JP2006094146A - Headphone unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a headphone unit that receives no effect of various noises and externally emits no switching noise due to a pulse component caused at class D amplification. <P>SOLUTION: The headphone unit includes: a digital converter 123 for converting a digital signal into a PWM signal; a class D amplifier 124 for amplifying the PWM signal from the digital converter; an acoustic unit 130 for receiving the PWM signal from the class D amplifier not via a filter means and reproducing sound; and a case 110 for accommodating the acoustic unit, and it is characterized in that the case is configured with a material containing a substance at least either of a metal and a metallic compound, and the digital converter and the class D amplifier are arranged in a space between the case and the acoustic unit. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a headphone device, and more particularly to a headphone device capable of reproducing sound by receiving a digital signal.

  In various types of devices such as portable CD players, MD players, and digitally compressed audio data reproducing devices, headphones such as in-ear and neckband are used.

In this type of equipment, digitally recorded music data and the like are D / A converted inside the playback equipment, and further, an analog signal is amplified to such an extent that a sufficient volume can be obtained during playback, and then output to the headphones. I am doing so. Note that this type of headphones is described in Patent Document 1 below, for example.
JP-A-10-66181 (first page, FIG. 1)

  When using the above general headphones, DA conversion and analog audio amplification are performed on the playback device side, and an analog audio signal is supplied to the headphones via a cord of about several tens of centimeters.

  In this case, various noises generated in the playback device may affect the analog signal, and may adversely affect sound quality, dynamic range, and the like. In addition, a high-frequency signal from a mobile phone or the like that exists in the vicinity of the headphone user also has an adverse effect on the analog signal through the headphone cord as a result of the headphone cord acting as an antenna.

  In recent years, class D amplifiers have been used for analog amplification from the viewpoint of low power consumption of playback equipment. This class D amplifier amplifies an audio signal by high-speed switching using a pulse having a sampling frequency 10 times or more that of the audio signal. Then, the PWM-modulated output signal is filtered by a low-pass filter to remove the sampling frequency component and output only the frequency component of the audio signal.

  However, if the filtering by this low-pass filter is not sufficient, the pulse component amplified in class D is radiated to the outside as switching noise through the headphones cord.

  The present invention has been made to solve the above-described problems, and is not affected by various kinds of noise generated inside the reproduction apparatus or various kinds of external noises. It is an object of the present invention to provide a headphone device in which switching noise due to the pulse component is not radiated to the outside.

The present invention for solving the above problems is as described below.
(1) The invention according to claim 1 is a digital converter for converting a digital signal into a PWM signal, a class D amplifier for amplifying the PWM signal from the digital converter, and a filter for the PWM signal from the class D amplifier. A headphone device comprising: an acoustic unit that receives sound without means and reproduces sound; and a case that houses the acoustic unit, wherein the case is made of a material having a substance containing at least one of a metal and a metal compound. The headphone device is characterized in that the digital converter and the class D amplifier are arranged in a space between the case and the acoustic unit.

  In the present invention, when various digital signals such as PCM signals are reproduced as sound by the acoustic unit, the digital converter disposed between the acoustic unit and the metal / metal compound-containing material case that accommodates the acoustic unit, and D Using a class amplifier, various digital signals such as PCM signals are converted into PWM signals by a digital converter, this PWM signal is class D amplified by a class D amplifier, and the PWM signal from the class D amplifier is passed through filter means. Without supplying to the acoustic unit.

(2) The invention described in claim 2 is characterized in that, in claim 1, the case also serves as a frame of the acoustic unit.
In the present invention, when various digital signals such as PCM signals are reproduced as sound by the acoustic unit, the acoustic unit is accommodated and disposed between the metal / metal compound-containing material case constituting the frame and the acoustic unit. Using a digital converter and a class D amplifier, various digital signals such as PCM signals are converted into PWM signals by a digital converter, the PWM signal is amplified by a class D amplifier, and a PWM signal is output from the class D amplifier. Is supplied to the acoustic unit without passing through the filter means.

  (3) The invention according to claim 3 is the digital signal converter according to claim 1 or 2, wherein the digital converter converts the PWM signal into a PWM signal having a sampling frequency equal to or included in the sampling frequency when the class D amplifier amplifies. It is characterized by that.

  In the present invention, when various digital signals such as PCM signals are reproduced as sound by the acoustic unit, the digital converter disposed between the acoustic unit and the metal / metal compound-containing material case that accommodates the acoustic unit, and D Using a class amplifier, various digital signals such as PCM signals are converted into PWM signals by a digital converter, this PWM signal is class D amplified by a class D amplifier, and the PWM signal from the class D amplifier is passed through filter means. Without supplying to the acoustic unit. At this time, the digital converter converts it to a PWM signal having the same sampling frequency as or included in the class D amplifier. Thereby, various digital signals such as PCM signals are amplified by the class D amplifier as PWM signals.

  (1) In the first aspect of the present invention, the case housing the acoustic unit is made of a material having a substance containing at least one of a metal and a metal compound, and the digital unit is formed in the space between the case and the acoustic unit. A converter and a class D amplifier are arranged, a digital signal is converted into a PWM signal by a digital converter, this PWM signal is amplified by a class D amplifier, and the PWM signal output from the class D amplifier is filtered. The sound is supplied to the sound unit without going through the means, and is reproduced as sound by the sound unit.

  Here, the case housing the acoustic unit is made of a material having a substance containing at least one of metal and metal compound, and the digital converter and the class D amplifier are arranged in the space between the case and the acoustic unit. Therefore, digital conversion into a PWM signal and class D amplification are executed within the case, so that it is not affected by various noises generated inside the reproduction apparatus or various external noises.

  The case housing the acoustic unit is made of a material having a substance containing at least one of a metal and a metal compound, and a digital converter and a class D amplifier are disposed in the space between the case and the acoustic unit. In addition, since the class D amplifier and the acoustic unit are shielded by the case, the switching noise due to the pulse component at the time of class D amplification is not radiated to the outside.

  Further, as described above, the class D amplifier and the acoustic unit are arranged in the case, and switching noise due to the pulse component at the time of class D amplification is not radiated to the outside. The PWM signal can be supplied to the acoustic unit without intervention, the headphone device can be miniaturized, and sound quality deterioration due to the filter is not generated.

  (2) In the invention described in claim 2, when various digital signals such as PCM signals are reproduced as sound by the acoustic unit, the acoustic unit is accommodated and the metal / metal compound-containing material case and the acoustic unit which constitute the frame Using a digital converter and a class D amplifier arranged between each of them, various digital signals such as PCM signals are converted into PWM signals by a digital converter, and the PWM signal is amplified by a class D amplifier by class D, The PWM signal from the class D amplifier is supplied to the acoustic unit without passing through the filter means.

  Here, the case that accommodates the acoustic unit is configured as a frame of the acoustic unit with a material having a substance containing at least one of metal and metal compound, and a digital converter and a space between the case and the acoustic unit Since the class D amplifier is arranged, digital conversion to PWM signal and class D amplification are executed in the case, so that the influence of various noises generated inside the reproduction apparatus or various external noises is affected. I will not receive it.

  The frame of the acoustic unit is made of a material having a substance containing at least one of metal and metal compound as a case, and a digital converter and a class D amplifier are arranged in the space between the case and the acoustic unit. In addition, since the class D amplifier and the acoustic unit are shielded by the case, the switching noise due to the pulse component at the time of class D amplification is not radiated to the outside.

  Further, as described above, the class D amplifier and the acoustic unit are arranged in the frame and case, and the switching noise due to the pulse component at the time of class D amplification is not radiated to the outside. The PWM signal can be supplied to the acoustic unit without using any means, the headphone device can be downsized, and the sound quality deterioration due to the filter can be prevented. Further, it is possible to promote downsizing also by being a frame and case.

  (3) In the invention described in claim 3, when various digital signals such as PCM signals are reproduced as sound by the acoustic unit, it is arranged between the metal / metal compound containing material case accommodating the acoustic unit and the acoustic unit. The digital converter and class D amplifier are used to convert various digital signals such as PCM signals into PWM signals having a sampling frequency suitable for class D amplification by the digital converter, and this PWM signal is class D by the class D amplifier. It amplifies and supplies the PWM signal from the class D amplifier to the acoustic unit without passing through the filter means.

  Here, since the digital converter converts the signal into a PWM signal having a sampling frequency that is the same as or included in the sampling frequency of the class D amplifier, it is efficiently amplified. For this reason, it is not affected by various noises generated inside the playback device or various external noises.

  The best mode for carrying out the present invention (hereinafter referred to as an embodiment) will be described below in detail with reference to the drawings. Here, an embodiment of a headphone device that receives various digital signals such as a PCM signal and outputs sound by performing digital conversion and amplification into a PWM signal inside the headphone device will be described.

  FIG. 1 is a block diagram showing an electrical configuration of a headphone device 100 and its peripheral devices according to the embodiment. In FIG. 1, reference numeral 10 denotes various playback devices such as a portable CD player, an MD player, or a digital compressed audio data playback device.

  The playback device 10 includes a digital signal output unit 11 that outputs digital signals from various recording media and broadcasts, an I / F unit 12 as an interface for outputting digital signals to the outside, and a headphone device to be described later. And a power supply unit 13 for supplying the power. The digital signal output unit 11 outputs a digital signal such as a PCM signal.

  A signal cable 20 includes a digital signal line 21 that transmits a digital signal from the playback device 10 to the headphone device 100, and a power supply line 22 that supplies power from the playback device 10 to the headphone device 100.

  Reference numeral 100 denotes a headphone device according to the present embodiment. The headphone device has a function of receiving a digital signal from the playback device 10 via the signal cable 20 and performing a digital conversion and amplification into a PWM signal inside the headphone device to output sound. have.

Reference numeral 110 denotes a case made of a material having a substance containing at least one of a metal and a metal compound in order to accommodate the acoustic unit.
Here, the metal compounds are various metal compounds such as metal oxides such as ferrite. In addition, a substance containing at least one of a metal and a metal compound is a metal compound such as a metal itself, a metal oxide itself as a sintered body, or a metal powder or metal oxide powder in a non-metal material such as plastic. Means mixed substances. Further, as a material having a substance containing at least one of a metal and a metal compound, a non-metallic material such as plastic, a material obtained by applying a metal powder or a metal oxide powder to a non-metallic oxide, a non-metallic material such as a plastic, etc. A metal-plated material, a material in which a metal film or a film-like metal oxide is attached to a non-metallic material such as plastic, and the like are applicable. And by using such a material, it is possible to shield by blocking, reflecting, and absorbing electromagnetic waves.

  A circuit unit 120 includes various circuits to be described later, and includes an I / F 122, a digital converter 123, a class D amplifier 124, and the like. The circuit unit 120 is disposed on the substrate 121 (see FIG. 2).

Here, the I / F 122 is an interface that functions to receive an input of a digital signal from the playback device 10.
The digital converter 123 digitally converts various digital signals such as a PCM signal input via the I / F 122 into a PWM signal. Here, the digital conversion is to convert various digital signals such as a PCM signal into a PWM signal having a sampling frequency equal to or included in the sampling frequency of the class D amplifier.

  The class D amplifier 124 amplifies the PWM signal from the digital converter 123 by class D amplification. If the sampling frequency of the class D amplifier 124 is one type, the digital converter 123 performs digital conversion into a PWM signal having the same sampling frequency as the sampling frequency of the class D amplifier 124. If the sampling frequency of the class D amplifier 124 is a plurality of types or has a followable frequency range, the digital converter 123 converts the digital signal to the PWM signal having the sampling frequency included in the sampling frequency of the class D amplifier 124. Perform the conversion.

  Reference numeral 130 denotes an acoustic unit as an electroacoustic transducer that converts an electrical signal into vibration of a diaphragm and outputs sound. The acoustic unit 130 is connected so as to reproduce the sound by receiving the PWM signal from the class D amplifier 124 without passing through the filter means.

  FIG. 2 is a partial cross-sectional view showing a mechanical cross-sectional configuration of the circuit unit 120 and the acoustic unit 130 which are main components of the headphone device 100 of the embodiment. In FIG. 2, reference numeral 110 denotes a case made of a material having a substance containing at least one of a metal and a metal compound as described above in order to accommodate the acoustic unit 130.

  Reference numeral 111 denotes a protector disposed in a direction in which the diaphragm 138 outputs sound in order to protect the diaphragm of the acoustic unit, and is provided with one or a plurality of holes for allowing sound to pass through.

  A circuit unit 120 includes an I / F 122, a digital converter 123, a class D amplifier 124, and the like. The circuit unit 120 is disposed on a substrate 121 (see FIG. 2), and includes a case 110 and the acoustic unit. 130 in the space between the two. In FIG. 2, the circuit unit 120 is arranged in a donut-shaped space existing around the magnet in the direction of the back surface of the diaphragm.

  Reference numeral 130 denotes an acoustic unit as an electroacoustic transducer that converts an electrical signal into vibration of a diaphragm and outputs sound. The acoustic unit 130 is connected so as to reproduce the sound by receiving the PWM signal from the class D amplifier 124 without passing through a filter means such as a low-pass filter.

  131 is a frame of the acoustic unit 130, 132 is a holder for holding the magnet part of the acoustic unit 130, 133 is a hole piece constituting a magnetic circuit, 134 is a magnet constituting the magnetic circuit, 135 is a hole piece constituting the magnetic circuit, 137 is a yoke constituting a magnetic circuit, 138 is a diaphragm that vibrates in accordance with an analog signal and outputs sound, and 139 is a voice that drives the diaphragm 138 by receiving an analog signal and vibrating between the magnetic circuits. It is a coil.

  Note that the configuration, arrangement, and operation principle of the magnet 134, the hall pieces 133, 135, the yoke 137, and the voice coil 139 are merely examples, and various modifications of the acoustic unit 130 are possible.

  FIG. 3 is an explanatory diagram illustrating an example of an external configuration when the headphone device 100 of the embodiment is configured as an in-ear headphone. Here, the housing 112 is configured to cover the outside of the case 110 of the headphone device 100 of FIG. 2, and the signal cable 20 extends to the outside from one end of the housing 112 on the opposite side of the protector 111.

  In addition, in order to satisfy the characteristic with respect to noise as will be described later, when applied to stereo headphones, it is desirable to arrange the circuit unit 120 in the space between the case 110 and the acoustic unit 130 on the left and right.

<Operation of headphone device>
In the headphone device 100 configured as described above, various digital signals such as PCM signals received from the playback device 10 via the I / F 122 are converted into PWM signals by the digital converter 123.

  If the sampling frequency of the class D amplifier 124 is one type, the digital converter 123 performs digital conversion into a PWM signal having the same sampling frequency as the sampling frequency of the class D amplifier 124. If the sampling frequency of the class D amplifier 124 is a plurality of types or has a followable frequency range, the digital converter 123 converts the digital signal to the PWM signal having the sampling frequency included in the sampling frequency of the class D amplifier 124. Perform the conversion.

  The class D amplifier 124 amplifies the PWM signal by a high-speed switching of a power element such as an FET using a pulse having a sampling frequency 10 times or more of the upper limit frequency (20 kHz) of the audio signal. The PWM signal is supplied to the acoustic unit 130 without passing through the filter means.

  As described above, the digital converter 1123 executes digital conversion into a PWM signal having a sampling frequency that matches the sampling frequency of the class D amplifier 1124. Therefore, the class D amplifier 1124 can be directly driven by the PWM signal from the digital converter 1123.

  Here, since the acoustic unit 130 cannot reproduce a frequency component higher than the upper limit frequency of the audio signal, even if the output of the class D amplifier 124 is a pulse component of the sampling frequency described above, Only the frequency component is output from the diaphragm 138 as sound.

  Here, the case 110 that accommodates the acoustic unit 130 is made of a material having a substance containing at least one of a metal and a metal compound, and an I / F 122, a digital converter is provided in a space between the case and the acoustic unit. 123 and the class D amplifier 124 are arranged, so that digital conversion into a PWM signal and class D amplification are executed in the case 110. Therefore, various noises generated in the reproduction apparatus 10 or external noises are generated. Not affected by various noises.

  In addition, the case 110 that accommodates the acoustic unit 130 is made of a material having a substance containing at least one of a metal and a metal compound, and an I / F 122, digital conversion is provided in a space between the case 110 and the acoustic unit 130. The class 123 amplifier and the class D amplifier 124 are disposed, the class D amplifier 124 and the acoustic unit 130 are disposed at a short distance, and are further shielded by the case 110. Switching noise due to the pulse component when amplified is not radiated to the outside.

  Furthermore, since the class D amplifier 124 and the acoustic unit 130 are arranged in the case 110 as described above, the switching noise due to the pulse component at the time of class D amplification is not radiated to the outside. Therefore, the PWM signal can be supplied to the acoustic unit 130 without passing through the filter means, and the headphone device can be downsized. Further, since it is not necessary to use filter means, sound quality deterioration due to the filter is not generated.

  Although a digital signal flows through the signal cable 20 from the playback device 10 to the headphone device 100, it is a low-level signal, so there is no concern about noise radiation. Even if external noise is mixed into the digital signal line 21 of the signal cable 20, components other than the sampling frequency are removed by the processing in the I / F 122 and the digital converter 123, so that there is an adverse effect. There is nothing.

  FIG. 4 is a partial cross-sectional configuration diagram showing a modification of the acoustic unit 130. FIG. 5 is a partial cross-sectional configuration diagram showing another modification of the acoustic unit 130. Here, the case 110 is characterized in that it also serves as the frame 131 in FIG. 1 of the above-described embodiment.

  Here, the case 110 that houses the acoustic unit 130 is configured as a frame of the acoustic unit with a material having a substance containing at least one of a metal and a metal compound, and the space between the case 110 and the acoustic unit 130 is within the space. Since the I / F 122, the digital converter 123, and the class D amplifier 124 are arranged, digital conversion into a PWM signal and class D amplification are executed in the case 110. It is not affected by various noises or various external noises.

  Further, the frame of the acoustic unit 130 is made of a material having a substance containing at least one of a metal and a metal compound as the case 110, and an I / F 122, digital conversion is provided in a space between the case 110 and the acoustic unit 130. Since the device 123 and the class D amplifier 124 are arranged, the switching noise due to the pulse component at the time of class D amplification is not radiated to the outside.

  Further, as described above, the class D amplifier 124 and the acoustic unit 130 are arranged in the case 110 that also serves as a frame, and switching noise due to the pulse component at the time of class D amplification is not radiated to the outside. The PWM signal can be supplied from the class amplifier 124 to the acoustic unit without passing through the filter means. As a result, it is not necessary to use components such as a coil and a capacitor for the filter means, and the headphone device 100 can be downsized. Furthermore, sound quality deterioration due to the filter is not generated. Further, the use of the case 110 also serving as a frame can facilitate downsizing.

<Other embodiments>
In the above embodiment, a specific example of the in-ear type headphone device 100 is shown in FIG. 3, but the embodiment can be applied to various headband devices of a neckband type or a headband type other than this.

  Further, instead of supplying power to the headphone device 100 from the playback device 10, it is also possible to supply power by providing a small and light battery such as a lithium battery or a fuel cell in the headphone device 100. By doing so, the power supply line 22 is not required for the signal cable 20. For this reason, an optical cable can be used as the digital signal line.

It is a functional block diagram which shows the electric constitution of the headphone apparatus of embodiment of this invention. It is a block diagram which shows the cross-sectional structure containing the circuit part of the acoustic unit which is the principal part of the headphone apparatus of embodiment of this invention. It is a block diagram which shows the external appearance structure of the headphone apparatus of embodiment of this invention. It is a block diagram which shows the other example of the cross-sectional structure containing the circuit part of the acoustic unit which is the principal part of the headphone apparatus of embodiment of this invention. It is a block diagram which shows the other example of the cross-sectional structure containing the circuit part of the acoustic unit which is the principal part of the headphone apparatus of embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Playback apparatus 20 Signal cable 21 Digital signal line 22 Power supply line 100 Headphone apparatus 110 Case 120 Circuit part 122 I / F
123 Digital converter 124 Class D amplifier 130 Acoustic unit

Claims (3)

A digital converter for converting a digital signal into a PWM signal;
A class D amplifier for amplifying the PWM signal from the digital converter;
An acoustic unit that receives the PWM signal from the class D amplifier without using a filter means and reproduces sound;
A headphone device comprising a case for housing the acoustic unit,
The case is made of a material having a substance containing at least one of a metal and a metal compound, and the digital converter and the class D amplifier are disposed in a space between the case and the acoustic unit.
A headphone device characterized by that. The case also serves as a frame of the acoustic unit,
The headphone device according to claim 1. The digital converter converts to a PWM signal having a sampling frequency equal to or included in the sampling frequency when the class D amplifier amplifies,
The headphone device according to claim 1, wherein the headphone device is provided.

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