an audio signal and outputs it by the speaker 8. It is converted into an acoustic signal.

Next, when the pulse modulation signals are sequentially output from the pulse modulation unit 13, the pulse period comparison unit 17 is operated as shown in FIG.
An absolute value signal as shown in FIG. 4C obtained as a result of integrating the pulse modulated signal as shown in FIG. 4A and then converting it into an absolute value, and a predetermined threshold value as shown in FIG. 4D. For example, when the absolute value signal is equal to or more than the threshold value and the polarity of the digital input signal is positive, the comparison signal synchronized with the high level or the low level of the pulse modulation signals sequentially input is compared with the polarity of the digital input signal. In the case of a negative value, the comparison signal in which the high and low levels of the pulse modulation signal are inverted is sequentially output.
The pulse-modulated signal shown in FIG. 4A is obtained by pulse-modulating the audio signal as shown in FIG. 4B. The longer the high-level pulse of the pulse-modulated signal, the larger the amplitude of the audio signal. , When the absolute value signal is less than or equal to the threshold value, the clock signal is sequentially output from the clock generator 16.
A comparison signal of timing and pulse width based on the clock signal as shown in (f) is sequentially output. Further, the polarity of the digital input signal, that is, the audio signal (b) can be detected by, for example, temporarily holding the result before conversion into the absolute value obtained by integrating (a) of the pulse modulation signal and making a determination by the zero crossing point. It is necessary to set the threshold value when the amplitude value of the absolute value (c) is large. As a guideline in this case, for example, the absolute value (c) at the time of outputting 1/8 of the maximum amplitude of the audio signal (b) is used. Are the values that match. The comparison signal sequentially output by repeating the above has a waveform as shown in FIG.
Here, the threshold value has the same function as that of comparing the pulse periods of the 1-bit pulse-modulated signals, and the comparison signal has a pulse period of the pulse-modulated signal that is longer than the threshold value.
That is, when the amplitude of the digital input signal is high, the high level and the period in which the comparison signal holds the high level and the low level period are synchronized with the high level and low level periods of the pulse modulation signal. Further, the pulse period comparison unit 1
When the high or low level comparison signal is sequentially output from 7, the drive unit 18 converts the comparison signal into a drive signal for turning on or off the switch element and sequentially outputs the drive signal.
The -DC converter 5 turns on or off the switch element according to the drive signal to power-amplify the pulse-modulated signal, rectify it by a diode or the like, convert it into a DC voltage, and sequentially output it to the switch section 15. In the second embodiment, the configuration of the power supply used for the AC-DC converter 5 is only for turning on or off the control signal, that is, the one-stone type using one switch element is used. There is no particular limitation as long as it is a separately excited type in which a clock signal is externally applied. Furthermore, the switch elements used in the switch section 15 and the AC-DC converter section 5 are preferably MOS-FETs because they need to perform switching at a relatively high speed. Further, although the PDM system is used for the 1-bit pulse modulation signal in the present embodiment, the operation of the power supply unit does not have any problem even if it is the PWM system.

As described above, according to the second embodiment of the present invention, the pulse modulator 1 receives the digital input signals sequentially input.
A pulse modulation signal for determining a DC voltage value output from the AC-DC conversion unit 5 based on the high or low level period of the pulse modulation signal, that is, the frequency, after being sequentially converted into 1-bit pulse modulation data by 3 Is determined by the pulse period comparison unit 17, and the audio signal power-amplified by the switch unit 15 is output to output the audio signal at the same timing as the increase in the amplitude of the digital input signal power-amplified by the switch unit 15 Since the switch element of the AC-DC converting unit 5 is turned on or off during the same period as the low level to correct the DC voltage value output from the AC-DC converting unit 5, distortion is generated during power amplification of the digital input signal. Audio signals can be taken out without increasing.

Further, the DC voltage has been fed back through the insulation of a photocoupler or the like in the past, but in the transmission of digital input / output signals, it is general to use an optical fiber in order to suppress radiated noise, and it is electrically insulated. Therefore, it is not necessary to insulate the input line to the absolute value extraction unit 11.

[0030]

As is apparent from the above description, the present invention is a pulse modulation signal for determining the DC voltage value output from the AC-DC converter based on the amplitude value of sequentially input digital input signals. Is determined by the pulse control unit,
Further, after delaying the digital input signal by the delay unit and outputting the audio signal power-amplified by the digital power amplification unit, A is generated at the same timing as the amplitude of the digital input signal power-amplified by the digital power amplification unit.
Since the DC voltage value output from the C-DC converter is corrected, the audio signal can be taken out without increasing distortion during power amplification of the digital input signal, and the DC voltage can be processed by digital signal processing based on the digital input signal. Since the value is corrected, integration such as IC is possible, and further, the DC voltage value is corrected in synchronization with the audio signal to reduce the capacity of the electrolytic capacitor used in the output stage of the AC-DC conversion unit to reduce the size. Since it is possible to reduce the size of the power supply unit, it is easy to reduce the size of the power supply unit.

Further, according to the present invention, after the digital input signals that are sequentially input are sequentially converted into 1-bit pulse modulation data by the pulse modulation unit, the AC is based on the high or low level period of the pulse modulation signal, that is, the frequency. A digital input signal that is power-amplified by the switch unit by determining the pulse-modulated signal for determining the DC voltage value output from the DC converter by the pulse-cycle comparison unit and outputting the audio signal whose power is amplified by the switch unit. The DC voltage value output from the AC-DC converter is corrected by turning on or off the switch element of the AC-DC converter at the same timing as the amplitude increase and during the same period as the high or low level of the pulse modulation signal. As a result, the audio signal can be taken out without increasing the distortion during power amplification of the digital input signal. In addition, since the DC voltage value is corrected by digital signal processing based on the digital input signal, integration such as IC is possible, and further, the AC-DC converter is used to correct the DC voltage value in synchronization with the audio signal. Since the capacity of the electrolytic capacitor used in the output stage can be reduced and downsized, the downsizing of the power supply unit is facilitated.

[Brief description of the drawings]

FIG. 1 is a block diagram of an audio switching power supply according to an embodiment of the present invention.

FIG. 2 is a diagram showing operation waveforms of respective parts of the block diagram of FIG.

FIG. 3 is a block diagram of an audio switching power supply according to another embodiment of the present invention.

FIG. 4 is a diagram showing operation waveforms of respective parts of the block diagram of FIG.

FIG. 5 is a block diagram showing a configuration of a conventional audio switching power supply.

[Explanation of symbols]

 1 Digital Power Amplifying Unit 2, 9, 16 Clock Generating Unit 3 Triangular Wave Generating Unit 4, 12 Level Comparing Unit 5 AC-DC Converting Unit 6 Pulse Control Unit 7 Power Supply Unit 10 Delaying Unit 11 Absolute Value Extracting Unit 13 Pulse Modulating Unit 14, 18 Driver section 15 Switch section 17 Pulse period comparison section

Claims (8)

[Claims] 1. A delay unit that delays digital input signals such as audio that are sequentially input according to a clock signal that is sequentially output from a clock generation unit, and then sequentially outputs the delayed digital signals, and pulse-modulates the delayed digital signals sequentially. A digital power amplification unit that sequentially amplifies the resulting pulse-modulated signal, an absolute value extraction unit that sequentially outputs inverted absolute value data obtained by extracting the absolute value of the digital input signal and then inverting the bits, and the inverted absolute value. A level comparison unit that sequentially outputs a pulse modulation signal obtained as a comparison signal by comparing data and a predetermined threshold value and the amplitude value of the clock signal that is sequentially output from the clock generation unit, and a timing according to the comparison signal. Pulse control unit that sequentially outputs a high or low level control signal and an AC power source that is sequentially input An audio switching power supply comprising: an AC-DC converter that converts a voltage value of a power supply into a DC voltage value based on the control signal and then sequentially outputs the DC voltage to the digital power amplifier. 2. The audio switching power supply according to claim 1, wherein the delay unit, the digital power amplification unit, and the level comparator operate at timings based on the same clock. 3. The audio switching power supply according to claim 1, wherein the clock signals sequentially output from the clock generator are output at a cycle faster than the sampling frequency of the digital input signal. 4. The audio switching power supply according to claim 2, wherein the clock signals sequentially output from the clock generator are output at a cycle faster than the sampling frequency of the digital input signal. 5. A pulse modulator that sequentially pulse-modulates digital signals such as audio that are sequentially input and sequentially outputs the resulting pulse-modulated signals, and a high- or low-level signal at a timing according to the pulse-modulated signals. A driver unit that sequentially outputs a drive signal, a switch unit that sequentially turns on and off switch elements according to the drive signal to perform power amplification, and data that corresponds to the period of the pulse modulation signal at a timing according to the pulse modulation signal. A pulse period comparison unit that sequentially outputs a pulse modulation signal obtained by performing comparison with a predetermined threshold value as a comparison signal, and a driver unit that sequentially outputs a high or low level drive signal based on the comparison signal. Insulating the sequentially input AC power supply and converting the voltage of the AC power supply into a DC voltage value based on the drive signal And an AC-DC conversion unit that sequentially outputs the DC voltage to the digital power amplification unit. 6. The audio switching power supply according to claim 5, wherein the pulse modulator and the pulse period comparator operate based on the same clock. 7. The audio switching power supply according to claim 5, wherein the pulse modulation signal output from the pulse modulation unit is output at a cycle faster than the sampling frequency of the digital input signal. 8. The audio switching power supply according to claim 6, wherein the pulse modulation signal output from the pulse modulator is output at a cycle faster than the sampling frequency of the digital input signal.