JP3286191B2 - Speaker drive circuit in audio system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to so-called audio equipment in general, which relates to an amplifier circuit for driving speakers of all audio equipment using speakers, efficiency, characteristics, power improvement, and the like.

[0002]

2. Description of the Related Art As is well known, conventional loudspeakers are generally known as linear transducers. To explain with a simple model, the speaker having the structure as shown in FIG. 1 oscillates in a range of ± △ x around the x point of the cone paper of the speaker by an input signal flowing through the voice coil. In this case, since the voice coil has the inductance (L), a force for causing the cone paper of the speaker to vibrate in the voice coil is generated in the magnetic field. This voltage is generally referred to as the back electromotive force △ EEV of the speaker. This simple model is shown in FIG. It is well known that a method of controlling the drive of a loudspeaker by performing positive feedback 1) and negative feedback 2) on the back electromotive force △ EEV is generally known. 1) For example, Japanese Patent Application No. 5-168962 2) For example, US Pat. No. 5,031,221

[0003] These generally known methods of positive feedback or negative feedback of a speaker drive are based on a model that handles only positive feedback or negative feedback due to an induced electromotive voltage generated in a voice coil of a speaker. . For the operation, a model is generally used in which the loop gain of the negative feedback is fixed to, for example, ± 0.5 and 1) and 2), and the damping factor is fixed to ± 1.

[0004]

In the prior art, as described above, any of the above-described techniques is merely an analysis of a so-called ideal model in which the back electromotive force in the voice coil of the speaker is positively or negatively fed back. The technology of the present invention is shown in FIG.
(B) and (c), respectively, the mechanical repulsion and movement of the speaker cone paper coming out of the support at the edge of the speaker cone paper, which was not considered in these prior art models and analysis. It is necessary to add a condition resulting from the distance limitation to the conventional general model, and analyze and consider the condition. By newly adding and considering the condition, a speaker driving condition that matches the actual condition is obtained.

From an electrical standpoint, the prior art is not a system that can continuously control positive or negative feedback. A major feature of the present invention is that, as shown in FIG. 2, in addition to the resistance caused by the mechanical twisting of the paper edge of the speaker cone, the operation of the speaker cone paper is controlled by simultaneously using the positive and negative feedback circuits. It is fundamentally different from the technical method and leads to more practical technical improvement.

[0006]

SUMMARY OF THE INVENTION In a movable magnetic drive system of an audio speaker system, an error component caused by a back electromotive force generated in a voice coil and a repulsive force generated at a peripheral edge of a speaker cone paper is corrected. To that end, the back electromotive force is simultaneously induced in the positive feedback and negative feedback amplifiers, and the output signal of each positive or negative different value is led to another differential classification circuit, and the resulting arbitrary output,
An error in the speaker drive output stage can be continuously corrected to an arbitrary value.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the speaker structure shown in FIG.
"Constriction" of corn paper for support at the edge of shika cone paper
And the resistance force FMF generated from this "constriction"
Works to always reduce the piston motion (△ x) of the speaker cone paper. When the speaker is operated as shown in FIG. 2B, the TOTAL force FT for driving the speaker
OTAL is a counter electromotive force (FM) generated in the voice coil.
V) and the repulsive force (F
It can be easily understood that MF) works as different conditions under the conditions of the positive feedback and the negative feedback by considering the principle of the spring in FIG.

In FIG. 3, a DC resistor connected in series to a voice coil of a speaker is installed. This resistance value is about 1/1 of the voice coil (generally 8Ω, 6Ω, 4Ω) of the speaker.
A low impedance value of about 00 is set and a value that does not cause a problem in the basic operation of the speaker is selected. An extremely small induced voltage (force) Vx generated at both ends of the resistance value is detected and used as an input signal of a positive feedback circuit and a negative feedback circuit as shown in FIG.

FIG. 4A shows a circuit model for positively feeding back the induced back electromotive force ΔEMV generated in the speaker voice coil. FIG. 4B shows circuit models that perform negative feedback on the contrary. Due to the generation of the induced back electromotive force △ EMV, the positive feedback operates in the direction where the EMV rises in the speaker part,
With negative feedback, EMV means acting as a lifting situation. The positive feedback and the negative feedback will be described in the context of the cone paper in which the loudspeaker moves, in the direction in which the positive feedback drives the TOTAL force driven by the loudspeaker (in the direction in which the back electromotive force is added to the cone paper movement direction). Negative feedback means that it acts as a direction deducted from the TOTAL force (a direction deducted from the moving direction of the cone paper and a brake is applied), respectively.

Summarizing the above, the total force FTOTAL for driving the speaker cone paper is described below. [For positive feedback] [In the case of negative feedback] When the back electromotive force is corrected by performing the positive feedback and the negative feedback, the actual situation of the operation of the cone paper of the speaker is as follows. In the case of positive feedback, the cone paper is easier to move than in the absence of steady-state feedback, because the back electromotive force increases in the direction of increasing the input signal, that is, the force pushing or pulling the cone is added. Become. On the other hand, in the case of negative feedback, the reverse is true, and the cone paper operates in a situation where the movement of the cone paper is hard to move as if the brake was applied. This detailed situation is shown in FIG.

In FIG. 5, when an ideal rectangular waveform signal is applied to the voice coil of the speaker, the movement of the speaker cone without the feedback circuit is determined by the input pulse time t.
= 0 is naturally delayed by the time Tp. On the other hand, in the case of the positive feedback, as described above, the positive feedback by the back electromotive force tends to increase the rising of the output signal.
The output signal rises earlier than p. Therefore, in the positive feedback, Tpp << Tp In the negative feedback, the situation is exactly the opposite, that is, Tp << TpN, and the negative feedback slows the rise of the movement of the speaker cone paper. Regarding the rise of the signal pulse, there is a difference in the rise time which is exactly the same as the condition of the rise of the input signal pulse. FIGS. 7A and 7B show the time relationships.

FIG. 6 shows a circuit based on a continuous variable feedback system in which a positive feedback circuit and a negative feedback circuit according to the present invention are combined. The feature of the circuit system of the present invention is that the signal of the induced back electromotive force taken out from the signal detection resistor RX is simultaneously input to each of the positive feedback circuit and the negative feedback circuit, and the output signal having the different signal is again input to the differential discriminating circuit. It is characterized by the following. By changing the resistances of RN and Rp for the gains of the positive feedback circuit and the negative feedback circuit, it is possible to realize continuous variable feedback by changing the resistances of the differential amplifiers of the subsequent stages and the resistance value of RGAIN. .

[0013]

8 and 9 show detailed circuit diagrams of a specific embodiment of the present invention, respectively. * 1 in Fig . 8 , * in Fig. 9
2. A major feature of the present invention is that a negative feedback and a positive feedback of US Pat. No. 5,031,221 and a use condition for matching a damping factor to a circuit constant as disclosed in Japanese Patent Application No. 5-168951 are not used. Ideally, even if it is required to fix the constant by positive or negative feedback, the feedback constant due to the induced electromotive force is different from the feedback constant due to the speaker diameter, the weight of the speaker cone paper and the different constant due to the twisting of the cone paper due to the speaker edge area. It is more important that the change in the generated constant has a larger condition difference than the generated constant due to the induced electromotive force.

Therefore, in the present invention, both the positive and negative feedback circuits are permanently provided, and the mechanical conditions generated for each of the different speakers are adjusted to any gain control conditions including the induced electromotive force correction conditions. The greatest feature of the present invention is to operate the loudspeaker under the best condition by setting the correction and the feedback circuit gain that continuously matches the conditions for each loudspeaker.

Consider a major feature in the generated sound coming out of a speaker driven by the circuit of the present invention. With positive feedback, the ideal output signal waveform as shown in FIG.
Shows an early rise at Pp. The time delay is shown in FIG.
It becomes Tpp as shown in FIG. However, after that, overshooting is repeated several times, and the saturation reaches a steady value. On the other hand, in the negative feedback, the rise is further delayed with respect to Tp having no feedback, and there is no overshooting at the value of TpN, and the rise is slower. The operation of the loudspeaker cone paper requires a repulsive force of mechanical torsion at the edge of the cone paper and a force to overcome the force for moving the weight of the cone paper, in addition to the generation of the back electromotive force. This relationship is presented by the equation and If the ease of movement of the speaker cone paper is displayed in terms of the suspension force of the vehicle's shock absorber, then: ▲ For positive feedback ... A direction to soften the suspension ▲ For negative feedback ... A direction to harden the suspension Therefore, it comes out of the speaker The sound is ▲ For positive feedback ... Suitable for music such as percussion instruments with beats.
Suitable for music in a field where a percussive soft hearing can be obtained. ▲ Negative feedback ... Suitable for classical music with many small elements such as classical music and organs. It is conceivable that such a case is met.

The positive feedback due to the back electromotive force acts to increase the rise of the output signal to the voice coil. In addition, the negative feedback acts as a reverse operation of the positive feedback so that the rising of the movement of the speaker cone paper is delayed. These functions operate in the same manner as the above-described respective conditions even when the output signal falls. By selectively adjusting these conditions in the positive and negative directions continuously by the operation sorting circuit, the speaker can be operated under the best conditions according to the integrated characteristics of the speaker.

[0017]

Therefore, it is needless to say that the characteristics of the loudspeaker of the present invention which can be expected in terms of the audibility are already described, and from the soft percussive condition of the positive feedback, the fine and classical sensation of the fine feedback in the negative feedback. By changing the gain on the circuit arbitrarily, it is possible to realize a really wide range of changes in audibility and sound quality. In particular, in the positive feedback, the output signal rises faster than when there is no feedback, and therefore, it is possible to express a high-frequency spectrum component having a fast rise. In terms of hearing, more signal spectra can be reproduced, and excellent frequency characteristics can be realized.

[Brief description of the drawings]

FIG. 1 is a structural diagram of a dynamic speaker.

FIG. 2 is an explanatory diagram showing a relationship between a back electromotive voltage and a repulsive force of the cone when the speaker moves the cone.

FIG. 3 is a diagram illustrating the operation of a speaker .

FIG. 4 is a circuit diagram showing a basic configuration of a circuit according to the present invention;
Positive feedback system, (b) shows negative feedback system

FIG. 5 is an explanatory diagram showing correspondence of speaker output waveforms driven by the circuit of the present invention.

FIG. 6 is a circuit diagram of the circuit of the present invention.

FIG. 7 is a driving characteristic diagram of a speaker according to the circuit of the present invention.

FIG. 8 is a configuration diagram showing one embodiment of a circuit diagram of the present invention.

FIG. 9 is a block diagram showing another embodiment of the circuit diagram of the present invention.

[Explanation of symbols]

 MV Voice coil Rx Series resistor RN Negative feedback circuit gain variable resistor RP Positive feedback circuit gain variable resistor RGAIN Differential amplifier gain variable resistor OP Operational amplifier

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04R 3/00 310

Claims (4)

(57) [Claims] In a movable magnetic drive system of an audio speaker system, in order to correct an error component generated from a back electromotive force of a voice coil, the back electromotive force (pressure) is simultaneously induced to a positive feedback and a negative feedback amplifier, In addition, each positive or negative output signal having a different value is guided to another differential classification circuit, and the error of the speaker driving output stage can be continuously corrected to an arbitrary value by the obtained arbitrary output. A speaker drive circuit in an audio system. A positive or negative feedback amplifier is installed at the same time for the induced back electromotive force (pressure), and the respective gains of the positive and negative feedback circuits are changed from 0 to the maximum value. 2. The speaker drive circuit in the audio system according to claim 1, wherein the value is continuously changed to an arbitrary value up to the maximum value of the positive feedback. The gain of positive feedback or negative feedback is arbitrarily changed according to the purpose of use of the speaker, so that the change in sound quality of the audibility from the loudspeaker is fixed to the desired audibility of the positive feedback or negative feedback. 2. The speaker drive circuit according to claim 1, wherein the speaker drive circuit can be changed continuously. 4. A driving amplifier for a dynamic speaker, a detection circuit for detecting an induced back electromotive force of the coil obtained by a resistor connected in series to a voice coil of the speaker, and a positive feedback signal detected by the detection circuit. Or a differential feedback circuit for negative feedback, a differential amplifier circuit for the signals of the two feedback circuits inserted between the amplifier and the two feedback circuits, and a gain variable means respectively provided for the feedback circuit and the differential amplifier circuit. A speaker drive circuit in an audio system, characterized in that: