JP2013219709A - Voice signal amplification device and television set - Google Patents

Abstract

An object of the present invention is to provide an audio signal amplifying apparatus capable of dealing with a loud audio signal while suppressing an increase in temperature of an amplifier.
An audio signal amplifying apparatus according to the present invention includes a peak amplitude level detecting unit for detecting a peak value of an amplitude of an audio signal, an average power level detecting unit for detecting an average power of the audio signal, and an audio signal. The sound output amplifier 3 to be amplified, the voltage variable power supply circuit 5 that applies a power supply voltage to the sound output amplifier 3, the peak value acquired from the peak amplitude level detection unit 6 and the average power acquired from the average power level detection unit 7 And a microcomputer 8 for controlling the power supply voltage.
[Selection] Figure 1

Description

  The present invention relates to an audio signal amplifying device and a television receiver including the same.

  In recent audio signal amplifying devices, the circuit configuration is changed from an analog IC to a digital IC, and the power efficiency is greatly improved. However, due to miniaturization of products and high integration of component mounting density, heat generation due to power loss at the time of large volume output is still a problem that cannot be ignored.

  On the other hand, Patent Document 1 proposes to improve power efficiency by reducing the number of switching times in a digital amplifier IC (audio signal amplifying apparatus) operating in a PWM modulation method.

  Patent Document 2 discloses a technique for reducing the temperature rise by reducing the amplitude of the input signal to the audio amplifier when an excessive temperature is detected.

  The audio signal amplifying device of Patent Document 3 suppresses a temperature rise without a sense of incongruity by continuously reducing the gain when an excessive temperature is detected.

  These audio signal amplifying devices are always driven under a constant power supply voltage in order to obtain rated audio output power defined as a product. However, if power is supplied at the same high voltage as when outputting a large volume even when a small volume is output, the power efficiency deteriorates and wasteful power consumption occurs.

  On the other hand, in Patent Document 4, the amplitude of the input audio signal is detected, and the dead time and power supply voltage of the switching element of the digital amplifier are adjusted according to the detection level and volume operation, thereby improving the heat generation due to the through current. The technology is disclosed.

Japanese Patent No. 4818900 JP-A-1-54802 JP 2008-236621 A International Publication No. 2011-001591

  In view of reliability and product life, it is needless to say that the audio signal amplifying apparatus is desirably used at a low temperature while suppressing heat generation. However, it is difficult to attach a heat sink to the audio amplifier due to restrictions on component placement due to miniaturization of audio amplifier devices and miniaturization of products.

  The rating of speaker audio output in a television receiver is defined by the effective value power when the distortion rate is 10% with a continuous sine wave. The temperature rise of the board and components due to the continuous sound is large, and if the power efficiency of the audio signal amplifying device is generally about 90%, the rated power is about 10 W + 10 W only by the board heat radiation without using the heat sink.

  However, when intermittent sounds such as music are output, the temperature rise is lower than the continuous sound, so even if the power supply voltage is further increased and a loud sound is output instantaneously, Can afford. In order to suppress heat generation, it is ideal to lower the power supply voltage to improve power efficiency and reduce power consumption, but when you need a sense of realism with intermittent music and large music power. Therefore, it is necessary to increase the power supply voltage so that the necessary audio output power can be obtained.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide an audio signal amplifying apparatus that can respond to a loud audio signal while suppressing an increase in the temperature of the amplifier.

  An audio signal amplification device of the present invention includes a peak amplitude level detection unit that detects a peak value of an amplitude of an audio signal, an average power level detection unit that detects an average power of the audio signal, an amplification circuit that amplifies the audio signal, A power supply circuit that applies a power supply voltage to the amplifier circuit, and a power supply voltage control unit that controls the power supply voltage based on the peak value acquired from the peak amplitude level detection unit and the average power acquired from the average power level detection unit.

  An audio signal amplification device of the present invention includes a peak amplitude level detection unit that detects a peak value of an amplitude of an audio signal, an average power level detection unit that detects an average power of the audio signal, an amplification circuit that amplifies the audio signal, A power supply circuit that applies a power supply voltage to the amplifier circuit, and a power supply voltage control unit that controls the power supply voltage based on the peak value acquired from the peak amplitude level detection unit and the average power acquired from the average power level detection unit. When the average power of the audio signal is less than the rated power, by allowing a power supply voltage exceeding the rated voltage according to the peak amplitude level, it is possible to cope with a loud audio signal while suppressing an increase in the temperature of the amplifier. .

1 is a block diagram illustrating a configuration of an audio output device according to Embodiment 1. FIG. It is a figure which compares and shows the volume control amount of a volume control part, and the output of an audio | voice output amplifier. It is a figure which shows the power supply voltage and power efficiency of an audio | voice output amplifier. It is a flowchart which shows operation | movement of a microcomputer. 10 is a block diagram illustrating a configuration of a television receiver according to Embodiment 2. FIG.

<A. Embodiment 1>
<A-1. Configuration>
FIG. 1 is a block diagram showing a configuration of an audio signal amplifying apparatus 10 according to the first embodiment. The audio signal amplifying apparatus 10 is an apparatus that amplifies an audio signal and outputs it to the loudspeaker 4. The audio signal amplifying apparatus 10 includes a volume control unit 2, a delay circuit 9, an audio output amplifier 3, and a microcomputer 8 in addition to the audio input unit 1 to which an audio signal is input. The volume control unit 2 adjusts the volume of the audio signal input to the audio input unit 1. Here, the volume setting amount set by the user is acquired from the microcomputer 8, and the volume is adjusted based on the volume setting amount. The delay circuit 9 delays the audio signal whose volume has been adjusted by the volume control unit 2 by a predetermined time. The audio signal delayed by the delay circuit 9 is amplified by the audio output amplifier 3 and output from the loudspeaker 4 as audio.

  The audio signal amplifying apparatus 10 further includes a voltage variable power supply circuit 5 that supplies power to the audio output amplifier, a peak amplitude level detection unit 6, and an average power level detection unit 7. The peak amplitude level detector 6 detects the peak amplitude level of the audio signal whose volume has been adjusted by the volume controller 2. The average power level detector 7 detects the average power of the audio signal whose volume has been adjusted by the volume controller 2 for a predetermined time. The microcomputer 8 acquires respective detection results from the peak amplitude level detection unit 6 and the average power level detection unit 7, and controls the output voltage of the voltage variable power supply circuit 5 based on these detection results.

  The voice input unit 1, the volume control unit 2, the delay circuit 9, the peak amplitude level detection unit 6, and the average power level detection unit 7 are realized by a voice DSP.

<A-2. Operation>
For example, an audio signal from a TV tuner or a recording / playback apparatus is input to the audio input unit 1. The maximum amplitude of the audio signal is an analog signal 2 Vrms and a digital signal 0 dBFS (full scale). An audio signal that has undergone predetermined signal processing such as filtering in the audio input unit 1 is sent to the volume control unit 2.

  The volume control unit 2 adjusts the volume of the input audio signal according to the volume setting value acquired from the microcomputer 8. The volume setting value is a value set by volume adjustment information input by the user using an operating means (not shown). The volume control unit 2 adjusts the volume so that the internal amplification degree is 0 dB when the volume is set to the maximum, and the attenuation amount increases as the volume is lowered.

  The audio signal whose volume is adjusted by the volume control unit 2 is delayed by a predetermined time by the delay circuit 9. Thereafter, the audio signal is amplified at a constant amplification factor by the audio output amplifier 3 and is output to the outside from the loudspeaker 4 as audio. Here, the audio output amplifier 3 has a gain of 24 dB (amplitude 16 times) and a fixed amplification factor. A recent general digital amplifier has a power efficiency of about 90% at maximum, and such a digital amplifier is used as the audio output amplifier 3. Even when the power efficiency is optimized by optimizing the power supply voltage, a pair of digital amplifiers is used. When 10 W + 10 W stereo output is performed from the loudspeaker 4, about 2 W is generated by the audio output amplifier 3 as a power loss and generates heat.

  FIG. 2 is a diagram showing the volume control amount in the volume control unit 2 and the output of the audio output amplifier 3 in comparison. In this figure, when an audio signal of 2 Vrms = 0 dBFS is input to the audio input unit 1, the attenuation Gc (dB) of the volume control unit 2, the gain (dBFS) of the output signal in the audio output amplifier 3, and the output voltage The effective value (Vrms), peak value (Vpp), and output power (W) of the loudspeaker 4 are shown. In addition, an example of the power supply voltage of the audio output amplifier 3 necessary for obtaining desired output power is also shown. The input impedance of the loudspeaker 4 is 8Ω. When the amount of attenuation Gc of the volume control unit 2 is set to -11 dB, the output power of the loudspeaker 4 is about 10 W + 10 W. Similarly, about 20 W + 20 W is obtained when set to -8 dB, and 1 W + 1 W is obtained when set to -21 dB. I understand that. Since the audio output waveform is clipped and distorted by the power supply voltage, the numerical values shown in italics in FIG. 2 are not actual outputs.

  In FIG. 3, the horizontal axis indicates the output power (W) of the loudspeaker 4, and the vertical axis indicates the power efficiency (%). The characteristics when the power supply voltage VDD = 13V and VDD = 20V of the audio output amplifier are shown. Is shown. When obtaining an output of 10 W from the loudspeaker 4, the power efficiency can be improved by setting the power supply voltage VDD to 13V rather than 20V. If the audio output of the loudspeaker 4 is the same, the power efficiency can be improved by lowering the power supply voltage VDD.

  The peak amplitude level detection unit 6 always detects the peak amplitude level of the audio signal whose volume has been adjusted by the volume control unit 2. The peak amplitude level detection value is transmitted to the microcomputer 8, and the microcomputer 8 acquires the second voltage V2 corresponding to the peak amplitude level detection value based on a comparison table (not shown) held inside. Here, V2 is set to be smaller as the peak amplitude level is smaller and larger as the peak amplitude level is larger.

  The voice DSP holds a peak value for a period of several ms, outputs the value to the microcomputer 8 at intervals of several ms, and the microcomputer 8 converts the peak value into the second voltage V2. Alternatively, processing up to conversion to the second voltage V <b> 2 by the voice DSP may be performed, and V <b> 2 may be output to the microcomputer 8. The data exchanged between the voice DSP and the microcomputer 8 may be relative data other than the peak value and the second voltage V2.

  The average power level detection unit 7 squares the amplitude of the audio signal whose volume is adjusted by the volume control unit 2 and calculates the average power for a certain time. The calculation result of the average power is transmitted to the microcomputer 8. The microcomputer 8 acquires a first voltage V1 corresponding to the calculation result of the average power input from the average power level detection unit 7 based on a comparison table (not shown) held inside. Note that the process of converting the calculated value of the average electric energy into the first voltage V1 may be performed by either the voice DSP or the microcomputer 8.

  The microcomputer 8 generates a control signal from the first voltage V1 determined based on the average power of the audio signal and the second voltage V2 determined based on the peak value, and outputs the control signal to the voltage variable power supply circuit 5, The output voltage of the voltage variable power supply circuit 5 is controlled.

  The operation of the microcomputer 8 is shown in a flowchart in FIG. First, the average power level detection unit 7 reads the time average power Pave of the input audio signal (step S1), and sets the first voltage V1 corresponding to the Pave (step S2). Next, Pave is compared with the rated output power Ptyp = 10 (W) (step S3). When Pave> Ptyp, the first voltage V1 obtained corresponding to Pave is compared with Vtyp (step S4). Here, Vtyp is a power supply voltage at which a rated audio output is obtained. When V1> Vtyp, V1 is decreased by the voltage variable amount ΔV over time (V1 = V1−ΔV, step S5), and the process proceeds to step S8. If V1 ≦ Vtyp, the process proceeds to step S8 without changing V1.

  When the time average power Pave is equal to or less than the rated output power Ptyp in step S3, the first voltage V1 obtained corresponding to Pave is compared with Vmax (step S6). Here, Vmax is a power supply voltage that does not exceed the maximum rated voltage of the audio output amplifier 3 or the maximum rating of the loudspeaker 4. If V1 <Vmax, V1 is increased by the voltage variable amount ΔV over time (V1 = V1 + ΔV, step S7), and the process proceeds to step S8. If V1 ≧ Vmax, V1 is not changed and the process proceeds to step S8. Thus, the first voltage V1 is between the rated voltage 13V at which the rated output power 10 (W) is obtained in steps S5 and S7, and the power supply voltage 20V that does not exceed the maximum voltage of the audio output amplifier 3 or the maximum rating of the loudspeaker 4. Voltage.

  Next, the microcomputer 8 reads the peak amplitude level Vpeak of the input audio signal from the peak amplitude level detector 6 (step S8). Then, the second voltage V2 is set according to Vpeak (step S9). Here, V2 is a voltage between the lower limit 5V and the upper limit 20V of the rated power supply of the audio output amplifier 3. Thereafter, the first voltage V1 and the second voltage V2 are compared (step S10). If V1> V2, the power supply voltage Vout is determined as V1 (step S11), and if V1 ≦ V2, the power supply voltage Vout is determined as V2 (step S12).

  The microcomputer 8 outputs a control signal to the voltage variable power supply circuit 5 so that the output voltage of the voltage variable power supply circuit 5 becomes the power supply voltages V1 and V2 determined in steps S11 and S12. Considering this, the delay circuit 9 delays the audio signal from the volume control unit 2 by several ms and outputs it to the audio output amplifier 3 (step S13).

<A-3. Effect>
The audio signal amplifying apparatus 10 according to the present embodiment includes a peak amplitude level detection unit 6 that detects a peak value of the amplitude of the audio signal, an average power level detection unit 7 that detects the average power of the audio signal, and an audio signal. A power supply based on the audio output amplifier 3 (amplifier circuit) to be amplified, the power supply circuit 5 for applying the power supply voltage to the amplifier circuit, the peak value acquired from the peak amplitude level detector and the average power acquired from the average power level detector And a microcomputer 8 (power supply voltage control unit) for controlling the voltage. When the peak value of the audio signal is small, the power supply voltage is increased, and when the peak value is large, the power supply voltage is decreased to increase the power efficiency. Further, when the average power is equal to or lower than the rated power, by allowing a power supply voltage higher than the rated voltage, it is possible to cope with a loud sound signal while suppressing a temperature rise of the amplifier circuit.

  Further, the microcomputer 8 (power supply voltage control unit) includes a first voltage V1 based on the average power level acquired from the average power level detection unit 7 and a second voltage based on the peak value acquired from the peak amplitude level detection unit 6. Since the lower one of V2 is used as the power supply voltage, the power efficiency can be increased by changing the power supply voltage higher when the peak value of the audio signal is smaller and lowering the power supply voltage when the peak value is larger. In addition, when the average power is less than or equal to the rated power, by allowing a power supply voltage that is higher than the rated voltage, it is possible to deal with a loud sound signal while suppressing an increase in the temperature of the amplifier circuit.

  In addition, the microcomputer 8 (power supply voltage control unit), when the average power Pave is less than the rated audio output power Ptyp, the loudspeaker 4 that receives the maximum rated voltage of the audio output amplifier 3 (amplifier circuit) or the output of the amplifier circuit. Since the first voltage V1 is set high within a range not exceeding the maximum rating, the power supply voltage is increased when the peak value of the audio signal is small, and the power supply voltage is decreased when the peak value is large, thereby increasing the power efficiency. be able to. In addition, when the average power is less than or equal to the rated power, by allowing a power supply voltage that is higher than the rated voltage, it is possible to deal with a loud sound signal while suppressing an increase in the temperature of the amplifier circuit.

<B. Second Embodiment>
<B-1. Configuration, operation>
FIG. 5 is a block diagram illustrating a configuration of the television receiver 20 according to the second embodiment, in which the audio signal amplifying device 10 according to the first embodiment is incorporated. The television receiver 20 includes an external input unit 11, a tuner unit 12, a video / audio input switching unit 13, a video signal processing unit 14, a display unit 15, an audio DSP / audio output amplifier unit 16, a loudspeaker 4, and a power supply unit 18. It has.

  An audio signal amplifying apparatus 10 is configured by the audio DSP / audio output amplifier unit 16, the microcomputer 8, and the voltage variable power supply circuit 5. The audio input unit 1, audio control unit 2, delay circuit 9, peak amplitude level detection unit 6, average power level detection unit 7 and audio output amplifier 3 in FIG. 1 are collectively shown in FIG. 2 as an audio DSP / audio output amplifier unit. 16.

  The external input unit 11 is an input interface such as an HDMI input, a network input, or an analog input. The tuner unit 12 is a television broadcast receiving unit. The video / audio input switching unit 13 selects one of the input signals from the external input unit 11 and the tuner unit 12. The video signal is subjected to predetermined video processing by the video signal processing unit 14 and displayed as a video on the display unit 15.

  On the other hand, the audio signal among the input signals selected by the video / audio input switching unit 13 is amplified by the audio signal amplifying apparatus 10 and output as audio from the loudspeaker 4. Since the operation of the audio signal amplifying apparatus 10 is the same as that of the first embodiment, the description thereof is omitted.

  The operation unit 17 is a remote operation reception unit from the remote controller, an operation key of the television receiver 20 main body, and the like, and the microcomputer 8 is configured by each component of the television receiver 20 based on the operation input to the operation unit 17. Is controlling.

<B-2. Effect>
The television receiver 20 according to the present embodiment includes the audio signal amplifying device 10 according to the first embodiment. When the peak value of the audio signal is small, the power supply voltage of the audio output amplifier 3 is increased, and when the peak value is large, the power supply voltage of the audio output amplifier 3 is changed to be low. When the average power of the audio signal is less than or equal to the rated power, the audio output amplifier 3 is allowed to have a power supply voltage higher than the rated voltage, thereby suppressing a rise in the temperature of the audio output amplifier 3 and a high volume audio signal. Can also respond.

  In the present invention, the embodiments can be appropriately modified and omitted within the scope of the invention.

  1 audio input unit, 2 volume control unit, 3 audio output amplifier, 4 loudspeaker, 5 voltage variable power supply circuit, 6 peak amplitude level detection unit, 7 average power level detection unit, 8 microcomputer, 10 audio signal amplification device, 11 external Input unit, 12 tuner unit, 13 video / audio input switching unit, 14 video signal processing unit, 15 display unit, 16 audio DSP / audio output amplifier unit, 17 operation unit, 18 power supply unit, 20 television receiver.

Claims (4)

A peak amplitude level detector for detecting the peak value of the amplitude of the audio signal;
An average power level detector for detecting an average power of the audio signal;
An amplifier circuit for amplifying the audio signal;
A power supply circuit for applying a power supply voltage to the amplifier circuit;
A power supply voltage control unit that controls the power supply voltage based on the peak value acquired from the peak amplitude level detection unit and the average power acquired from the average power level detection unit;
Audio signal amplifier. The power supply voltage control unit is a lower one of the first voltage based on the average power level acquired from the average power level detection unit and the second voltage based on the peak value acquired from the peak amplitude level detection unit. The power supply voltage is
The audio signal amplification device according to claim 1. When the average power is less than the rated audio output power, the power supply voltage control unit is configured so as not to exceed a maximum rated voltage of the amplifier circuit or a maximum rating of a speaker receiving the output of the amplifier circuit. Set the voltage higher,
The audio signal amplification device according to claim 2. The audio signal amplification device according to any one of claims 1 to 3,
Television receiver.

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