JP5338832B2 - Speaker circuit disconnection detection device - Google Patents

Description

  The present invention relates to an apparatus for detecting the presence or absence of disconnection in a speaker circuit including a speaker and a speaker cable connected to a low frequency amplifier circuit.

  As a conventional example of an apparatus for detecting the presence or absence of disconnection in a speaker circuit, Patent Document 1 discloses that an audio amplifier is connected to an AC transmitter that transmits a predetermined AC signal, and the speaker is connected to the audio amplifier via a cable. Further, a configuration in which a disconnection detection circuit is connected to the audio amplifier is disclosed. The disconnection detection circuit includes a connection switch, a rectifier, an A / D converter, a setter, and a comparator.

When disconnection is detected in the above-described conventional example, the connection switch connected between the audio amplifier and the disconnection detection circuit is switched to connect the disconnection detection circuit to the audio amplifier, and a predetermined AC signal is transmitted from the AC transmitter. The AC signal input to the audio amplifier and output from the audio amplifier is applied to the speaker circuit. The AC signal output from the audio amplifier is also input to the disconnection detection circuit, rectified by the rectifier, and the value converted by the A / D converter is compared with the value set by the setting device by the comparator. When the / D converted value is larger than the set value of the setting device, it is determined as abnormal and a disconnection state is notified.

JP 2003-274491 A

However, as in the conventional example described above, when disconnection is detected, the AC signal output from the AC transmitter is input to the audio amplifier, and the output of the audio amplifier is applied to the speaker circuit. Since it is close to the impedance of the speaker circuit, the voltage difference between the voltage when the disconnection detection circuit is disconnected and the voltage when it is not disconnected is small, and it is difficult to obtain high disconnection detection accuracy.
Moreover, since it is necessary to provide a connection switching device, a rectifier, an A / D converter, a setting device, and a comparator as the disconnection detection circuit, there is a problem that the circuit configuration becomes complicated.
In addition, the conventional technology has problems such as variations in internal resistance values of speaker connection cables, contact resistance values of connection terminals between the low-frequency amplifier circuit and the connection cables and the speakers, and deterioration in detection accuracy due to changes in ambient temperature. there were.
Accordingly, the present invention has been made for the purpose of providing a device capable of detecting the presence or absence of disconnection of a speaker circuit with high accuracy without adding a complicated circuit configuration.

An apparatus for detecting disconnection of a speaker circuit according to claim 1 comprises:
A disconnection detecting device for a speaker circuit comprising a connection cable and a speaker connected to the connection cable,
AC signal applying means for applying an AC signal to the speaker circuit via a resistor having an impedance sufficiently larger than the impedance of the speaker circuit;
The inter-terminal voltage in the speaker circuit to which an AC signal is applied by the AC signal applying means is detected, and compared with a predetermined voltage, it is detected that the speaker circuit is abnormal when the voltage exceeds a predetermined voltage. And disconnection detecting means for detecting that the speaker circuit is normal when the voltage is lower than the predetermined voltage.

In claim 2,
A speaker circuit composed of a connection cable and a speaker connected to the connection cable is a disconnection detection device for a speaker output device connected to an output unit of a low-frequency amplifier circuit,
The low-frequency amplifier circuit includes a shutdown mode in which the output impedance of the output unit is set to high impedance and no output signal is output, and a normal mode in which the output signal is output,
further,
AC signal applying means for applying an AC signal to the speaker circuit via a resistor having an impedance sufficiently larger than the impedance of the speaker circuit;
The inter-terminal voltage in the speaker circuit to which an AC signal is applied by the AC signal applying means is detected, and compared with a predetermined voltage, it is detected that the speaker circuit is abnormal when the voltage exceeds a predetermined voltage. Disconnection detecting means for detecting that the speaker circuit is normal when the voltage is lower than the predetermined voltage;
When detecting the presence or absence of disconnection,
The low frequency amplifier circuit is switched to the shutdown mode, the output impedance is set to high impedance, the AC signal is output from the AC signal applying means, applied to the speaker circuit, and between the terminals detected by the disconnection detecting means Comparing the voltage with a predetermined voltage, detecting that the speaker circuit is abnormal when the voltage is equal to or higher than the predetermined voltage, and detecting that the speaker circuit is normal when the voltage is lower than the predetermined voltage;
When not detecting the presence or absence of disconnection,
Control means for controlling the low-frequency amplifier circuit to switch to the normal mode and applying the output signal of the low-frequency amplifier circuit to the speaker circuit is provided.

In claim 3,
The AC signal is an AC signal of 15 kHz or more and 22 kHz or less.

According to the disconnection detecting device for a speaker circuit according to claim 1,
Since an AC signal is applied to the speaker circuit via a resistor having an impedance sufficiently larger than the impedance of the speaker circuit, there is a large voltage difference between the terminals when the speaker circuit is disconnected and when there is no disconnection. So you get
Detects the presence or absence of disconnection with high accuracy and is not easily affected by variations in the internal resistance value of speaker connection cables, contact resistance values of connection terminals between low-frequency amplifier circuits and connection cables and speakers, and changes in ambient temperature. be able to.

In claim 2,
The low frequency amplifier circuit to which the speaker circuit is connected has a shutdown mode in which the output impedance of its output section is set to high impedance and no output signal is output,
When detecting the presence or absence of disconnection, the low frequency amplifier circuit is switched to the shutdown mode, the output impedance is set to high impedance, and then the AC signal is applied to the speaker circuit.
An AC signal can be prevented from flowing into the low-frequency amplifier circuit.
Therefore, since a large voltage difference can be reliably obtained as a voltage between terminals depending on whether or not the speaker circuit is disconnected, it is possible to detect the presence or absence of disconnection with higher accuracy.

In claim 3,
Since the AC signal is an AC signal of 15 kHz or more and 22 kHz or less, it has a frequency sufficiently higher than the frequency of a normal low frequency signal, and may be applied to a speaker for detecting disconnection.

1 is a basic circuit configuration diagram of a disconnection detecting device for a speaker circuit according to the present invention. It is explanatory drawing explaining the principle of the disconnection detection in the disconnection detection apparatus of the said speaker circuit. It is explanatory drawing explaining the principle of the disconnection detection in the disconnection detection apparatus of the said speaker circuit. 1 is a circuit configuration diagram of a disconnection detecting device for a speaker circuit according to Embodiment 1. FIG. 3 is a flowchart for explaining a disconnection detection program according to the first embodiment.

An embodiment for implementing a disconnection detecting device for a speaker circuit according to the present invention will be described with reference to the drawings.
As shown in FIG. 1, the disconnection detecting device 10 for a speaker circuit according to the present invention includes:
A speaker circuit 14 comprising a speaker connection cable 142 and a speaker 141 connected to the connection cable 142;
AC signal applying means 13 for applying an AC signal to the speaker circuit 14 via a resistor 12 having an impedance sufficiently larger than the impedance of the speaker circuit 14;
Voltage detecting means 16 for detecting a voltage between the terminals of the speaker circuit 14 to which an AC signal is applied by the AC signal applying means 13 and converting the detected voltage into a direct current by a diode;
A / D conversion means 15 for converting the voltage between the terminals detected by the voltage detection means 16 into a digital signal;
The inter-terminal voltage converted into the digital signal is compared with a predetermined voltage, and when the voltage is equal to or higher than the predetermined voltage, it is detected that the speaker circuit 14 is disconnected and abnormal, and when the voltage is lower than the predetermined voltage The speaker circuit 14 includes a determination unit 19 that detects normality without disconnection.
The AC signal applying means 13 includes an AC signal oscillator 11.
The voltage detection means 16, the A / D conversion means 15 and the determination means 19 constitute a disconnection detection means 17.

The AC signal oscillator 11, the A / D conversion means 15, and the determination means 19 are built in the microcomputer unit 18. The AC signal oscillator 11 is realized by software written in the microcomputer unit 18, and the A / D conversion means 15 is realized by an A / D conversion circuit built in an analog input port of the microcomputer unit 18. The determination means 19 is realized by software programmed in the microcomputer unit 18.
In the microcomputer unit, a disconnection detection program is written as a control means.

  In the following, in the disconnection detecting device 10 for the speaker circuit, the impedance of the speaker circuit 14 is set to 8Ω, the impedance of the resistor 12 is set to 10 kΩ, and the AC signal is set to 19 kHz, 3Vp-p AC signal, for example. The disconnection detection operation in the case of the above will be described.

In the speaker circuit disconnection detecting device 10 configured as described above, when detecting the presence or absence of disconnection of the speaker circuit 14,
The disconnection detection program written in the microcomputer unit 18 is started. The disconnection detection program activates the AC signal oscillator 11 to generate an AC signal of 19 kHz and 3 Vp-p and applies it to the speaker circuit 14 via the resistor 12.
The voltage between the terminals of the speaker circuit 14 detected by the voltage detection means 16 is converted into a direct current and input to the A / D conversion means 15 via the analog input port of the microcomputer unit 18.

  The inter-terminal voltage converted into a digital signal is compared with a predetermined voltage by the determination means 19, and when the voltage is equal to or higher than the predetermined voltage, it is detected that the speaker circuit 14 is abnormal, and is less than the predetermined voltage. Sometimes it is detected that the speaker circuit is normal, and a notification signal corresponding to the presence or absence of disconnection in the speaker circuit 14 is output from the output port of the microcomputer unit 18. When the notification signal indicates a disconnection, a predetermined LED or display means such as a display or an acoustic means such as a buzzer is controlled to notify the speaker circuit of an abnormality.

Next, the reason why the determination means 19 can determine whether or not there is a disconnection will be described.
When the impedance r of the speaker circuit 14 is 8Ω and the impedance R of the resistor 12 is 10 kΩ,
When the speaker circuit 14 is not disconnected, the voltage between the terminals of the speaker circuit is about 0 Vp-p as shown in the following equation. (See Figure 2)

When the speaker circuit 14 is disconnected, the impedance in the speaker circuit becomes almost infinite, so that the voltage between terminals is about 3 Vp-p as shown in the following equation. (See Figure 3)

As described above, the voltage between the terminals is extremely different between the case where there is a disconnection and the case where there is no disconnection, so that the disconnection can be detected with high accuracy.

  Next, as a disconnection detecting device for a speaker circuit according to the first embodiment, a low-frequency amplifier circuit to which the speaker circuit is connected has a shutdown mode in which the output impedance of the output unit is set to high impedance and no output signal is output; Will be described in the case of having a normal mode for outputting.

In the disconnection detecting device 20 for the speaker circuit shown in FIG.
The low frequency signal output from the output unit of the low frequency amplifier circuit 30 is configured to be applied to the speaker circuit 24. The speaker circuit 24 includes a connection cable 242 and a speaker 241 connected to the connection cable 242. The speaker 241 may be a speaker arranged close to the low-frequency amplifier circuit 30 or an external speaker connected through a long connection cable 242.
The low frequency amplifier circuit 30 includes a shutdown control signal input terminal 31, and is configured such that a shutdown control signal output from the microcomputer 28 or a power supply circuit is input to the shutdown control signal input terminal 31. Has been.

  The low-frequency amplifier circuit 30 includes a shutdown mode in which the output impedance of the output unit is set to high impedance and no output signal is output, and a normal mode in which the output signal is output. When the shutdown control signal is input to the low frequency amplifier circuit 30, the shutdown mode is entered, the output impedance of the output unit is set to high impedance, and no output signal is output. When the shutdown control signal is not input, the normal mode is restored and an output signal is output from the output unit.

  A rectangular wave pulse signal of, for example, 19 kHz, 3 Vp-p generated by the microcomputer 28 is configured to be supplied to the speaker circuit 24 via the first resistor R1 and the first capacitor C1 as an AC signal. ing. The resistor value of the first resistor R1 is 10 kΩ, and the impedance is about 10 times or more the impedance (8Ω to 600Ω) of the speaker. The capacitance of the first capacitor C1 is set to about 0.1 μF so that the 19 kHz rectangular wave pulse signal can easily pass therethrough.

The voltage between the terminals of the speaker circuit 24 is taken out via the first capacitor C1, rectified by the diode 26, and supplied to the parallel circuit of the second capacitor C2 and the second resistor R2, Smoothed and a DC voltage of several hundred mV is obtained as a disconnection detection signal. The series circuit of the first capacitor C1 and the diode 26 corresponds to the voltage detection means 16 in FIG.
The disconnection detection signal is input to an analog port of the microcomputer 28 and is converted into a digital signal by a built-in A / D conversion circuit 25.

  A disconnection detection program as disconnection detection means is written in the microcomputer 28. For example, in order to detect the presence or absence of disconnection of the speaker circuit 24 at a predetermined timing such as when the apparatus is turned on, the disconnection detection is performed. It is set to start the program.

Hereinafter, the processing procedure of the disconnection detection program will be described with reference to FIG.
First, in step S1,
A shutdown control signal is output or the shutdown control signal is changed to an active state, and the low frequency amplifier circuit 30 is switched from the normal mode to the shutdown mode.
Next, in step S2,
The AC signal oscillation program is activated to generate a 19 kHz, 3 Vp-p rectangular wave pulse signal, which is applied to the speaker circuit 24 via the first resistor R1 and the first capacitor C1. The rectangular pulse signal is a pulse signal having an amplitude swinging from 0V to 3V, but is differentiated by passing through the first capacitor C1, and is a 3Vp-p AC signal swinging from -1.5V to + 1.5V. Applied to the speaker circuit 24.

In step S3,
While taking in the voltage between terminals and converting it to a digital signal,
Determination processing as determination means is started.
In step S4 of the determination process,
Compare the voltage between the terminals converted into a digital signal with a predetermined voltage,
When the voltage is not less than the predetermined voltage, the process proceeds to step S5.
When the voltage is less than the predetermined voltage, the process proceeds to step S6.

In step S5,
Terminate the AC signal oscillation program to stop the generation of the rectangular wave pulse signal,
It is detected that the speaker circuit 24 is disconnected and abnormal, and if necessary, it is disconnected by outputting a notification signal to the outside, sounding a buzzer, or blinking an LED or the like. Inform you.
In step S6,
Terminate the AC signal oscillation program to stop the generation of the rectangular wave pulse signal,
It is detected that the speaker circuit 24 is normal without disconnection. In this case, there is no need to notify.

In step S7, after the above disconnection detection processing is completed, the output of the shutdown control signal is stopped, or the shutdown control signal is changed to the inactive state, and the low frequency amplifier circuit 30 is switched from the shutdown mode to the normal mode. .
The presence or absence of disconnection is detected by the procedure as described above.

In the disconnection detecting device 20 for the speaker circuit of the first embodiment shown in FIG.
Since the AC signal applied to the speaker circuit 24 is applied via the resistor R1 having an impedance sufficiently larger than the impedance of the speaker circuit 24, between the terminals when the speaker circuit 24 is disconnected and when not disconnected The voltage difference can be sufficiently increased, and the detection accuracy of the presence or absence of disconnection can be increased. By setting the impedance of the resistor R1 to 10 times or more the impedance of the speaker circuit 24, sufficient detection accuracy can be obtained even when a speaker with high impedance is used.

Further, when detecting the presence or absence of disconnection of the speaker circuit 24, an AC signal is applied to the speaker circuit 24 with the output portion of the low-frequency amplifier circuit 30 in a high impedance state. It can prevent flowing into the output part of the circuit 30. Therefore, the difference in voltage between the terminals when the speaker circuit 24 is disconnected and when it is not disconnected can be sufficiently increased, so that the detection accuracy of the presence or absence of disconnection can be increased.
Further, since the AC signal applied to the speaker circuit 24 for detecting disconnection is generated by the program of the microcomputer 28, it is not necessary to provide another circuit such as an oscillation circuit, and the circuit configuration can be simplified.

Further, since the microcomputer 28 has a built-in A / D conversion circuit 25 that converts the voltage between terminals input to the analog port into a digital signal, there is no need to provide another circuit such as an A / D conversion circuit. The circuit configuration can be simplified.
Further, since the frequency of the AC signal is 15 kHz or more and 22 kHz or less, the frequency becomes sufficiently higher than a normal low frequency signal output from the low frequency amplifier circuit 30 to the speaker circuit 24 and is applied to the speaker 241. However, the reproduction efficiency of the speaker 241 is reduced to a frequency region, and the reproduction is performed with a lower sound pressure of the normal low frequency signal. In addition, the first capacitor C1 and the third resistor R3 constitute a high-pass filter that cuts off a low-frequency signal of 15 kHz or less, so that the low-frequency signal in the normal mode is wasted. It is also possible to prevent input to the port.

The present invention can be widely used for detecting the presence or absence of disconnection of a circuit including a speaker or an earphone.

DESCRIPTION OF SYMBOLS 10 Speaker circuit disconnection detection apparatus 11 AC signal oscillator 12 Resistor 13 AC signal application means 14 Speaker circuit 142 Speaker connection cable 141 Speaker 15 A / D conversion means 16 Voltage detection means 17 Disconnection detection means 15, 16, 19 Disconnection Detection means 18 Microcomputer unit 19 Determination means 20 Speaker circuit disconnection detection device 21 AC signal oscillator 24 Speaker circuit 241 Speaker 242 Connection cable 25 A / D conversion circuit 26 Diode 28 Microcomputer 30 Low frequency amplifier circuit R1 Resistor

Claims (3)

A disconnection detecting device for a speaker circuit comprising a connection cable and a speaker connected to the connection cable,
AC signal applying means for applying an AC signal to the speaker circuit via a resistor having an impedance sufficiently larger than the impedance of the speaker circuit;
The inter-terminal voltage in the speaker circuit to which an AC signal is applied by the AC signal applying means is detected, and compared with a predetermined voltage, it is detected that the speaker circuit is abnormal when the voltage exceeds a predetermined voltage. A disconnection detecting device for a speaker circuit, comprising: disconnection detecting means for detecting that the speaker circuit is normal when the voltage is lower than the predetermined voltage. A speaker circuit including a connection cable and a speaker connected to the connection cable is a disconnection detection device for a speaker circuit connected to an output unit of a low-frequency amplifier circuit,
The low-frequency amplifier circuit includes a shutdown mode in which the output impedance of the output unit is set to high impedance and no output signal is output, and a normal mode in which the output signal is output,
further,
AC signal applying means for applying an AC signal to the speaker circuit via a resistor having an impedance sufficiently larger than the impedance of the speaker circuit;
The inter-terminal voltage in the speaker circuit to which an AC signal is applied by the AC signal applying means is detected, and compared with a predetermined voltage, it is detected that the speaker circuit is abnormal when the voltage exceeds a predetermined voltage. Disconnection detecting means for detecting that the speaker circuit is normal when the voltage is lower than the predetermined voltage;
When detecting the presence or absence of disconnection,
The low frequency amplifier circuit is switched to the shutdown mode, the output impedance is set to high impedance, the AC signal is output from the AC signal applying means, applied to the speaker circuit, and between the terminals detected by the disconnection detecting means Comparing the voltage with a predetermined voltage, detecting that the speaker circuit is abnormal when the voltage is equal to or higher than the predetermined voltage, and detecting that the speaker circuit is normal when the voltage is lower than the predetermined voltage;
When not detecting the presence or absence of disconnection,
A disconnection detecting device for a speaker circuit, comprising: control means for controlling the low frequency amplifier circuit to switch to a normal mode and applying an output signal of the low frequency amplifier circuit to the speaker circuit. The disconnection detecting device for a speaker circuit according to claim 1, wherein the AC signal is an AC signal of 15 kHz or more and 22 kHz or less.

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