JPH0654997B2 - Amplifier protection circuit - Google Patents

Description

The present invention relates to an amplifier having a so-called DC protection circuit,
The amplifier is divided into a control information storage body which is a portion for setting the electric characteristics of the amplifier and an amplifier main body which is the other portion, and the control information storage body and the main body can be separated and combined. The present invention relates to a protection circuit for protecting a circuit and a load from an erroneous operation due to this separation / coupling in an amplifier and preventing noise.

[Prior Art] In an audio system, characteristics of an electric circuit including a preamplifier and a power amplifier are often adjusted according to a combination of a power amplifier and a speaker system, an installation environment, a kind of music to be played, and the like. Done.

However, such an adjustment is relatively difficult for a general user to appropriately perform even if only the frequency characteristic is adjusted by, for example, a tone control or a graphic.

By the way, the present applicant first made the speaker system cabinet smaller and capable of reproducing to a lower range by driving the speaker unit of the speaker system so as to cancel the atmospheric reaction to the vibrating body of this unit. Filed an audio device (Japanese Patent Application No. 62-33)
4262 (JP-A-1-302997) and the like). In such an audio device, the characteristics such as the Q value of the speaker system can be changed by changing the degree of cancellation of the atmospheric reaction. However, when the Q value (damping or braking characteristic) that affects the sound is adjusted, the frequency characteristic (especially the low frequency characteristic) also changes with the change of the Q value, so it is necessary to also compensate for this frequency characteristic. It is considered that it is almost impossible for general users to properly set both the sound quality and the frequency characteristic.

Therefore, in order to solve such a problem, the inventors of the present invention have provided an amplifier for driving the speaker unit, a control information storage body including a portion for setting the electrical characteristics of the amplifier, and other components. The control information storage body and the main body are separated by dividing the main body into
The user system or the like is configured to be freely connectable, and the user or the like can connect the speaker system or the music to be played by connecting a control information storage body prepared in advance according to the type of the speaker system or the kind of music to be played. The present invention has devised a drive device and a control information storage body that can easily set appropriate electrical characteristics for various types of devices. The present applicant filed a patent application on May 25, 1988 for the drive unit and the control information storage body.

[Problems to be Solved by the Invention] However, for the purpose of changing the characteristics of the audio device and the drive device in this way, a part of the circuit of the device is made into a cartridge like the control information container and can be replaced. In this case, noise is generated when the control information container, that is, the cartridge is inserted and removed. And
If the input / output signal to / from this cartridge is a digital signal, it is expected that an error will occur in the digital device, and when the signal is interrupted or a large noise is added, the signal is automatically muted or interpolated. Since such a system is generally known, it is possible to remove noise by applying such a system. However, when the cartridge directly inputs and outputs an analog signal such as an audio signal, the cross noise is mixed into the signal unless some means is devised and is output as sound (noise). There is an inconvenience that it will be done.

Further, in the device in which a part of the circuit is made into a cartridge as described above, it is necessary to detect the presence or absence of the cartridge. For example, when the electrical characteristics of the device are set by negative feedback, the amplifier on the main body side is in the non-feedback state with the cartridge containing the circuit for this negative feedback separated, and the noise component has a large gain (opened). The gain may be amplified and output, or the amplifier may oscillate to generate an output in the ultrasonic range, and the circuit element or the load may generate heat, deteriorate, or be destroyed without being noticed.

In the conventional power amplifier, a DC voltage is generated at the output end due to a mute circuit that inhibits output or a failure for a predetermined time immediately after power-on in order to prevent noise in an unstable operating state immediately after power-on. In many cases, a direct current protection circuit that detects this and shuts off the output to protect the circuit and load is provided.

It is an object of the present invention to divide an amplifier having the DC protection circuit into a control information storage body which is a portion for setting electric characteristics of the amplifier and an amplifier main body which is another portion, and these control information Separate the storage body from the main body
In an amplifier configured to be freely connectable, it is possible to prevent noise at the time of combining due to this separation / combination from being output as sound, or to perform abnormal operation such as oscillation during separation of the control information container from the main body or immediately after connection. It is an object of the present invention to provide a protection circuit for protecting a circuit and a load from noise and malfunction due to the transient operation of.

[Means for Solving the Problems] In order to achieve the above object, in the present invention, circuit elements are distributed and arranged in both the amplifier body and the control information storage body,
When the main body and the container are separated, a part of these circuit elements forms a DC bias circuit for applying a DC voltage to the input of the DC protection circuit, and the main body and the container are separated from each other. In the coupled state, all of the distributed circuit elements, a part of the connection terminals of the housing, and the corresponding main body side terminals substitute a substantially zero voltage for the input of the DC protection circuit in place of the DC bias circuit. It is configured to form a power supply voltage dividing circuit to be applied.

[Operation] Therefore, according to the present invention, since the DC voltage is added to the input of the DC protection circuit in the state where the main body and the housing are separated, the DC protection circuit detects the DC voltage and the amplifier is detected. Shut off the output of. On the other hand, in the state where the main body and the housing are coupled, the voltage added from the protection circuit of the present invention to the input of the DC protection circuit is zero. Therefore, if the amplifier is in the normal operation state, the output of the amplifier is the load. , For example to a speaker.

[Effect] As described above, according to the present invention, the separation / coupling of the control information container is detected, the output from the amplifier main body is cut off at the time of separation, and the output from the amplifier main body is output only at the time of connection and normal operation. Because it is enabled, noise and abnormal output due to the clicking noise at the time of coupling and disconnection of the control information storage body, the transient operation immediately after coupling and the abnormality or malfunction during the separation are blocked, and the noise is generated as sound. Discomfort is prevented, and the circuit and load are protected from heat generation, deterioration, destruction, etc. due to noise and abnormal output.

As a method of detecting the presence or absence of the control information container, that is, a cartridge, a method of using a connection terminal of a cartridge, for example, a contact of a connector itself, and a method of detecting with another switch are considered, but according to another switch, There are many problems such as accuracy and lack of certainty. In the present invention, since the presence or absence of the cartridge is detected by the contact itself of the connector, reliable detection can be performed.

Further, according to the present invention, the DC protection circuit (DC protection circuit) which the audio equipment originally has for protecting the speaker and the circuit is used as it is, so as to protect the control information storage body against separation / coupling. The configuration is simple.

Further, according to the present invention, by changing the constants or configurations of the circuits related to the power supply voltage dividing circuit for each type of main body, the output of the amplifier can be selectively output only when the main body and the control information container suitable for the main body are connected. Can be generated. That is, in the amplifier main body, it is possible to identify only the control information container that is suitable for itself. Moreover, since this identification is performed by the terminal for the protection circuit, it can be realized without increasing the number of terminals.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows the overall configuration of an amplifier according to an embodiment of the present invention. In the amplifier shown in the figure, an amplifier main body 1 and a cartridge 2 which are formed separately from each other are provided, a jack 31 provided on the main body 1 and a plug terminal portion 3 provided on the cartridge 2.
It is connected (connected) by a connector composed of 2.

The main body 1 includes a power amplifier 11, a feedback circuit 12, a DC protection circuit 13, a mute circuit 14, a relay 15, the jack 31 and the like. This jack 31
Is provided with nine main body side terminals P _{11 to} P ₁₉ .

The cartridge 2 includes a printed wiring board 21, a preamplifier 22 provided on the printed wiring board 21, a feedback amplifier 23, the plug-in terminal portion 32, and the like.
The plug-in terminal portion 32 is formed as a part of the printed wiring board 21, and nine connection terminals P _{21 to} P ₂₉ are provided as a circuit pattern on the printed wiring board 21.

By inserting the plug-in terminal portion 32 on the cartridge side into the jack 31 on the main body side, the corresponding terminals P ₂₁ and P ₁₁ , P ₂₂ and P ₁₂ , ..., P ₂₉ and P ₁₉ are connected respectively. , The main body 1 and the cartridge 2 are combined.

Of disposed in the cartridge 2 of the connection terminals P ₂₁ to P _29, the terminal P ₂₁ and P ₂₉ of the top ends are Burotekushon terminals, are shorter than the other terminals P ₂₂ to P _28. Also,
Power from the main body 1 to the cartridge 2 B +, B- connected by supply terminal P _22, P ₂₈ and the protection terminal P _21, resistor P ₂₉ as shown in FIG. 1 in the cartridge 2 _{R 1} and the resistor _{R 2} is there. Further, on the main body 1 side, the main body side terminals P ₁₁ and P ₁₉ are jumper-connected, and a resistor R ₃ is provided between the power source B + supply terminal P ₁₂ to the cartridge 2 and the connection point of the terminals P ₁₁ and P _19. The connection point is connected to the input of the DC protection circuit 13. The resistance values of these resistors R ₁ , R ₂ and R ₃ are set to R ₂ ≈R ₁ R ₃ .

These resistors R ₁ , R ₂ , and R ₃ form a DC bias circuit and a power supply voltage dividing circuit according to the state of separation and coupling between the main body 1 and the cartridge 2, and generate a DC voltage according to the state. To form a coupling / separation protection circuit for adding to the input of the DC protection circuit 13. The DC protection circuit 13 has a relay 15 during normal operation of the amplifier.
Is turned on to output the output of the power amplifier 11 to the speaker terminal P _O.
Is supplied to a speaker (not shown) connected to, and when the cartridge 2 is separated and a DC voltage is output from the coupling / separation protection circuit, the relay 15 is turned off to cut off the signal power supply to the speaker. However, this protects the speaker and the amplifier from the adverse effects of instability or abnormal operation of the amplifier during the separation of the cartridge 2.

The coupling / separation protection circuit of this embodiment is configured so that the mute circuit and the DC protection circuit for speaker protection that the audio device originally has when the power is turned on can be used as they are, and the number of terminals can be determined by the resistance value. The feature is that the type of cartridge can be identified without increasing the number.

First, a protection circuit of a general audio device corresponding to the DC protection circuit 13 and the mute circuit 14 of FIG. 1 will be described.

As such a protection function, there are a muting function at power-on and a DC protection function for preventing a DC voltage from being generated at the speaker terminal P _O. Normally, these two functions are not independent but operate in association with each other. As a result, the relay 15 connected in series to the output circuit is turned on.
It is realized by turning off. FIG. 2 shows an example of this circuit.

In the circuit of FIG. 2, when the power is turned on, the capacitor C ₁ is charged via the resistor R ₆ . Then, elapsed a certain time, the terminal voltage of the capacitor _{C 1} exceeds the base-emitter ON voltage of the transistor TR ₃ (V _BE = about 0.6V), the transistor TR ₃ is turned on,
The collector current of the transistor TR ₃ becomes a base current through the resistor R ₇ , and the transistor TR ₄ is turned on. As a result, the relay 15 is energized and turned on. A fixed time after the power is turned on until the relay 15 is turned on is the mute time when the power is turned on.
The values of the resistor R ₆ and the capacitor C ₁ are determined to be seconds.

An acoustic signal (alternating current) such as a music signal is output as an output of the power amplifier 11. However, if a DC voltage is generated at this output due to a device failure or the like, the speaker, which is a load, may be destroyed. It is necessary to turn off the relay 15 by detecting the DC component of the output. Transistor T
The DC protection circuit 13 consisting of R ₁ , diode D ₁ and transistor TR ₂ is for this purpose. In the circuit of FIG. 2, the output of the power amplifier 11 is a resistor R ₄ is applied as the capacitor C _2, since the AC component is bypassed to the earth side with the capacitor C _2, both ends of the capacitor C ₂ Generates a voltage corresponding to the DC component of the output of the power amplifier 11. Here, the time constant of the resistor R ₄ and the capacitor C ₂ is selected within the audible range. The voltage generated across the capacitor C ₂ is the resistance R
It is input to the DC protection circuit 13 through ₅ .

In DC protection circuit 13, the base-emitter ON voltage (V _BE, e.g. + 0.6V) of the transistor TR ₂ to input the higher voltage is applied transistor TR ₂ is turned on to discharge the charged electric charge of the capacitor _{C 1} Therefore, the relay 15 is turned off. Further, the DC protection circuit 13 receives inputs of the ON voltage between the base and emitter of the transistor TR ₃ from the ON voltage of the diode D ₁ (V _f , for example, 0.6 V) and the ON voltage between the emitter and base of the transistor TR ₁ (V _EB , for example, 0.6V) when the applied voltage lower than -0.6V minus the capacitor C conducting transistor TR ₁ and the diode _{D 1} is
_The relay 15 is turned off to remove the charge of ₁ . Therefore, the DC protection circuit 13 has an input voltage of −
Relay 1 only when in the range of 0.6V to + 0.6V
5 is turned on, and the relay 15 is turned off at a higher voltage or a lower voltage.

The operating time when the relay 15 is turned off is the relay 1
Although it is determined by the response speed of _{No. 5} , even if the DC input voltage to the DC protection circuit 13 is set to zero after turning it off once, the relay 15 does not turn on immediately and the capacitor C ₁ does not change the resistance R ₆
The transistor TR ₃ is turned on via the base-emitter ON voltage V _{BE of the} transistor TR ₃ by a delay of the mute time.

Next, the operation of the separation / coupling protection circuit in the circuit of FIG. 1 will be described with reference to FIG.

Cartridge 2 is missing when (to separate) are is, V ₁ output voltage V ₁ of the separation-coupling protection circuit by the resistor R ₃
Since this is input to the DC protection circuit, the relay 15 does not turn on. That is, in this case, the separation / coupling protection circuit is composed of only the resistor R ₃ and forms a DC bias circuit for adding a DC voltage to the input of the DC protection circuit.

When the cartridge 2 is inserted, the output voltage V ₁ of the separation / coupling protection circuit causes the potential difference between the power sources + B and −B to be the resistance R ₂
And the voltage is divided by R ₁ R ₃ , but here, since R ₂ ≈R ₁ R ₃ , V ₁ ≈0V,
The relay 15 is turned on after a certain time (mute time) determined by the protection circuit on the main body 1 side.

When the control information stored in the cartridge 2 is an analog circuit, when the cartridge 2 is inserted, a large transient noise is initially generated, but it takes a certain amount of time to settle in a steady state. Therefore, even if the cartridge 2 is inserted, the output of the apparatus (the speaker output in the case of a power amplifier) is cut off for a while, and it is necessary to output it after the transient noise disappears. This has the same meaning as mute when the power of an ordinary amplifier is turned on. Further, noise is also generated when the cartridge 2 is removed, but in this case, it is necessary to turn off the output before the contacts of the connector are separated. This can be achieved by making the protection terminal of the connector shorter than the terminals of other signals and power supplies so that it can be cut earlier than the other terminals. The connector itself can be used for disconnecting, but muting is required when plugging in.

In the amplifier of FIG. 1, when the cartridge 2 is inserted as described above, the mute circuit 14 operates in the same manner as when the power is turned on. Therefore, the mute time is the time until the noise due to the power on and the cartridge is inserted. The transient noise when the cartridge 2 is inserted can be prevented only by setting the time longer than the time until the transient noise disappears.

The connection for the terminal P ₂₁ and P ₂₉ are is formed shorter than the other terminals, pull out the cartridge 2 when the other terminal P ₂₁ and P ₂₉ before the terminal omission noise is generated by the terminal P ₁₁ and P
The output V ₁ of the separation / coupling protection circuit becomes zero from ₁₉ and the relay 15 is turned off. Therefore, when the noise is generated when the cartridge 2 is pulled out, the relay 15 is already turned off, so that the noise at this time can be prevented from being generated from the speaker.

Even when one of P ₂₁ and P ₂₉ separates first by pulling out the cartridge obliquely, for example, if only P ₂₁ separates, the voltage V
₁ is determined by the resistance R ₃ and the resistance R _2, and R ₂ ≈R ₁ R
_Since R ₂ <R _{3 according} to ₃ , V ₁ becomes a negative voltage, and if the resistance values of the resistors R ₃ and R ₂ are set so that this voltage becomes smaller than −0.6 V, the protection operates. To do. Even if only P ₂₉ is separated, since V ₁ is + B, the protection operates.

Generally, setting R ₁ = R ₃ = 2R ₂ facilitates setting. In this case, assuming that E ₁ = E ₂ = 12V, V is obtained when there is no cartridge 2 and when only the terminal P ₂₉ is separated.
₁ = + 12V, and when only the terminal P ₂₁ is separated, V ₁
= -4V, and the protection can be operated sufficiently.

Thus, when E ₁ = E ₂ , the resistance R ₁ = R ₃ = 2
If R _{3 is set} , almost the purpose can be achieved, but the resistance value satisfying this is infinite. Further, if E ₁ ≠ E ₂ , the degree of freedom is increased. Even if E ₁ ≈E ₂ and R ₁ = R ₃ = 2R ₂ , the degree of freedom of the resistance value itself is still high.

In any case, in FIG. 3, the output voltage V ₁ of the separation / coupling protection circuit when the cartridge 2 is inserted is
Ignoring resistor R ₅ The output voltage V ₁ ′ when only the connection terminal P ₂₁ is separated is The output voltage V ₁ ″ when only the connection terminal P ₂₉ is separated is V ₁ ″ = E ₁ . Therefore, V ₁ ≈0
And a resistance value such that V ₁ ′ ≠ 0 may be set.

In this way, by utilizing the high degree of freedom in selecting the resistance values R ₁ , R ₂ , and R ₃ , the cartridge can be identified using only two terminals for protection. Conventionally, a terminal different from that for protection is required for identifying the cartridge, and there is a disadvantage that a large number of terminals are required.

For example, the main body A and the cartridge a are compatible, the body B is compatible with the cartridge b,
Assume they are not compatible with each other. In this case, E ₁ = E ₂ =
Assuming 12V, let A and a and system be R ₁ = R ₃ = 2R
₂ = 10 kΩ, and the system of B and b is R ₁ = R ₃ = 2
If R ₂ = 1 kΩ and a is inserted into B, R ₁ = 10 kΩ, R ₂ = 5 kΩ,
Since R ₃ = 1 kΩ, V ₁ ≈3.5 V, V ₁ ′ = 8
Since V and V ₁ ″ = 12V, both of which are larger than 0.6V, the transistor T of the DC protection circuit 13 is
R ₂ turns on and relay 15 does not turn on. In addition, b is A
In the above formula, R ₁ = 1k
Ω, R ₂ = 0.5 kΩ, R ₃ = 10 kΩ, so V
_{1 ≒ -10V, V 1 '≒} -11V, V 1 "= 12V , and the both the absolute value is larger than 0.6V, _{V 1} ≒
When −10V and V ₁ ′ ≈−11V, the transistor TR ₁ of the DC protection circuit 13 is turned on, and V ₁ ″ = 1
When the voltage is 2V, the transistor TR ₂ of the DC protection circuit 13 is turned on.
Does not turn on.

Thus, it is possible to identify whether or not the cartridge can be used for the main body only by setting the resistance value.

The amplifier of FIG. 1 can be formed into various types of speaker drive circuits by selecting the signal input to the feedback terminal P _F and the polarity and frequency characteristics of the feedback amplification circuit 23 of the cartridge 2. For example, a motional signal corresponding to the movement of the vibrating body of the speaker unit is detected by some method and is input to the feedback terminal P _F , and the polarity of the feedback amplifier circuit 23 is made negative so that this motional signal is negatively fed back to the input side. Then, a motional feedback (MFB) circuit can be formed,
A negative impedance circuit is formed by detecting the driving current of the speaker unit and inputting it to the feedback terminal P _F to make the polarity of the feedback amplifier circuit 23 positive so that this driving current signal is positively fed back to the input side. can do.
Here, normally, the cartridge 2 is configured such that a speaker unit as a load is formed with a circuit for canceling atmospheric reaction of the unit with respect to the vibrating body, for example, the above-mentioned MFB circuit or negative impedance circuit. The preamplifier 22 of the cartridge 2 is set (preset) to have appropriate frequency characteristics as an equalizer amplifier.

FIG. 4 shows Japanese Patent Application No. 62-334 filed by the applicant earlier.
The configuration of an acoustic device in which a speaker system with a resonance port similar to a conventional bass reflex type speaker system is driven by using the negative impedance generating circuit shown in Japanese Patent Laid-Open No. 262 (1998) -302997 as a drive circuit is shown. The negative impedance generation circuit 60 in the figure comprises an amplifier circuit 61, a resistor R _S, and a feedback circuit 63. Here, the amplifier circuit 61 is the power amplifier 11 of FIG.
The feedback circuit 63 corresponds to the feedback circuit 12 and the feedback amplifier 23 shown in FIG.

In the negative impedance generating circuit (driving circuit) 60, the output of the amplifier circuit 61 having the gain A is given to the speaker unit 7 as a load. Then, the load current detection resistor R _S causes the current I flowing through the speaker unit 7.
_L is detected and positively fed back to the amplifier circuit 61 via the feedback circuit 63 having the transfer gain β. In this way, the drive circuit 60
The output impedance Z _{O of} is calculated as R _O = R _S (1-Aβ). From this equation, if Aβ> 1, R _O becomes an open stable negative resistance.

FIG. 5 shows an electrical equivalent circuit of the audio device of FIG. In the figure, the parallel resonant circuit Z ₁ is based on the equivalent motional impedance of the unit 7, r _O indicates the equivalent resistance of the vibration system, S _O indicates the equivalent stiffness of the vibration system, and m _O indicates the vibration system. The equivalent mass is shown. The series resonance circuit Z ₂ is based on the equivalent motional impedance of the Helmholtz resonator constituted by the resonance port 8 and the cabinet 9, and r _C is the cavity 9 of the resonator.
1 shows the equivalent resistance, S _C shows the equivalent stiffness of the cavity 91, r _P shows the equivalent resistance of the resonance port 8, and m _P shows the equivalent mass of the resonance port 8. In addition, A in the figure
Is the force coefficient, and when the unit 7 is an electrodynamic direct emission speaker, B is the magnetic flux density in the magnetic gap, _V
Let A be the total length of the conductor of the voice coil, then A = B _V. Further, Z _V in the figure is the internal impedance (non-motional impedance) of the unit 7, and when the unit 7 is an electrodynamic direct emission speaker, it mainly becomes the resistance R _{V of the} voice coil and includes a slight inductance. There is.

Next, the operation of the audio device of FIG. 4 will be described. When a drive signal is applied from the negative impedance drive circuit 60 to the unit 7, the unit 7 electromechanically converts the drive signal to drive the diaphragm 71 back and forth (left and right in FIG. 4) back and forth. The diaphragm 71 converts this reciprocating motion into mechanical sound. Here, since the drive circuit 60 has a negative impedance drive function, the internal impedance of the unit 7 is equivalently reduced (ideally invalidated). Therefore, the unit 7 faithfully responds to the drive signal input to the drive circuit 60 to drive the diaphragm 71, and is independent of the Helmholtz resonator constituted by the resonance port 8 and the cabinet 9. Give driving energy to. At this time,
The front side (right side in FIG. 4) of the diaphragm 71 forms a direct radiating portion for directly radiating sound to the outside, and the rear side (left side in FIG. 4) of the diaphragm 71 is a cabinet. It constitutes a resonator driving unit for driving the Helmholtz resonator composed of 9 and the resonance port 8.

Therefore, the sound is directly radiated from the diaphragm 71 as indicated by the arrow a in the figure, and the air in the cabinet 9 is caused to resonate, so that the resonance radiating portion (resonance) is generated as indicated by the arrow b in the figure. Sound of sufficient sound pressure is resonantly radiated from the opening of the port 8. Then, by adjusting the air equivalent mass in the resonance port 8 in the Helmholtz resonator, according to the resonance frequency _OP is set lower than the Helmholtz resonance frequency _OP conventional bass reflex type speaker system, and adjusting the equivalent resistance of the resonance port 8 By setting the Q value to an appropriate level, a sound pressure of an appropriate level can be obtained from the opening, and by further increasing or decreasing the input signal level, for example, the sound as shown by the solid line in FIG. The frequency characteristic of pressure can be obtained. In FIG. 6, the two-dot chain line shows the frequency characteristic and impedance characteristic of the closed type speaker system, and the broken line shows the frequency characteristic and impedance characteristic of the bass reflex type speaker system.

Hereinafter, the operation when the speaker system using the Helmholtz resonator is driven by negative impedance will be described.

FIG. 7 is an electrically equivalent circuit when Z _V −Z _O = 0 in FIG. 5, that is, the internal impedance (non-motional impedance) of the unit 7 is equivalently completely disabled. Here, the coefficient attached to the value of each element is omitted.

The following is clear from this equivalent circuit.

First, the parallel resonance circuit Z ₁ having the equivalent motional impedance of the unit 7 is AC short-circuited with zero impedance at both ends. Therefore, the parallel resonant circuit Z ₁ has a Q value of 0 and is substantially no longer a resonant circuit. That is, in this unit 7, the concept of the minimum resonance frequency which is simply held in the state where the unit 7 is attached to the Helmholtz resonator is no longer present. After that, the lowest resonance frequency of the unit 7
_{When the term "O} equivalent amount" is used, the above concept that has been substantially invalidated is merely called. As described above, as a result of the unit resonance system (parallel resonance circuit) Z ₁ being substantially not a resonance circuit, the only resonance system in this acoustic device is the Helmholtz resonance system (series resonance circuit) Z ₂ .

In addition, as a result of the vibration system not being a resonance circuit substantially, the unit 7 linearly responds to the drive signal input in real time without any transient response, and faithfully generates an electric signal (drive signal E _O ). The mechanical conversion is performed and the diaphragm 71 is displaced. That is, it is a complete braking state (so-called speaker dead state). In this state, the output sound pressure frequency characteristic near the lowest resonance frequency _O equivalent value of this speaker is 6 dB / oct. On the other hand, the characteristic in the normal voltage driving state is 12 dB / oct.

On the other hand, the series resonance circuit Z ₂ based on the equivalent motional impedance of the Helmholtz resonator has the drive signal source E _O.
Since it is connected to the parallel resonant circuit Z ₁ with no impedance, the parallel resonant circuit Z ₁ and the series resonant circuit Z ₂ coexist independently regardless of each other. . Therefore, the volume of the cabinet 9 (inversely proportional to S _C ) and the shape and size of the resonance port 8 (in proportion to m _P ) do not affect the direct radiation characteristic of the unit 7, and the resonance frequency of the Helmholtz resonator and The Q value is not affected by the equivalent motional impedance of the unit 7. That is, the characteristic value of the Helmholtz resonator and the characteristic value of the unit 7 can be set independently. Further, the series resistance of the series resonant circuit Z ₂ is r _C +
Since r _{P is the} only value, which is usually a sufficiently small value, the Q value of the series resonance circuit Z ₂ , that is, the Helmholtz resonator can be set to be sufficiently high.

From another point of view, the unit vibration system is not actually a resonance system, so it is displaced according to the drive signal input,
It is virtually unaffected by external forces, especially atmospheric reactions due to the equivalent stiffness S _C of the cabinet. Therefore, the diaphragm 71 of the unit 7 is equivalently a wall when viewed from the cabinet side, and the existence of the unit 7 when viewed from the Helmholm resonator is nullified. Therefore, the resonance frequency and the Q value as the Helmholtz resonator do not depend on the non-motional impedance of the unit 7, and the resonance frequency is set to a frequency at which the Q value of the resonance becomes very small in the normal driving method. Also in this case, the Q value can be maintained at a sufficiently large value. Further, the Helmholtz resonance system is also a virtual speaker that emits sound independently of the unit vibration system. Although this virtual speaker is realized with a small diameter corresponding to the port diameter, it is equivalent to an extremely large diameter speaker as an actual speaker when viewed from its bass reproduction capability.

Comparing the above with a conventional method in which a conventional bass reflex type speaker system is driven at a constant voltage by an ordinary power amplifier, in the conventional method, as is well known, a plurality of resonances of a unit vibration system Z ₁ and a Helmholtz resonance system Z ₂ are known. The system existed, and the resonance frequency and Q value of each resonance system were closely dependent on each other. For example, if the port is made long or thin (m _P becomes large) in order to reduce the resonance frequency of the Helmholtz resonance system Z ₂ , the unit vibration system Z ₁ has a high Q value and the Helmholtz resonance system Z ₂ has a low Q value. it becomes, to reduce the volume of the cabinet and (S _C becomes larger), or longer port, even if kept constant resonance frequency of the Helmholtz resonance system Z ₂ and thin, the unit vibration system Z ₁
, The Q value and the resonance frequency were high, and the Q value was even lower in the Helmholtz resonance system Z ₂ . That is,
Since the output sound pressure frequency characteristics of the speaker system are closely related to the characteristics of the speaker unit, the volume of the cabinet, and the size of the port, a sophisticated design technique is required to match them, and the output sound pressure It is generally considered impossible to downsize the cabinet (system) without compromising frequency characteristics, especially low-frequency characteristics, and to easily expand the sound reproduction band of existing systems without compromising other characteristics such as sound quality. It was being done. Further, the relationship between the frequency in the band lower than the resonance frequency _OP in the Helmholtz resonance system Z ₂ and the resonance acoustic radiation ability is 12 dB / oct with respect to the decrease in the frequency, as seen from the sound pressure level.
When the resonance frequency is set to be extremely low with respect to the basic idea of the bass reflex type speaker system, it becomes extremely difficult to correct by increasing or decreasing the input signal level.

In the amplifier of this embodiment, as described above, the speaker system using Helmholtz resonance is driven by negative impedance, so that the unit vibration system and Helmholtz resonance system characteristics and dimensions of the system can be set independently, and Even if the resonance frequency of the Helmholtz resonance system is set low, the Q value and the bass reproduction capability can be maintained high, and the resonator drive capability of the unit vibration system is strong (6
dB / oct), it is possible to correct the swell of frequency characteristics by increasing / decreasing the input signal level, for example, increasing / decreasing the normal sound quality adjustment level, so that the frequency characteristics and sound quality are not impaired. The cabinet can be miniaturized to make the speaker system compact, and the sound quality of the existing speaker system can be improved as compared with the conventional constant voltage drive, or the sound reproduction band, especially the bass side can be easily expanded. Can be driven.

In the _above, Z V _-Z O = has been described only for the case of 0, if _-Z O <0 even if the _Z V _-Z O = 0 the _Z V _-Z O = 0 The characteristics between the case of 1 and the case of the conventional constant voltage driving method can be obtained. Therefore, instead of positively utilizing this property, for example, adjusting the Q value of the Helmholtz resonance system by adjusting the port diameter or inserting a mechanical Q damper such as glass wool or felt in the cabinet. , Negative impedance −
This can be done by adjusting Z _O.

Further, in this case, it is extremely difficult for a general user to appropriately set the output impedance and increase / decrease of the input signal level with a variable resistor, a changeover switch or the like, but as shown in FIG. Suitable cartridge 2
By changing the frequency characteristic of the transfer characteristic and the pre-amplifier 22 of the feedback circuit 63 by combining by selecting a proper negative impedance value -Z _O and equalizer characteristics, etc. music to be systems and play to be driven because it to set, setting to an appropriate value, such as the negative impedance value -Z _O and equalizer characteristic becomes very easy.

The closed speaker system is the speaker system with the resonance port removed from the resonance port,
Therefore, in terms of the equivalent circuits in FIGS. 5 and 7, the equivalent mass m _P of the resonance port is ∞, that is, the equivalent capacitor m _P.
It can be understood that / A ² is short-circuited. That is, even in a closed loudspeaker system, the minimum resonance frequency of the speaker unit is controlled regardless of the cabinet volume by driving with a power amplifier that includes negative impedance in the output impedance and increasing or decreasing the input signal level of this power amplifier. Reproduction with relatively high quality can be realized up to the vicinity of the _O equivalent value.

FIG. 8 shows a basic configuration of a negative impedance generating circuit for driving a vibrator such as a speaker unit with negative impedance.

The circuit shown in FIG.
To load Z _L. Then, the current I _L flowing through the load Z _L is detected and positively fed back to the amplifier 61 via the feedback circuit 63 having the transfer gain β. In this way, the output impedance Z _{O of the} circuit is obtained as Z _O = Z _S (1-Aβ) ... (4). If Aβ> 1 from the equation (4), Z _O becomes an open stable negative impedance. Here, Z _S is the impedance of the sensor that detects the current.

Therefore, in the circuit of FIG. 8, a desired negative impedance component can be included in the output impedance by appropriately selecting the type of impedance Z _S. For example, in the case of detecting the current _{I L} by the voltage across the impedance _{Z S} is the impedance _{Z S}
Is a resistance R _S , the negative impedance component is a negative resistance component, the inductance L _S is a negative inductance component, and the capacitance C _S is a negative capacitance. Further, the integrator used in the feedback circuit 63, it is possible to make the negative impedance component and negative resistance component by detecting and integrating the voltage across the inductance L _S as the impedance Z _S, further feedback circuit 63 using differentiator, negative impedance component be detected by differentiating the voltage across the capacitance C _S as the impedance Z _S becomes a negative resistance component. As the current detection sensor, these impedance elements R _S and L are used.
_S , C _S, etc., as well as C.I. T. It is also possible to use a current probe such as a Hall element.

A concrete example corresponding to such a circuit is, for example, Japanese Patent Publication Sho 59.
-51771 and the like.

It is also possible to detect the current on the non-grounded side of the speaker 7. A specific example of such a circuit is shown, for example, in Japanese Examined Patent Publication No. 54-33704. Figure 9 shows BTL
This is an example of connection, but it is easy to apply to the circuit of FIG. Reference numeral 64 in FIG. 9 is an inverting circuit.

FIG. 10 shows a concrete circuit example of an amplifier including a negative resistance component in the output impedance.

Output impedance _{Z O} of the amplifier of FIG. 10 _{is, Z O = R S (1} -R b / R a) = 0.22 (1-30 / 1.6) = -3.9 the (Omega). Further, in FIG. 10, a portion 2 surrounded by a dotted line
Corresponds to the control information circuit in the cartridge 2 of FIG.

The amplifier shown in FIG. 11 is different from the amplifier shown in FIG. 1 in that a bias resistor R ₃ ′ is connected between the power source-B supply terminal P ₁₈ and the protection terminal P ₁₉ on the main body 1 side to freely set the resistance value. Here is an example of increasing the degree. Also in this amplifier, the concept of setting each resistance value is the same as that of FIG. 1, and when the cartridge is not inserted, the resistance R _{3 is provided} between the power sources + B and −B.
And the voltage divided by R ₃ ′ is DC protection circuit 13
To turn off the relay 15 at -0.6V to +0.
Make sure that the voltage is not in the range of up to 6V, that is, that the DC bias voltage outside the above range is added to the input of the DC protection circuit 13 from this voltage dividing circuit, and between the power supplies + B and -B when the cartridge is inserted. The voltage divided by resistors R ₁ R ₃ and R ₂ R ₃ ′ turns on the relay 15 in the DC protection circuit 13 −
The resistance values R ₁ , R ₂ , R ₃ and R ₃ ′ are set so that the voltage is in the range of 0.6V to + 0.6V.

The amplifier shown in FIG. 12 is different from the amplifier shown in FIG. 1 in that the protection terminals are set to terminals other than the terminals at both ends and the resistance on the cartridge 2 side is one. In this case, only one protection terminal may be shorter than the other terminals. In this amplifier, each resistance value R ₁₁ , R
₁₂ and R ₁₃ are divided by resistors R ₁₂ and R ₁₃ between the power sources + B and −B when the cartridge is not inserted, and the voltage V ₁ is V ₁ <−
0.6V, + 0.6V <V ₁ , and when the cartridge is inserted, the resistors R ₁₁ R ₁₂ and R are provided between the power supplies + B and -B.
_The voltage V ₁ divided by ₁₃ is -0.6V <V ₁ <+ 0.6V
To be set.

[Modification of Embodiment] The drive circuit may be any drive circuit that drives the vibrating body of the electroacoustic transducer so as to cancel the reaction from the surroundings. For example, as disclosed in Japanese Patent Publication No. 58-31156. It may be a so-called MFB circuit.

Further, by giving the output impedance frequency characteristics, it is possible to improve the degree of freedom in setting Q _OC , Q _{OP and the} like.

[Brief description of drawings]

1 is a circuit configuration diagram of an amplifier according to an embodiment of the present invention, FIG. 2 is a configuration diagram of a protection circuit of FIG. 1, and FIG. 3 is a diagram for explaining the operation of the amplifier of FIG. Fig. 4 is a circuit configuration diagram of an audio device using the amplifier of Fig. 1, Fig. 5 is an electrical equivalent circuit diagram of the audio device of Fig. 4, and Fig. 6 is an audio device of Fig. 4. FIG. 7 is a sound pressure frequency characteristic diagram of sound radiated from the device, FIG. 7 is an equivalent circuit diagram when Z _V −Z _O = 0 in FIG. 5, and FIGS. 8 and 9 show negative impedance. A basic circuit diagram of a circuit to be generated, FIG. 10 is a specific circuit diagram of negative resistance driving, and FIGS. 11 and 12 are main circuit diagrams showing other embodiments of the present invention. 1: Amplifier main body, 2: Cartridge (control information storage body), 7: Speaker unit, 11: Power amplifier, 1
2: Feedback circuit, 13: DC protection circuit, 31:
Main unit side jack, 32: Cartridge side insertion terminal portion, 6
0: Negative impedance generation circuit, R ₁ , R ₂ , R ₃ ,
_{R 3, R 11, R 12} , R 13: the resistance, P ₁₁ ~P _19: main body side terminal, P ₂₁ ~P _29: cartridge-side connection terminals.

Claims (2)

[Claims] 1. An output unit in which a DC voltage at an output end during normal operation is set to substantially zero, and when the absolute value of the DC voltage at the output end exceeds a predetermined voltage, this is detected to output from the output end. And an amplifier body having a DC protection means for shutting off the output of the control body, and a control information storage body which is formed separately from this body and is separable and connectable to this body. The output from the output terminal of the amplifier, whose electrical characteristics are set according to the control information stored in the control information storage body, is prohibited or enabled according to the separated or coupled state of the control information storage body. A protection circuit, which is disposed in the main body, adds a direct current bias voltage to an input voltage of the direct current protection means when the control information storage body and the main body are separated, and the control information storage body and the main body When combining Flow bias circuit is formed as a whole by circuit elements including circuit elements constituting a flow bias circuit and distributed in both the control information storage body and the main body, and a part of connection terminals of the control information storage body and corresponding main body side terminals, A power supply voltage dividing circuit which outputs a voltage of substantially zero in place of the DC bias voltage, and a protection circuit. 2. A part of the connection terminals of the control information container forming the power supply voltage dividing circuit or at least one of the corresponding main body side terminals is formed shorter than the other terminals. The protection circuit according to item 1.