KR20100136886A - Power amplifier method and device for audio amplifier - Google Patents

Abstract

PURPOSE: In the power control method of the audio amplifier and apparatus thereof is the audio play process, by making low the power provided to the power switching circuit part the effectiveness is improved. CONSTITUTION: The level of the input audio signal is detected(510). The fixed audio volume level is received(520). The audio output level is presumed correlation between the inputted audio sound level modifier and the audio signal level as the natural disposition(530, 540). It copes with the presumed audio output level as described above and the power value provided to the power switching circuit part is in advance instituted(550).

Description

Apparatus and method for controlling power of audio amplifier

TECHNICAL FIELD The present invention relates to a digital audio amplifier system, and more particularly, to an audio amplifier power supply control apparatus and method for variably supplying power supplied to a power switching circuit portion of an audio amplifier.

Digital audio systems typically use an audio power amplifier.

Class A, B, AB and D classes are used as audio power amplifiers. Among them, class D audio amplifier can reduce amplification efficiency degradation caused by class A audio amplifier, class B audio amplifier and class AB audio amplifier.

In this case, the class D audio amplifier converts an audio signal into a pulse width modulated (PWM) signal and switches the audio signal. In addition, Class D audio amplifiers are classified into an open loop and a closed loop.

Class D audio amplifiers typically drive power switching circuits with high fixed power values corresponding to the maximum audio output. These high-powered, Class-D audio amplifiers cause the device to generate heat and cause noise in the surrounding electronics.

Therefore, a technique is needed to properly control the power supplied to the class D audio amplifier.

An object of the present invention is to provide an audio amplifier power control apparatus and method for variably controlling the power provided to an audio amplifier according to the level of an input audio signal.

 In order to solve the above problems, according to an embodiment of the present invention, in the power supply control method of the audio amplifier,

Estimating an audio output level based on a correlation between an input audio signal level and an audio output change factor;

Presetting power supplied to a power switching circuit in response to the estimated audio output level;

And amplifying an audio signal by variably controlling power supplied to the power switching circuit unit according to the set power.

 In order to solve the above other problem, according to an embodiment of the present invention, in the power supply control apparatus for an audio amplifier,

A digital signal processor for estimating an output level of the audio signal based on a correlation between an input audio signal level and an output change factor of the audio signal, and generating a power control value corresponding to the output level of the estimated audio signal;

A variable power supply for supplying variable power according to a power control value generated by the digital signal processor;

And a power switching circuit unit configured to amplify switching power of the pulse width modulated signal according to the variable power supplied from the variable power supply.

The digital signal processor according to an embodiment

A signal level detector for detecting audio signal levels of a plurality of channels;

An output change factor analyzer for analyzing an audio level change factor related to the audio output using the volume level value and the gain value of the audio amplifier system;

An audio output predictor for predicting an audio output level based on a correlation between the audio signal level detected by the signal level detector and an output level change factor analyzed by an output change factor analyzer;

The apparatus may include a power control value generator configured to set a power control value corresponding to the audio output level estimated by the audio output predictor.

Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1A is a block diagram of a class D audio amplifier system in a closed loop according to the present invention.

The closed loop class D audio amplifier system simultaneously changes the duty of the PWM signal and the level of the PWM signal when the power supply is changed. Therefore, the closed loop class D audio amplifier system does not affect the audio output even if the power supply is varied.

The closed loop class D audio amplifier system of FIG. 1A includes a volume change unit 110a, a microcontroller 120a, a digital signal processor 130a, a pulse width modulator 140a, a variable power supply unit 150a, and power. The switching circuit unit 160a, the feedback unit 170a, the LPF unit (Low Pass Filter) 180a, and the speaker unit 190a.

First, a plurality of channels of analog or digital audio signals are input to an audio amplifier.

The volume change unit 110a is attached to the remote controller or the panel to generate volume key information selected by the user.

When the microcontroller 120a receives the volume key information selected by the user, the microcontroller 120a converts the volume key information into a corresponding volume level value. The microcontroller 120a also loads gain values inside the audio amplifier that affect the audio output. For example, a gain value in the audio amplifier includes a gain value of the digital signal processor 130a and a gain value of the pulse width modulator 140a. The microcontroller 120a presets a gain value of the digital signal processor 130a and a gain value of the pulse width modulator 140a according to the number of channels of the audio signal, and sets the gain value when the reproduction operation is performed. 130a and the pulse width modulator 140a.

The digital signal processor 130a converts the audio signal input according to the control signal of the microcontroller 120a into pulse code modulation (PCM) audio data.

The digital signal processor 130a analyzes an audio level change factor that affects the audio output, such as a volume level value input from the microcontroller 120a and a signal gain value of the audio amplifier system, and inputs the audio signal level and the audio. The audio output level is estimated based on the correlation between the level change factors, and the power supplied to the power switching circuit 160a is set in advance corresponding to the estimated audio output level. The digital signal processor 130a outputs a power control signal corresponding to the estimated audio output level to the variable power supply 150a.

In this case, the digital signal processor 130a may process the power control signal transmitted to the variable power supply unit 150a in a stepwise manner and a linear form.

That is, the digital signal processor 130a transmits a power control signal matching the reference value of each step to the variable power supply unit 150a in the case of the step type, and is proportional to the audio signal level output without the reference value for each step in the case of the linear type. The linear value is transferred to the variable power supply unit 150a.

In addition, the digital signal processor 130a adjusts the tracking time of the power control signal for the output audio signal using a buffer to prevent sound distortion.

The pulse width modulator 140a compares the carrier signal level with the level of the PCM signal output from the digital signal processor 130a to generate a PWM signal having a low voltage.

The variable power supply unit 150a supplies a variable voltage corresponding to the power control value input from the digital signal processor 130a to the power switching circuit unit 160a. In one embodiment, the variable power supply unit 150a may be implemented using a resistor ratio.

The power switching circuit 160a amplifies the low voltage PWM signal generated by the pulse width modulator 140a into a PWM signal having a large output according to the variable voltage supplied from the variable power supply 150a. In one embodiment, the power switching circuit 160a amplifies a small output PWM signal of about 3.3V into a large output PWM signal of about 5V to 40V.

The feedback unit 170a feeds back the PWM signal output from the power switching circuit unit 160a to the power switching circuit unit 160a to correct an error between the input and output signals of the power switching circuit unit 160a.

The LPF unit 180a low-pass filters the PWM signal power amplified by the power switching circuit unit 160a to remove noise and restore the original audio signal.

The speaker unit 190a reproduces the audio signal extracted from the LPF unit 180a as a sound.

FIG. 1B is an overall block diagram of an open / close loop type D audio amplifier system according to the present invention.

The class D audio amplifier system of the open / close loop method varies the level of the PWM signal while maintaining the duty of the PWM signal when the power supply is changed. In this case, the audio output is changed when the power supply is changed in the class D audio amplifier system of the open / close loop method. Therefore, in order to maintain the magnitude of the output signal from the variable power supply, the class D audio amplifier system of the open / close loop method should adjust the reference volume by the changed power value.

In the closed loop class D audio amplifier system of FIG. 1A, an open loop class D audio amplifier system may be implemented using blocks other than the feedback unit 170a.

Volume switching unit 110b, microcontroller 120b, digital signal processing unit 130b, pulse width modulation unit 140b, variable power supply unit 150b, power switching of the class D audio amplifier system of the opening and closing loop method of FIG. The circuit unit 160b, the LPF unit (Low Pass Filter) 180b, and the speaker unit 190b are provided.

Volume change unit 110b, microcontroller 120b, pulse width modulator 140b, variable power supply unit 150b, power switching circuit unit 160b, low pass filter 180b, speaker of FIG. The unit 190b includes the volume change unit 110a, the microcontroller 120a, the pulse width modulator 140a, the variable power supply unit 150a, the power switching circuit unit 160a, the LPF unit 180a, and the speaker of FIG. 1A. Since the function is the same as that of the unit 190a, the description of the operation is omitted.

The digital signal processor 130b estimates the audio output level based on the correlation between the input audio signal level and the audio level change factor, and presets the power supplied to the power switching circuit unit 160b in response to the estimated audio output level. And outputs a power control signal corresponding to the estimated audio output level to the variable power supply 150b. At this time, the digital signal processor 130b links the reference volume (digital gain) to the power value when the power is changed by the estimated audio output level. That is, the digital signal processor 130b changes the supply power value according to the estimated audio output level, and adjusts the reference volume value (digital gain) by the changed supply power value to maintain the magnitude of the output signal by the changed supply power. do.

2 is a detailed view of the digital signal processing units 130a and 130b of FIGS. 1A and 1B.

The digital signal processor of FIG. 2 includes an audio signal processor 210, an audio signal level detector 220, an output change factor analyzer 230, an audio output predictor 250, and a power control value generator 260. .

The audio signal processor 210 converts audio signals input through a plurality of channels into Pulse Code Modulation (PCM) audio data, and performs signal processing such as an equalizer and an enhancement.

The audio signal level detector 220 detects peak-peak values of audio signal levels of a plurality of channels signaled by the audio signal processor 210.

The output change factor analyzer 230 analyzes an audio level change factor that affects the audio output, such as a volume level value obtained from the microcontroller 120 and a gain value inside the audio amplifier.

The audio output predictor 250 selects the largest level value among the audio signal levels of the plurality of channels detected by the audio signal level detector 220, and analyzes the selected audio signal level and the output change factor analyzer 230. The audio output level is estimated based on the correlation between the audio level change factors. For example, the predicted audio output level is the product of the input audio signal level, the audio volume level, and the gain value inside the audio amplifier.

The power control value generator 260 presets a power control value corresponding to the audio output level estimated by the audio output predictor 250, and outputs the power control value to the variable power supply 150. At this time, the power control value generator 260 generates different power control values according to the open / close loop method and the closed loop method.

3 is a circuit diagram of the power switching circuits 160a and 160b and the LPF units 180a and 180b of FIGS. 1A and 1B.

The power switching circuit unit 160 includes a PMOS transistor P1 and an NMOS transistor N1. The PWM signal is divided into a first PWM signal Q1 and a second PWM signal Q2 having the same phase. The PMOS transistor P1 is switched according to the first PWM signal Q1, and the actual power supply voltage VCC2 is applied to the source. The NMOS transistor N1 is also switched in accordance with the second PWM signal Q2, and its drain is connected to the drain of the PMOS transistor P1 and its source is connected to the actual ground voltage VSS2. Here, VCC1 and VSS1 are ideal voltages applied from the voltage source, and VCC2 and VSS2 are voltages dropped by a predetermined value by the resistors R1 and R2 in the conductive line 50 connecting the voltage source and the power switching circuit unit 160. The actual voltage applied to the power switching circuit unit 160. In addition, R1 and R2 are resistances generated in the conductive line connecting between the voltage source and the power switching circuit unit 160. In another embodiment, the power switching circuit unit 160 may be configured as an NN type as well as a PN type.

4 is a first embodiment of a power supply control method of a closed loop class D audio amplifier according to the present invention.

First, audio signal levels input to a plurality of channels are detected (step 410).

Next, the audio volume level set by the user is acquired from the remote controller or the like (step 420).

Next, an audio level change factor in the audio amplifier affecting the audio output is analyzed (step 430). In this case, the audio level change factor includes an audio volume level and an internal gain value of the audio amplifier.

Next, the largest level value is selected among the audio signal levels of the plurality of channels, and the audio output level is predicted based on the correlation between the selected audio signal level and the audio level change factor (step 440).

In this case, the predicted audio output level may be determined as in Equation 1.

Expected audio output level = input audio signal level x volume gain x gain value inside the audio amplifier

Subsequently, the power supplied to the power switching unit 160 is preset in correspondence with the estimated audio output level (steps 450 to 476).

The power setting process (steps 450 to 476) will be described in more detail. The power is divided into a plurality of ranges, for example, "LOW", "Middle", and "High" by the user.

First, it is checked whether the predicted audio output level is within a predetermined power range "LOW" (step 450).

Subsequently, if the predicted audio output level is within the power range "LOW", the power supply of the power switching unit 160 is set to the "LOW" amplifier power value (step 472).

Then, if the predicted audio output level is not within the power range "LOW", it is again checked whether the predicted audio output level is within the predetermined power range "Middle" (step 460).

Subsequently, if the predicted audio output level is within the predetermined power range "Middle", the supply power is set to the "Middle" amplifier power value (step 476).

Then, if the predicted audio output level is not within the predetermined "Middle", the power supply is set to the "High" amplifier power value (step 474).

The amplifier power value finally set is variably supplied to the power switching circuit 160 (step 480).

According to the present invention, the power value supplied to the power switching circuit unit 160 is preset in the digital signal processing step by using the correlation between the level of the input audio signal and the gain value inside the audio amplifier, and the power value is output to the audio signal. It varies in stages according to the level. Referring to FIG. 7A, the power supply 710 may be followed step by step according to the level of the audio signal 720 output. For example, if the level of the output audio signal 720 is 0.5V, the supply power supply 710 is 0.7V, and if the level of the output audio signal 720 is 2V, the supply power supply 710 is 2.3V.

5 is a second embodiment of a power supply control method of a closed loop class D audio amplifier according to the present invention.

First, steps 510 to 540 are the same as steps 410 to 440 of FIG. 4, and thus description thereof is omitted.

In operation 550, a power control value corresponding to the predicted audio output level is determined.

Subsequently, the linear variable power supply close to the audio output level is supplied to the power switching circuit unit 160a according to the power control value (step 560).

As a result, the present invention determines a power supply value that varies linearly according to the audio output level predicted in the previous block of the power switching circuit unit 160a. Referring to FIG. 7B, the power supply 730 linearly follows the level of the output audio signal 740. For example, the supply power values corresponding to the peak values of the output audio level are generated in advance.

6 is an embodiment of a power supply control method of an open / close loop type D audio amplifier according to the present invention.

First, processes 610 to 640 are the same as processes 410 to 440 of FIG. 4, and thus description thereof is omitted.

Then, it is checked whether the predicted audio output level is the currently set power range (operation 650). At this time, if the predicted audio output level is the currently set power range, the currently set power value is supplied to the power switching circuit unit 160b.

Subsequently, if the predicted audio output level is equal to or greater than the currently set power range, the supply power value is set higher than the currently set power value (step 662). In this case, increasing the power supply value changes the level of the final output signal, thereby reducing the reference volume value by the increased supply power value (step 664). For example, if the maximum power supply is 30V, the current power supply is 20V, and the predicted audio output level is 28V, the power supply is set to 30V, and the audio volume value is decreased by 10V higher than the current power supply 20V.

Subsequently, if the predicted audio output level is less than or equal to the currently set power range, the supply power value is lower than the currently set power value (step 672). In this case, since the level of the final output signal is changed by lowering the power supply value, the reference volume value is increased by the power supply value (step 674). For example, if the maximum power supply is 30V, the current power supply is 20V, and the predicted audio output level is 7V, the power supply is set to 10V, and the audio volume value is increased by 10V lower than the current power supply 20V.

As a result, in the class D audio amplifier of the open / close loop method, the reference volume value is linked to the power value changed according to the estimated audio output level, thereby maintaining the magnitude of the output signal by the variable power supply.

8A and 8B are waveform diagrams of a power control signal followed by an audio output in the digital signal processing units 130a and 130b according to the present invention.

Referring to FIG. 8A, when the power supply 808 follows the output audio signal 802, sound quality distortion occurs due to a phenomenon in which the audio signal is clipped 810 by the power supply in the power up region 803.

Therefore, the digital signal processing units 130a and 130b may adjust the tracking time of the power control signal for the audio output level by using buffering. That is, as illustrated in FIG. 8B, the sound quality distortion phenomenon is generated by raising (823) and maintaining (824) the power supply 828 before the output audio signal 822 by using the buffering time in the digital domain. prevent.

9A and 9B show a comparison of power control in the prior art with the present invention in an audio amplifier.

In the prior art audio amplifier, as shown in FIG. 9A, since a predetermined power level 910 is constantly supplied regardless of the input audio level, the audio amplifier is actually compared with the level 920 of the audio signal actually amplified and output through the power amplifier. There is a problem that a relatively large amount of power consumption is unnecessary. In FIG. 9A, the energy loss region 930 between the supply power level and the output audio signal is indicated by a dotted line.

On the other hand, the audio amplifier of the present invention predicts the audio output in advance from the digital signal processing units 130a and 130b using the correlation between the level of the input audio signal and the gain value of the audio system and supplies it to the power switching circuit units 160a and 160b. Variable power supply. Accordingly, the present invention can vary the supply power level 940 according to the dynamically changing output audio signal 950 as shown in FIG. 9B. Therefore, the audio amplifier of the present invention can lower the power supplied to the power switching circuit during audio reproduction at a low output generally used while maintaining the maximum output of the audio, thereby improving efficiency. In addition, the audio amplifier of the present invention can lower power consumption and reduce heat generation, thereby reducing the size of the heat sink and the noise factor.

The present invention can also be embodied as computer readable codes on a computer readable recording medium. The computer-readable recording medium includes all kinds of recording devices in which data that can be read by a computer system is stored. Examples of computer-readable recording media include ROM, RAM, CD-ROM, magnetic tape, hard disk, floppy disk, flash memory, optical data storage, and the like. The computer readable recording medium may also be distributed over a networked computer system and stored and executed as computer readable code in a distributed manner.

The above description is only one embodiment of the present invention, and those skilled in the art to which the present invention pertains may implement it in a modified form without departing from the essential characteristics of the present invention. Therefore, the scope of the present invention should be construed to include various embodiments which are not limited to the above-described examples but are within the scope equivalent to those described in the claims.

Figure 1a is a block diagram of a closed loop class D audio amplifier system according to the present invention.

1B is an overall block diagram of a class D audio amplifier system of an open / close loop type according to the present invention.

FIG. 2 is a detailed view of the digital signal processor of FIGS. 1A and 1B.

3 is a circuit diagram illustrating an exemplary embodiment of the power switching circuit unit and the LPF unit of FIGS. 1A and 1B.

4 is a first embodiment of a power supply control method of a closed loop class D audio amplifier according to the present invention.

5 is a second embodiment of a power supply control method of a closed loop class D audio amplifier according to the present invention.

6 is an embodiment of a power supply control method of an open / close loop type D audio amplifier according to the present invention.

7A and 7B show the relationship between the audio signal output and the power supply according to the present invention.

8A and 8B are waveform diagrams of a power control signal following an audio output in order to prevent audio output distortion in a digital signal processor according to the present invention.

9A and 9B show a comparison of power control in the prior art with the present invention in a power amplifier.

Claims (16)

In the power supply control method of the audio amplifier, Estimating an audio output level based on a correlation between an input audio signal level and an audio level change factor; Presetting a power value supplied to a power switching circuit unit corresponding to the estimated audio output level; And amplifying an audio output signal by variably controlling power supplied to the power switching circuit unit according to the set power value. The method of claim 1, wherein the audio output change factor is And a volume level set by a user and an internal gain value of the audio amplifier. The method of claim 2, wherein the internal gain of the audio amplifier is a gain value of the digital signal processor and a gain value of the pulse width modulator. The method of claim 1, wherein the predicted audio output level is a value obtained by multiplying an input audio signal level by a set audio volume level and a gain value in the audio amplifier. The method of claim 1, wherein the input audio signal level is A method for controlling power supply of an audio amplifier, characterized in that the largest signal level among the audio levels detected in a plurality of channels. The method of claim 1, wherein the power value supplied to the power switching circuit is set in stages corresponding to the estimated audio output level. The method of claim 1, wherein the power value supplied to the power switching circuit is linearly set in correspondence to the estimated audio output level. The method of claim 1, wherein the tracking time of the power control signal with respect to the audio output level is adjusted. The method of claim 1, wherein the setting of the power value supplied to the power switching circuit part comprises: And linking a reference volume value to a power value changed according to the estimated audio output level. The method of claim 9, wherein the linking of the reference volume value to the power value comprises: If the estimated audio output level is greater than or equal to the currently set power range, the supply power value is set higher than the currently set power value and the reference volume value is decreased by the increased supply power value, and the estimated audio output level is the power currently set. If within the range, the power supply value is lower than the currently set power value, and the reference volume value is increased by the lowered power supply value. In the power supply control device of the audio amplifier, A digital signal processor which estimates an output level of the audio signal based on a correlation between the input audio signal level and the audio level change factor, and presets a power supply control value corresponding to the output level of the estimated audio signal; A variable power supply for supplying variable power according to a preset power control value in the digital signal processor; And a power switching circuit for amplifying switching power of the pulse width modulated signal according to the variable power supplied from the variable power supply. The method of claim 11, wherein the digital signal processing unit A signal level detector for detecting audio signal levels of a plurality of channels; An output change factor analyzer for analyzing an audio level change factor related to the audio output using the volume level value and the gain value of the audio amplifier system; An audio output predictor for predicting an audio output level based on a correlation between the audio signal level detected by the signal level detector and the audio level change factor analyzed by an output change factor analyzer; And a power control value generator for setting a power control value corresponding to the audio output level estimated by the audio output predicting unit. The apparatus of claim 11, wherein the digital signal processor further comprises a buffer for adjusting a tracking time of a power control signal with respect to an audio output level. 12. The apparatus of claim 11, further comprising a microcontroller for providing an audio level change factor corresponding to a user audio volume level and a gain of an audio amplifier system in the digital signal processor. 12. The apparatus of claim 11, wherein the power control value generator generates different power control values according to the open / close loop method and the closed loop method. A computer-readable recording medium having recorded thereon a program for executing the method of claim 1.

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