JPS5836880B2 - Protective device for movable ring type electrical ↓-mechanical converter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a protection device for a movable wire type electro-mechanical converter having a movable wire that is driven and displaced in a magnetic field by an electromagnetic force generated by the supply of a drive signal. It was done for that purpose.

For example, loudspeakers, cutters, and other moving wire electromechanical converters may receive excessive electrical input for various reasons, which can damage the equipment. It is well known that various protection measures have been proposed in the past.

FIG. 1 is a block diagram of a conventional protection device for a movable wire type electro-mechanical converter. In FIG. 1, 1 is a signal input terminal, 2 is an amplifier, and 3 is a drive signal input terminal. This is an output terminal, and a movable wire type electro-mechanical converter is connected to the output terminal 3.

Further, 4 is a DC component detection unit, 5 is a storage unit, 6 and I are a control unit, 8 is a positive power supply unit, 9 is a negative power supply unit, 10 and 11 are overcurrent detection units, and the above-mentioned DC component The component detection unit 4 detects the DC voltage at the output terminal 3, and
The overcurrent detectors 10 and 11 detect overcurrent to the load, and the detection results in the respective detectors 4, 10, and 11 described above are provided to the storage unit 5.

Then, in the storage unit 5, if the detection result of the DC component detection unit 4 exceeds a predetermined setting value, or the detection result of the overcurrent detection units 10 and 11 exceeds a predetermined setting value. When it is determined that one or both of the above conditions has occurred, this is stored and a control signal is given to the control units 6 and 7.

The stored contents of the storage unit 5 described above can be reset manually or automatically at fixed time intervals.

The control units 6 and 7 operate to stop the operation of each power supply unit 8 and 9 based on the control signal given from the storage unit 5, and perform electrical-to-mechanical conversion according to protection conditions set in advance in the protection device. It is designed so that the equipment can be protected.

In the conventional protection device shown in FIG. The electrical-to-mechanical converter is protected by setting protection conditions so that AC components exceeding a predetermined value are not applied.
This conventional protection device protects the electrical-to-mechanical converter when an AC component exceeding the value of the maximum AC component allowed within the protection conditions set for the electrical-to-mechanical converter is supplied. Although the protective operation is performed satisfactorily based on the detection results of the overcurrent detectors 10 and 11 in the device, the voltage is lower than the maximum allowable AC component value for the electrical-to-mechanical converter, and When electrical input exceeding the continuous rated input of the mechanical converter is continuously supplied, the overcurrent detection unit 10
, 11 is below the predetermined value, the protection device does not perform a protective operation, and therefore, the electrical-to-mechanical converter receives continuous AC input that is greater than the continuous rated input value. As a result of this, the temperature of the movable wire increases to a level that eventually causes the movable wire to burn out and destroy the electrical-to-mechanical converter.

In order to prevent the electrical-mechanical converter from being destroyed due to the above causes, if the setting level for starting the protective operation in response to the detection result from the overcurrent detector in the protection device is set low,
For example, if the protection device starts operating at the continuous rated input value of an electrical-to-mechanical converter, the electrical-to-mechanical converter can only be converted with driving power below the continuous rated input that was originally allowed for the electrical-to-mechanical converter. Furthermore, when the drive signal is a musical tone signal, the protection device is operated even at the peak value that often appears in the drive signal.

The present invention provides a protection device that satisfactorily solves the problems of the conventional protection devices described above, and will be described below with reference to the accompanying drawings. The specific contents of the device protection device will be explained in detail.

FIG. 2 is a block diagram of an embodiment of the protection device for a movable ring type electro-mechanical converter of the present invention. In the following explanation, the electro-mechanical converter SP in the figure is It is described as a moving ring type speaker.

In FIG. 2, 1 is a signal input terminal, 2 is an amplifier, and the signal supplied to the input terminal 1 is amplified in the amplifier 2 and then sent to the bridge circuit BC via the switch SW.
given to.

Although the switch SW is shown as a mechanical switch in the figure, electronic switching means, relays, etc. may be used in implementation.

The bridge circuit BC has a slight direct potential difference (reference voltage) between points A and B, and connects resistors Ra, Rb, Rc, for example.
and the DC resistance Rs of the movable wire of the speaker.The four-terminal bridge configured as shown in the diagram has an equilibrium condition as shown in the following equation regarding the DC resistance. .

Ra-Rc-Rs-Rb... (■) When power is supplied to the movable coil, it generates heat and its temperature rises, but as the material of the winding that composes the movable coil, the temperature coefficient of resistance is O. If a wire other than the above is used, the direct current resistance value of the movable wire will change due to the heat generated by the movable wire when power is supplied to the movable wire.

Therefore, when power is not supplied to the movable wire ring, the resistance value of the resistor Rb is changed so that the 4-terminal bridge satisfies the above formula (1).
If the terminal bridge is balanced, A of the 4-terminal bridge,
Even if a drive signal is applied between points B, no unbalanced output will appear between points C and D of the four-terminal bridge as long as the four-terminal bridge satisfies the balanced condition.

However, when the temperature of the movable wire changes due to the supply of power to the movable wire, the DC resistance value of the movable wire changes, and the four-terminal bridge no longer satisfies the equilibrium condition of equation (1). A signal corresponding to a change in the resistance value of the movable wire (change in mud temperature of the movable wire) appears between points C and D in .

If a material with a positive temperature coefficient of resistance is used for the movable wire, as the temperature rises due to the heat generated by the movable wire due to the supply of electric power to the movable wire, the DC resistance value of the movable wire will increase. Become.

Now, taking as an example a case where a copper wire is used as the movable wire ring, the following equation (2) shows the relationship between the change in resistance of the movable wire ring and the temperature of the movable wire ring.

However, To is the room temperature ゜C1r1 is the DC resistance value Ω at room temperature
, T is the temperature after the rise in °C, r2 is the DC resistance value after the rise Ω,
It is.

The movable coil is an impeder consisting of DC resistance and inductance. However, due to the change in the DC resistance value of the movable wire due to the temperature change of the movable wire, a signal corresponding to the temperature change of the movable wire appears between points C and D of the 4-terminal bridge. It is.

The detection signal corresponding to the temperature of the movable wire appearing between points C and D of the four-terminal bridge is passed through a low-pass filter LPF to remove signal components in the audible frequency band, and then sent to an amplifier At.
Then, the signal level is adjusted by a level adjuster VRt, and the signal is applied as a first signal to an adder ADD.

The first signal applied from the level adjuster VRt to the adder ADD is caused by the rise in temperature of the movable wire due to power supply, which causes the DC resistance of the movable wire to rise above the DC resistance value at normal temperature. As explained above, the detection signal is based on the detection signal representing the unbalanced state that occurs in the four-terminal bridge (bridge circuit BC), that is, the detection signal corresponding to the temperature of the movable wire. When the temperature of the coil reaches a predetermined temperature, the first signal at a predetermined signal level is sent to the adder AD.
It is easy to adjust the level regulator VRt to give D.

The continuous rating of a speaker is such that the speaker will not be destroyed even when continuously supplied with music signals, audio signals, or sine wave signals for testing, and the distortion will only occur to the extent that it does not affect the auditory sense. The power supply value is determined in the current state.

When power exceeding the continuous rating is supplied to the speaker, distortion in the reproduced sound increases, and when power exceeding the continuous rating is continuously supplied to the speaker, the temperature of the moving wire increases. Due to the rise, the adhesive strength of the adhesive used to bond between the windings and between the windings and the coil bobbin decreases.
The connections between the windings and between the coil bobbin and the windings may become separated, or the insulation coating of the windings may be torn, causing a layer short between the windings and destroying the speaker. The device uses the above-mentioned first signal, that is, a signal obtained based on the detection signal corresponding to the temperature of the movable wire, to control the movable wire when the temperature of the movable wire reaches a predetermined temperature value. Since it is possible to cut off the power supply to the wire, the device of the present invention can prevent the speaker from being destroyed due to the above-mentioned causes.

In addition, in FIG. 2, the signal sent from the amplifier 2 via the switch SW is transmitted via the variable resistor VR to the circuit arrangement consisting of the equalizer circuit EQ1, the rectifying filter circuit RF, the amplifier Aps, and the level adjuster VRp. A signal (second signal) corresponding to the amplitude of the speaker drive signal is supplied from the level adjuster VRp in the circuit arrangement described above to the adder ADD.

The equalizer circuit EQ is designed to have a frequency response characteristic that is substantially opposite to the impedance change characteristic with respect to the frequency of the movable wire in the speaker, as shown by curve I in FIG.

The equalizer characteristics of the equalizer circuit EQ described above will be explained as follows.

In other words, if the impedance change characteristic with respect to frequency of the movable wire in a speaker is as shown by curve I in FIG. 3, and if the movable wire is driven by a constant voltage source, The amount of power consumed by the coil is determined by the third curve, which has a frequency characteristic opposite to that of curve I in Figure 3.
The frequency characteristic of the temperature rise of the movable wire ring, which is proportional to the effective power in the movable wire ring, is as shown by the curve ■ in FIG. 3.

Therefore, by focusing on the amplitude of the drive signal of the movable train wheel and cutting off the power supply to the movable train wheel when the amplitude exceeds a predetermined value, it is possible to minimize human power. In order to protect the speaker, an equalizer circuit EQ is required which has a frequency response characteristic opposite to the impedance change characteristic with respect to frequency of the movable wire in the speaker.

The output signal from the equalizer circuit EQ described above is rectified and then smoothed by the rectification filter circuit RF, and the attack time determined by the charging time constant of the filter network in this rectification filter circuit RF and the recovery determined by the discharge time constant. The time is, for example, the maximum input signal duration tolerance guaranteed to the speaker,
In addition, good results can be obtained if it is determined in relation to the heat dissipation characteristics of the movable coil.

The output signal of the rectifying filter circuit RF is amplified by an amplifier Ap, and then its signal level is adjusted by a level adjuster VRp, and then applied as a second signal to an adder ADD.

The second signal applied from the level adjuster VRp to the adder ADD is a signal corresponding to the amplitude of the speaker drive signal as described above, but the maximum input guaranteed to the speaker is the movable ring. It is easy to adjust the level adjuster VRp so that the second signal having a predetermined signal level is applied to the adder ADD when the signal is applied to the adder ADD.

The output signal from the adder ADD is given to the storage unit MA, which stores this fact when the first and second signals each exceed a predetermined signal level, and , gives a signal to the control unit CC to operate it.

This storage unit MA may be configured such that its stored contents are manually reset, or may be configured such that it is automatically reset at fixed time intervals.

The control unit CC operates according to a signal from the storage unit MA,
A control signal is applied to the switch SW to operate the switch SW and cut off the drive signal being supplied from the amplifier 2 to the movable wire of the speaker.

As described above, the protective operation for the movable wire in the electromechanical converter by the protection device of the present invention is such that when the first and second signals each exceed a predetermined signal level,
In other words, the amount of heat generated by the movable wire wheel is expressed as an amount proportional to the product of the electric power supplied to the movable wire and its supply time;
The process is performed when the temperature of the movable coil, which is determined based on the heat capacity of the movable coil and the amount of heat radiated from the movable coil according to the heat radiation characteristics of the movable coil, exceeds a predetermined temperature. Therefore, with the protection device of the present invention, it goes without saying that if an excessive current exceeding the maximum rating flows through the movable wire wheel, but also when the current exceeds the maximum rating for the movable wire wheel. Even if a current that is below the rating and exceeds the continuous rating flows continuously, the supply of drive current to the moving wire is cut off by the operation of the switch SW, which protects the moving wire of the electrical-to-mechanical converter. is carried out well.

Figures 4a and 4d are waveform diagrams for explaining the operation of the protection device of the present invention, and Figure 4a is a waveform example diagram of the drive signal supplied to the movable line shaft. In FIG. 4A, the drive signals are each shown as having a constant amplitude to simplify the explanation.

4b shows the temperature change that occurs in the movable wire when the drive signal shown in FIG. 4a is supplied to the movable wire, and FIG. 4C shows the change in temperature of the adder ADD. The output signal waveform is shown, and FIG. 4d also shows the output signal waveform from the storage section MA and the control signal waveform output from the control section CC.

The drive signal waveform shown from time t to time t3 in FIG. As shown in the figure, the time t1 at which the drive signal starts to be supplied.
Thereafter, the temperature gradually increases with a time delay due to a thermal time constant determined by the heat capacity and thermal resistance of the movable wire, and the temperature decreases due to heat radiation from the movable wire. At time t2, the amount of heat supplied and the amount of heat dissipated are in equilibrium and reach a certain constant temperature Ta, and thereafter until time t4, which is slightly delayed due to the thermal time constant of the movable wire, from time t3 when the supply of the drive signal is stopped. The temperature of the movable wire ring is maintained at Ts.

The drive signal supplied to the movable ring between time t1 and time t3 is a continuous rated input, and it does not have any adverse effect on the electrical-mechanical converter.
Based on the drive signal supplied to the movable wire wheel from time t1 to time t3, the signal level of the first signal is adjusted so that no control signal is given from the control unit CC to the switch SW. Adjust by adjusting the device VRt.

Es in FIG. 4C is the voltage value of the first signal from the level regulator VRt when the temperature of the movable wire is at the temperature Ts in FIG. 4b; Temperature T in the diagram
m is a temperature near the highest temperature allowed for the movable wire ring, and voltage Em in FIG. 1 is the voltage value of the signal.

Note that the temperature To in FIG. 4b indicates room temperature.

Further, the voltage Em in FIG. 4C is determined when the voltage value of the first signal exceeds this voltage value Em, when the voltage value of the second signal exceeds this voltage value Em, and , when the sum of the voltages of the second signal exceeds this voltage value Em, this can be stored in the storage unit MA and used as a reference voltage value when applying a signal to the control unit CC. be.

In FIG. 4, when the supply of the drive signal is stopped at time t3, the temperature of the movable wire gradually decreases, and in the illustrated example, reaches the normal temperature To at time t5.

Next, as shown in FIG. 4a, from time t5, the supply of a drive signal with an amplitude greater than the continuous rating and smaller than the maximum input is started to the movable wire wheel, and the temperature of the movable wire wheel increases. After time t5, the temperature increases according to the input, and at time t, the temperature Ts
The temperature reaches Tm at time t7.

Therefore, at time t7, the first signal becomes the voltage Em as shown in FIG.
As a result of the operation of the control unit CC and the operation of the control unit CC, the control unit C
A control signal as shown in FIG. 4D is applied from C to switch SW, and the supply of drive current to the movable wire wheel is cut off at time t7.

Next, at time t8 after the temperature of the movable wire has decreased to room temperature To, the memory content in the memory section has already been reset (cleared), and the magnitude of the drive signal given at that time is the same as that of the movable wire. Assuming that the second signal is of the maximum rating at time t, the second signal becomes the voltage Em as shown in FIG. Then, a control signal as shown in FIG. 4d is applied to the switch SW, and the supply of drive current to the movable wire wheel is cut off at time t.

The reason why the temperature and voltage values shown in FIGS. 4b and 4c rise slightly even after the drive current is cut off is due to the time delay in temperature rise due to the existence of a thermal time constant of the movable coil.

Therefore, the temperature Tm may be set at a temperature slightly lower than the maximum temperature allowed for the movable wire, taking into consideration the time delay in temperature rise due to the presence of the thermal time constant of the movable wire. is necessary.

Each state before time tlo in Fig. 4 that has been explained so far is a case where the initial temperature at which the temperature of the movable wire begins to rise and rise due to the supply of the drive signal to the movable wire is normal temperature To. However, in actual operation of the movable wire, the magnitude of the drive signal supplied to the movable wire is constantly changing, and the temperature of the movable wire during operation is higher than the room temperature To. It becomes.

The waveform diagram shown after time t [ in FIG. 4 shows the temperature (
The illustrated example is for explaining a case where the temperature is Ts).

At time tto, a drive signal of continuous rated magnitude begins to be supplied to the movable wire ring, and at time tll, the temperature of the movable wire wheel reaches Ts, and after time t11, the temperature of the movable wire wheel is maintained at temperature Ts. When a drive signal larger than the continuous rating is supplied to the movable wire at time t12, the temperature of the movable wire starts to rise based on the temperature Ts at time t12, and reaches the temperature Tm at time t13. Then, the time t13 is reached by the operation of the storage unit MA and the control unit CC.
A control signal is supplied to the switch SW, and the supply of the drive signal to the movable train wheel is stopped at time t13.

During the time interval from time tl2 to time t, a drive signal of the same magnitude as the drive signal that started being supplied to the movable wire wheel from time t12 is supplied to the movable wire wheel at room temperature, and the movable wire wheel is moved. This is significantly shorter than the time required to raise the temperature of the wire to Tm.

This means that, depending on the temperature of the moving train, if the drive signal supplied to the moving train is greater than or equal to the continuous rated value, the length of the allowable drive signal supply time will be It means that the value changes.

Therefore, if the drive signal supplied to the movable wire wheel is greater than the continuous rating of the movable wire wheel, the first
When the sum of the signal and the second signal exceeds a predetermined voltage value, a control signal is generated by the operation of the storage unit MA and the control unit CC, and the control signal causes the switch S to be activated.
By operating W and cutting off the supply of the drive signal to the movable train, the movable train can be well protected.

As is clear from the above description, the movable wire type electro-mechanical converter protection device of the present invention includes a movable wire that is driven and displaced in a magnetic field by an electromagnetic force generated by the supply of a drive signal. Temperature detection means comprising a bridge circuit constructed by using the movable wire itself on one side of the bridge to which the above drive signal is supplied in the movable wire type electro-mechanical converter; means for obtaining a first signal corresponding to the temperature of the movable wire based on the detection signal obtained corresponding to the temperature of the movable wire; and based on the drive signal supplied to the movable wire, means for obtaining a second signal corresponding to the amplitude of the drive signal; and a means for storing when the first and second signals each exceed a predetermined signal level; A movable wire electro-mechanical converter comprising means for causing a control signal to be issued and means for causing the control signal from the control section to cut off the supply of a drive signal to the movable wire. Since it is a protection device, the first signal is generated in real time based on the detection signal corresponding to the temperature of the movable wire, so that the protective operation for the movable wire can be performed well. Memorizing when the first signal and the second signal corresponding to the amplitude of one drive signal supplied to the movable wire each exceed a predetermined signal level, and Since the protection of the electro-mechanical converter is achieved by cutting off the supply of drive signals to the movable wire wheels by the control signal, it is possible to achieve protection of the electro-mechanical converter by cutting off the supply of drive signals to the movable wire wheels. By performing protective operations related to the temperature rise of the movable wire ring and the temperature rise in response to large pulsed inputs, the electric-to-mechanical converter can be By determining the maximum allowable input in the electro-mechanical converter and appropriately setting the start level of the protective operation, it is possible to easily provide effective protection against deformation of the voice coil.
Damage to the vibrating parts such as bottoming of the damper and voice coil and edge breakage is prevented, and efficiency reductions due to demagnetization of the permanent magnets are also well protected.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of an example of a conventional protection device, Fig. 2 is a block diagram of an embodiment of the protection device for a movable ring type electro-mechanical converter of the present invention, and Fig. 3 is a block diagram of a speaker FIG. 4 a = d is a waveform chart for explaining the operation. 1... Input terminal, 2, At, Ap...
Amplifier, 3...Output terminal, 4...DC component detection section, 5, MA...Storage section, 6,
7, CC...control unit, 10, 11...
・・Overcurrent detection section, SW・・・・Switch, ■R・
...Variable resistor, BC...Bridge circuit, SP...Speaker, Rs...Movable wire ring (resistance of the movable wire ring), Ra=Rc. ·····resistance,
LPF...Low pass filter, EQ...Equalizer circuit, RF...Rectification filter circuit, VRt
, VRp...Level adjuster, ADD...
・Adder.

Claims (1)

[Claims] 1 Due to the electromagnetic force generated by the supply of the drive signal,
A movable wire type electrical-to-mechanical converter equipped with a movable wire ring that is driven and displaced in a magnetic field, which is composed of a bridge circuit configured by using the movable wire itself on one side of the bridge to which the above-mentioned drive signal is supplied. temperature detection means; means for obtaining a first signal corresponding to the temperature of the movable wire based on a detection signal obtained by the temperature detection means corresponding to the temperature of the movable wire; means for obtaining a second signal according to the amplitude of the drive signal based on the drive signal supplied to the wire; and when the first and second signals each exceed a predetermined signal level. means for storing this fact and causing the control section to issue a control signal; and means for causing the control signal from the control section to cut off the supply of the drive signal to the movable wheel. Protective device for movable ring type electro-mechanical converter.