JP2005080114A - Device with audio signal amplification function, and amplifier control method for audio broadcast receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To freely switch a main amplifier 51 to an AM mode as an AB class amplifier and a normal mode as a D class amplifier in a device 37 with audio signal amplification function. <P>SOLUTION: An FM/AM tuner 40 has an S meter which measures a receiving level of received radiowave of an AM radio broadcast station under channel selection built-in. When the receiving level of the received radiowave of the AM radio broadcast station under channel selection is less than a predetermined value, the main amplifier 51 operates in the AM mode. On the contrary to this, when the receiving level is equal to or more than the predetermined value, the main amplifier 51 operates in the normal mode. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a device with an audio signal amplification function and an amplifier control method for an audio broadcast receiver mounted on an automobile or the like, and more specifically, audio that appropriately amplifies output from a source by using a plurality of types of amplifiers having different power efficiencies. The present invention relates to an apparatus with a signal amplification function and an amplifier control method for an audio broadcast receiver.

  A typical apparatus with an audio signal amplification function mounted on an automobile includes, for example, an AM radio, an FM radio, a CD player, a DVD player, and an MD (minidisc) reproducing / recording apparatus. The apparatus with an audio signal amplification function is equipped with a D-class (class D) amplifier having high power efficiency, and amplifies the demodulated signal of FM radio, the CD reproduction signal, the DVD reproduction signal, or the MD reproduction signal by the amplifier, Output from the speaker. However, when the AM radio demodulated signal is amplified by a D-class amplifier, the D-class amplifier generates a high-frequency signal in the middle band in accordance with its operation, and is mixed in the AM tuner. Therefore, noise (eg, beat sound) in the output audio from the speaker increases. In order to avoid this, in the conventional apparatus with an audio signal amplification function, only the output from the AM tuner is amplified by an AB class (AB class) amplifier that is inferior in power efficiency to the D class.

On the other hand, in Patent Document 1, in multi-channel audio, a general channel signal is amplified by a first class (eg, AB class) amplifier, whereas only a predetermined channel signal (eg, a subwoofer channel signal) has power. When an AM tuner is selected as a source in an amplifying apparatus that amplifies using a second class (for example, D class) amplifier having higher efficiency than the first class amplifier, the second class amplifies the predetermined channel signal. The amplifier is deactivated, i.e., the audio output from the subwoofer is discontinued, thereby avoiding the noise output from the subwoofer associated with amplifying the AM source signal by the second class amplifier.
JP 2001-237659 A

  In a conventional apparatus with an audio signal amplification function, the performance of an amplifier with high power efficiency is completely wasted for amplification of AM radio broadcasting.

  The power amplifying apparatus disclosed in Patent Document 1 can stop the operation of the second class amplifier that amplifies the predetermined channel signal and avoids noise output from the speaker. However, for the predetermined channel signal, audio output from the speaker is possible. Is not performed at all, and the speaker output is stopped.

  An object of the present invention is to provide an audio signal amplifying function capable of avoiding an increase in noise associated with the operation of a high power efficiency amplifier while ensuring audio output to a user, and further making full use of the high power efficiency amplifier An apparatus and an amplifier control method for an audio broadcast receiver are provided.

The apparatus with an audio signal amplification function of the present invention has the following.
Input selection means for selecting one source from a plurality of sources including a first source related to an audio reception radio wave in a predetermined frequency band and at least one second source different from the first source ,
A first class amplifier for amplifying audio signals;
A second class amplifier for amplifying an audio signal with higher power efficiency than the first class amplifier;
Amplifier selecting means for selecting an amplifier for amplifying an audio signal from a source selected by the input selecting means from a first class amplifier and a second class amplifier;
Reception level detection means for detecting a reception level of an audio reception radio wave related to the first source, and reception of an audio reception radio wave related to the first source when the input selection means selects the first source. Control means for controlling the amplifier selection means such that the amplifier selection means selects the first class amplifier and the second class amplifier, respectively, depending on whether the level is below or above a predetermined level.

The following specific modes can be added in any combination to the apparatus with an audio signal amplification function of the present invention.
(A) When the input selection means has selected the second source, the control means causes the amplifier selection means to select the second amplifier.
(B) The input selection means is for selecting the source selected in the source selector for user operation, and the control means is selected by the amplification selection means when the selection source in the source selector is changed. It is determined whether or not the amplifier needs to be changed, and based on this determination, the amplifier selection means is instructed to change the selected amplifier.
(C) The predetermined frequency band is a medium wave (MW) band.
(D) The first class amplifier is an A class or AB class amplifier, and the second class amplifier is a D class amplifier.
(E) The apparatus with an audio signal amplification function is mounted on an automobile.

  The second source is, for example, a CD, DVD or MD playback device, or an FM tuner. A DVD playback signal includes a video signal in addition to an audio signal, but what is amplified by the first or second amplifier is an audio signal among the DVD playback signals. The source may be a source that outputs a video signal in addition to an audio signal as long as the source outputs at least an audio signal (eg, a DVD player and a TV tuner). The apparatus with an audio signal amplifying function of the present invention is not limited to an apparatus mounted on an automobile, and includes an apparatus placed at home or the like.

According to the amplifier control method for an audio broadcast receiver of the present invention,
Detect the reception level of audio reception radio waves in the specified frequency band,
When the detected reception level is lower than a predetermined reference level, the first class amplifier amplifies the audio signal related to the audio reception radio wave,
When the detected reception level is higher than a predetermined reference level, the audio signal related to the reception radio wave for audio is amplified by the second class amplifier of the second class from the first class amplifier for power efficiency.

The following specific modes can be added to the amplifier control method for an audio broadcast receiver of the present invention.
The predetermined frequency band is a medium wave band, the first class amplifier is an A class or AB class amplifier, and the second class amplifier is a D class amplifier.

  When the reception level of the audio reception radio wave related to the first source is large, even if the audio signal from the first source is amplified by the second class amplifier, the level of noise generated by the second class amplifier is: As a result, the noise in the output of the second class amplifier is not uncomfortable for the user.

  Thus, while the first source is selected, an audio output obtained by amplifying the audio signal from the first source by the amplifier is ensured, and the user does not feel uncomfortable due to noise increase under a predetermined condition. The audio signal from the first source can be amplified using a second class amplifier with high power efficiency.

  FIG. 1 is a functional block diagram of an apparatus 10 with an audio signal amplification function. The apparatus 10 with an audio signal amplification function includes an input selection unit 13, a first class amplifier 15, a second class amplifier 16, a reception level detection unit 18, a control unit 19, and an amplifier selection unit 20. The input selection means 13 includes a first source 11 related to audio reception radio waves in a predetermined frequency band, and at least one second source 12a, 12b,... As a source other than the first source 11. One source is selected from a plurality of sources including. The first class amplifier 15 amplifies the audio signal. The second class amplifier 16 amplifies the audio signal with higher power efficiency than the first class amplifier 15. The amplifier selection unit 20 selects an amplifier that amplifies the audio signal from the source selected by the input selection unit 13 from the first class amplifier 15 and the second class amplifier 16. The reception level detecting means 18 detects the reception level of the audio reception radio wave related to the first source (the reception level corresponds to the electric field strength of the reception radio wave). When the input selection unit 13 selects the first source, the control unit 19 determines whether the reception level of the audio reception radio wave related to the first source is lower or higher than a predetermined level. Controls the amplifier selection means 20 to select the first class amplifier 15 and the second class amplifier 16, respectively.

  The apparatus 10 with an audio signal amplification function is mounted on, for example, an automobile. The first source 11 is an AM tuner that receives, for example, an AM broadcast radio wave in a medium wave (MW) band, and a demodulated signal of the AM radio received radio wave is output from the AM tuner. The second sources 12a, 12b,... Are, for example, FM tuners, tape players, CD players, DVD players, MD players, and the like, and audio reproduction signals are output from these sources. For example, the first class amplifier 15 is an AB class amplifier, and the second class amplifier 16 is a D class amplifier. The audio output means 17 is, for example, a speaker or a headphone, and converts an input electric signal from the first class amplifier 15 or the second class amplifier 16 into audio and outputs the audio. The speaker may be built in the display device. The source selector 21 is operated by a user, and the user instructs a desired source to the apparatus 10 with an audio signal amplification function through an operation in the source selector 21. The source selector 21 is, for example, an operation key provided on the front surface of the apparatus 10 with an audio signal amplification function or a remote-controlled handy operator. The input selection means 13 selects one source corresponding to the user selection based on the user selection in the source selector 21.

  When the input selection unit 13 selects any one of the second sources 12a, 12b,..., The amplifier selection unit 20 amplifies the audio signal from the input selection unit 13 to the second class amplifier 16. And output to the audio output means 17. Even if an audio signal from one source selected from the second sources 12a, 12b,... Is amplified by the second class amplifier 16 having high power efficiency, a high frequency generated by the second class amplifier 16 is generated. Since the noise does not have any influence on the second source, the audio output means 17 outputs the audio related to the electric signal obtained by amplifying the audio signal from the second source by the second class amplifier 16 having high power efficiency. Outputs well.

When the input selection means 13 has selected the first source, it is further divided into the following cases (a) and (b).
(A) When the reception level of the broadcast radio wave related to the first source is less than a predetermined value.
(B) The broadcast radio wave reception level relating to the first source is equal to or higher than a predetermined value.

  If the audio signal from the first source is amplified by the second class amplifier 16 in the case of (a), the second class amplifier 16 makes the frequency band the same as the AM radio wave by the amplification operation. That is, a high-frequency signal in the middle band is generated, and this high-frequency signal is input to the tuner 14, and as a result, the S / N ratio of the output of the tuner 14 deteriorates. On the other hand, although the first class amplifier 15 is inferior to the second class amplifier 16 in power efficiency, it does not generate a high frequency signal in the middle band in the amplification operation, and the reception level of the broadcast related to the first source Even if it is low, the S / N ratio of the output of the tuner 14 is not deteriorated. Therefore, in the case of (a), the audio signal from the first source is amplified by the first class amplifier 15, and the output of the first class amplifier 15 is sent to the audio output means 17.

  In the case of (b), the output of the first source 11 is amplified by the second class amplifier 16 as in the case of amplifying the audio signal from the second source. This is because even if the second-class amplifier 16 generates a high-frequency signal in the mid-band, and enters the tuner 14 as noise, the tuner 14 has sufficient broadcast radio waves related to the first source. This is because the S / N ratio of the output of the tuner 14 is maintained at a sufficiently large level, regardless of the noise being mixed into the tuner 14 due to the operation of the second class amplifier 16. Thus, the audio signal from the first source is amplified by the high power efficiency second class amplifier 16, and the output of the second class amplifier 16 is sent to the audio output means 17.

  The device 10 with an audio signal amplification function will be described more specifically. The input selection means 13 selects the source selected in the source selector 21 for user operation. When the selection source in the source selector 21 is changed, the control means 19 determines whether or not the selection amplifier needs to be changed by the amplification selection means 20, and based on the determination, the control means 19 Instructs the change of the selective amplifier. Thus, the change of the selective amplifier by the amplification selecting means 20 is performed only when the user operates the source selector 21 to change the selected source.

  FIG. 2 is a flowchart of an amplifier control method for an audio broadcast receiver. In S26, the reception level F of the audio reception radio wave in the predetermined frequency band is detected. In S27, the reception level F detected in S26 is compared with the reference value Fr. When F <Fr, the process proceeds to S28, and when F ≧ Fr, the process proceeds to S29. In S28, the first class amplifier 15 amplifies the audio signal from the first source. In S 29, the audio signal from the first source is amplified by the second class amplifier 16 whose power efficiency is higher than that of the first class amplifier 15.

In the determination of S27 in FIG. 2, when F = Fr, the process proceeds to S29. However, the process may proceed to S28 instead of S29. A further embodiment of the amplifier control method for an audio broadcast receiver in FIG. 2 is as follows. The audio broadcast receiver amplifier control method of FIG. 2 can be added in any combination of the following specific examples.
-The predetermined frequency band is a medium wave band.
The first class amplifier is an A class or AB class amplifier.
The second class amplifier is a D class amplifier.

  FIG. 3 is a configuration diagram of Embodiment 1 of the apparatus 37 with an audio signal amplification function according to the present invention. The apparatus 37 with an audio signal amplification function is mounted on an automobile. The FM / AM tuner 40 can receive radio broadcast waves from a plurality of radio broadcast stations via an antenna 41, and can receive radio waves received by a radio broadcast station designated by the user of the device 37 with an audio signal amplification function. Demodulate and output. The CD / DVD player 42 reproduces a CD or DVD and outputs a reproduction signal. The MD recorder / reproducer 43 reproduces the MD and outputs a reproduction signal. The external input auxiliary terminal 44 is optionally connected to a cable by the user, and outputs an external audio signal sent via the cable to the selector 49. The selector 49 selects one of the outputs from the FM / AM tuner 40, the CD / DVD player 42, the MD recorder / reproducer 43, and the external input auxiliary terminal 44 based on the control signal from the microcomputer 48, and selects it. Send to preamplifier 50. The microcomputer 48 instructs the FM / AM tuner 40 whether the reception band of the FM / AM tuner 40 is AM or FM, and which radio broadcast is selected in each band. The FM / AM tuner 40 has a built-in S meter that measures the level of the received radio wave of the selected AM radio broadcast station. The main amplifier 51 has a normal mode and an AM mode, and operates as a D class amplifier in the normal mode, and operates as an AB class amplifier in the AM mode. The main amplifier 51 amplifies the input signal from the preamplifier 50 in either the normal mode or the AM mode and sends it to a speaker (not shown). The microcomputer 48 outputs a control signal for normal mode or AM mode to the main amplifier 51.

  The operation of the first embodiment will be described. When the microcomputer 48 instructs the selector 49 to select the output of the CD / DVD player 42, the MD recorder / reproducer 43, or the auxiliary input terminal 44, or the microcomputer 48 instructs the selector 49 to perform FM / AM When instructed to select the output of the tuner 40 and the microcomputer 48 instructs the FM / AM tuner 40 to receive the FM band, the main amplifier 51 operates in a normal mode, that is, a D class amplifier. Further, the microcomputer 48 instructs the selector 49 to select the output of the FM / AM tuner 40, and the microcomputer 48 instructs the FM / AM tuner 40 to select the AM radio broadcast of the AM band. Even when the reception level F of the radio waves received by the station AM radio broadcast station is equal to or higher than the predetermined level Fr, the main amplifier 51 operates in the normal mode, that is, the D class amplifier. On the other hand, the microcomputer 48 instructs the selector 49 to select the output of the FM / AM tuner 40, the microcomputer 48 instructs the FM / AM tuner 40 to select the AM radio broadcast of the AM band, When the reception level F of the radio wave received by the selected AM radio broadcast station is less than the predetermined level Fr, the main amplifier 51 operates in the AM mode, that is, the AB class amplifier.

  FIG. 4 is a configuration diagram of Embodiment 2 of the apparatus 37 with an audio signal amplification function. Only differences from the first embodiment will be described. The selector 56 selects the output from the S meter of the FM / AM tuner 40 or the constant voltage terminal 55 based on the band selection control signal from the microcomputer 48 and sends it to the level changer 57. The microcomputer 48 causes the selector 56 to select the output from the S meter of the FM / AM tuner 40 when the FM / AM tuner 40 selects the AM band, and otherwise sets the selector 56 to a constant voltage terminal. 55 is selected. The voltage level of the constant voltage terminal 55 is maintained at a constant voltage sufficiently higher than the voltage level from the S meter. The level changer 57 changes the level of the input voltage to the level changer 57 to a level suitable for the comparator 58. The comparator 58 distinguishes between the case where the input level from the level changer 57 is greater than or equal to a predetermined value and the case where it is less than the predetermined value. In the former case, the comparator 58 outputs the normal mode output of the main amplifier 51 as a logic. In the latter case, the AM mode output of the main amplifier 51 is output to the logic interface 59. The logic interface 59 changes the input from the comparator 58 to a control signal for the main amplifier 51 and outputs it to the main amplifier 51.

  The operation of the second embodiment will be described. When the microcomputer 48 instructs the selector 49 to select the output of the CD / DVD player 42, the MD recorder / reproducer 43, or the auxiliary input terminal 44, or the microcomputer 48 instructs the selector 49 to perform FM / AM When the microcomputer 48 instructs to select the output of the tuner 40 and the microcomputer 48 instructs the FM / AM tuner 40 to receive the FM band, the microcomputer 48 sends an output from the constant voltage terminal 55 to the selector 56. To select. As a result, the comparator 58 sends the output for the normal mode of the main amplifier 51 to the logic interface 59, so that the main amplifier 51 operates in the normal mode, that is, the D class amplifier. Further, when the microcomputer 48 instructs the selector 49 to select the output of the FM / AM tuner 40, and the microcomputer 48 instructs the FM / AM tuner 40 to select AM radio broadcast of AM band, The selector 56 selects the output of the S meter of the FM / AM tuner 40 instead of the output from the constant voltage terminal 55. When the reception level F of the selected AM radio broadcast station reception radio wave in the FM / AM tuner 40 is equal to or higher than the predetermined level Fr, the voltage level sent from the level changer 57 to the comparator 58 is equal to or higher than a predetermined reference value. Therefore, the comparator 58 sends the output for the normal mode of the main amplifier 51 to the logic interface 59, and the main amplifier 51 operates in the normal mode, that is, the D class amplifier. On the other hand, when the reception level F of the selected radio wave received by the FM / AM tuner 40 is less than the predetermined level Fr, the voltage level sent from the level changer 57 to the comparator 58 is a predetermined reference. Since it is less than the value, the comparator 58 sends the AM output of the main amplifier 51 to the logic interface 59, and the main amplifier 51 operates in the AM mode, that is, the AB class amplifier.

  FIG. 5 is a configuration diagram of Embodiment 3 of the apparatus 37 with an audio signal amplification function. Only differences from the first embodiment will be described. In the third embodiment, the main amplifier 51 in the first embodiment is separated into an AB class main amplifier 64 and a D class main amplifier 65. The AB class main amplifier 64 corresponds to the AM mode of the main amplifier 51, and the D class main amplifier 65 corresponds to the normal mode of the main amplifier 51. The input side selector 67 and the output side selector 68 are switched by a common control signal from the microcomputer 48, and the input side selector 67 outputs the output of the preamplifier 50 to either the AB class main amplifier 64 or the D class main amplifier 65. The output side selector 68 determines which of the outputs of the AB class main amplifier 64 and the D class main amplifier 65 is sent to the speaker side. When the input side selector 67 selects the AB class main amplifier 64 and the D class main amplifier 65, the output side selector 68 also selects the AB class main amplifier 64 and the D class main amplifier 65, respectively. It is like that.

  The operation of the third embodiment will be described. When the microcomputer 48 instructs the selector 49 to select the output of the CD / DVD player 42, the MD recorder / reproducer 43, or the auxiliary input terminal 44, or the microcomputer 48 instructs the selector 49 to perform FM / AM When the microcomputer 48 instructs to select the output of the tuner 40 and the microcomputer 48 instructs the FM / AM tuner 40 to receive the FM band, the microcomputer 48 instructs the input side selector 67 and the output side selector 68 to An instruction is given to select the D-class main amplifier 65. As a result, the output of the selector 49 is amplified by the preamplifier 50 and the D-class main amplifier 65 and output from the speaker. Further, the microcomputer 48 instructs the selector 49 to select the output of the FM / AM tuner 40, and the microcomputer 48 instructs the FM / AM tuner 40 to select the AM radio broadcast of the AM band. Even when the reception level F of the radio waves received by the station AM radio broadcast station is equal to or higher than the predetermined level Fr, the microcomputer 48 instructs the input side selector 67 and the output side selector 68 to select the D class main amplifier 65. . As a result, the output of the selector 49 is amplified by the preamplifier 50 and the D-class main amplifier 65 and output from the speaker. On the other hand, the microcomputer 48 instructs the selector 49 to select the output of the FM / AM tuner 40, the microcomputer 48 instructs the FM / AM tuner 40 to select the AM radio broadcast of the AM band, When the reception level F of the radio wave received by the selected AM radio broadcast station is less than the predetermined level Fr, the microcomputer 48 selects the AB class main amplifier 64 as the input side selector 67 and the output side selector 68. Instruct. As a result, the output of the selector 49 is amplified by the preamplifier 50 and the AB class main amplifier 64 and output from the speaker.

  FIG. 6 is a flowchart according to the fourth embodiment. The method according to the flowchart is performed in the apparatus 37 with an audio signal amplification function of FIG. In S74, it is determined whether or not the user has performed an audio output switching operation of the device 37 with an audio signal amplification function, for example, a switching operation from CD reproduction to AM radio broadcast output. If the determination is “positive”, the process proceeds to S75, and if “no”, the method according to the flowchart ends. In S75, mute is executed. As a result, any audio output from the speaker is suspended until S89 described later. In S76, it is determined whether or not AM radio broadcast has been selected as the switching destination in S74. If the determination is "correct", the process proceeds to S82, and if "No", the process proceeds to S78. In S78, it is determined whether or not the operation mode of the main amplifier 51 (FIG. 3) is the AM mode. If the determination is “positive”, the process proceeds to S79. If the determination is “No”, the process proceeds to S88. . In S79, the operation mode of the main amplifier 51 is switched to the D class mode (normal mode). Thereby, an audio signal from a source other than the AM radio broadcast is amplified by the D class amplifier and output from the speaker. In S82, the voltage output S of the S meter is detected. In S83, the output S is compared with a predetermined reference value Sr. S and Sr correspond to the aforementioned F and Fr. In S38, when S <Sr, the process proceeds to S84, and when S ≧ Sr, the process proceeds to S88. In S83, when S ≧ Sr, the process may advance to S78 or S79 instead of S88. In S84, the main amplifier 51 is switched to the AB class mode (AM mode). In S88, the selector 49 is switched, and the source selected by the selector 49 is switched to the source currently selected by the user as the source. In S89, the mute is canceled.

It is a functional block diagram of an apparatus with an audio signal amplification function. It is a flowchart of the amplifier control method for audio broadcast receivers. It is a block diagram of Example 1 of this invention. It is a block diagram of Example 2 of this invention. It is a block diagram of Example 3 of the present invention. It is a flowchart of Example 4 of the present invention.

Explanation of symbols

10: device with audio signal amplification function, 13: input selection means, 15: first class amplifier, 16: second class amplifier, 17: audio output means, 18: reception level detection means, 19: control means, 20: amplifier Selection means 20, 21: Source selector.

Claims (7)

Input selection means for selecting one source from a plurality of sources including a first source related to an audio reception radio wave in a predetermined frequency band and at least one second source different from the first source ,
A first class amplifier for amplifying audio signals;
A second class amplifier for amplifying an audio signal with higher power efficiency than the first class amplifier;
Amplifier selecting means for selecting an amplifier for amplifying an audio signal from a source selected by the input selecting means from the first class amplifier and the second class amplifier;
A reception level detection means for detecting a reception level of an audio reception radio wave according to a first source; and when the input selection means selects the first source, the audio reception radio wave according to the first source Control means for controlling the amplifier selection means so that the amplifier selection means selects the first class amplifier and the second class amplifier, respectively, depending on whether the reception level is below or above a predetermined level;
A device with an audio signal amplifying function.   2. The audio signal amplification function according to claim 1, wherein the control means causes the amplifier selection means to select the second amplifier when the input selection means selects the second source. Equipment. The input selection means is for selecting a source selected in a source selector for user operation,
When the selection source in the source selector is changed, the control unit determines whether or not the selection amplifier needs to be changed by the amplification selection unit, and based on the determination, the control unit selects a selection amplifier. 3. The apparatus with an audio signal amplifying function according to claim 1, wherein the apparatus instructs change.   4. The apparatus with an audio signal amplification function according to claim 1, wherein the predetermined frequency band is a medium wave band.   5. The apparatus with an audio signal amplification function according to claim 1, wherein the first class amplifier is an A class or AB class amplifier, and the second class amplifier is a D class amplifier. Detect the reception level of audio reception radio waves in the specified frequency band,
When the detected reception level is lower than a predetermined reference level, the first class amplifier amplifies the audio signal related to the audio reception radio wave,
When the detected reception level is above the predetermined reference level, the audio signal related to the audio reception radio wave is amplified by a second class amplifier having a power efficiency higher than that of the first class amplifier.
An amplifier control method for an audio broadcast receiver.   8. The audio broadcasting according to claim 7, wherein the predetermined frequency band is a medium wave band, the first class amplifier is an A class or AB class amplifier, and the second class amplifier is a D class amplifier. Amplifier amplifier control method.

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