JP2005006215A - Beep sound generating method in audio amplifier, audio amplifier and portable digital audio device mounted with the audio amplifier - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To attain miniaturization and to reduce cost by generating beep sound from a load 33 and to generate beep sound also for confirmation when the power is supplied in a switching amplifier 31 which amplifies a one-bit signal from a ΔΣ modulation block 32 to give the amplified signal to the load 33 being an electromechanical transducer to make the amplified signal sound. <P>SOLUTION: The one-bit signal is switched and amplified by transistors Q1 to Q4. A transistor Q5 for pulling up to voltage V1 of a high level and a resistor R are connected to the output sides of LPFs F1 and F2 for smoothing the output of the transistors Q1 to Q4 to convert the outputs into an analog signal. A control microcomputer 34 that is always energized drives the transistor Q5 to generate the beep sound. Then, even though the load 33 for normal audio reproduction is shared for beep sound generation, the beep sound can be generated regardless of whether the ΔΣ modulation block 32 for generating sound data is started directly after the power is supplied. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for generating a beep sound using an audio amplifier suitably implemented in a portable digital audio device, and also relates to the audio amplifier and a portable digital audio device equipped with the audio amplifier.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in an audio device or the like, a beep sound generating device is provided to inform an operator of an operation state during operation. This beep sound generation device is generally configured to include a beep sound generation circuit that generates a rectangular wave that is the source of a beep sound, and a buzzer that electromechanically converts an output signal of the beep sound generation circuit. Yes.
[0003]
FIG. 3 is a view showing a typical prior art of such a beep sound generating device, which is shown in Japanese Utility Model Laid-Open No. 5-699796. In the beep sound generation device 1, the beep sound generation circuit 3 is provided in the microcomputer 2, and the beep sound generation circuit 3 generates the rectangular wave in response to an operation from the remote controller 4 or the operation key 5. A beep sound is generated by giving to the buzzer 7 via the beep sound controller 6. The microcomputer 2 is configured to set the volume of the beep sound in accordance with the use state of the device by switching and controlling a plurality of resistance attenuation circuits of the beep sound controller 6 with a switching element.
[0004]
However, in such a conventional technique, when the device is the audio device, another electromechanical transducer such as the buzzer 7 must be mounted in addition to the electromechanical transducer such as a speaker or a headphone. However, there is a problem that the cost and space are increased, which is disadvantageous particularly in a portable audio device. There is also a problem that a beep sound may not be perceived by a user whose ears are blocked by headphones, which is particularly noticeable in the case of headphone audio.
[0005]
Therefore, in order to solve such problems, the present applicant has previously proposed Japanese Patent Application No. 2003-26163. The configuration of the headphone audio device 11 is shown in FIG. In the headphone audio device 11, generally, digital audio data recorded on the mini-disc 12 is read by the optical pickup 13, and the system LSI 14 performs demodulation and conversion into a digital (PWM) signal. After being amplified by the switching amplifiers 15 and 16, the digital (PWM) signal is restored to an analog audio signal by the low-pass filters 17 and 18, and is electromechanically converted by the headphones 19 to be sonicated.
[0006]
The system LSI 14 includes a signal processing circuit 21 that demodulates a signal read by the optical pickup 13 into a digital signal, an ATRAC expansion processing circuit 22 that expands the digital signal demodulated by the signal processing circuit 21, and the ATRAC expansion. An oversampling circuit 23 that samples the multi-bit digital signal decoded by the processing circuit 22 at a frequency higher than the sampling frequency of the multi-bit digital signal, and the over-sampled multi-bit digital signal is converted into a 1-bit digital signal. A ΔΣ modulation circuit 24 for conversion and a PWM modulation circuit 25 for converting the 1-bit digital signal into the PWM signal are configured, a beep sound generation circuit 26, the beep sound data, and the oversampling circuit 23. Multi from And an adder circuit 27 for supplying the bit digital signal to the ΔΣ modulation circuit 24.
[0007]
Then, in response to an operation on the operation button 28, the system controller 29 causes the beep sound generation circuit 26 to generate beep sound data, so that the amplified beep sound is audible from the headphones 19, as described above. The problem caused by Japanese Utility Model Publication No. 5-69796 has been resolved.
[0008]
[Patent Document 1]
Japanese Utility Model Publication No. 5-69796 (Publication date: September 21, 1993)
[0009]
[Patent Document 2]
Japanese Patent Application No. 2003-26163 (Filing date: February 3, 2003)
[0010]
[Problems to be solved by the invention]
In the above configuration, in order to generate a beep sound, it is necessary to turn on the beep sound generation circuit 26 before the ΔΣ modulation circuit 24 and operate the beep sound generation circuit 26. Therefore, if a beep sound is generated for confirmation at power-on, the system controller 29 needs to make various settings in the system LSI 14 including a DSP (digital signal processor) in a short time. There was a time-consuming part in the microcomputer program that runs the system.
[0011]
An object of the present invention is to provide a method for generating a beep sound in an audio amplifier capable of generating a beep sound for confirmation at power-on, an audio amplifier, and a portable digital audio device equipped with the same.
[0012]
[Means for Solving the Problems]
A method for generating a beep sound in an audio amplifier according to the present invention generates an beep sound in an electromechanical transducer using an audio amplifier that amplifies an audio signal from an audio signal source and applies the amplified audio signal to the electromechanical transducer. In the method, a power element is connected with respect to at least one terminal of the electromechanical conversion element, the operation of the audio amplifier is controlled, and control means that is energized at all times drives the power element and applies a predetermined voltage to the power amplifier. A beep sound is generated by giving to a terminal.
[0013]
According to the above configuration, in the audio amplifier, in order to generate a beep sound in response to an operation or the like, the electrical amplifier that synthesizes the audio signal is suitable for the case where the audio device equipped with the audio amplifier is portable. A beep sound is generated in the mechanical conversion element. When the electromechanical conversion element is shared for normal reproduction and beep sound reproduction in this way, a power element is connected to at least one terminal of the electromechanical conversion element, and a predetermined voltage such as a power source is applied to the power element. Further, the power element is driven by a control means such as a microcomputer that is always energized in the system.
[0014]
Therefore, even when an audio signal source or a buffer amplifier that controls a power element that drives the electromechanical conversion element during normal playback is not activated immediately after power-on, the beep sound can be generated. A beep sound can be generated for confirmation.
[0015]
In the audio amplifier of the present invention, an audio signal from an audio signal source is amplified and applied to the electromechanical transducer, and a predetermined voltage is applied to at least one terminal of the electromechanical transducer. A power element capable of controlling the operation of the audio amplifier, and the control means that is always energized drives the power element to generate a beep sound in the electromechanical transducer. To do.
[0016]
According to the above configuration, in generating a beep sound in response to an operation or the like in the audio amplifier, the audio signal is sonicated so that the audio device on which the audio amplifier is mounted is suitable for a portable type. A beep sound is generated in the electromechanical transducer. When the electromechanical conversion element is shared for normal reproduction and beep sound reproduction in this way, a power element is connected to at least one terminal of the electromechanical conversion element, and a predetermined voltage such as a power source is applied to the power element. Further, the power element is driven by a control means such as a microcomputer that is always energized in the system. Specifically, the control means generates a rectangular wave that is the source of a beep sound, and when there is one power element, between the other terminal having a fixed potential such as a GND potential, In response to the rectangular wave, the power element drives the electromechanical conversion element by turning on / off the power supply voltage. When there are two power elements, the polarities are opposite to each other with the other terminal. The electromechanical conversion element is driven by push-pull by applying the power supply voltage.
[0017]
Therefore, even when an audio signal source or a buffer amplifier that controls a power element that drives the electromechanical conversion element during normal playback is not activated immediately after power-on, the beep sound can be generated. A beep sound can be generated for confirmation.
[0018]
Furthermore, in the audio amplifier of the present invention, the audio signal source outputs a digital audio signal, and the audio amplifier switches a power supply voltage in response to the digital audio signal, and its output. The beep sound power element is connected to the output side of the low-pass filter.
[0019]
According to the above configuration, the audio digital amplifier is provided with control means such as a microcomputer for volume control, mute control, and the like, and a beep sound is generated using the control means. be able to. The signal that becomes the beep is switched by the power element of the digital audio signal, and is superposed after the amplitude-amplified digital signal is converted into an analog signal by a low-pass filter, which has a harmful effect on the power element of the digital audio signal. It doesn't reach.
[0020]
A portable digital audio device according to the present invention includes the above-described audio amplifier.
[0021]
According to the above configuration, the electromechanical conversion element can be shared for normal reproduction and beep sound reproduction, which is suitable for downsizing and can also generate a beep sound for confirmation at power-on. A portable digital audio device can be realized.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.
[0023]
FIG. 1 is a block diagram showing an electrical configuration of a switching amplifier 31 which is an audio amplifier according to an embodiment of the present invention. In this switching amplifier 31, the ΔΣ modulation block 32 includes a ΔΣ conversion circuit (not shown), and from a analog input, a multi-bit digital input, or a 1-bit signal (PDM: pulse density modulation signal), first, a series of binary signals. In addition, an example is shown in which two series of 1-bit signals (normal phase signal and reverse phase signal) are generated based on the generated binary signal, and each is output from the 1-bit output terminals P11 and P12. However, it goes without saying that the digital signal for driving the switching element may be a PWM (Pulse Width Modulation) signal.
[0024]
Between the power line of the high voltage V1 connected to the power supply terminal E1 and the GND line, there are a series circuit composed of N-channel output transistors Q1 and Q2 and a series circuit composed of N-channel output transistors Q3 and Q4. An H bridge circuit is connected. The gates of the output transistors Q1 and Q4 are driven by the buffers B11 and B12 in response to the positive-phase 1-bit signal output from the positive-phase output terminal P11 of the ΔΣ modulation block 32. In addition, the gates of the output transistors Q3 and Q2 are driven by the buffers B21 and B22 in response to a 1-bit signal having a negative phase output from the negative phase output terminal P12 of the ΔΣ modulation block 32. Thus, the output transistors Q1 and Q4 and the output transistors Q3 and Q2 perform switching in a reciprocal operation, and the load 33 is push-pull driven between the positive phase output and the negative phase output.
[0025]
The connection point of the output transistors Q1 and Q2 is a negative phase output terminal, and is connected to a negative phase output terminal P22 via a low-pass filter F2 including a coil L2 and a capacitor C2. The connection point of the output transistors Q3 and Q4 is It becomes a positive phase output terminal and is connected to a positive phase output terminal P21 via a low-pass filter F1 including a coil L1 and a capacitor C1. A load 33 composed of an electroacoustic transducer such as the headphones is connected between the output terminals P21 and P22.
[0026]
Each circuit in the switching amplifier 31 such as the ΔΣ modulation block 32 and a power supply circuit (not shown) is controlled by a control microcomputer 34, for example, volume control or mute control is performed.
[0027]
It should be noted that in this switching amplifier 31, the output terminal of one of the low-pass filters F1 and F2 (F1 in FIG. 1), that is, the positive-phase output terminal P21 and the high voltage V2 connected to the power supply terminal E2. A series circuit composed of a P-channel transistor Q5 and a resistor R is interposed between the power supply line and a beep output from the beep signal output terminal P31 of the control microcomputer 34. It is driven by a signal. Therefore, even if the ΔΣ modulation block 32 and the buffers B11, B12; B21, B22 are not started immediately after the power is turned on, the beep signal from the control microcomputer 34 that is always energized can be audible. Although the transistors Q1 to Q5 are shown as MOS transistors in FIG. 1, it goes without saying that the transistors may be bipolar transistors.
[0028]
FIG. 2 is a timing chart for explaining the operation of the switching amplifier 31 configured as described above. This operation shows a case where a beep sound is generated during normal sound reproduction. In the ΔΣ modulation block 32, for example, a 1-bit signal is generated by over-sampling an input multi-bit digital signal at a frequency 24 times, and a positive phase component is supplied from the positive phase output terminal P11 and a negative phase component is supplied from the reverse phase component. It is output from the phase output terminal P12, amplified by buffers B11, B12; B21, B22, respectively, and applied to the gates of the transistors Q1, Q4; Q3, Q2.
[0029]
Until a beep sound is generated at time t1, the beep signal output from the beep signal output terminal P31 is fixed at a high level, the P-channel transistor Q5 is turned off, and the drain potential of the transistor Q5 is turned off. VD has the same potential as that of the positive-phase output terminal P21. As a result, music can be reproduced from the load 33 without affecting the switching operation of the transistors Q1 to Q4.
[0030]
On the other hand, when the output of the beep sound is started at time t1, the beep signal becomes a rectangular wave of 1 kHz, for example, and the transistor Q5 responds to this by turning on / off in the 1 kHz cycle. When repeatedly turned on by this, the high voltage V2 is superimposed on the analog audio signal smoothed by the low-pass filter F1 (in normal sound reproduction, the high voltage V2 is set higher), The potential of the positive-phase output terminal P21 becomes a level that is lowered from the high voltage V2 by a voltage drop due to the resistor R2. The potential of the output terminal P21 is a value obtained by dividing the high voltage V2 by the ON resistance of the transistor Q5 and the resistance R.
[0031]
On the other hand, when the transistor Q5 is off, the analog audio signal is output as it is. In this way, the output sound from the load 33 is superposed with a 1 kHz signal on the reproduction signal, and can be heard as a beep sound. When the generation of the beep sound ends at time t2, the beep signal is fixed at the high level again.
[0032]
The beep signal is not limited to a rectangular wave, but may be a triangular wave or the like. In the above description, the transistor Q5 and the resistor R are provided on the positive phase output terminal P21 side, the positive phase output terminal P21 is pulled up to the high voltage V2, and the reverse phase output terminal P22 side is a transistor. Although the transistors Q5 and Q2 are still driven, the transistor Q5 and the resistor R may be provided on the opposite-phase output terminal P22 side, and on the opposite-phase output terminal P22 side, GND or negative A pull-down transistor and a resistor may be provided in the power supply, and push-pull driving may be performed between the transistor Q5 and the resistor R on the positive-phase output terminal P21 side.
[0033]
With the configuration as described above, in the switching amplifier 31 of the present invention, when generating a beep sound in response to an operation or the like, a beep sound is generated in the load 33 which is an electromechanical transducer that synthesizes an audio signal. The electromechanical conversion element is shared to reduce the size and cost, and the switching amplifier 31 can be suitably implemented as a portable audio device.
[0034]
Further, when the beep sound is generated, the control microcomputer 34, which is always energized on the system without using the ΔΣ modulation block 32 or the buffers B11, B12; Therefore, even if the ΔΣ modulation block 32 and the buffers B11, B12; B21, B22 are not started up immediately after the power is turned on, the control microcomputer 34 can generate the beep sound only by outputting a rectangular wave. In addition, the burden on the microcomputer program is very light, and a beep sound can be generated for confirmation at power-on.
[0035]
Furthermore, the switching amplifier 31 of the present invention includes H-bridge transistors Q1 to Q4 that switch the power supply voltage V1 in response to a 1-bit signal, and low-pass filters F1 and F2 that smooth the output. Since the transistor Q5 that generates the beep is connected to the output side of the low-pass filter F1, the 1-bit signal that has been switched and amplified by the transistors Q1 to Q4 is converted into an analog signal by the low-pass filter. Since the beep sound is superimposed, the transistors Q1 to Q4 are not adversely affected.
[0036]
【The invention's effect】
As described above, the method for generating a beep sound in the audio amplifier according to the present invention is suitable for a case where an audio device equipped with the audio amplifier is portable when generating a beep sound in response to an operation or the like. A beep sound is generated in an electromechanical transducer that synthesizes a signal, the electromechanical transducer is shared for normal reproduction and beep reproduction, and a power element is connected to at least one terminal of the electromechanical transducer. A predetermined voltage such as a power source is applied to the power element, and the power element is driven by a control means such as a microcomputer that is constantly energized in the system.
[0037]
Therefore, even when an audio signal source or a buffer amplifier that controls a power element that drives the electromechanical conversion element during normal playback is not started immediately after power-on, the beep sound can be generated. A beep can also be generated for confirmation.
[0038]
Further, as described above, the audio amplifier according to the present invention generates an audio signal so that a beep sound in response to an operation or the like is generated so that the audio device on which the audio amplifier is mounted is portable. A beep sound is generated in the electromechanical conversion element to be audible, the electromechanical conversion element is shared for normal reproduction and beep sound reproduction, and a power element is connected to at least one terminal of the electromechanical conversion element. A predetermined voltage such as a power source is applied to the element, and the power element is driven by a control means such as a microcomputer that is constantly energized in the system.
[0039]
Therefore, even when an audio signal source or a buffer amplifier that controls a power element that drives the electromechanical conversion element during normal playback is not started immediately after power-on, the beep sound can be generated. A beep can also be generated for confirmation.
[0040]
Furthermore, as described above, the audio amplifier according to the present invention is a power element having a bridge configuration in which the audio signal source outputs a digital audio signal, and the audio amplifier switches a power supply voltage in response to the digital audio signal. And a low-pass filter that smoothes the output, and the power element of the beep sound is connected to the output side of the low-pass filter.
[0041]
Therefore, it is possible to generate a beep sound using a control means such as a microcomputer provided in an audio digital amplifier for volume control and mute control. Also, a signal that becomes a beep sound is switched by the power element of the digital audio signal, and is superimposed after the amplitude-amplified digital signal is converted into an analog signal by a low-pass filter. It doesn't reach.
[0042]
The portable digital audio device of the present invention is equipped with the audio amplifier as described above.
[0043]
Therefore, a portable digital device that can share an electromechanical transducer for normal playback and beep sound reproduction, is suitable for miniaturization, and can generate beep sound for power-on confirmation. Audio equipment can be realized.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an electrical configuration of a switching amplifier that is an audio amplifier according to an embodiment of the present invention.
FIG. 2 is a timing chart for explaining the operation of the switching amplifier of the present invention.
FIG. 3 is a block diagram of a typical prior art beep generator.
FIG. 4 is a block diagram of a headphone audio apparatus previously proposed by the present applicant.
[Explanation of symbols]
31 Switching amplifier (audio amplifier)
32 ΔΣ modulation block (audio signal source)
33 Load (electromechanical transducer)
34 Control microcomputer (control means)
B11, B12; B21, B22 Buffer (buffer amplifier)
C1, C2 Capacitors F1, F2 Low-pass filters L1, L2 Coils Q1-Q4 Output transistors (power elements)
Q5 Transistor (Power element)
R resistance

Claims (4)

In the method of generating a beep sound in the electromechanical transducer using an audio amplifier that amplifies an audio signal from an audio signal source and applies the amplified audio signal to the electromechanical transducer
Connecting a power element with respect to at least one terminal of the electromechanical transducer;
A beep in an audio amplifier, wherein the control means for controlling the operation of the audio amplifier, and a control means that is always energized drives the power element and applies a predetermined voltage to the terminal to generate a beep sound. Sound generation method. In an audio amplifier that amplifies an audio signal from an audio signal source, applies it to an electromechanical transducer, and synthesizes it,
A power element capable of applying a predetermined voltage to at least one terminal of the electromechanical transducer;
An audio amplifier characterized in that a control means that controls the operation of the audio amplifier and is always energized drives the power element to generate a beep sound in the electromechanical conversion element. The audio signal source outputs a digital audio signal,
The audio amplifier includes a bridge-structured power element that switches a power supply voltage in response to the digital audio signal, and a low-pass filter that smoothes the output thereof.
3. The audio amplifier according to claim 2, wherein the power element for the beep sound is connected to an output side of the low-pass filter. 4. A portable digital audio device comprising the audio amplifier according to claim 2 or 3.

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