JP2010016440A - Audio amplification device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem that the conventional power amplification device achieves reduction in power consumption by changing power supply voltage according to a signal level to be amplified, the circuit is complicated and cost increases, moreover, a voice delays, and a synchronization shift arises when it is used in a home theater system. <P>SOLUTION: The reduction in power consumption and avoidance of the voice delay can be achieved by composing the device with: a volume which adjusts a sound volume of an input signal of a power amplification circuit for a low frequency band and a power amplification device for a middle-high frequency band; a volume control circuit which outputs a volume position detection signal while controlling the volume; a signal level detection circuit which detects an amplitude of an output signal of the power amplification circuit for the low frequency band; a voltage variable power supply circuit which supplies power to the power amplification circuit of the low band frequency and the power amplification device for the middle-high frequency band; a power supply voltage control circuit which controls voltage of the voltage variable power supply circuit based on the detection result of the signal level detection circuit and the volume position detection signal output from the volume control circuit. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a power amplifying apparatus that reduces power consumption by changing a power supply voltage according to a signal level.

  2. Description of the Related Art Conventionally, a power amplifying apparatus that reduces power consumption by changing a power supply voltage according to a signal level to be amplified detects a level of a signal input to an amplifier circuit and controls the power supply voltage accordingly. A configuration is known in which a signal is detected and input to a power amplifier circuit through a delay circuit (for example, Patent Document 1). There is also a method of detecting the position of the volume and controlling the power supply voltage based on the detected volume position (for example, Patent Document 2).

  FIG. 9 shows the configuration of the power amplifying apparatus according to the first conventional example. An audio signal is input to the input 1, and this audio signal is input to the signal level detection circuit 7. The detection signal output from the signal level detection circuit 7 is sent to the power supply voltage control circuit 8. The power supply voltage control circuit 8 increases the output voltage of the voltage variable power supply circuit 6 when the level of the audio signal is high, and the level of the audio signal. Is low, the output voltage of the voltage variable power supply circuit 6 is controlled to be low, and the power loss of the power amplifying circuit 3 is reduced as much as possible. On the other hand, the audio signal input to the input 1 is converted into a digital signal by the A / D converter 12 and input to the delay circuit 13, and after being delayed for a predetermined time, is converted back to an analog signal by the D / A converter 14 and is returned to the power amplifier circuit 3. Is output to the speaker output 9. FIG. 10 shows the relationship between the voltage variable power supply circuit 6 and the output signal of the power amplifier circuit 3. During the period indicated by A where the signal is below a certain level, the output voltage of the voltage variable power supply circuit 6 is low and power consumption is suppressed, and during the period indicated by B when the signal level is above a certain level, the voltage of the voltage variable power supply circuit 6 increases. A large-amplitude output can be output. FIG. 10A shows a waveform when the delay time of the delay circuit 13 is zero, and FIG. 10B shows a waveform when a constant delay time is set. When the level of the audio signal suddenly increases when the delay time is zero, the output voltage of the voltage variable power supply circuit 6 cannot be changed suddenly, which is shown in the case of the delay time zero in FIG. Thus, distortion occurs in the signal waveform. In order to prevent the distortion of the signal waveform, a waveform having a certain delay time after the detection of the signal level and delaying the change in the signal level is the waveform with the delay time in FIG. In addition, the distortion of the signal waveform can be prevented from occurring by setting the delay time to an appropriate value.

FIG. 11 shows a configuration of a power amplifying device according to a second conventional example. The audio signal input to the input 1 is input to the power amplification circuit 3 after the amplitude is changed by the volume 2 controlled by the volume control circuit 5. A volume setting value signal set by the volume control circuit 5 is input to the power supply voltage control circuit 8, and the power supply voltage control circuit 8 changes the output voltage of the voltage variable power supply circuit 6 in accordance with this value. In FIG. 11, the maximum level of the signal input to the input 1 is generally determined, and the maximum level of the output signal level of the power amplifier circuit 3 is also determined by the volume position. FIG. 12 shows an example of the relationship between the maximum output signal level and the volume position. In the example shown in FIG. 12, the output of the voltage variable power supply circuit 6 changes in two stages of voltage A and voltage B. This indicates that the signal is distorted when a signal of the maximum output level is output at a volume position where the amplitude of the maximum output signal exceeds the voltage A at the volume position 38. In order to prevent this distortion, when a signal indicating that the volume position is 38 or more is sent from the volume control circuit 5 to the power supply voltage control circuit 8, the output of the voltage variable power supply circuit 6 is controlled to be raised to the voltage B. As a result, when the volume position is assumed to be low and the signal level is low, the power supply voltage is lowered to reduce power consumption. When the volume position is assumed to be high and the signal level is high, the power supply voltage is raised to prevent signal distortion. be able to.
Japanese Patent Laid-Open No. 2-72016 JP-A-8-162854

  However, the power amplifying apparatus according to the first conventional example has a problem that the circuit is complicated and expensive, and in the case of a home theater system, there is a delay in the sound, resulting in a synchronization error with the video. Further, in the power amplifying apparatus according to the second conventional example, in the case of an actual home theater system, the frequency characteristics of channels other than the subwoofer channel and the subwoofer channel are as shown in FIG. When the maximum signal level other than the subwoofer channel is set to a as shown in FIG. 12, the maximum signal level of the subwoofer channel is b and the power supply voltage needs to be controlled to the voltage B at the volume position 18. Because the value of the volume position where the power supply voltage should be controlled to a high voltage decreases, the power supply voltage is always controlled to a high voltage at the volume position that is normally used, and the effect of reducing power consumption is no longer exhibited. It had the problem of end. Also, in a system that does not have a subwoofer channel, in general, in order to compensate for the characteristics of a speaker, a design in which the low-range amplifier gain is increased with respect to the middle and high ranges is widely performed. Also in this case, when the power supply voltage control is performed according to the volume position, the maximum signal level of FIG. 12 is obtained in the low frequency region C of FIG. 13 when the middle / high frequency region D of FIG. As in the case of having a subwoofer channel, a state occurs in which the power supply voltage must be controlled to be high at the volume position that is normally used.

  An object of the present invention is to provide a power amplifying device that can effectively reduce power consumption with a small increase in cost and does not cause the adverse effect of synchronization between video and audio.

  In order to solve the above-described conventional problems, the invention according to claim 1 of the present invention includes a low frequency power amplifier circuit that amplifies only a low frequency of an audio signal, a mid frequency other than a low frequency, and a high frequency. A power amplifier circuit for middle and high frequencies, a volume for adjusting a volume of an input signal of the power amplifier circuit for low frequency and the power amplifier circuit for middle and high frequencies, and a volume adjusted by the volume. A volume control circuit that controls and outputs a volume position detection signal, a signal level detection circuit that detects an amplitude of an output signal of the low-frequency power amplifier circuit, the low-frequency power amplifier circuit, and the mid-high frequency power Based on a voltage variable power supply circuit that supplies power to the amplifier circuit, a detection result of the signal level detection circuit, and a volume position detection signal output from the volume control circuit, the power supply of the voltage variable power supply circuit. The power supply voltage control circuit controls the power supply voltage control circuit so that the amplitude of the maximum output signal does not exceed the power supply voltage depending on the position of the volume for the middle / high frequency signal. Controls the output of the circuit, prevents distortion of the output signal, and for subwoofer channels with higher signal levels, detects the signal level and sets the power supply voltage when the signal level exceeds a certain value. It operates to set it to a high value and otherwise to a low value. In the case of a low-frequency signal, the signal level rise speed is slow, so that distortion occurs at the rise of the signal as shown in FIG. 7 without providing a delay circuit as in the power amplifier according to the first conventional example. Has the effect of not occurring.

  According to a second aspect of the present invention, there is provided a power amplifying circuit for amplifying an audio signal, a volume for adjusting a volume of an input signal of the power amplifying circuit, a volume adjusted by the volume, and a volume position detection. A volume control circuit that outputs a signal; a signal level detection circuit that detects an amplitude of an output signal of the power amplification circuit; a voltage variable power supply circuit that supplies power to the power amplification circuit; and a detection result of the signal level detection circuit And a power supply voltage control circuit for controlling the voltage of the voltage variable power supply circuit based on the volume position detection signal output from the volume control circuit, even when there is no low frequency power amplifier circuit, For medium and high frequency signals, the voltage variable power supply circuit prevents the maximum output signal amplitude from exceeding the power supply voltage depending on the position of the volume. Controls output, prevents distortion of output signal, detects signal level for low frequency components with high signal level, and raises power supply voltage when signal level exceeds a certain value It works to set it to a low value otherwise. In the case of a low-frequency signal, since the rising speed of the signal level is slow, distortion occurs at the rising edge of the signal as shown in FIG. 10 without providing a delay circuit as in the power amplifier according to the first conventional example. Has the effect of not occurring.

  The invention according to claim 3 of the present invention is an amplitude suppression circuit that is provided after the output of the volume with respect to the audio amplifying device of claim 1 of the present invention and outputs the output to the low-frequency power amplifier circuit. The low-frequency signal distortion is less likely to occur, the signal level detection value for setting the output voltage of the voltage variable power supply circuit can be set high, and the power supply voltage is low. The number of states can be increased, and the effect of reducing power can be further increased.

  According to a fourth aspect of the present invention, the audio amplifying apparatus according to the second aspect of the present invention further includes an amplitude suppression circuit provided after the output of the volume and outputting the output to the power amplifier circuit. Thus, the same effect as that of the third aspect of the present invention can be obtained.

  The audio amplifying apparatus of the present invention performs power supply voltage control by volume position detection for a middle / high frequency signal having a fast change speed at the rise of the signal level, and the change speed at the rise of the signal level is slow, but the average level Since the power supply voltage is controlled by detecting the signal level for high low frequencies, distortion can be prevented without the addition of a delay circuit, resulting in a small increase in cost and synchronization with the video. There is an advantage that power reduction can be measured effectively without causing it to occur.

    Hereinafter, the best mode for carrying out the power amplifying device of the present invention will be described in detail with reference to FIGS.

(Embodiment 1)
FIG. 1 is a block diagram of an audio amplifying apparatus according to a first embodiment of the present invention. In FIG. 1, 101 is an input, 102 is a volume, 103 is a power amplifier circuit for a mid / high frequency signal, and 104 is a low frequency. Power amplifier circuit for signal, 105 is a volume control circuit, 106 is a voltage variable power supply circuit, 107 is a signal level detection circuit, 108 is a power supply voltage control circuit, 109 is a mid / high range speaker output, 110 is a low range speaker output is doing.

  The operation of the audio amplifying apparatus configured as described above will be described below.

  First, the maximum value of the signal level of the signal input to the input 101 is generally determined to be a constant value. For example, in the case of a device such as a CD or DVD, 2V rms is the maximum value of the output signal level. Therefore, the maximum output signal level output from the middle / high frequency signal power amplifier circuit 103 and the low frequency power amplifier circuit 104 is determined by the position of the volume. FIG. 2 shows an example of this relationship. In FIG. 2, the maximum output signal level of the middle / high frequency signal power amplifier circuit 103 is the maximum output signal level a, and the maximum output signal level of the low frequency power amplifier circuit 104 is the maximum output signal level b. Further, the voltage of the voltage variable power supply circuit 106 can take two values A and B, and the maximum output signal level a of the power amplifier circuit 103 for the middle / high frequency signal at the position of the volume 38 has the value of the power supply voltage A. Exceed. Therefore, when the volume position is between 0 and 38, the power supply voltage is A and no distortion occurs in the output of the mid / high band signal power amplifier circuit. When the volume is between 38 and 50, the maximum output signal level a exceeds the value of A, so that distortion occurs if the power supply voltage remains A. Therefore, according to the present invention, in the case of the example of FIG. 8, when the volume is 38 or more, the power supply voltage control circuit 108 changes the output voltage of the voltage variable power supply circuit 106 to the value B by the volume position detection signal input from the volume control circuit 105. . With the above operation, the power amplification can be achieved by changing the power supply voltage without causing distortion in the power amplification circuit 103 for the middle / high frequency signal. On the other hand, when considering the low-frequency power amplifier circuit 104, the maximum output signal level b of the low-frequency power amplifier circuit 104 exceeds the power supply voltage A at the volume position 18 in the example of FIG. It is necessary to change the output voltage of the power supply circuit 106 to the value B. Thus, it is necessary to change the output voltage of the voltage variable power supply circuit 106 to a value B at a position that is significantly lower than the volume position 38 that changes the power supply voltage set in accordance with the power amplifier circuit 103 for the middle / high frequency signal. Therefore, there is a possibility that the power reduction effect is obtained only when used at a very low volume position, and the power reduction effect is almost lost in actual use. On the other hand, in the present invention, the output signal level of the low-frequency power amplifier circuit 104 is detected by the signal level detection circuit 107, and the signal level of the power supply voltage control circuit 108 is detected by the detection signal output from the signal level detection circuit 107. When the voltage exceeds a certain value, the output voltage value of the voltage variable power supply circuit 106 is set to B, and when it is below, it is set to A. As a result, the output voltage of the voltage variable power supply circuit can be controlled without distortion of the signal waveform as shown in FIG. In this case, if a signal of medium / high frequency is included in the signal, the phenomenon that the signal waveform is distorted due to the change of the power supply not in time for the change of the signal occurs as shown in FIG. 10, in order to prevent this As shown in FIG. 9, it is necessary to provide a delay circuit after signal level detection and amplify its output. However, when only a low frequency component is included in the signal, as shown in FIG. The change rate of the power supply voltage can be set so as not to cause distortion.

  As described above, according to the present embodiment, it is possible to realize a power amplifying apparatus that can sufficiently reduce power in an actual use state, is cost-effective by providing a delay circuit, and does not cause a synchronization shift with video. It becomes.

  In the present embodiment, the voltage of the variable power supply circuit is described in two stages of A and B. However, the voltage is not limited to the two stages and may be set in a plurality of stages.

(Embodiment 2)
Next, FIG. 4 shows a configuration diagram of an audio amplifying apparatus according to the second embodiment. The second embodiment is a case where the low-frequency power amplifier circuit is not provided in the first embodiment, and the portions described in the first embodiment are omitted. Reference numeral 203 denotes a power amplifier circuit, and reference numeral 209 denotes a speaker output.

  The operation of the audio amplifying apparatus configured as described above will be described below.

In many cases, the frequency characteristics shown in FIG. 5 are used to compensate for the characteristics of the speaker in the low frequency range. In this case, in the middle / high frequency band (part D in FIG. 5), the same as in the first embodiment. The maximum output signal level is the maximum output signal level a in FIG. 2, but the maximum output signal level is the maximum output signal level b in FIG. 2 in the low frequency band (C portion in FIG. 5). Therefore, in the case of the second embodiment, similarly to the first embodiment, the power supply voltage control based on the volume position detection is a point where the maximum output signal level a that matches the signal level in the middle / high range exceeds the power supply voltage (example in FIG. 12 Then, the control is performed at the volume position 38), and the power supply voltage is controlled by detecting the signal level for the low frequency signal.
As described above, according to the present embodiment, as in the first embodiment, a sufficient power reduction effect can be obtained in an actual use state, and a cost can be increased by providing a delay circuit. An apparatus can be realized.

(Embodiment 3)
FIG. 6 shows a configuration diagram of an audio amplifying apparatus according to the third embodiment. In the third embodiment, as in the first embodiment, an amplitude limiting circuit 311 is provided after the output of the volume 2, and the output of the amplitude limiting circuit 311 is input to the low frequency power amplifier circuit 4. is there.

  FIG. 7 shows the relationship between the power supply voltage and the output signal of the low-frequency signal power amplifier circuit 104 in the configuration of the third embodiment. When the amplitude limiting circuit 311 is provided for the signal waveform and power supply voltage without the amplitude limiting circuit 311 indicated by the broken line, the signal waveform and power supply voltage indicated by the solid line are obtained. Since the amplitude is suppressed at the portion where the signal level increases, the signal level for switching the voltage of the voltage variable power supply circuit 6 can be increased from the detection voltage 1 to the detection voltage 2 in the example of FIG. Therefore, according to the third embodiment, the range in which the output voltage of the voltage variable power supply circuit 6 can be set to a low state without causing distortion is widened, and the effect of reducing power can be further enhanced.

(Embodiment 4)
FIG. 8 shows a configuration diagram of an audio amplifying apparatus according to the fourth embodiment. In the fourth embodiment, the amplitude limiting circuit 311 is provided after the output of the volume 2 and the output of the amplitude limiting circuit 311 is input to the power amplifier circuit 3 as in the second embodiment.

  As in the third embodiment, the power reduction effect is improved by inputting the output of the volume 102 to the power amplifier circuit 103 via the amplitude limiting circuit 311.

  The audio amplifying apparatus of the present invention can reduce power consumption by changing the power supply voltage in accordance with the signal level, and is therefore useful for measures against power consumption related to an audio system having the power amplifying apparatus.

Configuration diagram of an audio amplifying apparatus according to a first embodiment FIG. 4 is a diagram illustrating the relationship between the signal level and the volume position in the audio amplifying apparatus according to the first embodiment. FIG. 3 is an output relation diagram of the voltage variable power supply circuit and the low frequency signal power amplifying circuit in the audio amplifying apparatus according to the first embodiment; Configuration diagram of audio amplifying apparatus according to Embodiment 2 The figure which shows the frequency characteristic in the audio amplification apparatus concerning Embodiment 2. Configuration diagram of audio amplifying apparatus according to Embodiment 3 Output relation diagram of voltage variable power supply circuit and low frequency signal power amplifier circuit in audio amplifier according to third embodiment Configuration diagram of audio amplifying apparatus according to Embodiment 4 1 is a configuration diagram of a power amplification device according to a first conventional example. Output relation diagram of voltage variable power supply circuit and power amplifier circuit according to first conventional example The block diagram of the power amplifier concerning 2nd prior art example FIG. 7 is a diagram showing the relationship between the signal level in the middle / high frequency band and the volume position in the audio amplifying apparatus according to the second conventional example. The figure which shows the frequency characteristic in the audio amplifier concerning 2nd Example

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Input 102 Volume 103 Medium / high frequency signal power amplifier circuit 104 Low frequency signal power amplifier circuit 105 Volume control circuit 106 Voltage variable power supply circuit 107 Signal level detection circuit 108 Power supply voltage control circuit 109 Middle / high frequency speaker output 110 Low Speaker output 203 Power amplifier circuit 209 Speaker output 311 Amplitude limiting circuit

Claims (4)

A low-frequency power amplifier circuit that amplifies only the low frequency of the audio signal, a mid-high frequency power amplifier circuit that amplifies mid- and high-frequency signals other than the low frequency, and the low-frequency power amplifier circuit A volume for adjusting the volume of the input signal of the middle / high frequency power amplifier circuit, a volume control circuit for controlling the volume adjusted by the volume and outputting a volume position detection signal, and the low frequency power amplifier circuit. A signal level detection circuit for detecting the amplitude of the output signal, a voltage variable power supply circuit for supplying power to the low frequency power amplifier circuit and the mid / high frequency power amplifier circuit, and a detection result of the signal level detection circuit; An audio power control circuit configured to control a voltage of the voltage variable power supply circuit based on a volume position detection signal output from the volume control circuit; Amplifier. A power amplification circuit for amplifying an audio signal; a volume for adjusting a volume of an input signal of the power amplification circuit; a volume control circuit for controlling a volume adjusted by the volume and outputting a volume position detection signal; and the power amplification A signal level detection circuit for detecting the amplitude of the output signal of the circuit; a voltage variable power supply circuit for supplying power to the power amplifier circuit; a detection result of the signal level detection circuit; and a volume position detection output from the volume control circuit An audio amplifying apparatus comprising: a power supply voltage control circuit that controls a voltage of the voltage variable power supply circuit based on a signal. 2. The audio amplifying apparatus according to claim 1, further comprising an amplitude suppression circuit that is provided after the output of the volume and outputs the output to the low-frequency power amplifier circuit. 3. The audio amplifying apparatus according to claim 2, further comprising an amplitude suppression circuit that is provided after the output of the volume and outputs the output to the power amplifier circuit.

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