JP3694621B2 - Speaker control system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a speaker control system that controls a drive current supplied to a speaker.
[0002]
[Prior art]
A device for converting an electrical audio signal into sound is a speaker, and various systems such as an electrodynamic type, an electrostatic type, and a piezoelectric type are adopted. For example, an electrodynamic (dynamic) speaker is a cone-shaped cone that is a vibrating body, a permanent magnet disposed near the top of the cone, and a voice that is fixed to the cone near the permanent magnet. And a coil. By inputting the amplified audio signal to the voice coil, a magnetic flux is generated around the voice coil. Therefore, a force acts on the voice coil arranged near the permanent magnet, and the cone vibrates by this force. Conversion from an electrical audio signal to sound is performed.
[0003]
Further, when driving the above-described speaker, it is necessary to vibrate the cone with the voice coil, so that a certain amount of driving power is required. For this reason, a minute audio signal is amplified by the amplifier device, and the amplified audio signal is input to the speaker. In a recent amplifier device, a power IC configured using a power transistor or the like is used in an output stage, and this power IC operates so as to maintain an output voltage even when a connected load fluctuates.
[0004]
[Problems to be solved by the invention]
By the way, the power IC used in the above-described conventional amplifier device operates so that the output voltage becomes constant even when the load fluctuates. When the voltage is lowered, there is a problem that an excessive current flows to increase the voltage across the both ends. For example, when the voice coil of a speaker with a load impedance of 4Ω is partially short-circuited and the load impedance is reduced to 0.5Ω, it is about Since it is necessary to flow eight times the current, the drive current increases rapidly.
[0005]
In addition, since such a fluctuation in current value occurs as a result of the operation of the power IC used in the output stage of the amplifier device, in a control device or the like that controls the operation of the amplifier device, An abnormality was not detected when an excessive current flowed through the voice coil. If this abnormality can be detected at an early stage, it is possible to perform control such as stopping the operation of the power IC and to prevent failure due to excessive current supply for a long time.
[0006]
The present invention has been created in view of such a point, and an object thereof is to provide a speaker control system capable of preventing an excessive drive current from flowing through the speaker. Another object of the present invention is to provide a speaker control system capable of detecting an abnormality of a speaker or the like.
[0007]
[Means for Solving the Problems]
In order to solve the above-described problems, the speaker control system according to the present invention detects the drive voltage applied to the speaker by the voltage detection means, and detects the drive current supplied to the speaker by the current detection means. The magnitude of the drive current is limited by the drive current limiting means so as not to exceed a predetermined maximum current value set according to the magnitude of the set drive voltage. The maximum current value is set according to the magnitude of the drive voltage, and the drive current supply operation exceeding this is limited, so even if the drive voltage suddenly decreases due to load fluctuations of the speaker, this drive It is possible to prevent an excessive drive current from flowing in order to keep the voltage constant.
[0008]
In particular, the maximum current value described above is desirably set for each drive voltage in consideration of the minimum impedance of a speaker that is allowed to be connected. Operation is assured for speakers with each load impedance that is allowed to be connected, and excessive drive current supply is ensured in the event of a sudden drop in drive voltage caused by a short circuit of the speaker's voice coil, etc. Can be prevented.
[0009]
In addition, drive control means for controlling the current supply operation of the drive means for driving the speaker is provided, and when the drive current supply operation is restricted by the drive current limiting means described above, the drive current supply operation by the drive means is stopped. It is desirable to make it. When the speaker is abnormal and the drive current exceeds a predetermined maximum current value, it is possible to prevent the drive means from being broken by stopping the excessive current supply operation by the drive means.
[0010]
In addition, when the drive current supply operation is limited by the above-described drive current limiting means, it is desirable to notify the occurrence of abnormality by the notification means. When an excessive current value exceeding the maximum current value flows and its supply operation is restricted, the fact is output as an abnormality occurrence notification, making it easy to take measures and display based on this notification .
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an amplifier device according to an embodiment to which the speaker control system of the present invention is applied will be described with reference to the drawings.
[0012]
FIG. 1 is a diagram illustrating a configuration of an amplifier device according to an embodiment. The amplifier device 100 of this embodiment shown in the figure includes a speaker driving unit 110, a driving current limiting circuit 120, and a control unit 130. In practice, the sound volume and sound quality are controlled with respect to the audio signal input to the amplifier device 100, but the configuration relating to these control mechanisms will be omitted.
[0013]
The speaker driving unit 110 outputs a driving current for driving the speaker 200 connected to the amplifier device 100 based on the input audio signal. For example, it is configured by a power IC packaged including a power transistor, and the drive current is controlled according to the amplitude value of the input audio signal.
[0014]
The drive current limiting circuit 120 is for limiting the current supply operation when the current value supplied from the speaker driver 110 to the speaker 200 exceeds a predetermined maximum current value. The current detection unit 3, the current control unit 4, and resistors 5 to 7 are included.
[0015]
The potential difference detection unit 2 detects a voltage between terminals of the speaker 200, and detects a potential difference between both ends of a resistor 5 connected between the terminals. This detection result is output toward the determination unit 11 as a driving voltage for the speaker 200. Since the resistor 5 is used to detect the voltage across the speaker 200, the resistor 5 has an impedance (resistance value) sufficiently larger than the load impedance of the speaker 200 so as not to affect the driving operation of the speaker 200. Used.
[0016]
The current detection unit 3 is for detecting the drive current supplied to the speaker 200. The current detection unit 3 measures the voltage across the two resistors 6 and 7 inserted on the signal path to which the drive current is supplied. A drive current value is detected based on the measured value. This detection result is output toward the determination unit 11. Specifically, one resistor 6 is inserted on a signal line connected to the positive output terminal of the speaker driving unit 110, and is generated at both ends of the resistor 6 when a drive current flows through the signal line. The voltage between terminals is measured by the current detection unit 3. The other resistor 7 is inserted on a signal line connected to the negative output terminal of the speaker driving unit 110, and a terminal voltage generated at both ends of the resistor 7 when a drive current flows through the signal line. Is measured by the current detector 3. In addition, since the value of the drive current of the speaker 200 flowing through each of the two resistors 6 and 7 described above is the same during normal operation, either one may be omitted. Since these resistors 6 and 7 are used to detect the drive current flowing through the speaker 200, the impedance (resistor) is sufficiently smaller than the load impedance of the speaker 200 so as not to affect the driving operation of the speaker 200. Value) is used.
[0017]
The current control unit 4 limits the supply operation when an excessive drive current is supplied to the speaker 200. The current control unit 4 includes a determination unit 11 and switches 12 and 13 for performing the limit operation. Has been. One switch 12 is inserted in a signal line that connects the positive output terminal of the speaker drive unit 110 and one input terminal of the speaker 200, and limits the supply operation of the drive current flowing on the signal line. Used for. The other switch 13 is inserted in a signal line that connects the negative output terminal of the speaker driving unit 110 and the other input terminal of the speaker 200, and restricts the supply operation of the drive current flowing on this signal line. Used to do.
[0018]
The determination unit 11 receives the detection results of the potential difference detection unit 2 and the current detection unit 3, and controls the open / close state of the switches 12 and 13 based on the detection results. Specifically, in the determination unit 11, a maximum current amount corresponding to the value of the inter-terminal voltage (drive voltage) of the speaker 200 detected by the potential difference detection unit 2 is set in advance, and is detected by the current detection unit 3. If the drive current value does not exceed the maximum current value, the switches 12 and 13 are controlled in a fully closed state. That is, in this case, the operation for limiting the drive current is not performed. On the other hand, when the value of the drive current detected by the current detection unit 3 exceeds the maximum current value described above, the determination unit 11 limits the drive current by opening and closing the switches 12 and 13 with a predetermined duty ratio. Then, control is performed so that the value of the drive current detected by the current detection unit 3 does not exceed the maximum current value. When the drive current limiting operation is performed in this manner, the determination unit 11 sends a predetermined notification signal for notifying the controller 130 that the drive current is limited.
[0019]
Further, the control unit 130 illustrated in FIG. 1 controls the entire amplifier device 100. When the control unit 130 receives the notification signal output from the determination unit 11 in the current control unit 4, the control unit 130 sends an operation stop instruction to the speaker drive unit 110 to stop the drive current supply operation to the speaker 200. .
[0020]
The potential difference detection unit 2 and the resistor 5 described above are the voltage detection means, the current detection unit 3, the resistor 6 and the resistor 7 are the current detection means, and the current control unit 4 including the determination unit 11 and the switches 12 and 13 is the drive current limiting unit. In addition, the control unit 130 corresponds to a drive control unit.
[0021]
The amplifier device 100 of the present embodiment has such a configuration, and the operation thereof will be described next. FIG. 2 is a flowchart showing an operation procedure of the amplifier device 100, and mainly shows an operation procedure by the drive current limiting circuit 120.
[0022]
When the drive current limiting circuit 120 starts operating, first, the potential difference detection unit 2 detects the potential difference V1 across the resistor 5 (step 100). The detected potential difference value is output to the determination unit 11 in the current control unit 4 as the drive voltage V <b> 1 applied to the speaker 200.
[0023]
In addition, the current detection unit 3 measures the voltage V2 across the resistor 6 and divides the voltage V2 across the resistor 6 by the resistance value R1 of the resistor 6 so that one signal line connecting the speaker driving unit 110 and the speaker 200 is connected. And the voltage V3 across the resistor 7 is measured, and the voltage V3 across the resistor 7 is divided by the resistance value R2 of the resistor 7 so that the other of the speaker driver 110 and the speaker 200 is connected. A drive current I2 flowing through the signal line is detected (step 101). The detected drive currents I1 and I2 are output toward the determination unit 11 in the current control unit 4. Note that the detection operation of the drive voltage V1 and the detection operation of the drive currents I1 and I2 are performed at the same timing.
[0024]
Next, the determination unit 11 in the current control unit 4 includes a predetermined maximum current value Imax corresponding to the driving voltage V1 of the speaker 200 detected using the potential difference detection unit 2 and the speaker detected by the current detection unit 3. 200 drive currents I1 and I2 are compared, and it is determined whether or not each of these current values I1 and I2 is equal to or greater than the maximum current value Imax (step 102). Actually, since the drive currents I1 and I2 flowing into both ends of the voice coil (not shown) of the speaker 200 are the same, in this embodiment, these average values I3 (= (I1 + I2) / 2) and The maximum current value Imax is compared.
[0025]
FIG. 3 is a diagram showing the relationship between the detected drive voltage V1 and the maximum current value Imax. There is a relationship of I = V1 / Z between the drive voltage V1 applied to the voice coil having the predetermined impedance Z and the current value I flowing at this time. Therefore, when there is no abnormality such as a short circuit in the voice coil of the speaker 200, the value of the current that flows corresponding to the detected drive voltage V1 is determined. A somewhat high value is set as the maximum current Imax corresponding to the drive voltage V1. Also, if the load impedance of the speaker 200 is different, the value of the flowing current will be different even if the drive voltage V1 is the same. Therefore, in this embodiment, the minimum load impedance of the speaker 200 that is generally used is 2 [Ω]. A drive current value corresponding to each drive voltage V1 is obtained, and a value obtained by adding about 1 [A] to the drive current value in consideration of malfunction or sound quality deterioration is set as the above-described maximum current value Imax.
[0026]
Therefore, in step 102 described above, it is determined whether or not the drive current I3 corresponding to the detected drive voltage V1 is included in the hatched area in FIG. When the drive current I3 is equal to or greater than the maximum current value Imax corresponding to the drive voltage V1 at that time, that is, when the detected current value I3 is included in the hatched region in FIG. In step 102, an affirmative determination is made, and then the determination unit 11 performs open / close control of the switches 12 and 13, thereby limiting the drive currents I1 and I2 supplied to the speaker 200 (step 103). For example, the determination unit 11 repeatedly opens and closes the switches 12 and 13 in a predetermined cycle, and adjusts the duty ratio between the open state and the closed state at this time, so that the drive currents I1 and I2 supplied to the speaker 200 are Control is performed so as to be approximately equal to the maximum current value Imax corresponding to the driving voltage V1 at the time. Note that the current value when the current is limited does not necessarily need to match the maximum current value Imax corresponding to the driving voltage V1 at that time, and may be equal to or less than the maximum current value Imax.
[0027]
When the drive currents I1 and I2 are thus limited, the determination unit 11 then outputs a notification that the drive current is limited to the control unit 130 (step 104). Thereafter, returning to step 100, the operation after the detection operation of the drive voltage V1 is repeated.
[0028]
Further, when the drive current I3 is less than the maximum current value Imax corresponding to the drive voltage V1 at that time, that is, when the detected current value I3 is not included in the hatched region in FIG. In step 102 described above, a negative determination is made, and then the process returns to step 100 to repeat the operation for detecting the drive voltage V1.
[0029]
As described above, the drive current limiting circuit 120 of this embodiment has a drive current that exceeds the current value (maximum current value Imax) that flows when the speaker 200 that is normal and has the smallest load impedance is connected. When the current is supplied to 200, the drive current supply operation is limited. Therefore, it is possible to prevent an excessive driving current from flowing even when the voice coil of the speaker 200 is short-circuited.
[0030]
In addition, when such a drive current supply operation is limited, a notification to that effect is output from the drive current limit circuit 120, and therefore the control unit 130 that has received this notification has the power in the speaker drive unit 110. The operation of the IC can be stopped, and by supplying an excessive current for a long time, an unexpected situation such as a failure of the speaker driving unit 110 can be avoided.
[0031]
FIG. 4 is a diagram showing the relationship between the drive voltage V1 and the maximum current value Imax, and shows the relationship between the drive voltage V1 and the maximum current value Imax when the load impedance of the connected speaker 200 is taken on the horizontal axis. ing. In the region where the load impedance of the speaker 200 is approximately 2 [Ω] or less, the drive voltage V1 increases rapidly as the load impedance increases. In the region where the load impedance is 2 [Ω] or more, the load impedance is high. The reason why the drive voltage V1 does not increase so much is that the characteristics of the power IC incorporated in the speaker drive unit 110 are actually non-linear. Thus, in this embodiment, since the drive current is limited by the drive current limiting circuit 120, for example, the voice coil of the speaker 200 is partially short-circuited and the drive voltage V1 is suddenly reduced. However, the value of the drive current that can be supplied also decreases as the drive voltage V1 decreases, and an excessive drive current can be prevented from being supplied to the speaker 200.
[0032]
FIG. 5 is a diagram showing the relationship between the drive voltage and the drive current when the speaker 200 is driven by a conventional amplifier device that does not use the drive current limiting circuit 120 of the present embodiment. Compared with the relationship shown in FIG. 4, it can be seen that, when the driving voltage of the speaker 200 is lowered, an excessive driving current has flowed in an attempt to maintain this value.
[0033]
In addition, this invention is not limited to the said embodiment, A various deformation | transformation implementation is possible within the range of the summary of this invention. For example, in the above-described embodiment, the drive current supplied to the speaker 200 is limited by adjusting the duty ratio for opening and closing the switches 12 and 13 in the current control unit 4. The current value flowing in the signal line may be controlled in an analog manner using the element.
[0034]
Further, in the above-described embodiment, when the drive current limiting operation is performed by the drive current limiting circuit 120, a case in which the notification is sent to the control unit 130 to stop the operation of the speaker driving unit 110 has been described. However, instead of stopping the operation of the speaker driving unit 110, or in parallel with this stopping operation, an alarm may be output to the user. For example, if a predetermined indicator lamp is turned on by the output of this alarm, a user who has confirmed the lighting state of the indicator lamp can know that an abnormality has occurred in the amplifier device 100 or the speaker 200. Measures such as sending out repairs early can be taken.
[0035]
【The invention's effect】
As described above, according to the present invention, the maximum current value is set according to the magnitude of the drive voltage, and the supply operation of the drive current exceeding this is limited. Even when the drive voltage becomes smaller, it is possible to prevent an excessive drive current from flowing in order to keep the drive voltage constant.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a configuration of an amplifier device according to an embodiment.
FIG. 2 is a flowchart showing the operation of each part of the drive current control circuit.
FIG. 3 is a diagram illustrating a relationship between a driving voltage and a maximum current.
FIG. 4 is a diagram illustrating a relationship between a drive voltage and a drive current subjected to current limitation.
FIG. 5 is a diagram illustrating a relationship between a conventional driving voltage and a driving current.
[Explanation of symbols]
2 Potential difference detection unit 3 Current detection unit 4 Current control unit 5, 6, 7 Resistance 11 Determination unit 12, 13 Switch 100 Amplifier device 110 Speaker drive unit 120 Drive current limiting circuit 130 Control unit 200 Speaker

Claims (4)

Driving means for driving the speaker;
Voltage detecting means for detecting a driving voltage applied to the speaker;
Current detection means for detecting a drive current supplied to the speaker;
Based on the current value detected by the current detection means so as not to exceed a predetermined maximum current value set according to the magnitude of the drive voltage detected by the voltage detection means, the speaker is supplied to the speaker. Drive current limiting means for limiting the drive current;
A speaker control system comprising: In claim 1,
When the drive current detected by the current detection means exceeds the maximum current value set for each drive voltage in consideration of the minimum impedance of the speaker that is allowed to be connected, the drive current limiting means A speaker control system for limiting a current value supplied to the speaker from the driving means. In claim 2,
Drive control means for controlling supply operation of the drive current by the drive means;
When the drive current supply operation supplied to the speaker is restricted by the drive current limiting means, the drive control means stops the drive current supply operation by the drive means. Speaker control system. In claim 2,
A speaker control system, further comprising a notification unit that notifies the occurrence of an abnormality when a drive current supply operation supplied to the speaker is limited by the drive current limiting unit.

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