JPH0884393A - Broken wire detector - Google Patents

Abstract

PURPOSE: To detect a broken wire of a detected body whose sound volume is abruptly changed or whose input impedance is considerably changed without malfunction. CONSTITUTION: The detector has voltage and current comparators 7,8 provided to detect a broken coil of a speaker or the like and the operation of the voltage comparator 7 is inhibited at a specific input voltage or below and when the signal whose level is smaller than the inhibit level is given at the detection of a broken coil, a monostable multivibrator 17 is self-held and a sound signal is given again to release automatically the self-hold operation and a time domain filter 17, a C and a R used to eliminate a pulse with a comparatively short time width are arranged to a post-stage of the current comparator 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wire breakage detecting device for an object to be detected such as a voice coil of a speaker, and more particularly to a wire breakage detecting device suitable for the object to be detected whose impedance varies greatly.

[0002]

2. Description of the Related Art Conventionally, a configuration shown in FIG. 3 has been known as a disconnection detection circuit for detecting a disconnection state of a motor, a coil of a heater, a heating element, or the like.

In FIG. 3, reference numeral 1 is a disconnection of a heater coil or the like.
The object to be detected (load) for detecting the state, the heater
Both ends of the coil are terminals T₁And T₂Connected to these ends
Child T ₁And T₂Is the power switch S₁Commercial power through
It is connected to the line of the source circuit 2.

A current detecting sensor 3 such as a current transformer is arranged between the switch S ₁ and the terminal T ₁ . The two lines of the power supply circuit 2 are connected in parallel with the object to be detected 1 to the input side of the first rectifier circuit 4, and the output end of the current detection sensor 3 is connected to the input side of the second rectifier circuit 5. There is.

The rectified output terminals of the first and second rectifier circuits 4 and 5 are connected to the input terminals of the first and second comparators 7 and 8, respectively, and the output terminals of the first and second comparators 7 and 8 are connected to each other. It is connected to the input terminal of the AND gate circuit 9.

The output terminal of the AND gate circuit 9 is connected to the clock terminal CK of the D-type flip-flop circuit (hereinafter referred to as D-FF) 10, the D terminal of the D-FF 10 is grounded, and the preset terminal PR is connected to it. Switch S for reset
₂ is connected and the other end is grounded. Positive output terminal Q is connected to an external output terminal T _3, the external output terminal T ₃ is connected to an alarm unit and a protective circuit such as a lamp or a CRT, or a buzzer for display.

The operation in the case of detecting the disconnection state of the detected object of the above-mentioned conventional structure is as follows when the switch S ₁ for power supply is closed.
A predetermined voltage is supplied from the power supply circuit 2 to the detected object 1. At this time, the pulsating current voltage rectified by the first rectifier circuit 4 is supplied to the first comparator 7. Here, the first comparator 7 functions as a voltage detector that changes from the low level “L” to the high level “H” and detects that the power supply circuit 2 is connected to the detected object 1.

On the other hand, when the switch S ₁ for power supply is closed, a current also flows through the current detection sensor 3, and the second comparator 8 detects this current. The second comparator 8 is configured to change from “H” to “L” when a current flows, and this “L” signal is supplied to the AND gate circuit 9. Therefore, since the "H" and "L" signals are supplied to the input terminal of the AND gate circuit 9, the output of the AND gate circuit 9 is set to L and supplied to the clock terminal CK of the D-FF 10. Therefore, the positive output Q of the D-FF 10, that is, H is output from the output terminal T ₃ .

Here, when the switch S ₁ for power supply is opened again, the output of the first comparator 7 changes to "L", regardless of the output of the second comparator 8, the AND gate circuit 9 is connected. Output holds "L" state and D-
The positive output Q of FF10 is made "H", and the detection operation is prohibited.

Next, if the detected object 1 is broken again with the switch S ₁ for power supply closed, the first and second comparators 7 and 8 are both at "H" and the AND gate circuit 9 is connected. Is output as "H". Therefore, D
-The output of FF10 can hold "L" and detect the disconnection state.

Therefore, after the disconnection state is detected, the D-FF 10
In order to return the "L" state to the original "H" state, the reset switch S ₂ is closed and reset.

[0012]

In the disconnection detecting device described in the above-mentioned conventional configuration, when the detected object 1 is, for example, a heater coil, the power supply circuit 2 for driving the heater coil is often fixed. Even if it is a variable type, it does not change with time and the amount of change is known in advance. Therefore, it is possible to detect the disconnection state by appropriately selecting a threshold value for simple detection.

Here, considering the case where the object to be detected 1 as a load is replaced with a speaker, since the drive circuit constituting the power supply circuit 2 is a power amplifier for amplifying an acoustic signal, the following various problems occur. Occurs.

[0014] (i) a speaker in the frequency - the impedance characteristic resonance frequency f ₀ near the first speaker as shown in FIG. 4
1 shows a value of several + Ω to several hundreds Ω or more (200Ω), and the valley portion 12 has a value of several Ω (3 to 4Ω). Therefore, erroneous detection will occur when a disconnection is detected in the signal band near f ₀ where the impedance is high. (B) The output of the current detection sensor 3 does not always maintain a waveform similar to the voltage, and when the voltage changes every moment, the current detection sensor 3 and the second comparator 8 are It becomes necessary to make the time constant longer than the time constant of the first comparator 7 which constitutes the voltage detector. (C) The detection signal also depends on the volume of the sound emitted from the speaker, and erroneous detection occurs even when the volume is low or when the volume greatly changes. (D) In the D-FF 10, it is necessary to manually reset the reset switch S ₂ after detecting the disconnection state. And the like.

The present invention is intended to provide a disconnection detecting device which solves the above-mentioned problems, and its object is to provide a drive signal applied to a speaker from a drive circuit, an input impedance, and the like which are significantly changed. An object of the present invention is to provide a wire breakage detecting device which can detect the wire breakage state of a coil without erroneous detection and can also automatically reset the detection signal holding means.

[0016]

DISCLOSURE OF THE INVENTION The disconnection detecting apparatus of the present invention has a voltage comparing means 7 connected in parallel to an object to be detected 1 for detecting the disconnection state as shown in FIG. In the disconnection detecting device, which comprises a current comparing means 8 for comparing the current output through the current detecting sensor 3 connected in series with the reference current, the disconnection detecting device is connected to the subsequent stage of the voltage comparing means 7.
Detection stopping means Tr1 for prohibiting the operation at a specific input voltage or less to avoid interruption of the disconnection detection signal, and self-holding means 17, D1, Tr for holding the signal when the disconnection is detected.
1 and time domain filter means 17 and C connected to the subsequent stage of the current comparison means 8 to remove short-time pulses generated when a signal having a large impedance change is input.
R, the self-holding means 17, D1, T for repairing the disconnection state of the detected object 1 and supplying a signal to the detected object 1.
A disconnection detection device characterized by automatically releasing r1.

[0017]

The disconnection detecting device of the present invention is provided with the voltage comparing means and the current comparing means for detecting the drive signal supplied to the speaker coil of the object to be detected, and the time for removing the detected signal below the time which is after the current comparing means. Have a domain filter,
The voltage comparison means prohibits operation below a specific input voltage, and a self-holding circuit is provided so as not to prohibit operation when a signal below the input voltage is input when a speaker disconnection is detected. Since the holding operation of the self-holding circuit is automatically canceled by inputting the audio signal at the time of restoration, the disconnection state can be detected without erroneous detection even in a speaker with a large impedance change and a large volume change, and the holding operation You can get the one that can be reset automatically.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A disconnection detecting device of the present invention will be described below with reference to FIGS.
Will be described in detail. In this example, the detected object 1 as a load is a speaker, and a disconnection detection device capable of automatically detecting the disconnection state of the speaker coil or the like is provided.

FIG. 1 shows a system diagram of an embodiment of the present example, in which terminals T ₁ and T ₂ at both ends of the object to be detected 1 have a power amplifier 1
The output signal from 6 is supplied through the primary winding (about 1 turn) of the current detection sensor 3 such as a current transformer. Reference numeral 15 denotes a driving sound source connected to the input side of the power amplifier 16.

The output signal of the power amplifier 16 is the speaker 1
And is supplied in parallel to the first comparator 7 via the first rectifier circuit 4. The first comparator 7 is configured to determine whether a predetermined input is supplied to the speaker 1 and to invert to "L" level when the input becomes equal to or higher than a predetermined voltage.

The output terminal of the current detection sensor 3 such as a current transformer on the secondary winding side is directly supplied to the second comparator 8. The second comparator 8 outputs "L" when the current exceeds a predetermined value. The signal is converted into a pulse inverted to the “level” and retriggerable monostable multivibrator (hereinafter referred to as MM
Input) 17 B input terminal. M. The A input terminal of M17 is grounded, and is configured to perform a down edge operation triggered by the falling edge of the input pulse.

This M. As will be described later, M17 is a time domain filter (Time Domain Filter) for removing a pulse of a short time (for example, 1 second or less) of a predetermined time or less.
er), the negative output terminal Q bar is connected to the base of the LED driving transistor Tr2 through the base resistor, the emitter of the transistor Tr2 is grounded, and the collector is the cathode of the LED and the output buffer 18. It is connected to the input side and the output side of the output buffer 18 is connected to the external output terminal T ₃ .

On the other hand, the output terminal of the first comparator 7 functioning as a voltage comparator is connected to the base of the transistor Tr1 via a base resistor, and the emitter of the transistor Tr1 has an M.V. It is connected to the C pin of M17 and is grounded, and the collector is M.M. Connected to R pin of M17.
M. External capacitor C between the C and R pins of M17
, And the resistor R is connected to the R pin, and the other end of the resistor R and M.P. The CLR terminal of M17 is connected to a voltage source of + Vcc.

The operation of the above disconnection detecting device will be described with reference to the drawings. First, a case where the speaker 1 as the detected object is not broken will be described. The output signal from the power amplifier 16 flows to the primary winding side of the current detection sensor 3 including a current transformer and drives the speaker 1. The voltage induced on the secondary winding side of the current detection sensor 3 is supplied to the second comparator 8.

The second comparator 8 supplies an input voltage and a comparison reference voltage to an inverting input terminal and a non-inverting input terminal of an operational amplifier structure, for example, and changes from "H" to "L" when a predetermined current or more flows. The pulse is applied to M. It is supplied to the B input terminal of M17.

On the other hand, the same output signal supplied from the power amplifier 16 to the current detection sensor 3 passes through the first rectifying circuit 4 and is supplied to the non-inverting input terminal of, for example, an operational amplifier which constitutes the first comparator 7. And is compared with the comparison reference voltage V _REF connected to the inverting input terminal. The first comparator 7 determines the presence / absence of a predetermined input signal, and outputs the "L" level when the voltage is equal to or higher than the comparison reference voltage V _REF .

The output of the first comparator 7 is adapted to be supplied to the base of the switching transistor Tr1 constituting the prohibition circuit via a resistor. A diode D ₁ is connected between this base and the positive output Q of MM17. Further, the capacitor C and the resistor R for determining the pulse width are M. M17 has, for example, two NAND gate circuits
In the case of the cascade connection configuration, since the NAND gate circuits are connected between the cascade-connected NAND gate circuits, the M.M. M
17, that is, IC _{1 of the} time domain filter (C-M
OS-4538) by shorting or operating the capacitor C connected to M.S. The function of M17 will be stopped or operated.

On the other hand, M. If the speaker 1 is not broken, the B input terminal of M17 is provided with an "L" level pulse by the operation of the second comparator 8. Therefore,
M. The "L" level is output to the negative output terminal Q of M17, and the "H" level is output to the positive output terminal Q. Base of the transistor Tr1 is "off" state in order to keep the blocked "L" level by the diode D _1.

Further, L connected to the negative output terminal Q bar
ED driving transistor Tr2 is because not illuminate LED is not excited to the external output terminal T ₃ is outputted "H". Further, when a transient signal is supplied, such as when the sound range of the signal of the power amplifier 16 becomes a frequency near the resonance frequency f _{0 of the} speaker, or when the sound source changes abruptly,
Since the second comparator outputs the "H" level and makes a false detection, the M.M. Negative if the time width during which the second comparator 8 outputs the H level is shorter than the time width defined by the time constant of the capacitor C and the resistor R connected to the C and R pins of IC ₁ that determines the pulse width of M17. The "H" level is not output to the output terminal Q bar, and the operation of holding the "L" level is continued. For this purpose, the values of the pulse width selecting capacitor C and the resistor R may be appropriately selected so as to achieve the above object. Further, by utilizing the above property, it is not necessary to interpose the second rectifier circuit 5 between the current detection sensor 3 and the second comparator 8 as in the conventional case, and the time constants of the first and second rectifier circuits are not required. It is possible to adopt a configuration that can save the trouble of adjustment.

Next, the operation when the speaker 1 is disconnected will be described. When the speaker coil is broken, C.I. When an "H" level pulse exceeding the time set by the capacitor C and the resistor R connected to the R pin is supplied from the second comparator 8 to the B input terminal, the M.M. The negative output terminal Q bar of M17 becomes "H" level, and the LED driving transistor T
When r2 is energized, the LED is turned on and the disconnection detection signal (“L”) is output to the external output terminal T ₃ via the output buffer 18.

On the other hand, M. The positive output terminal Q of M17 outputs "L" level. At this time, the base of the transistor Tr1 through the diode D ₁ "L"
The base potential is pulled down to the "L" level.

Therefore, the IC ₁ stops the function of stopping the detection operation at the time of inputting a low voltage, and keeps the LED in the lit state regardless of the input level to the B input terminal.

In the above-mentioned state, IC ₁ maintains the original initial state, and therefore when a signal is input again when the broken speaker is repaired and replaced, the M.M. The "L" pulse is input to the B input terminal of M17, the positive output terminal Q is held at "H" level, the transistor Tr1 is held at the normal base via potential, and the capacitor C and the resistor R of the CR pin of IC ₁ are held. Works fine.

Further, the LED on the side of the negative output terminal Q bar is driven by the L.M. M17 can be automatically restored without providing the reset switch S ₂ on the clear terminal CLR.

FIG. 2 shows a system diagram in the case where a plurality of disconnection detecting devices described above are prepared and connected to a plurality of speakers to monitor the disconnection state from a hall or a studio.

In FIG. 2, reference numerals 1A, 1B, 1C and 1D denote a plurality of loudspeakers arranged in the studio 22. These speakers are power amplifiers 16A and 16B via acoustic sound sources 15A, 15B, 15C and 15D in the monitor room 23. , 16C, 16D, and sound is emitted from the speakers 1A, 1B, 1C, 1D. Each of these power amplifiers 16A, 16B,
The signals from 16C and 16D are the disconnection detection device 20 of this example.
The disconnection state of the speaker coil is detected by A, 20B, 20C and 20D, the external output terminals T _3, ..., And the disconnection detection signal is transmitted through the drive circuits 24A, 24B, 24C and 24D to the CRT. The display means such as an LED or the alarm means such as a buzzer or a bell is driven.

When the operation room on the monitor side monitored by the operator and the place where the plurality of speakers are arranged are separated from each other, such as in the above-mentioned studio, hall or stadium, the monitor side is not When two speakers were disconnected, it was almost impossible to monitor. However, by adding the disconnection detection device described above to each speaker, the maintainability can be greatly improved.

[0038]

According to the disconnection detection device of the present invention, a time domain filter is provided after the current detection sensor so as to mask the detection signal for a predetermined time or less, so that erroneous detection due to pulse noise for a short time is avoided. In addition, the voltage detector is designed to prohibit the operation of the mono-multivibrator at a specific voltage or less, so that it is possible to avoid erroneous detection with a small acoustic signal, and it is stable at any acoustic signal input. Thus, it is possible to detect the disconnection state of the speaker and improve the maintainability in a stadium or the like.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a disconnection detecting device of the present invention.

FIG. 2 is a circuit diagram showing an application example of the disconnection detection device of the present invention.

FIG. 3 is a circuit diagram of a conventional disconnection detection device.

FIG. 4 is an explanatory diagram of frequency-impedance characteristics of a speaker.

[Explanation of symbols]

 1 Detected Object (Speaker) 3 Current Detection Sensor 4 First Rectifier Circuit 7 First Comparator 8 Second Comparator 17 Retriggerable Monostable Multivibrator

Claims (1)

[Claims] 1. A voltage comparing means connected in parallel to an object to be detected for detecting a disconnection state, and a current output via a current detection sensor connected in series to the object to be compared with a reference current. A disconnection detection device comprising a current comparison means, which is connected to a subsequent stage of the voltage comparison means and which has a detection stop means for prohibiting an operation at a specific input voltage or less to avoid interruption of a disconnection detection signal, and a disconnection means. The self-holding means at the time of detection, and the time domain filter means connected to the latter stage of the current comparing means for removing a short-time pulse generated when a signal is input to a load whose impedance changes drastically are provided. A disconnection detecting device, characterized in that the disconnection state of the detection body is restored and the self-holding means is automatically released when a signal is supplied to the detection body.