JP2007049437A - Speaker system, speaker, and power superposer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high efficiency power-superposed speaker system capable of superposing/separating the power source and sound signals in a simple circuit constitution. <P>SOLUTION: A PWM converter 22 modulates sound signals inputted to a power superposer 20 into PWM signals, and the superposing circuit 23 converts the signals into bipolar PPM signals superposed on a power voltage to output superposed signals which are inputted to an amplifier-containing speaker 30. A separating and PWM restoring circuit 31 separates the superposed signals into the original PWM signals and the power voltage, and the PWM signals are amplified by a PWM driver 32 and inputted to a speaker 34 through a low-pass filter 33 to output as sounds. <P>COPYRIGHT: (C)2007,JPO&amp;INPIT

Description

  The present invention relates to a speaker system for audio output, and more particularly to a system having a speaker with a built-in amplifier.

  Conventionally, in general audio devices, amplifiers and speakers are housed in separate housings, but with the spread of portable portable players and personal computers, the demand for speakers with built-in amplifiers that can be connected to them increases. (For example, Patent Document 1).

  In order to operate an amplifier built-in speaker, it is necessary not only to input an audio signal but also to supply power to the amplifier in the speaker. Therefore, the conventional speaker with a built-in amplifier requires two input lines, a power line and a signal line. If a plurality of speaker input lines are required in this way, it is not only inconvenient to arrange the speakers, but also a factor that impairs the appearance.

  Therefore, in recent years, a power supply in which a power line and a signal line that an amplifier built-in speaker should have is shared by superimposing a sound signal on a power supply voltage and transmitting the power supply and the sound signal to the speaker through a single wiring. Superimposed speaker systems have been developed.

JP 2004-229250 A

  In the power superimposed speaker system, a circuit for superimposing the audio signal and the power supply voltage on the audio signal transmitting side and a circuit for separating the both again on the speaker side are complicated, which causes an increase in cost.

  The present invention has been made to solve the above-described problems, and provides a high-efficiency power supply type speaker system that can superimpose / separate a power supply and an audio signal with a simple circuit configuration. It is aimed.

  A speaker system according to the present invention includes a PWM modulator that modulates an audio signal into a PWM (Pulsed Wave Modulation) signal, and a superposition that converts the PWM signal into a bipolar PPM (Pulse Position Modulation) signal and that is superimposed on a power supply voltage. A superposition circuit that generates a signal; a separation circuit that separates the PWM signal from the superposition signal; and a speaker that outputs sound based on the PWM signal obtained by the separation circuit.

  According to the present invention, since the audio signal is converted into the impulse of the PPM signal and superimposed on the power supply voltage, it is not necessary to use a special modulation / demodulation circuit as in the case of superimposing the analog signal on the power supply, and is relatively simple. With the configuration, the audio signal and the power supply voltage can be superimposed / separated, which can contribute to cost reduction of the speaker system. Further, since the speaker is driven by power amplification in the state of a pulse signal (PWM signal), the power efficiency is higher than that of a speaker system using a conventional analog amplifier.

<Embodiment 1>
FIG. 1 is a diagram showing a configuration of a speaker system according to Embodiment 1 of the present invention. As shown in the figure, this speaker system includes an audio signal source 10, a power supply superimposing device 20, and an amplifier built-in speaker 30.

  The audio signal source 10 is a device that outputs an audio signal, such as a portable player or a personal computer.

  The power superimposing device 20 is a device that superimposes the audio signal output from the audio signal source 10 on the power supplied from a predetermined power supply line and transmits it to the speaker 30 with built-in amplifier. ) A converter 22 and a superimposing circuit 23 are provided. The power supply circuit 21 is a circuit that generates a predetermined power supply voltage for driving the amplifier built-in speaker 30 from the power supply supplied from the power supply line. The PWM converter 22 is a circuit that performs PWM modulation on the audio signal and outputs it as a PWM signal. The superimposing circuit 23 is a circuit that converts a PWM signal into a bipolar (bipolar) PPM (Pulse Position Modulation) signal and generates a superimposed signal by superimposing it on a power supply voltage.

  Here, the bipolar PPM signal is a PPM signal having positive and negative pulses. When converting a PWM signal into a PPM signal, for example, the rising edge of each pulse of the PWM signal is converted into a positive pulse, and the falling edge is converted into a negative pulse. In this case, the pitch from the positive pulse to the next negative pulse in the converted PPM signal corresponds to each pulse width of the conversion source PWM signal.

  The amplifier built-in speaker 30 is a speaker device that outputs sound based on the superimposed signal transmitted from the power supply superimposing device 20, and includes a separation / PWM reproduction circuit 31, a PWM driver 32, a low-pass filter 33, and a speaker 34. The separation and PWM reproduction circuit 31 is a circuit that receives a superimposed signal from the power supply superimposing device 20 and separates the original power supply voltage and the PWM signal from the superimposed signal. The PWM driver 32 is an amplifier circuit that amplifies the PWM signal. The low-pass filter 33 is a circuit that removes unnecessary high-frequency components contained in the PWM signal, and a signal is input to the speaker 34 through the low-pass filter 33.

  The operation of this speaker system will be described below. The audio signal output from the audio signal source 10 is input to the PWM converter 22 of the power supply superimposing device 20. The PWM converter 22 performs PWM modulation on the input audio signal and inputs it to the superimposing circuit 23 as a PWM signal. The superimposing circuit 23 converts the PWM signal into a bipolar (bipolar) PPM signal, and also generates a superimposed signal by superimposing the PPM signal on the power supply voltage generated by the power supply circuit 21 as shown in FIG. . FIG. 2 shows an example in which PPM conversion is performed in which the rising edge of the PWM signal is converted into a positive impulse and the falling edge is converted into a negative impulse. The superimposing circuit 23 transmits the generated superimposing signal to the speaker 30 with a built-in amplifier.

  The superimposed signal input from the power supply superimposing device 20 (superimposing circuit 23) to the amplifier built-in speaker 30 is input to the separation and PWM reproduction circuit 31. The separation and PWM reproduction circuit 31 reproduces the original PWM signal by separating the PPM signal (positive and negative impulses) that is a high-frequency component of the superimposed signal and inputs it to the PWM driver 32. At the same time, the DC component of the superimposed signal is supplied to the PWM driver 32 as a power supply voltage. As a result, as shown in FIG. 2, the power supply voltage and the PWM signal are separated from the superimposed signal.

  The PWM driver 32 amplifies the PWM signal obtained by the separation and PWM reproduction circuit 31. Thereby, the PWM signal has electric power capable of driving the speaker 34. The amplified PWM signal is input to the speaker 34 and output as sound after unnecessary high frequency components are removed by the low-pass filter 33. That is, the speaker 34 according to the present embodiment is driven by the PWM signal amplified by the PWM driver 32.

  According to the present embodiment, since the audio signal is converted into the impulse of the PPM signal and superimposed on the power supply voltage, it is not necessary to use a special modulation / demodulation circuit as in the case of superimposing the analog signal on the power supply. The audio signal and the power supply voltage can be superimposed / separated with a simple configuration, which can contribute to cost reduction of the speaker system. Further, since the speaker is driven by power amplification in the state of a pulse signal (PWM signal), the power efficiency is higher than that of a speaker system using a conventional analog amplifier.

  In this embodiment, a low-pass filter 33 is interposed between the PWM driver 32 and the speaker 34. The low-pass filter 33 not only removes noise components associated with PWM modulation but also so-called unnecessary radiation ( It functions to remove EMC (Electro Magnetic Compatibility). This unnecessary radiation is generated, for example, by a wiring (so-called “speaker cord”) for transmitting the amplified PWM signal, etc., so that the speaker 30 with a built-in amplifier includes the PWM driver 32 as in this embodiment, and the PWM signal is amplified. Is performed close to the speaker 34, unnecessary radiation is reduced. If the unnecessary radiation is reduced, it can be expected that the low-pass filter 33 can be omitted from the amplifier built-in speaker 30 of the present embodiment. In this case, the cost can be further reduced. When the low-pass filter 33 is omitted, the PWM signal amplified by the PWM driver 32 is directly input to the speaker 34. However, a component having a frequency higher than a certain level cannot be output due to the characteristics of the speaker. As a result, it is possible to output normal sound.

  Further, in the PWM driver 32, unnecessary radiation may be generated because large power is switched at a high speed when the PWM signal is amplified. However, in the system according to the present embodiment, the PWM driver 32 is mounted on the speaker 30 with a built-in amplifier. Thus, the structure is isolated from other circuits (circuits of the power supply superimposing device 20 and the audio signal source 10). Therefore, it is possible to take countermeasures against unnecessary radiation for the PWM driver 32 alone, and there is an advantage that countermeasures against unnecessary radiation of the entire system can be facilitated.

  Furthermore, since transmission of the power supply voltage and the audio signal from the power supply superimposing device 20 to the amplifier built-in speaker 30 is performed by the superimposed signal, both transmissions can be performed by a single wiring. Therefore, when the power supply superimposing device 20 and the amplifier built-in speaker 30 are housed in separate housings, the degree of freedom of arrangement of the amplifier built-in speaker 30 can be improved and a decrease in the aesthetic appearance of the speaker system can be suppressed.

<Embodiment 2>
FIG. 3 is a diagram showing the configuration of the speaker system according to Embodiment 2 of the present invention. As shown in the figure, the speaker system includes an audio signal source 10, a power supply superimposing device 20, and an amplifier built-in speaker 40. Note that the audio signal source 10 and the power supply superimposing device 20 are the same as those shown in the first embodiment, and a description thereof will be omitted here.

  The amplifier built-in speaker 40 is a speaker device that outputs sound based on the superimposed signal transmitted from the power supply superimposing device 20, and includes a separation / PWM reproduction circuit 41, a low-pass filter 42, an equalizer 43, a PWM amplifier 44, and a speaker 45. I have. The separation and PWM reproduction circuit 41 is a circuit that receives the superimposed signal output from the power supply superimposing device 20 and separates the original power supply voltage and the PWM signal from the superimposed signal. The low-pass filter 42 is a circuit that removes a high-frequency component from the PWM signal. In the present embodiment, the low-pass filter 42 functions as a demodulation circuit that demodulates the PWM signal into an analog audio signal. The equalizer 43 is a circuit that adjusts the overall frequency characteristics of the audio signal to correct the sound quality. The PWM amplifier 44 is a circuit that amplifies the audio signal, and the speaker 45 is driven by the audio signal amplified by the PWM amplifier 44.

  The operation principle of the PWM amplifier is different from that of the conventional analog amplifier. That is, in the PWM system amplifier, the input audio signal is once modulated after being modulated into a PWM signal and then amplified, and then demodulated into an analog audio signal suitable for speaker driving by a low-pass filter and output. Since the amplification operation is performed on the pulse signal (PWM signal) as described above, highly efficient amplification is possible.

  The operation of this speaker system will be described below. The audio signal output from the audio signal source 10 is converted into a PWM signal by the PWM converter 22 of the power supply superimposing device 20 as in the first embodiment. Then, it is converted into a bipolar PPM signal by the superimposing circuit 23 and superimposed on the power supply voltage, and is output from the power superimposing device 20 as a superimposed signal.

  The superimposed signal transmitted from the power superimposing device 20 to the amplifier built-in speaker 40 is input to the separation and PWM reproduction circuit 41. The separation and PWM regeneration circuit 41 separates the PPM signal (positive and negative impulses) that is the high-frequency component of the superimposed signal, regenerates the original PWM signal, and inputs it to the low-pass filter 42. At the same time, the DC component of the superimposed signal is supplied to the equalizer 43 and the PWM amplifier 44 as a power supply voltage.

  The PWM signal obtained by the separation and PWM reproduction circuit 41 is demodulated into an analog audio signal by the low-pass filter 42 and input to the equalizer 43. The equalizer 43 adjusts the overall frequency characteristic of the input audio signal, and inputs the adjusted audio signal to the PWM amplifier 44. The PWM amplifier 44 amplifies the audio signal. As a result, the audio signal has electric power that can drive the speaker 45. The amplified audio signal drives the speaker 45, and audio is output from the speaker 45.

  Also in this embodiment, since the audio signal is converted into an impulse of the PPM signal and superimposed on the power supply voltage, the audio signal and the power supply voltage can be superimposed / separated with a relatively simple configuration, and the cost of the speaker system can be increased. It can contribute to reduction.

  In this embodiment, the PWM signal is demodulated into an analog audio signal prior to amplification. However, since the amplification of the audio signal is performed by a PWM amplifier, the conventional analog signal is the same as in the first embodiment. Power efficiency is higher than a speaker system using an amplifier. In addition, since the PWM signal is demodulated into an audio signal before amplification, an equalizer 43 can be interposed, and an advantage that the sound quality can be improved is obtained.

  Furthermore, since the power supply voltage and the audio signal are transmitted from the power supply superimposing device 20 to the amplifier built-in speaker 40 by the superimposed signal, both can be transmitted by a single wiring. Accordingly, when the power superimposing device 20 and the amplifier built-in speaker 40 are housed in separate housings, the degree of freedom of arrangement of the amplifier built-in speaker 40 can be improved, and a decrease in the appearance of the speaker system can be suppressed.

1 is a diagram showing a configuration of a speaker system according to Embodiment 1. FIG. 6 is a diagram for explaining the operation of the speaker system according to Embodiment 1. FIG. 6 is a diagram illustrating a configuration of a speaker system according to Embodiment 2. FIG.

Explanation of symbols

3 audio signal source, 20 power supply superposition device, 21 power supply circuit, 22 PWM converter, 23 superposition circuit, 30 amplifier built-in speaker, 31 separation and PWM reproduction circuit, 32 PWM driver, 33 low-pass filter, 34 speaker, 40 amplifier built-in speaker , 41 Separation and PWM regeneration circuit, 42 Low-pass filter, 43 Equalizer, 44 PWM system amplifier, 45 Speaker.

Claims (9)

A PWM modulator that modulates an audio signal into a PWM (Pulsed Wave Modulation) signal;
A superposition circuit that converts the PWM signal into a bipolar PPM (Pulse Position Modulation) signal and generates a superposition signal superimposed on the power supply voltage;
A separation circuit for separating the PWM signal from the superimposed signal;
A speaker system comprising: a speaker that outputs sound based on the PWM signal obtained by the separation circuit. The speaker system according to claim 1,
An amplifier that amplifies the PWM signal obtained by the separation circuit;
The speaker is
The speaker system is driven by the PWM signal amplified by the amplifier. The speaker system according to claim 1,
A demodulation circuit that demodulates the PWM signal obtained by the separation circuit into an analog audio signal;
A PWM amplifier for amplifying the analog audio signal;
The speaker is
The speaker system is driven by the analog audio signal amplified by the amplifier. The speaker system according to claim 3, wherein
The speaker system further comprising an equalizer for correcting the sound quality of the analog audio signal. A separation circuit that receives a superimposed signal in which a bipolar PPM signal is superimposed on a power supply voltage and separates a PWM signal corresponding to the PPM signal from the superimposed signal;
A speaker device comprising: a speaker that outputs sound based on the PWM signal obtained by the separation circuit. The speaker device according to claim 5, wherein
An amplifier for amplifying the PWM signal;
The speaker is
The speaker device is driven by the PWM signal amplified by the amplifier. The speaker device according to claim 5, wherein
A demodulation circuit for demodulating the PWM signal into an analog audio signal;
A PWM amplifier for amplifying the analog audio signal;
The speaker is
The speaker device is driven by the analog audio signal amplified by the amplifier. The speaker device according to claim 7, wherein
The speaker device further comprising an equalizer for correcting the sound quality of the analog audio signal. A PWM modulator that modulates an audio signal into a PWM signal;
A power superimposing device comprising: a superposition circuit that converts the PWM signal into a bipolar PPM signal and generates a superposition signal superimposed on the power source voltage.

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