Reproducing device, and reproducing method

The present invention relates to a reproduction device and a reproduction method.

In recent years, many portable playback devices have been distributed in the market. FIG. 7 is a diagram showing a configuration example of a conventional portable playback device. As shown in this figure, the conventional portable playback device has a D-class headphone amplifier 100, coils 104, 105, capacitors 106 to 109, and output terminals 110 to 112. Here, the D-class headphone amplifier 100 has an oversampling filter 101, a delta-sigma PWM conversion circuit 102, and a switching driver 103, and the audio signal oversampled by the oversampling filter 101 is converted to delta-sigma PWM. It is converted into a 1-bit signal by the circuit 102, and the power is amplified and output by the switching driver 103.

The coil 104 and the capacitor 106 and the coil 105 and the capacitor 107 each constitute a low-pass filter, and the 1-bit signal output from the D-class headphone amplifier 100 is passed through the audible band signal, and the other signals are attenuated. Capacitors 108 and 109 are coupling capacitors that cut off the DC component. The audio signal output from the capacitors 108 and 109 is supplied to the output terminals 110 and 111. The output terminal 112 is connected to the ground.

By connecting headphones having a 3-pole plug to the output terminals 110 to 112 of such a portable playback device, the user can hear the sound of the played music or the like.

By connecting the output terminals 110 to 112 to devices other than headphones (for example, in-vehicle devices or home-use stationary devices), audio such as played music can be heard by these devices. ..

By the way, when the portable playback device is used by connecting to another device, it is necessary to adjust the volume level of the audio signal reproduced by the portable playback device. As such a method, for example, as shown in Patent Document 1, there is a method in which a volume level is detected on the device side and the volume level is automatically set based on the detection result.

Further, as shown in FIG. 8, an output terminal 120 is newly added to the portable playback device side, and the newly added output terminal 120 is connected to a device using a 4-pole plug as shown in FIG. A technology that allows the portable playback device and the device to communicate with each other to set an appropriate volume level, and for example, the device can operate playback, pause, and skip-up / down processing in the portable playback device. Has also been proposed.

More specifically, in the conventional example shown in FIG. 8, the output terminal 110 and the terminal 131 of the 3-pole plug are connected, the output terminal 111 and the terminal 132 are connected, the output terminal 120 and the terminal 133 are connected, and the output terminal 112. And terminal 134 are connected. Further, the terminal 133 is connected to the control unit of the device. On the other hand, in the portable playback device, the output terminal 120 is connected to the pull-up resistor 121 and also to the control unit. The portable playback device and the device can communicate with each other via the output terminal 120 and the terminal 133 to perform various controls.

<patcit num="1"><text>Japanese Patent Application Laid-Open No. 2007-89218 (Claims, Abstracts, Paragraph 0047, etc.)</text></patcit>

<p> By the way, in recent years, it has become common to use a plurality of headphones properly according to the purpose or environment. In such a case, since each headphone has different frequency characteristics, impedance characteristics, and sensitivity characteristics, it is necessary to change the volume level, equalizer characteristics, etc. of the portable playback device each time the headphones are changed, which is complicated. There is a problem that there is.</p><p> Further, since the technique described in Patent Document 1 is provided with a function of adjusting the volume level or the like on the device side, the volume level or the like can be adjusted according to the type of the device. However, there is a problem that it cannot be applied to headphones that do not have such a function. Further, since the portable playback device outputs an audio signal at a preset volume level, for example, when the preset volume level is small, it is necessary to amplify it with a large gain on the device side. There is also the problem that the S / N ratio decreases.</p><p> Further, in the method using the 4-pole terminal shown in FIGS. 8 and 9, the volume level and the like can be adjusted for the device having the 4-pole terminal. However, there is a problem that it cannot be applied to headphones that do not have such a function.</p><p> The present invention has been made based on the above circumstances, and an object of the present invention is to provide a reproduction device and a reproduction method capable of setting an optimum environment according to the characteristics of a connected device. The purpose.</p>

<p> In order to achieve the above object, in the playback device of the present invention, the output terminal to which the external device is connected, the detection means for detecting that the external device is connected to the output terminal, and the external device are connected by the detection means. When it is detected, an output means that outputs an inspection signal to an external device via the output terminal, and a measuring means that measures the level of ripple that appears on the power supply line while outputting the inspection signal. And a specific means for specifying the type of the external device based on the measurement result by the measuring means.</p><p> Further, the reproduction device of another invention has, in addition to the above-mentioned invention, a setting means for setting the environment of the device based on the specific result by the specific means.</p><p> Further, in the reproduction device of another invention, in addition to the above invention, the output means outputs a signal including a sine wave having a predetermined frequency as an inspection signal, and the measuring means outputs a sine wave. I am trying to measure the level of ripple that appears on the power line connected to.</p><p> Further, in the reproduction device of another invention, in addition to the above-mentioned invention, the output stage has a switching driver and a low-pass filter for attenuating the harmonic component included in the signal output from the switching driver, and outputs the output. The means outputs a signal including a sine wave having a frequency lower than the cutoff frequency of the low-pass filter as an inspection signal.</p><p> Further, in addition to the above-described invention, the reproduction device of another invention has a first switching element arranged between the output stage and the measuring means and a second switching element arranged between the output stage and the ground. It has a switching element and a control means for switching the first switching element and the second switching element according to the output voltage applied to the power supply line.</p><p> Further, the reproduction device of another invention has, in addition to the above-mentioned invention, a storage means for storing data including music and a reproduction means for reproducing predetermined data stored in the storage means, and outputs the data. The means outputs an inspection signal obtained by reproducing predetermined data stored in the storage means by the reproducing means.</p><p> Further, in the reproduction device of another invention, in addition to the above-mentioned invention, the setting means sets the volume level corresponding to each external device.</p><p> Further, in the playback device of another invention, in addition to the above invention, when the external device is a headphone, the playback device of another invention sets the volume level corresponding to the type specified by the specific means, and the external device sets the volume level. In the case of other devices, the volume level is set to a predetermined level.</p><p> Further, in the reproduction device of another invention, in addition to the above-mentioned invention, the setting means sets the equalizer characteristics corresponding to each external device.</p><p> Further, in the reproduction device of another invention, in addition to the above-mentioned invention, the measuring means has an amplifier circuit that amplifies the signal of the power supply line with a predetermined gain.</p><p> Further, the reproduction method of the present invention detects that an external device is connected to the output terminal, and when it is detected that the external device is connected, an inspection signal is sent to the external device via the output terminal. It outputs, measures the level of ripple that appears on the power supply line when outputting the inspection signal, identifies the type of external device based on the measurement result, and sets the environment of the device based on the specific result. , And so on.</p>

<p> According to the present invention, it is possible to provide a reproduction device and a reproduction method capable of setting an optimum environment according to the characteristics of a connected device.</p>

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the following, (A) a configuration example of the embodiment, (B) an outline of the operation of the embodiment, (C) details of the operation of the embodiment, and (D) a modified embodiment will be described in this order. .. The reproduction method of the present invention will be described as the operation of the reproduction device according to the embodiment of the present invention.

(A) Configuration example of the embodiment

FIG. 1 is a diagram showing a configuration example of the reproduction device 1 according to the embodiment of the present invention. As shown in this figure, the playback device 1 of the present invention includes a D-class headphone amplifier 10, a central control unit 11, a temporary storage unit 12, a large-capacity storage unit 13, coils 14, 15, capacitors 16 to 19, and a headphone connector 20. , Plug detector 25, capacitor 26, load detector 27, battery 28, and regulator 29 are the main components.

Here, the D-class headphone amplifier 10 as a part of the output means has an oversampling filter 10a and a delta-sigma PWM (Pulse Width). Modulation) It has a conversion circuit 10b and a switching driver 10c, and converts the digital signal obtained by reproducing the content data including the music stored in the large-capacity storage unit 13 into a 1-bit signal and outputs it. To do. Here, the oversampling filter 10a oversamples the input digital signals of the R (Right) channel and the L (Left) channel, and outputs the digital signals, for example, by performing noise shaping processing. The delta-sigma PWM conversion circuit 10b converts the digital signal output from the oversampling filter 10a into a 1-bit signal. The switching driver 10c as a part of the output stage performs the switching operation based on the 1-bit signals of the R channel and the L channel output from the delta-sigma PWM conversion circuit 10b, and is operated by the DC power supplied from the regulator 29. Amplifies and outputs the power of the bit signal. The power supply terminal of the switching driver 10c is connected to the output of the regulator 29 and the ground, respectively.

The central control unit 11 as a part of the output means, a part of the specific means, a part of the setting means, and a part of the reproduction means is, for example, by a CPU (Central Processing Unit) and / or a DSP (Digital Signal Processor) or the like. Each part of the device is controlled according to the program stored in the built-in storage unit (not shown), and the content data stored in the large-capacity storage unit 13 is acquired and subjected to decoding processing. To play. Further, as described later, the impedance of the AV device connected to the headphone connector 20 is measured, and the environment is set based on the measurement result.

The temporary storage unit 12 is a semiconductor storage device that is configured by, for example, RAM (Random Access Memory) or the like, and temporarily stores a program or data to be executed by the central control unit 11. Further, the temporary storage unit 12 has a role of a buffer when reading data from the large-capacity storage unit 13.

The large-capacity storage unit 13 as a storage means is configured by, for example, a flash memory or the like, stores a plurality of content data, and reads out and supplies a predetermined content data according to the control of the central control unit 11. .. A storage medium such as an HDD (Hard Disk Drive) or an optical disk may be used instead of the flash memory.

The coil 14 and capacitor 16 and the coil 15 and capacitor 17 as part of the output stage form a low-pass filter for the L channel and the R channel, respectively, and are audible from the 1-bit signal output from the D-class headphone amplifier 10. Passes the signal in the band and attenuates the rest. Capacitors 18 and 19 are coupling capacitors, which cut off the DC components contained in the L channel and R channel signals, respectively. The L-channel and R-channel audio signals output from the capacitors 18 and 19 are supplied to the L-channel terminal 22 and the R-channel terminal 23 of the headphone connector 20, respectively.

The headphone connector 20 as an output terminal has a plug detection terminal 21, an L channel terminal 22, an R channel terminal 23, and a ground terminal 24, and an external device (headphone or AV (Audio Visual) device) is provided in the relevant portion. The plug of the connection cable is connected. The plug detection terminal 21 as a part of the detection means is a switch for detecting that the plug has been inserted. That is, when the plug is inserted, it is in an open state, and when the plug is unplugged, it is in a conductive state with the L channel. In addition to this, for example, when the plug is inserted, it may be connected to the ground, and when the plug is removed, it may be opened. The L channel terminal 22 is a terminal connected to the output side of the capacitor 18 and outputs an audio signal of the L channel. The R channel terminal 23 is a terminal connected to the output side of the capacitor 19 and outputs an audio signal of the R channel. The ground terminal 24 is connected to the ground.

The plug detection unit 25 as a part of the detection means detects whether or not the plug of the headphone or AV device (hereinafter, appropriately referred to as headphone or the like) is inserted by detecting the state of the plug detection terminal 21. It detects and notifies the central control unit 11 of the detection result.

The capacitor 26 is a bypass capacitor and has a function of releasing a high frequency component superimposed on the power supply line to the ground.

The load detection unit 27 as a measuring means measures the impedance of the headphones or the like connected to the headphone connector 20 by detecting the ripple level of the power supply line at the point A in the vicinity of the capacitor 26.

Here, the load detection unit 27 has a band filter 27a, an error amplifier 27b, and a fluctuation detection circuit 27c. The band filter 27a is a bandpass filter that extracts and outputs a component of a predetermined band from the ripple component generated at point A when the inspection signal is output to the headphone connector 20. The error amplifier 27b as an amplifier circuit amplifies the ripple component output from the band filter 27a with a predetermined gain and outputs it. The fluctuation detection circuit 27c is a circuit that digitizes and outputs the ripple level. Specifically, for example, it is configured by an A / D (Analog to Digital) circuit, and the ripple voltage is converted into the corresponding digital data and output. In addition to this, for example, a comparator may be used to output the comparison result in comparison with a predetermined threshold value, or the ripple component may be PWM-converted and detected by the pulse width. .. Alternatively, when the ripple component is PWM-converted, an output signal having a duty ratio of 100% or 0% is generated by changing the peak value and the bias level of the triangular wave to be used, and the pulse is counted. May be good.

The battery 28 is composed of a secondary battery that outputs DC power. Specifically, it is composed of a nickel hydrogen battery, a nickel cadmium battery, a lithium ion battery, or the like.

The regulator 29 is composed of, for example, a DC / DC (Direct Current / Direct Current) converter or the like, boosts the DC voltage output from the battery 28, and controls the voltage so that it is always constant.

(B) Outline of operation of the embodiment

Next, an outline of the operation of the embodiment of the present invention will be described. In the reproduction device 1 of the embodiment of the present invention, the impedance of the headphones or the like connected to the headphone connector 20 is adjusted by utilizing the fact that ripple is generated in the power supply line due to load fluctuation and the ripple level is changed by the load impedance. Measure and set the optimum volume level and equalizer characteristics.

That is, when the user connects a plug of a predetermined headphone (not shown) to the headphone connector 20 of the playback device 1, the plug detection unit 25 detects this and notifies the central control unit 11. The central control unit 11 acquires the detection reference database from the temporary storage unit 12 and sets the detection environment based on the acquisition reference database.

As the detection reference database, for example, the database shown in FIG. 2 (A) is used. The central control unit 11 refers to the "inspection audio setting" shown in this database, sets the volume level to "15", sets the EQ (equalizer) off, and turns surround off. Set.

Next, the central control unit 11 acquires and reproduces "inspection data", which is audio data for detecting the load impedance, stored in the large-capacity storage unit 13, and supplies the data to the D-class headphone amplifier 10. To do. The D-class headphone amplifier 10 generates a 1-bit audio signal (inspection signal: 127 Hz, 0 dB sine wave signal as shown in Inspection signal in FIG. 2 (A)) corresponding to the inspection data. Output.

The inspection signal output from the D-class headphone amplifier 10 is supplied to the coils 14 and 15, respectively. Since the counter electromotive force corresponding to the load impedance is generated in the coils 14 and 15, a ripple corresponding to the counter electromotive force is generated at the point A.

FIG. 3 is a diagram showing the relationship between the load impedance value and the ripple level. Figure 3 (A) shows the waveform (HP OUT) of the output signal to the headphones when a 127 Hz inspection signal is applied to the headphones with a load impedance value of 16 ohms, and the waveform of the ripple at point A (VDD0). It shows that. In Fig. 3 (A), the ripple is 0.48V. In addition, Fig. 3 (B) shows the waveform of the output signal to the headphones and the waveform of the ripple at point A when a 127 Hz inspection signal is applied to the headphones with a load impedance value of 32 ohms. .. In Fig. 3 (B), the ripple is 0.23V. Furthermore, Fig. 3 (C) shows the waveform of the output signal to the headphones when a 127 Hz inspection signal is applied to the headphones with a load impedance value of 22 k ohms, and the waveform of the ripple at point A. .. In Fig. 3 (C), the ripple is 0V (none). That is, as shown in FIG. 3, there is a certain correlation between the load impedance value and the ripple level.

The band filter 27a of the load detection unit 27 extracts a signal in a predetermined band (127 Hz signal in this example) from the voltage at point A and supplies it to the error amplifier 27b. The error amplifier 27b amplifies the signal supplied from the band filter 27a with a predetermined gain and supplies it to the fluctuation detection circuit 27c. The fluctuation detection circuit 27c detects the ripple level included in the signal supplied from the error amplifier 27b and supplies it to the central control unit 11. For example, if 16 ohm headphones are connected, a ripple level of 0.48V will be detected.

The central control unit 11 specifies the impedance value of the headphones according to the detection result of the fluctuation detection circuit 27c, sets the volume level according to the specified impedance value, and sets the equalizer characteristics. Specifically, the central control unit 11 refers to the detection reference database shown in FIG. 2A, specifies the impedance value of the headphones, and sets the optimum volume level and equalizer characteristics for the impedance value. Specifically, when the ripple level is 0.48V, the load impedance is specified to be 16 ohms. Regarding the audio setting in that case, setting # 1 is selected as the volume level, and setting #A is selected as the EQ curve.

Also, if the ripple level is 0.23V, the load impedance is specified to be 32 ohms. Regarding the audio setting in that case, setting # 2 is selected as the volume level, and setting #B is selected as the EQ curve.

Furthermore, if the ripple level is 0.00V, the load impedance is specified to be 22k ohms. Regarding the audio setting in that case, setting # 3 is selected as the volume level, and setting #C is selected as the EQ curve. More specifically, when the load impedance is 22k ohms, it is not the headphones that are connected, but the AV equipment (eg, in-vehicle equipment or home stationary equipment). In that case, set the volume level to a predetermined value (a value that can secure the S / N ratio and has little distortion). As a result, the gain on the in-vehicle device or the stationary device for home use can be set low, so that it is possible to prevent the S / N ratio from being lowered and to reduce the occurrence of distortion.

As described above, in the embodiment of the present invention, when a headphone or an AV device is connected to the playback device 1, an inspection signal is output from the D-class headphone amplifier 10 to generate ripples in the power supply line. The level is detected by the load detection unit 27, and the optimum volume level and equalizer characteristics according to the impedance value of the load are set by the central control unit 11. Therefore, it is not necessary to change the volume level and the equalizer characteristics every time the headphones are changed, so that the burden on the user can be reduced.

In addition, if the volume level and equalizer characteristics can be set to the user's favorite values, for example, when headphones are selected and used according to the purpose of use or environment of use, it depends on the purpose of use or environment of use. It can be set to the optimum volume level and equalizer characteristics.

Furthermore, when the playback device 1 is shared by a plurality of users, if the volume level and the equalizer characteristics are set for each headphone used by each user, the music or the like can be enjoyed with the characteristics that match the tastes of the individual users. be able to.

Further, when an AV device is connected instead of headphones, the volume level is set to a predetermined value, so that it is possible to prevent the S / N ratio from being lowered and to prevent the occurrence of distortion.

(C) Details of operation of the embodiment

Next, the detailed operation of the embodiment of the present invention will be described.

FIG. 4 is a flowchart illustrating an example of processing executed when the power switch is turned on in the reproduction device 1 shown in FIG. When the processing of the flowchart shown in this figure is started, the following steps are executed.

Step S10: The central control unit 11 starts supplying power to each part of the device. As a result, the DC power output from the regulator 29 is supplied to the switching driver 10c.

Step S11: The central control unit 11 refers to the output of the plug detection unit 25 and detects whether or not the plug is inserted. As a result, if the plug is inserted, the process proceeds to step S12, and if not, the process ends. Specifically, when the user connects the plug of the headphone or AV device connection cable to the headphone connector 20, the plug detection terminal 21 is in the open state, so the plug detection unit 25 detects this. , Notify the central control unit 11. The central control unit 11 recognizes that the plug is inserted based on the notification from the plug detection unit 25.

If it is determined that the plug is not inserted, the previously set values are maintained as the volume level and equalizer characteristics without executing the detection operation described later.

Step S12: The central control unit 11 calls the inspection standard database stored in the temporary storage unit 12 and sets the inspection environment. Specifically, as the inspection standard database, the database shown in FIG. 2 (B) is called. In the database shown in this figure, information on the inspection signal, information on the inspection audio setting, and information on the inspection circuit setting are stored as information on the inspection environment setting. That is, it is shown that a sine wave having a frequency of 127 Hz and a volume of 0 dB is used as the inspection signal. The inspection audio settings also indicate that the volume level is 15, EQ is off, and surround is off. In addition, as the inspection circuit setting, it was shown that BPF (Band Pass Filter) with a pass band of 30 to 500 Hz is used as the band filter 27a, and 10 dB is set as the gain of the error amplifier 27b. ing.

Step S13: The central control unit 11 acquires and reproduces the inspection data stored in the large-capacity storage unit 13 or the temporary storage unit 12. Specifically, as shown in FIG. 2B, the inspection data is audio data for generating an inspection signal having a frequency of 127 Hz, a volume of 0 dB, and a waveform of a sine wave. Is. The inspection data is, for example, MP3 (MPEG-1 Audio Layer-3), which is a signal having the same frequency, the same volume, the same waveform, and the same phase of both channels for both the L channel and the R channel. It is generated by being compressed based on the standards such as.

When the reproduction of the inspection data is started, the audio data decoded by the central control unit 11 is converted into a 1-bit signal by the D-class headphone amplifier 10 and output to the coils 14 and 15.

Step S14: The central control unit 11 acquires the fluctuation detection data X from the load detection unit 27. That is, when the output of the inspection signal is started from the D-class headphone amplifier 10, a ripple corresponding to the load impedance is generated at the point A. The band filter 27a extracts a signal in a predetermined band (in this example, a signal of 30 to 500 Hz) from the signal at point A and supplies it to the error amplifier 27b. The error amplifier 27b amplifies the signal output from the band filter 27a with a predetermined gain (10 dB in this example) and outputs the signal. The fluctuation detection circuit 27c A / D-converts the signal output from the error amplifier 27b, and supplies the obtained fluctuation detection data (digital data) X to the central control unit 11.

Step S15: The central control unit 11 compares the fluctuation detection data X with the ripple level of the inspection reference database. Specifically, the central control unit 11 compares the threshold value A in the first row of the third column from the right in FIG. 2B with the data X. As a result, if the data X is equal to or less than the threshold value A, the process proceeds to step S16, and if not, the process proceeds to step S17.

The threshold value A is determined based on, for example, actual measurement. That is, since this threshold value A differs depending on the settings of the inspection data, the band filter 27a, the error amplifier 27b, and the fluctuation detection circuit 27c, an appropriate value is determined by actual measurement. The same applies to the threshold values B and C.

Step S16: When the fluctuation detection data X is equal to or less than the threshold value A, the central control unit 11 considers that an AV device is connected as a load instead of headphones, as shown in FIG. 2 (B). From, "setting # 1" is acquired from the database as an audio setting, and the setting information corresponding to the acquired setting # 1 is acquired from, for example, the temporary storage unit 12, and the volume adjustment unit and the volume adjustment unit inside the central control unit 11 Set for the equalizer setting section. As a result, the volume level and equalizer characteristics corresponding to setting # 1 are set. Then, the process ends.

Step S17: The central control unit 11 compares the threshold value B with the fluctuation detection data X. As a result, if the fluctuation detection data X is equal to or less than the threshold value B, the process proceeds to step S18, and if not, the process proceeds to step S19.

Step S18: Since the fluctuation detection data X is larger than the threshold value A and equal to or lower than the threshold value B, the central control unit 11 considers that the load impedance value is 100 ohms as shown in FIG. 2 (B). Therefore, "setting # 2" is acquired from the database as an audio setting, and the setting information corresponding to the acquired setting # 2 is acquired from, for example, the temporary storage unit 12, and the volume adjustment unit and the volume adjustment unit inside the central control unit 11 Set for the equalizer setting section. As a result, the volume level and equalizer characteristics corresponding to setting # 2 are set. Then, the process ends.

Step S19: The central control unit 11 compares the threshold value C with the fluctuation detection data X. As a result, if the fluctuation detection data X is equal to or less than the threshold value C, the process proceeds to step S20, and if not, the process proceeds to step S21.

Step S20: Since the fluctuation detection data X is larger than the threshold value B and equal to or less than the threshold value C, the central control unit 11 considers that the load impedance value is 32 ohms as shown in FIG. 2 (B). Therefore, "setting # 3" is acquired from the database as an audio setting, and the setting information corresponding to the acquired setting # 3 is acquired from, for example, the temporary storage unit 12, and the volume adjustment unit and the volume adjustment unit inside the central control unit 11 Set for the equalizer setting section. As a result, the volume level and equalizer characteristics corresponding to setting # 3 are set. Then, the process ends.

Step S21: Since the fluctuation detection data X is larger than the threshold value C, the central control unit 11 considers that the load impedance value is 16 ohms as shown in FIG. 2 (B). 4 is acquired from the database, and the setting information corresponding to the acquired setting # 4 is acquired from, for example, the temporary storage unit 12 and set for the volume adjustment unit and the equalizer setting unit inside the central control unit 11. .. As a result, the volume level and equalizer characteristics corresponding to setting # 4 are set. Then, the process ends.

According to the above processing, when the headphone or AV device is connected to the headphone connector 20 when the power is turned on, for example, the inspection environment is based on the inspection standard database shown in FIG. 2 (B). Is set, and the inspection data is read out and reproduced. As a result, ripple is generated at point A according to the load impedance, and the load impedance can be specified by detecting the level.

Further, since the optimum volume level and equalizer characteristics are set based on the specified load impedance, it is not necessary to change the volume level or the equalizer characteristics every time the user changes the headphones or the like. Therefore, the operability of the user can be improved.

Also, when an AV device is connected to the headphone connector 20, the volume level is set to a predetermined value. As a result, the gain of the amplifier in the AV device can be suppressed to a low level, so that it is possible to prevent the S / N ratio from being lowered and to prevent the occurrence of distortion.

Even when an AV device is connected and the volume is set to a predetermined value, when the headphones are connected, the volume level is changed to the optimum level according to the headphones, so the music is played at a loud volume. Etc. are reproduced, and it is possible to prevent the user's ears from being burdened.

Further, in the above embodiment, a normal three-pole plug can be used for the connection between the headphones or the AV device and the playback device 1. This makes it possible to measure and set the impedance of any headphone or AV device on the market.

Further, in the above embodiment, the impedance is measured based on the level of ripple appearing on the power supply line. Therefore, it is possible to prevent the sound quality from being deteriorated as compared with the case where the function for measuring the impedance is directly connected to the headphones or the AV device. That is, since the circuit for impedance measurement is not connected in parallel or in series to the headphones or AV equipment, it is not affected by the impedance of the measurement circuit. As a result, deterioration of sound quality can be prevented.

Further, in the above embodiment, since a sine wave having a single frequency is used as the inspection signal, it is possible to accurately measure the impedance in the reproduction band of the headphones or the AV device.

Further, in the above embodiment, since the band filter 27a is provided in the load detection unit 27 to extract the signal having the frequency corresponding to the inspection signal, the ripple component can be detected efficiently and accurately. Can be done. Thereby, the detection accuracy can be improved.

Further, in the above embodiment, since the error amplifier 27b is provided in the load detection unit 27 to amplify the ripple component, the ripple can be accurately detected even when the amplitude of the inspection signal is small. Impedance can be measured. As a result, the amplitude of the inspection signal can be reduced, so that it is possible to prevent a loud sound from being output from the headphones or the speaker of the AV device during measurement.

(F) Deformation implementation mode

The above-described embodiment is a preferable example of the present invention, but the present invention is not limited thereto, and various modifications and changes can be made without departing from the gist of the present invention. is there.

(F-1) First embodiment of modification

For example, in the above embodiment, the load impedance is detected in four stages and the audio is set according to each load impedance. For example, the load impedance is applied to the AV device and other devices (headphones). It may be detected separately and the optimum setting may be made for each of the AV device and the headphone.

FIG. 5 is a flowchart for realizing such a process. When the processing of the flowchart shown in this figure is started, the following steps are executed.

Step S30: The central control unit 11 starts supplying power to each unit of the device. As a result, the DC power output from the regulator 29 is supplied to the switching driver 10c.

Step S31: The central control unit 11 refers to the output of the plug detection unit 25 and detects whether or not the plug is inserted. As a result, if the plug is inserted, the process proceeds to step S32, otherwise the process proceeds to step S38. Specifically, when the user connects the plug of the headphone or AV device connection cable to the headphone connector 20, the plug detection terminal 21 is in the open state, so the plug detection unit 25 detects this. , Notify the central control unit 11. The central control unit 11 recognizes that the plug is inserted based on the notification from the plug detection unit 25.

Step S32: The central control unit 11 calls the inspection standard database stored in the temporary storage unit 12 and sets the inspection environment. Specifically, as the inspection standard database, the database shown in FIG. 2 (C) is called. In the database shown in this figure, information on the inspection signal, information on the inspection audio setting, and information on the inspection circuit setting are stored as information on the inspection environment setting. That is, it is shown that a sine wave having a frequency of 127 Hz and a volume of 0 dB is used as the inspection signal. The inspection audio settings also indicate that the volume level is 15, EQ is off, and surround is off. Further, as the inspection circuit setting, it is shown that BPF having a pass band of 30 to 500 Hz is used as the band filter 27a, and 10 dB is set as the gain of the error amplifier 27b.

Step S33: The central control unit 11 acquires and reproduces the inspection data stored in the large-capacity storage unit 13 or the temporary storage unit 12. Specifically, as shown in FIG. 2C, the inspection data is audio data for generating an inspection signal having a frequency of 127 Hz, a volume of 0 dB, and a waveform of a sine wave. Is. The inspection data is a signal in which both the L channel and the R channel have the same frequency, the same volume, the same waveform, and the phases of both are synchronized, and the signals are compressed based on a standard such as MP3. Will be generated.

When the reproduction of the inspection data is started, the audio data decoded by the central control unit 11 is converted into a 1-bit signal by the D-class headphone amplifier 10 and output to the coils 14 and 15.

Step S34: The central control unit 11 acquires the fluctuation detection data X from the load detection unit 27. That is, when the output of the inspection signal is started from the D-class headphone amplifier 10, a ripple corresponding to the load impedance is generated at the point A. The band filter 27a extracts a signal in a predetermined band (in this example, a signal of 30 to 500 Hz) from the signal at point A and supplies it to the error amplifier 27b. The error amplifier 27b amplifies the signal output from the band filter 27a with a predetermined gain (10 dB in this example) and outputs the signal. The fluctuation detection circuit 27c compares the signal output from the error amplifier 27b with a predetermined threshold value, outputs a high level (H) when the output of the error amplifier 27b is larger than the threshold value, and outputs a high level (H) in other cases. Output low level (L). The fluctuation detection data X obtained in this way is supplied to the central control unit 11.

Step S35: The central control unit 11 determines whether or not the value of the fluctuation detection data X acquired in step S34 is H, and if it is H, proceeds to step S36, and in other cases, proceeds to step S36. To step S37. For example, when an AV device is connected, the fluctuation detection data X becomes L, so the process proceeds to step S37.

Step S36: The central control unit 11 sets the volume level to the default level because it is considered that the headphones are connected to the headphone connector 20. That is, the central control unit 11 acquires the information regarding the setting # 2 corresponding to the headphones shown in the database shown in FIG. 2C from the temporary storage unit 12 and sets the information in the internal volume setting unit. As a result, the volume level is set to the default value for headphones.

Step S37: Since it is considered that the AV device is connected to the headphone connector 20, the central control unit 11 can set the volume level to a predetermined value (prevents a decrease in the S / N ratio and suppresses the occurrence of distortion). Value). That is, the central control unit 11 acquires the information related to the setting # 1 corresponding to the AV device shown in the database shown in FIG. 2C from the temporary storage unit 12 and sets it in the internal volume setting unit. As a result, the volume level is set to a predetermined value. As a result, it is possible to suppress a decrease in the S / N ratio and reduce the occurrence of distortion.

Step S38: The central control unit 11 refers to the output of the plug detection unit 25, determines whether or not the plug has been unplugged from the headphone connector 20, proceeds to step S39 if unplugged, and processes otherwise. To finish.

Step S39: The central control unit 11 determines whether or not the content data is currently being reproduced, and if it is being reproduced, proceeds to step S40, and if not, proceeds to step S41.

Step S40: The central control unit 11 suspends the reproduction of the content data. Then, the process proceeds to step S41.

Step S41: The central control unit 11 refers to the output of the plug detection unit 25 and determines whether or not the plug has been reconnected. As a result, when the plug is reconnected, the process returns to step S32, and the impedance detection process is executed in the same manner as in the case described above. If it is not reconnected, the process ends.

According to the above embodiment, when an AV device is connected to the headphone connector 20, the volume level is set to a predetermined value. As a result, the gain of the amplifier in the AV device can be suppressed to a low level, so that it is possible to prevent the S / N ratio from being lowered and to prevent the occurrence of distortion.

Even when an AV device is connected and the volume is set to a predetermined value, when the headphones are connected, the volume level is changed to the default value, so music etc. can be played at a loud volume. It is possible to prevent the burden on the user's ears.

(F-2) Second embodiment of modification

FIG. 6 is a diagram showing a configuration example of the second modification embodiment. In the reproduction device 1A shown in this figure, a power supply circuit 50 is added to the block shown in FIG. Other configurations are the same as in Fig. 1. The parts corresponding to FIG. 1 are designated by the same reference numerals and the description thereof will be omitted.

The power supply circuit 50 includes resistors 51, 52, coils 53, switching elements 54, 55, gate signal generation circuit 56, error amplifier 57, basic signal generation circuit 58, reference voltage generator 59, and capacitor 60. , Has the role of reducing the ripple contained in the DC voltage supplied to the switching driver 10c. Since ripples still appear at point A in FIG. 6, the load impedance can be detected by detecting the ripples as in the case of FIG.

Here, the switching element 54 as the first switching element is the first switching element arranged between the output of the regulator 29 and the switching driver 10c. Further, the switching element 55 as the second switching element is a second switching element arranged between the output of the regulator 29 and the ground.

The switching elements 54 and 55 are metal oxide field effect transistors (MOSFETs) that are complementary to each other. In this embodiment, the switching element 54 is a P-type transistor, and the switching element 55 is an N-type transistor. The source of the switching element 54 is connected to the regulator 29, and the drain of the switching element 54 is connected to the coil 53. Further, the source of the switching element 55 is connected to the ground, and the drain of the switching element 55 is connected to the drain of the switching element 54 and the coil 53.

Further, the control circuit composed of the gate signal generation circuit 56 and the basic signal generation circuit 58 as a part of the control means pulse-width-modulates a predetermined basic signal with a value corresponding to the power supply voltage supplied to the switching driver 10c. This is a circuit that generates a gate signal and supplies the gate signal to the switching elements 54 and 55. In the control circuit, the basic signal generation circuit 58 as a part of the control means is a circuit that generates a basic signal having a predetermined waveform at a predetermined frequency fo. The frequency fo of the basic signal is a predetermined value that is 10 times or more the upper limit of the audio band (usually 20 kHz), and the waveform of the basic signal is a triangular wave, a sawtooth wave, or the like. In this embodiment, the frequency fo of the basic signal is set to 200 kHz. The gate signal generation circuit 56 is a circuit that compares the basic signal with the output signal of the error amplifier 57 and sets the gate signal to a high level or a low level according to the comparison result.

The low-pass filter composed of the coil 53 and the capacitor 60 is configured as a second-order passive filter. The cutoff frequency fc of this low-pass filter is set to be about 1/100 of the frequency fo of the basic signal. Therefore, in this embodiment, the cutoff frequency fc of the low-pass filter is set to 2 kHz. The amount of attenuation by the low-pass filter is set to be at least 80 dB at the frequency fo of the basic signal. That is, the reactance value of the coil 53 and the capacitance value of the capacitor 60 are set so as to have such characteristics.

Further, the reference voltage generation unit 59 as a part of the control means divides a predetermined target voltage VDD0 by resistors 51 and 52 to obtain a reference voltage Vref (= VDD0 · R2 / (R1 + R2)) (here. , R1 and R2 are circuits or elements that generate the respective resistance values of resistors 51 and 52).

Further, the error amplifier 57 as a part of the control means is a voltage obtained by dividing the reference voltage Vref by the reference voltage generator 59 and the output voltage VDD from the power supply circuit 50 by the resistors 51 and 52 (= VDD · R2 / (= VDD · R2 / ( It is a circuit that compares with R1 + R2)) and sets the output signal as a voltage value according to the difference between the two. That is, the error amplifier 57 is an output voltage error output circuit that outputs a voltage error signal corresponding to the error between the output voltage VDD of the power supply circuit 50 and the predetermined reference voltage Vref.

Next, the operation of the above embodiment will be described with a focus on the power supply circuit 50. In the power supply circuit 50, the switching element 54 operates as a series switch between the input and the output, and the switching element 55 operates as a shunt switch between the output and the ground. Since the switching element 54 and the switching element 55 are complementary to each other and are supplied with the same gate signal, when one is in the on state, the other is in the off state, and the gate signal from the gate signal generation circuit 56 is used. Push-pull operation is performed accordingly.

On the other hand, the error amplifier 57 compares the reference voltage Vref generated by the reference voltage generator 59 with the voltage obtained by dividing the output voltage VDD of the power supply circuit 50 by the resistors 51 and 52, and responds to the difference between the two. The voltage value error signal is supplied to the gate signal generation circuit 56.

The gate signal generation circuit 56 compares the value of the basic signal from the basic signal generation circuit 58 with the value of the error signal from the error amplifier 57, and the value of the error signal of the error amplifier 57 is the basic value from the basic signal generation circuit 58. When it is larger than the signal value, the gate signal is set to a high level (predetermined voltage Vo, Vo 0), and when the error signal value of the error amplifier 57 is less than or equal to the value of the basic signal from the basic signal generation circuit 58, the gate is set. The signal is set to low level (zero voltage), and the gate signal is continuously output in chronological order.

The gate signal generation circuit 56 compares the error signal of the error amplifier 57, which is two inputs, with the fundamental signal of the sawtooth wave, and when the voltage value of the error signal of the error amplifier 57 is higher than the voltage value of the fundamental signal, , The voltage value of the gate signal that is the output is Vo, otherwise the voltage value is zero. Similarly, the error signal of the error amplifier 57 and the fundamental signal of the triangular wave are compared, and when the voltage value of the error signal of the error amplifier 57 is higher than the voltage value of the fundamental signal, the voltage value of the gate signal which is the output is Vo, otherwise the voltage value is zero.

In this way, when the voltage value of the error signal from the error amplifier 57 increases, the duty ratio of the gate signal increases (that is, the period during which the switching element 54 is in the ON state becomes shorter), and the error signal from the error amplifier 57 increases. As the voltage value of the gate signal decreases, the duty ratio of the gate signal decreases. Therefore, when the output voltage VDD of the power supply circuit 50 becomes higher than the predetermined target voltage VDD0, the output value of the error amplifier 57 becomes large, and when the output value of the error amplifier 57 becomes large, the duty ratio of the gate signal becomes large. When the duty ratio of the gate signal increases, the ratio of the switching element 54 in the on state decreases, and the ratio of the switching element 55 functioning as a shunt switch in the on state increases, thereby increasing the output voltage. VDD decreases.

On the other hand, when the output voltage VDD is lower than the predetermined voltage VDD0, the output value of the error amplifier 57 becomes smaller, and when the output value of the error amplifier 57 becomes smaller, the duty ratio of the gate signal becomes smaller. When the duty ratio of the gate signal becomes smaller, the ratio of the period in which the switching element 54 is in the ON state increases, and the ratio of the period in which the switching element 55 is in the ON state decreases, whereby the output voltage VDD increases.

In this way, the power supply circuit 50 sets the power supply voltage VDD to the predetermined voltage VDD0 regardless of whether the load fluctuates and the DC voltage supplied to the switching driver 10c becomes higher or lower than the predetermined voltage VDD0. To control.

Therefore, when measuring the load impedance when a headphone or an AV device is connected to the headphone connector 20, the ripple at point B in FIG. 6 is suppressed by the action of the power supply circuit 50. By the way, inside the power supply circuit 50, there is a low-pass filter composed of a coil 53 and a capacitor 60. Therefore, when a headphone or an AV device is connected to measure the load impedance, a back electromotive force is generated by the ripple current flowing through the coil 53, and a ripple voltage is generated at the point A by the back electromotive force. Since the magnitude of the ripple current has a certain correlation with the load impedance, by measuring the level of the ripple voltage generated at the point A, the same as in the case of the embodiment shown in FIG. , Load impedance can be measured.

As described above, in the case of the second modification embodiment shown in FIG. 6, since the power supply circuit 50 is newly added, it is possible to suppress the ripple included in the power supply voltage supplied to the switching driver 10c. it can. As a result, when the normal content data is reproduced, the noise component included in the audio signal can be suppressed, so that the S / N ratio can be improved.

Further, in the second modification, the counter electromotive force generated in the coil 53 existing in the power supply circuit 50 is detected at the point B, and the load is loaded by the load detection unit 27 according to the ripple level based on the counter electromotive force. Since the impedance is measured, the optimum volume level and equalizer characteristics can be set according to the headphone or AV device connected to the headphone connector 20 as in the case of the embodiment shown in FIG.

(F-3) Other embodiments of modification

In each of the above embodiments, a sine wave having a single frequency is used as the inspection signal, but for example, an inspection signal in which sine waves having a plurality of frequencies are mixed may be used. For example, impedance may be measured at each of the low frequency and the high frequency using two types of inspection signals of high frequency and low frequency, and the impedance may be determined in a complex manner based on these. According to such a method, the impedance can be obtained with higher accuracy. Needless to say, signals having three or more frequencies may be used.

Further, in the above embodiment, the measurement is performed only once using a sine wave of a single frequency, but the measurement is performed a plurality of times and the judgment is made based on the average value. May be good. According to such a method, the measurement can be performed with higher accuracy.

Further, instead of using a fixed frequency inspection signal, for example, the frequency may be swept (for example, in the range of 30 Hz to 20 kHz) within the audible band. According to such an embodiment, impedance characteristics in a wide range can be obtained. Since the impedance characteristics obtained in this way are expected to differ greatly depending on the model of the headphones, in particular, by using the characteristics as a unique ID for identifying the headphones, for example, the headphones can be used. The types can be distinguished and the optimum characteristics can be set for each headphone. Further, if the equalizer characteristics are set based on the impedance characteristics of the headphones in the audible band, the optimum equalizer characteristics can be set for each individual headphone.

Further, in the above embodiment, the signal of 127 Hz is used as the inspection signal, but it may be within the reproduction band. Specifically, for example, it may be set in the range of 30 Hz to 20 kHz. Comparing the high frequency and the low frequency, the low frequency has a higher level of counter electromotive force generated in the coils 14 and 15, so that the ripple level is higher and the impedance can be easily measured. That is, the closer the frequency is to direct current (DC), the higher the energy stored in the coils 14 and 15, and the higher the ripple level.

Further, for example, when a frequency of 15 kHz or higher is selected as the inspection signal, it is difficult for the human ear to hear it, so that the level of the sound output from the headphones or the like can be substantially lowered. For frequencies of 20 kHz or higher, since the frequency is higher than the cutoff frequency of the low-pass filter composed of the coil 14, the capacitor 16, and the coil 15 and the capacitor 17, ripple is unlikely to occur, so it is better to be within the cutoff frequency. desirable.

Further, in the above embodiment, the sine wave is used as the inspection signal, but the music signal can also be used as the inspection signal. In that case, since the signal level of the music signal changes according to the time, a predetermined point is set in advance and the output level at that point is detected, or the average value of the ripple for a certain period is obtained and used for this. The impedance value may be determined based on the above. According to such a method, it is possible to prevent the user from being uncomfortable due to the output of a sine wave from the headphones or the like.

Further, in the above embodiment, the inspection signal is output from both the L channel and the R channel. For example, the inspection signal is output one by one and the measurement is performed for each channel. May be good. According to such a method, for example, when there is a difference in impedance between the left and right channels, the bias of the left and right output volumes is corrected by setting the volume level so as to cancel the difference. Can be done.

Further, in the above embodiment, the load detection unit 27 is provided with the band filter 27a and the error amplifier 27b, but these are not always essential. For example, the band filter 27a can be omitted if the inspection signal is sufficiently larger than the noise signal. Further, the error amplifier 27b can be omitted when the detection level of the inspection signal is sufficiently high.

Further, in the above embodiment, the audio settings shown in FIG. 2 are set based on the setting information stored in advance at the time of manufacturing the playback device. However, for example, the user can arbitrarily set the audio settings after shipment. You may be able to do it. For example, the user may arbitrarily change the setting information (volume level, equalizer characteristics, etc.) registered in advance.

Further, in the above embodiment, the threshold value as a reference for determining the impedance is stored in advance at the time of manufacturing the reproduction device, but for example, the measured value actually measured after purchase is stored as the threshold value or the determination value. The determination may be made based on this. For example, when a headphone is connected and a user requests to actually measure and register, the impedance is measured at a plurality of different frequencies, and the impedance value at the plurality of frequencies is determined by the headphone. In addition to storing as an ID, input of setting information corresponding to the ID is accepted, and these are stored in association with each other. Then, when the same headphones are connected again, the same impedance value (ID) is searched, and if a matching impedance value exists, the setting is performed based on the setting information stored in association with each other. .. According to such a method, since the headphones and the setting information can be related to each other in a substantially one-to-one manner, the setting information can be changed for each headphone.

Further, in the above embodiment, the volume level and the equalizer characteristic are set based on the detection result of the load impedance, but other settings may be made. For example, a volume limit (maximum settable volume level) may be set, or surround may be set. Alternatively, assuming that the connected devices differ depending on the purpose of use (for example, commuting, jogging, driving, etc.), or the connected devices differ depending on the user, the list of playable contents may be changed or not shown. The display settings of the display unit (for example, font size, type, background image type, etc.) may be set. More specifically, for example, when commuting, a list of classic songs is displayed, when jogging, up-tempo pop songs are displayed as a list, and when driving, a relaxing easy listening type is displayed. A list of songs is displayed, and so on.

Further, in the above embodiment, the processes shown in FIGS. 4 and 5 are executed when the power is turned on. For example, it is detected by the plug detection unit 25 that the plug has been inserted. It may be executed at the time.

Further, in the above-described embodiment, a portable playback device that only reproduces music has been described as an example, but the present invention can also be applied to other devices. For example, it can be applied to a stationary playback device, or can be applied to a device that plays back data stored in a storage medium other than a memory (for example, an optical disk or an HDD (Hard Disk Drive)). The present invention can also be applied to mobile phones and the like. Further, the present invention can be applied not only to a device having a sound recording (or recording) function but also to a device having a sound recording (or recording) function.

The present invention can be applied to, for example, a portable reproduction device.

<figref num="1">It is a block diagram of the reproduction apparatus which concerns on embodiment of this invention.</figref><figref num="2">It is a figure which shows an example of the detection standard database.</figref><figref num="3">It is a figure which shows the relationship between an impedance value and a ripple level.</figref><figref num="4">It is a flowchart explaining an example of the process executed in the reproduction apparatus shown in FIG.</figref><figref num="5">It is a flowchart explaining an example of other processing executed in the reproduction apparatus shown in FIG.</figref><figref num="6">It is a block diagram of the reproduction apparatus which concerns on other embodiment of this invention.</figref><figref num="7">It is a block diagram which shows the configuration example of the reproduction apparatus which uses the conventional 3-pole plug.</figref><figref num="8">It is a block diagram which shows the configuration example of the reproduction apparatus which uses the conventional 4-pole plug.</figref><figref num="9">This is an example of a 4-pole plug.</figref>

Code description

1 Playback device 10 D-class headphone amplifier (part of output means) 10c switching driver (part of output stage) 11 Central control means (part of output means, specific means, setting means, reproduction means) 13 Large-capacity storage unit (storage means) 14,15 coil (part of output stage) 16,17 Capacitor (part of output stage) 20 Headphone connector (output terminal) 21 Plug detection terminal (part of detection means) 25 Plug detector (part of detection means) 27 Load detector (measuring means) 27a Band filter (Band filter) 27b Error amplifier (amplifier circuit) 54 Switching element (first switching element) 55 Switching element (second switching element) 56 Gate signal generation circuit (part of control means) 57 Error amplifier (part of control means) 58 Basic signal generation circuit (part of control means) 59 Reference voltage generator (part of control means)