JPH09148861A - Acoustic equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize an acoustic equipment which is capable of adjusting the state of the sound signal outputted according to the impedance of a connection destination and reducing the handling time when an equipment to be connected is changed. SOLUTION: A classification decision part 25 and an insertion decision part 24 detect that a plug for analog is inserted into a headphone jack. Based on this detection, a rectangular wave generation part 27 generates a rectangular wave. After a low-pass filter converts this rectangular wave into a signal for impedance decision of a sine wave, an amplifier amplifies the wave and the wave is outputted from the jack. A detection circuit detects the signal level of the signal for decision and converts the level into a DC level. A detection signal decision part 29 judges the input impedance of a connected equipment from the DC level of the detection signal. Based on this judgment, a level calculation part 30 calculates the output level of a sound signal and a low frequency sound emphasis level, instructs the low frequency sound level to an equipment function part and sets attenuation amount to an attenuator.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an audio device that can be connected to a device having a different input impedance, such as another audio device connected to a line output cable or a headphone. Related to audio equipment that is shared.

[0002]

2. Description of the Related Art Conventionally, audio equipment such as a radio and an 8 mm VTR has been used by connecting other audio equipment such as an amplifier connected through a line output cable and equipment such as earphones and headphones. In order to connect these, various output terminals such as a headphone jack, an earphone jack, and a connection terminal for a line output cable are provided. Further, in audio equipment such as portable audio equipment that is required to be downsized, audio equipment that shares an output terminal to each connected equipment is also widely used.

However, when sharing output terminals of different output formats, such as a monaural audio signal and a stereo audio signal, such as earphones and headphones, the user needs to switch the output format of the audio device according to the connected device. There is. Therefore, in order to reduce the trouble at the time of switching, for example, Japanese Utility Model Laid-Open No. 62-141294 discloses an audio device that determines the output format required by a connected device and switches the output format of an output terminal.

Here, an audio device for switching the output format will be described. As shown in FIG. 5, in the conventional audio equipment, the signal processing circuit 51 outputs monaural and stereo audio signals via the source changeover switch 52. These signals are output to a headphone / earphone changeover switch (hereinafter simply referred to as a switch) 53.
After selecting one of the signal lines, each signal line 54
It is transmitted to the R terminal 55a and the L terminal 55b of the jack, which is an output terminal, via a.54b. Further, the jack is provided with a ground terminal 55c and an insertion detection terminal 55d, and can detect whether or not a plug such as an earphone plug or a headphone plug 56, which is not shown, is inserted.

When the plug is not inserted, the hold circuit 61 has not received the insertion signal indicating the insertion of the plug from the insertion detection terminal 55d. In this state, the hold circuit 61 switches the switch 53 to the earphone side.

When the plug is inserted, the hold circuit 61
Receives the insertion signal from the insertion detection terminal 55d, and causes the switch 53 to select the earphone side until a certain detection period T elapses. As a result, during the detection period T, the monaural signal from the signal processing circuit 51 is applied to the L terminal 55b of the jack, and the oscillation circuit 6 is applied to the R terminal 55a.
The signal from 2 is applied.

The signal from the oscillation circuit 62 applied to the R terminal 55a is amplified by the amplification circuit 63 and then converted into a detection signal having a substantially constant voltage by the rectification circuit 64 and the smoothing circuit 65. . The comparator 66
It is determined whether or not the level of the detection signal is higher than a predetermined comparison potential, and based on this, a headphone / earphone switching signal (hereinafter, simply referred to as a switching signal) is output to the hold circuit 61. The amplifier circuit 63 has a high input impedance in order to suppress the influence on the signal line 54a. The amplification degree of the amplifier circuit 63 is set by the comparator 66 due to noise generated in the circuits 63, 64, 65. It is set large enough to prevent malfunction.

For example, when an earphone plug (not shown) which is an analog plug is inserted into the jack, the R terminal 55a and the ground terminal 55c are short-circuited via the earphone plug. As a result, the potential of the R terminal 55a is approximately G.
The signal becomes ND level and no signal is input to the amplifier circuit 63. Therefore, the level of the detection signal becomes lower than the comparison potential, and the comparator 66 outputs the L level switching signal indicating the earphone.

On the other hand, as shown in the figure, when the headphone plug 56, which is a stereo plug, is inserted into the above jack, the R terminal 55a and the ground terminal 55c are insulated from each other by the electrical insulation portion 56a of the headphone plug 56. ing. Therefore, the output of the oscillation circuit 62 is directly applied to the amplification circuit 63, and the level of the detection signal is
It becomes higher than the comparison potential. Based on this, the comparator 66 outputs an H level switching signal indicating headphones to the hold circuit 61.

When a predetermined detection period T elapses after the plug is inserted, the hold circuit 61 switches the switch 53 based on the switching signal, and holds the state until the plug is removed and the insertion signal is interrupted.

As a result, the audio equipment detects whether the R terminal 55a and the ground terminal 55c are short-circuited, distinguishes between the earphone plug and the headphone plug 56, and outputs the audio signal. The format can be switched between stereo and monaural.

[0012]

However, the audio device having the above-described configuration is connected, for example, to a headphone via the headphone plug 56 and to an amplifier such as a component stereo via a line output cable. As in the case, it is impossible to distinguish connected devices having the same output format and different input impedances.

Generally, when a headphone having an input impedance of 16Ω or 32Ω is connected, the audio equipment adjusts the sound quality such as the bass emphasis level indicating the frequency characteristic and the sound output level. On the other hand, 47 KΩ
When connecting to another device such as the above amplifier via a line output cable having an input impedance of, the audio device outputs the audio signal as it is without adjusting the state of the audio signal such as output level and sound quality. Therefore, in each case, the audio equipment needs to output audio signals in states that are significantly different from each other.

As a result, when the output terminals for both are shared, the user needs to adjust the state of the audio signal output by the audio device according to the connected device, and the operation at the time of switching the connected device is required. The problem is that it becomes complicated.

In addition, even if the optical signal cable is mistakenly inserted, the conventional audio equipment determines whether or not the inserted plug is the headphone plug 56, so that the output format is stereo side. There is a risk of malfunction such as switching to. Therefore, the user needs to instruct the acoustic device to perform a recovery process from a malfunction, such as an operation of switching to a monaural signal, and the operation becomes more complicated.

The present invention has been made in view of the above problems, and an object thereof is to adjust the state of an audio signal to be output in accordance with the impedance of a connection destination, and to change the connected equipment. It is to realize audio equipment that can be reduced.

[0017]

In order to solve the above-mentioned problems, an audio device according to the invention of claim 1 is an audio device in which an output terminal of an audio signal to a connecting device having a different input impedance is shared. It is characterized by the following measures.

That is, by generating a predetermined judgment signal,
A signal output means for outputting from the output terminal, and a determining means for determining the input impedance of the connection device connected to the output terminal based on the output level of the determination signal output to the output terminal by the signal output means. An audio signal control means for controlling the state of the audio signal output from the output terminal, such as a bass enhancement level indicating a frequency characteristic or an output level, is provided based on the determination by the determination means.

In the above arrangement, the output terminal of the audio device is connected to another audio device such as an amplifier or a connected device such as headphones through a line output cable or a headphone plug. In this state, the signal output means outputs a predetermined determination signal from the output terminal.
The determination means detects the output level of the determination signal that changes according to the input impedance of the connected device, for example, by converting it into a direct current level in a detection circuit, and based on this, detects the input impedance of the connected device. Identify. The audio signal control means controls the state of the audio signal output from the output terminal, such as the frequency characteristic of the audio signal indicated by the bass emphasis level or the output level of the audio signal, according to the identified input impedance.

Therefore, the audio device can output an audio signal in a state corresponding to the input impedance of the connected device from the output terminal to the connected device. Therefore, even when the input impedances of the connection device first connected to the output terminal and the connection device next connected to the output terminal are different from each other, the audio device can adjust the state of the audio signal according to the connection device. As a result, the time and effort required for switching the connected device can be significantly reduced.

In order to solve the above-mentioned problems, an audio equipment according to a second aspect of the present invention has the structure of the first aspect of the invention.
It is characterized in that it is provided with a connection determining means for determining whether or not a connected device is connected to the output terminal and outputting a determination signal to the signal output means when a connection is detected.

According to the above arrangement, the signal output means is
When the connection determination means detects the connection of the connected device,
The determination signal and the audio signal control means output the determination signal, and adjust the state of the audio signal according to the input impedance of the connected device.

Therefore, it is possible to prevent malfunction of the determination means and the audio signal control means due to, for example, an audio signal output from the output terminal during the connection of the connected device or during the period when the connected device is not connected. Therefore, the audio device can prevent an undesired change in the state of the audio signal during the above period when the connected device does not change. Further, when a device is newly connected, the audio device can reliably adjust the state of the audio signal according to the connected device.

In order to solve the above-mentioned problems, an audio equipment according to a third aspect of the present invention has the configuration of the first or second aspect of the invention, wherein an optical signal cable for transmitting an optical signal can be connected to the output terminal. It is determined whether or not the optical signal cable is connected to the output terminal, and when the optical signal cable is connected, an optical cable determination that causes the audio signal control means to stop the control of the audio signal. It is characterized by having means.

Therefore, when the optical signal cable is connected to the output terminal, the audio signal control means does not adjust the state of the audio signal according to the judgment of the optical cable judgment means. As a result, the audio device can prevent erroneous adjustment of the audio signal due to the connection of the optical signal cable.

In order to solve the above-mentioned problems, an audio equipment according to a fourth aspect of the present invention has the configuration of the first, second or third aspect of the invention, and when the power is turned on, the signal output means is used for the determination. It is characterized by including a power supply monitoring means for outputting a signal.

When the power of the audio device is turned on, the power supply monitoring means causes the signal output means to output the judgment signal, and the judgment means and the sound signal control means make the sound signal according to the input impedance of the connected equipment. Adjust the state of. Therefore, even if the connected device is switched when the power is turned off, the audio device can output the audio signal in a state according to the current connected device. Therefore, even if the connected device is switched during the power-off period, it is possible to prevent erroneous determination of the input impedance and prevent erroneous adjustment of the state of the audio signal.

In order to solve the above-mentioned problems, an audio equipment according to a fifth aspect of the present invention has the structure of the first, second, third or fourth aspect of the invention, wherein the frequency of the determination signal output by the signal output means is Is characterized by being set to an inaudible frequency.

Therefore, even if the connected device reproduces the judgment signal, the user cannot hear it. Therefore, even when the connected device is in operation, the acoustic device can determine the input impedance of the connected device and adjust the state of the audio signal without damaging the ear of the user.

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of the present invention.
The following is a description based on FIG. That is, the audio device according to the present embodiment is, for example, a portable audio device such as a radio or an 8 mm VTR, and outputs an audio signal to a device having a different input impedance, such as headphones or another audio device, through a common output terminal. it can.

As shown in FIG. 2, the audio equipment 1 has an equipment function unit 2 for generating a stereo audio signal according to the function of the audio equipment 1, and the equipment function unit 2 outputs L. The stereo signals of R and R are output from a headphone jack (hereinafter simply referred to as a jack) 5 via an attenuator 3 that adjusts an audio output level and an amplifier 4 that amplifies the sound with a predetermined amplification degree.

The amplifier 4 used is capable of driving an audio device having a low input impedance, such as music headphones having an input impedance of 16Ω. Further, in the following description, for convenience of explanation, a signal line for transmitting an L channel audio signal is respectively provided between the device function section 2, the attenuator 3, the amplifier 4, and the jack 5 as an L signal line 6a and an R channel audio signal. Signal lines that transmit signals are collectively referred to as R signal lines 6b.

Further, the acoustic device 1 has the device function section 2
And a control circuit 7 for controlling the attenuator 3 and the like. The control circuit 7 controls the device function unit 2 to adjust the bass enhancement level indicating the frequency characteristic of the stereo signal, and also controls the attenuation amount of the attenuator 3 to adjust the signal level.
As a result, the audio device 1 can output an audio signal having a desired signal level and sound quality from the jack 5.

The jack 5 has, for example, φ3.
It is a 5 mm jack and can be connected to an analog plug such as a headphone plug 8 or a line output cable plug (not shown). Furthermore, a digital plug such as a plug of a digital optical cable (not shown) can be inserted into the jack 5.

The jack 5 is connected to both the signal lines 6a and 6a.
L terminal 5a and R terminal 5b connected to b and always G
When the analog plug is inserted, each terminal 5a to 5c includes an L electrode 8a, an R electrode 8b, and a ground electrode 8c provided on the analog plug. , Electrically connected to each other. As a result, the audio device 1 can output a stereo audio signal to a connected device (neither is shown) such as headphones or an amplifier connected to the analog plug.

Further, an insertion detection terminal 5d for detecting whether or not a plug such as the digital plug or the analog plug is inserted into the jack 5, and a plug type detection for detecting whether or not the inserted plug is an analog plug. Terminal 5e
Are provided.

When the plug is inserted, the insertion detection terminal 5d is short-circuited with the ground terminal 5c by, for example, a switch which is pressed by the plug to conduct electricity. As a result, the potential of the insertion detection terminal 5d becomes the GND level, unlike when the plug is not inserted.

The plug type detection terminal 5e is formed so as to be electrically connected to the ground electrode 8c of the analog plug when the analog plug is inserted.
Accordingly, when the analog plug is inserted, the plug type detection terminal 5e and the ground terminal 5c are the same as the ground electrode 8c.
Short-circuited. On the other hand, in the digital plug, the position corresponding to the ground electrode 8c of the analog plug is covered with a non-conductor. Therefore, when the digital plug is inserted, the plug type detection terminal 5e and the ground terminal 5c are insulated. As a result, the potential of the plug type detection terminal 5e does not reach the GND level, unlike when the analog plug is inserted.

The insertion detection terminal 5d and the plug type detection terminal 5e are connected to the in2 terminal and the in3 terminal of the control circuit 7, respectively, and the control circuit 7 monitors the potentials of the in2 terminal and the in3 terminal, Insertion / non-insertion of plugs and plug types can be identified.

Furthermore, the audio equipment 1 according to the present embodiment is
A low-pass filter (abbreviated as LPF below) 9 that changes the rectangular wave output from the out2 terminal by the control circuit 7 into a sine wave for the connection destination impedance detection operation.
And the signal lines 6a and 6b between the attenuator 3 and the amplifier 4.
To L. P. F. And an output switch 10 for selecting whether or not to apply the input impedance determination signal output from the output terminal 9. The output switch 10 is controlled by the out3 terminal of the control circuit 7, and each of the signal lines 6a and 6b described above is controlled.
, An input impedance determination signal is output in accordance with an instruction from the control circuit 7. In the following, the input impedance determination signal will be simply referred to as the determination signal.

Further, each signal line 6a on the output side of the amplifier 4
A detection circuit 12 for detecting the determination signal is connected to 6b via an input switch 11 whose conduction / interruption is controlled by the out3 terminal of the control circuit 7. The detection circuit 12 rectifies and detects the determination signal and applies a detection signal corresponding to the signal level of the determination signal to the control circuit 7. The control circuit 7 determines the connection impedance from the DC level of the detection signal applied to the in1 terminal,
The attenuator 3 is used to instruct the device function section 2 of the bass enhancement level of the audio signal and to set the attenuation amount that determines the output level of the audio signal
Can be set to

The detection circuit 12 has, for example, a resistor R1 having one end connected to the L signal line 6a and a resistor R2 having one end connected to the R signal line 6b when the input switch 11 is turned on. A diode D1 having the other ends of the resistors R1 and R2 connected to the anode side, a capacitor C1 having one end connected to the cathode side of the diode D1 and the other end grounded, and the capacitor C1 provided in parallel And a resistor R3 for discharging the electric charge of the capacitor C1. As a result, when the input switch 11 is turned on, the resistors R1 and R2 input the sum signal of the determination signals applied to the signal lines 6a and 6b to the diode D1, and the diode D1 and the capacitor C1 change the input signal. The signal level can be converted into a direct current level and applied to the in1 terminal as the potential at the connection point between the two. As a result, the control circuit 7
The input impedance of the device connected to the jack 5 can be determined by the signal level of the determination signal, that is, the DC level of the detection signal applied to the in1 terminal.

Now, the structure of the main part of the control circuit 7 will be described. As shown in FIG. 1, the control circuit 7 controls the device function unit 2 to control the device control unit 21 that sets the sound quality of the audio signal such as the bass enhancement level, and the attenuation amount of the attenuator 3 via the out1 terminal. And an attenuator control unit 22 for setting. As a result, the control circuit 7 can set a desired output level or bass enhancement level in the audio signal output by the audio device 1.

In the control circuit 7, a power source confirmation section (power source monitoring means) 23 for confirming whether or not the power source of the audio equipment 1 is in an ON state, and an insertion for detecting the state of the jack 5 shown in FIG. A determination unit (connection determination unit) 24, a type determination unit (optical cable determination unit) 25, and the above-mentioned units 23 and 24.
25 based on the detection result of L.25, and the determination signal control unit 26 that instructs the period for outputting the determination signal, and the L.L. P. F. A rectangular wave generator (signal output means) 27 that outputs a rectangular wave to the switch 9 and a switch controller 28 that controls the output switch 10 and the input switch 11 are provided.

The insertion determining section 24 can determine whether or not the plug is inserted in the jack 5 from the insertion signal applied to the in3 terminal. Also, the plug insertion can be detected by monitoring the potential of the in3 terminal. On the other hand, the type determining unit 25 can determine whether the plug inserted in the jack 5 is an analog plug or a digital plug based on the plug type signal applied to the in2 terminal.

Further, the judgment signal control section 26 can control the output of the judgment signal according to the ON / OFF state of the power supply and the state of the jack 5. When outputting the determination signal, the switch control unit 28 connects the switches 10 and 11 to each other and outputs a signal to the rectangular wave generation unit 27, the detection circuit 12 shown in FIG. Line 6
Connect to a6b. In addition, the rectangular wave generation unit 27 outputs a rectangular wave whose frequency is set to an inaudible frequency such as 30 KHz or 40 KHz from the out2 terminal.

As a result, the determination signal generated from the rectangular wave is output to the signal lines 6a and 6b, and the detection circuit 12 detects the determination signal to generate a detection signal.
In the control circuit 7 according to the present embodiment, when the determination signal is output, the determination signal control unit 26 sets the attenuation amount of the attenuator 3 to the maximum via the attenuator control unit 22 to reduce the attenuation. The device function unit 2 is separated from each of the signal lines 6a and 6b after the device 3.

On the other hand, when the judgment signal is not output, the rectangular wave generator 27 is operated according to the instruction from the judgment signal controller 26.
Stops the output of the rectangular wave, and the switch control unit 28
The ut3 terminal is controlled to shut off both switches 10 and 11. Thereby, the circuit for detecting the connection impedance can be separated from the signal lines 6a and 6b.

Further, the control circuit 7 determines the input impedance of the device connected to the jack 5 from the DC level of the detected signal based on the detected signal determination section (determination means) 2
9 and a level calculation unit (voice signal control means) 30 for instructing the device control unit 21 and the attenuator control unit 22 for the output level of the voice signal and the bass enhancement level according to the determination.

The detection signal judging section 29 judges whether or not the potential of the in1 terminal is higher than a predetermined judgment level A set in advance, and a line output cable (not shown) having an input impedance as high as 47 KΩ. Is the above Jack 5
Or a headphone (not shown) having an input impedance as low as 16Ω or 32Ω is connected via the headphone plug 8 shown in FIG.

The judgment level A is set so that it can be distinguished whether the connection impedance is low or high.
It is preset between the detection signal levels in each case.

As a result, the control circuit 7 sets the bass enhancement level and the attenuation amount according to the input impedance of the device connected to the jack 5 to the device function section 2 and the attenuator 3.
The audio device 1 can output an audio signal having a desired frequency characteristic and output level from the jack 5.

In the above structure, the operation of each part at the time of connection destination impedance detection control will be described step by step based on the flowchart shown in FIG.

That is, the first step 1 (hereinafter,
In (abbreviated as S1), the power supply confirmation unit 23 of the control circuit 7 confirms whether or not the power supply of the audio equipment 1 is in the ON state. When it is confirmed in S1 that the power is turned on, the insertion determination unit 24 monitors the potential of the in3 terminal, and the jack 5
It is determined whether or not a plug has been inserted into (S2). When the insertion determination unit 24 detects the insertion of the plug (when the potential of the in3 terminal changes to the GND level), in S3, the type determination unit 25 determines that the inserted plug is for analog according to the potential of the in2 terminal. Identify whether or not.

When it is determined in S3 that the inserted plug is an analog plug (when the potential of the in2 terminal is at the GND level), in the subsequent steps S4 and S5, the determination signal control unit 26 causes the rectangular wave generation unit 27 to operate. Also, the switch control unit 28 is instructed to output the determination signal.

Specifically, in S4, the switch control unit 28 makes the output switch 10 and the input switch 11 shown in FIG. 2 conductive via the out3 terminal according to an instruction from the determination signal control unit 26. As a result, L. P. F. 9
Is the L signal line 6a and the R signal line 6 on the input side of the amplifier 4.
b, and the detection circuit 12 is connected to each of the signal lines 6a and 6b on the output side of the amplifier 4. The determination signal control unit 26 also instructs the attenuator control unit 22 to increase the attenuation amount, and the attenuator control unit 22 increases the attenuation amount of the attenuator 3 via the out1 terminal. Thereby, the attenuator 3 attenuates the audio signal from the device function unit 2 during the output period of the determination signal. As a result, it is possible to prevent the sound signal from being mixed into the amplifier 4 and prevent the detection circuit 12 from being erroneously detected due to the abnormal sound.

Then, in step S5, the rectangular wave generator 27 shown in FIG. 1 responds to the instruction from the determination signal controller 26.
For example, a rectangular wave set to an inaudible frequency such as 30 KHz or 40 KHz is output from the out2 terminal (waveform (a) in FIG. 4). The above L. P. F. 9 converts this rectangular wave into a sine wave (waveform in FIG. 4B) and outputs it to the signal lines 6a and 6b via the output switch 10. Amplifier 4
Amplifies this determination signal and then outputs it to the inserted analog plug via the jack 5 shown in FIG.

In the present embodiment, since the frequency of the determination signal is set to the non-audible frequency, the determination is made from the connected device, for example, when the user wears headphones connected to the analog plug. The user cannot hear this determination signal even when the determination signal is output.

On the other hand, the output judgment signal is also applied to the detection circuit 12 through the conductive input switch 11. The detection circuit 12 rectifies and detects the input determination signal and converts it into direct current. The converted detection signal is applied to the in1 terminal of the control circuit 7, and the detection signal determination unit 29 shown in FIG. 1 reads the DC level of the detection signal from the potential of the in1 terminal (S6). In S6, the detection signal determination unit 29,
When the DC level of the detection signal, that is, the signal level of the determination signal is read, the rectangular wave generation unit 27 stops the output of the rectangular wave and stops the output of the determination signal (S7).

By the way, the signal level of the output judgment signal changes depending on the input impedance of the plug inserted into the jack 5. Therefore, the signal level of the determination signal is different between when the headphone plug 8 having an input impedance of 16Ω or 32Ω is inserted and when the line output cable having an input impedance of 47KΩ is connected, and the detection circuit 12 generates the signal level. The DC level of the detected signal also varies.

For example, when the headphone plug 8 is inserted, the amplifier 4 outputs a determination signal having a relatively small signal level as shown by the waveform (c) in FIG. Therefore, the DC level of the detection signal output by the detection circuit 12 is also lower than the predetermined determination level A as shown in the waveform of (d).

On the other hand, when the line output cable is connected, the waveform of the determination signal has a signal level higher than that of the waveform of (c) as shown by the waveform of (e) in FIG.
Further, as in the waveform of (f), the DC level of the detection signal is also higher than that of the waveform of (d), and the determination level A
Is over.

Therefore, in S8, the detection signal determination unit 2
Reference numeral 9 compares the DC level of the detection signal read in S6 with the determination level A to determine the connection impedance.

In S8, when the level of the determination signal is equal to or lower than the determination level A, the detection signal determination section 29 determines that the headphone plug 8 is inserted in the jack 5 shown in FIG. In this case, the level calculation unit 30 uses the audio device 1
The bass enhancement level and the signal level of the audio signal output by are set according to the headphone plug 8.

That is, the level calculation unit 30 confirms whether or not the data indicating the previously set audio output level or bass enhancement level is stored in the RAM or the non-volatile memory of the microcomputer (not shown) (S).
9). When the data is stored, the level calculation unit 30
The device control unit 21 specifies the bass enhancement level based on this data to the device function unit 2, and the attenuator control unit 22 sets the attenuation amount based on the audio output level indicated by the data to the attenuator 3. Set (S10).

As a result, the audio device 1 outputs the audio signal at the same output level and bass enhancement level as when the headphone plug 8 was previously inserted. The above data is data when the headphone plug 8 is inserted, and is updated when the user changes the volume, sound quality, etc. while the headphone plug 8 is inserted.

If data indicating the bass emphasis level and the like are not stored in S9, the level calculation unit 30
Controls the device function unit 2 and the attenuator 3 in substantially the same manner as S10, sets the audio output level to a predetermined initial level such as the center of a variable range, and, for example, the bass enhancement circuit of the device function unit 2. The bass emphasis level is adjusted to a predetermined level by stopping (not shown) or the like (S1).
1). As a result, the audio device 1 outputs an audio signal having a predetermined output level and flat frequency characteristics.

On the other hand, when the DC level is higher than the judgment level A in S8, the detection signal judging section 29 judges that the line output cable is connected to the jack 5 shown in FIG. In this case, the level calculation unit 30 determines S1
The device function unit 2 and the attenuator 3 are controlled in a manner substantially similar to 0, the bass enhancing circuit is stopped, and the attenuation amount of the attenuator 3 is minimized (S12). As a result, the jack 5 shown in FIG. 2 outputs an audio signal having a flat frequency characteristic and a maximum audio output level.

When the bass emphasizing level and the attenuation amount are set in S9 to S12, the switch control unit 28 cuts off the output switch 10 and the input switch 11 shown in FIG. 2 via the out3 terminal (S1).
3) The connection impedance detection operation ends. In this state, the L.V. P. F. 9 and the detection circuit 12 are separated from the L signal line 6a and the R signal line 6b, and do not prevent the audio device 1 from outputting an audio signal.

As a result, when an analog plug such as the headphone plug 8 or the plug of the line output cable shown in FIG. 2 is inserted into the jack 5, the audio equipment 1 determines the desired signal level and frequency according to the impedance of the connection destination. A voice signal with characteristics can be output.

On the other hand, when the inserted plug is a digital plug, the potential of the in3 terminal does not reach the GND level. Therefore, in S3, the insertion determination unit 24 determines that the inserted plug is not an analog plug, and the connection destination impedance detection operation ends. In this case, in the audio device 1 shown in FIG. 1, the determination signal is not applied to the L signal line 6a and the R signal line 6b, and the device function unit 2 and the attenuator 3 do not change the bass enhancement level or the attenuation amount. . This ensures that when a digital plug is inserted,
It is possible to prevent undesired changes in the bass enhancement level and the attenuation amount.

If the insertion determining unit 24 cannot detect the insertion of the plug in S2, the process returns to S1 and S1 and S2 are repeated. Therefore, the audio device 1 waits for the insertion of the plug while the power is on. As a result, the output of the determination signal can be stopped during the period when the plug is not newly inserted, such as when the plug is not inserted or while the plug is being inserted.

Further, when the power-off of the audio equipment 1 is detected in the above S1, the power supply confirming section 23 monitors the power supply of the audio equipment 1 and waits until the power is turned on (S14). When it is detected that the power is turned on, the insertion determination unit 24 determines whether or not the plug is inserted based on the potential of the in3 terminal (S15). If the plug is inserted in S15, the process proceeds to S3, and the subsequent connection destination impedance detection operation is continued. If the plug is not inserted, the process returns to S2 to wait for the insertion of the plug.

By the way, when the power is off, the plugging / unplugging cannot be detected because the respective parts of the audio equipment 1 are not operating. As a result, when the power is turned off with the plug still inserted and the plug is replaced when the power is turned off, it is determined in the processing of S1 to S13 that the plug before the power is turned off is still inserted, and the newly inserted plug is inserted. Control cannot be performed according to the input impedance of.

However, by executing the processing of S14 and S15, the acoustic device 1 always measures the impedance of the connection destination when the plug is inserted when the power is turned on. As a result, even if the plugs are replaced when the power is off, the audio device 1 can control the output level of the audio signal and the bass emphasis level according to the input impedance of the inserted plug. Since the insertion determination unit 24 and the like can be stopped when the power is turned off, the power consumption can be reduced as compared with the configuration in which the plug insertion is constantly monitored.

As described above, the acoustic device 1 according to the present embodiment has the rectangular wave generator 27 and the L.W. P. F. 9, a detection circuit 12 for detecting the signal level of the determination signal output to the jack 5 shown in FIG. 2, and a detection circuit for determining the input impedance of the device connected to the jack 5 according to the DC level of the detection signal. A signal determination unit 29 and a level calculation unit 30 for instructing the output level of the audio signal and the bass enhancement level according to the input impedance of the connected device are provided. In response to an instruction from the level calculation unit 30, the device control unit 21 and the attenuator control unit 22 set the bass enhancement level and the attenuation amount in the device function unit 2 and the attenuator 3 illustrated in FIG. 2, respectively.

As a result, the audio equipment 1 can output from the jack 5 an audio signal having a frequency characteristic and a signal level according to the input impedance of the connected equipment. Since the state of the audio signal such as frequency characteristics and output level can be automatically adjusted, the user has to adjust the state of the audio signal according to the input impedance of the newly connected device as in the past. Absent. As a result, in the audio device 1 that shares the jack 5 that connects devices with different input impedances, it is possible to reduce the time and effort required when switching the connected devices.

Furthermore, the level calculation section 3 according to the present embodiment.
0 stores the state of the audio signal when the headphone plug 8 shown in FIG. 2 is inserted into the jack 5, and when the headphone plug 8 is inserted again, the state can be returned to the previous state. Therefore, the audio device 1 can adjust the state of the audio signal according to the usage situation of the user.

In addition to the above-mentioned structure, an insertion judging section 24 for judging whether or not a plug is inserted into the jack 5 is provided according to the potential of the insertion detecting terminal 5d shown in FIG. In addition, since the rectangular wave generation unit 27 outputs the determination signal, the period for outputting the determination signal can be set based on the time of inserting the plug, that is, the time when the connected device is changed. As a result, the rectangular wave generation unit 27 does not output the determination signal and the detection circuit 12 illustrated in FIG. Do not detect the signal. Therefore, for example, it is possible to prevent the malfunction of the detection circuit 12 due to the audio signal output from the device function unit 2 or the like. As a result, the acoustic device 1 can prevent an undesired state change of the audio signal in the period in which the connected device does not change, and when the connected device changes, the audio device 1 surely changes the state of the audio signal according to the connected device. Can be adjusted.

Furthermore, the audio device 1 according to the present embodiment is
A type determination unit 25 for determining the type of the plug inserted into the jack 5 according to the potential of the plug type detection terminal 5e shown in FIG. As a result, when the digital plug is inserted, the operation of the rectangular wave generation unit 27 can be stopped and the detection signal determination unit 29 can stop the input impedance determination of the connected device. Therefore, when the digital plug is inserted, the audio device 1 does not adjust the state of the audio signal of the audio device 1 and can prevent an undesired change in the state of the audio signal due to erroneous insertion of the digital plug.

In addition, the above-mentioned audio equipment 1 includes the audio equipment 1
A power source confirmation unit 23 for confirming the on / off state of the power source is provided, and a determination signal can be output from the jack 5 when the power source is turned on. Therefore, during the period in which the audio device 1 cannot detect the switching of the connected device, such as during power-off,
Even when the connected device is switched, the state of the audio signal can be reliably adjusted according to the input impedance of the connected device.

Further, in the audio device 1 according to the present embodiment, the frequency of the rectangular wave generated by the rectangular wave generator 27 is set to an inaudible frequency such as 30 KHz or 40 KHz. Therefore, even if the judgment signal output from the jack 5 is reproduced, the user cannot hear the judgment signal. As a result, the acoustic device 1 measures the input impedance of the connected device without damaging the user's ear even when the analog plug is inserted while the headphones are worn or the amplifier or the like is in operation. , Bass emphasis level and audio output level can be adjusted.

In the acoustic device 1 according to the present embodiment, the detection signal determination unit 29 shown in FIG. 1 determines whether the line output cable is connected or the headphones are connected depending on the DC level of the detection signal. However, the present invention is not limited to this. For example, the case where headphones with an input impedance of 16Ω are connected and the case where headphones with a 32Ω input are connected may be further distinguished. By distinguishing the three cases, the level and frequency characteristics of the audio signal output by the audio device 1 can be adjusted more finely according to the input impedance of the connected device. Regardless of how many input impedances are divided, by adjusting the output level and the frequency characteristic of the audio signal according to the identified input impedance, substantially the same effect as this embodiment can be obtained.

[0084]

As described above, the audio equipment according to the invention of claim 1 generates the predetermined determination signal and outputs it from the output terminal, and the signal output means outputs the signal to the output terminal. Based on the output level of the determination signal, the determination means for determining the input impedance of the connected device connected to the output terminal, and the state of the audio signal output from the output terminal based on the determination of the determination means And a voice signal control means for controlling the.

Therefore, the audio device can output the audio signal in the state corresponding to the input impedance of the connected device from the output terminal to the connected device. Therefore, unlike the conventional case, the user does not need to change the state of the audio signal according to the switched connection device. As a result, in an audio device that shares output terminals to connected devices with different input impedances, it is possible to reduce the trouble when switching the connected devices.

As described above, the audio equipment according to the invention of claim 2 is, in the configuration of the invention of claim 1, determined whether or not a connection device is connected to the output terminal, and detects the connection when the connection device is connected. This is a configuration including connection determination means for outputting a determination signal to the signal output means.

Therefore, the audio equipment can prevent malfunction of the judging means and the audio signal control means and maintain the state of the audio signal while the connected equipment is not changed, while the audio equipment is connected, when the connected equipment is connected. The state of the audio signal can be reliably adjusted according to the input impedance. Therefore, the audio device can more reliably determine the input impedance of the connected device, and can prevent an undesired change in the state of the audio signal.

As described above, the audio equipment according to the invention of claim 3 has the configuration of the invention of claim 1 or 2 as described above.
It is determined whether or not the optical signal cable is connected to the output terminal, and if the optical signal cable is connected, the audio signal control means is provided with an optical cable determination means for stopping control of the audio signal. It has a structure.

Therefore, when the optical signal cable is connected to the output terminal, the audio signal control does not adjust the state of the audio signal. As a result, erroneous adjustment of the audio signal due to the connection of the optical signal cable can be prevented, and the acoustic device can more reliably adjust the state of the audio signal.

As described above, in the audio equipment according to the invention of claim 4, in the configuration of the invention of claim 1, 2 or 3, when the power is turned on, the determination signal is output to the signal output means. This is a configuration including a power supply monitoring means for outputting.

Therefore, the erroneous determination of the input impedance due to the switching of the connected device during the power-off period can be prevented, and the audio device can more surely adjust the state of the audio signal according to the input impedance of the connected device. Has the effect.

As described above, in the audio equipment according to the invention of claim 5, in the configuration of the invention of claim 1, 2, 3 or 4, the frequency of the determination signal output by the signal output means is: The configuration is set to the inaudible frequency.

According to the above configuration, even if the connected device reproduces the determination signal, the user cannot listen to it. As a result, the audio device has the effect of being able to adjust the state of the audio signal during operation of the connected device without damaging the ears of the user.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention and showing a main configuration of a control circuit provided in an audio device.

FIG. 2 is a block diagram showing a main configuration of the audio device.

FIG. 3 is a flowchart showing an operation at the time of connection destination impedance detection control in the audio device.

FIG. 4 is a waveform diagram showing waveforms of various parts in the above-described audio equipment during impedance detection control of a connection destination.

FIG. 5 shows a conventional example and is a block diagram showing a main configuration of an audio device.

[Explanation of symbols]

 23 power supply confirmation section (power supply monitoring means) 24 insertion determination section (connection determination means) 25 type determination section (optical cable determination means) 27 rectangular wave generation section (signal output means) 29 detection signal determination section (determination means) 30 level calculation section (Voice signal control means)

Claims (5)

[Claims] 1. An audio device which shares an output terminal for audio signals to connected devices having different input impedances, and a signal output means for generating a predetermined determination signal and outputting the signal from the output terminal. Based on the output level of the determination signal output from the output means to the output terminal, the determination means for determining the input impedance of the connected device connected to the output terminal, and the output terminal based on the determination of the determination means And an audio signal control means for controlling the state of the audio signal output from the audio device. 2. A connection determination means for determining whether or not a connection device is connected to the output terminal and outputting a determination signal to the signal output means when connection is detected. 1. The audio device according to 1. 3. An optical signal cable for transmitting an optical signal can be connected to the output terminal, and it is determined whether or not the optical signal cable is connected to the output terminal, and the optical signal cable is connected. 3. The audio equipment according to claim 1, wherein the audio signal control means is provided with an optical cable determination means for stopping the control of the audio signal when the audio signal is connected. 4. The audio equipment according to claim 1, further comprising a power supply monitoring means for causing the signal output means to output the determination signal when the power is turned on. 5. The audio device according to claim 1, wherein the frequency of the determination signal output by the signal output means is set to an inaudible frequency.