JP7159544B2 - Speed detection circuit and drive controller - Google Patents

Description

The present invention relates to a speed detection circuit for detecting the speed of a moving part such as a diaphragm of a speaker or a coil bobbin, and a drive control device using the speed detection circuit.

As a powerful technology for improving sound quality by improving speaker distortion, MFB (Motional Bandwidth Control) controls the motion of the vibration system by negatively feeding back the signal indicating the vibration of the vibration system of the speaker to the amplifier, which is the drive system. Feed Back) type drive control device is known (see, for example, Patent Document 1).

Japanese Patent Application Laid-Open No. 2004-200934

By the way, in order to realize a speaker capable of reproducing low frequencies with a small-diameter diaphragm, it is necessary to increase the amplitude of the diaphragm. In order to realize such a large-amplitude vibration without impairing the sound quality, it is conceivable to employ an MFB drive control device as the drive control device for the speaker. In order to appropriately control the movement of the diaphragm over a wide frequency band including low frequencies in this type of MFB type drive control device, it is necessary to perform feedback control of the position, velocity and acceleration of the diaphragm. desired. However, providing a position detection sensor, a speed detection sensor, and an acceleration detection sensor for the vibration system poses a problem of increasing the size, weight, and cost of the drive control device. Speed detection sensors, in particular, have a complicated mechanism for detecting speed and are difficult to miniaturize.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide technical means for eliminating the need for a speed detection sensor in a drive control device for controlling the drive of a speaker or the like.

The present invention adds a component of a band below a predetermined cutoff frequency of a signal obtained by differentiating an output signal of a position detection sensor and a component of a band above the cutoff frequency of a signal obtained by integrating an output signal of an acceleration detection sensor. Provided is a speed detection circuit characterized by outputting a speed detection signal.

Further, the present invention provides a drive control device using such a speed detection circuit, that is, a position detection sensor for detecting the position of an object to be driven, an acceleration detection sensor for detecting the acceleration of the object to be driven, and the position sensor for detecting the acceleration of the object to be driven. A velocity detection signal obtained by adding a component of a band below a predetermined cutoff frequency of a signal obtained by differentiating the output signal of the detection sensor and a component of a band above the cutoff frequency of the signal obtained by integrating the output signal of the acceleration detection sensor. and a parameter generation circuit for generating control parameters for driving control of the object to be driven based on respective output signals of the position detection sensor, the acceleration detection sensor and the speed detection circuit. To provide a drive control device characterized by:

According to this invention, since the speed detection signal is generated from the output signal of the position detection sensor and the output signal of the acceleration detection signal, no speed detection sensor is required. Therefore, it is possible to avoid an increase in size, weight, and cost of a drive control device that controls the drive of a speaker or the like.

Here, it is conceivable to lengthen the voice coil in order to realize large-amplitude driving of the loudspeaker while suppressing the increase in cost. However, if the length of the voice coil is lengthened, the drive current will also flow through the coil windings in the sections not located in the magnetic field among the entire sections of the voice coil, resulting in a decrease in efficiency.

Therefore, in a preferred aspect, the object to be driven by the drive control device is composed of a plurality of voice coils arranged in the axial direction through which the magnetic field passes, and the drive control device detects the voice coils of the plurality of voice coils based on the output signal of the position detection sensor. A selection means is provided for selecting a voice coil positioned within the magnetic field from among the coils and energizing the selected voice coil.

According to this aspect, a voice coil positioned within the magnetic field is selected from among the plurality of voice coils, and the selected voice coil is energized, thereby preventing a decrease in efficiency.

1 is a circuit diagram showing the configuration of a drive control device using a speed detection circuit that is an embodiment of the present invention; FIG. FIG. 3 is a cross-sectional view showing a configuration example of a speaker that is subject to drive control by the drive control device; It is a figure which shows the structural example of the position detection sensor in the same drive control apparatus. It is a figure which shows the structural example of the acceleration detection sensor in the same drive control apparatus. FIG. 4 is a cross-sectional view showing an example of mounting a position detection sensor and an acceleration detection sensor in the same speaker; FIG. 4 is a diagram for explaining the function of a same-speed detection circuit; It is a figure explaining the transfer characteristic of the series circuit of the differentiation circuit and 1st-order LPF in the same embodiment. It is a figure explaining the transfer characteristic of the series circuit of the integration circuit and 1st-order HPF in the same embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a circuit diagram showing the configuration of a drive control device 1000 to which a speed detection circuit 300 according to one embodiment of the invention is applied. This drive control device 1000 is a device that uses various sensors to drive and control the moving coil type speaker 100 illustrated in FIG. Before describing the drive control device 1000, the configuration of the speaker 100 shown in FIG. 2 will be described, and then various sensors provided in the drive control device 1000 will be described.

In FIG. 2, the frame 101 functions as a housing that supports the diaphragm 111 and other parts. At the bottom of the frame 101 , on the side opposite to the diaphragm 111 , a ring-shaped top plate 102 and a ring-shaped (cylindrical) ring-shaped (cylindrical) plate 102 extend in the direction opposite to the sound output direction (downward in the figure). A magnetized permanent magnet 103 and a yoke 104 serving as the bottom are provided in sequence. A cylindrical center pole 105 protrudes toward the top plate 102 from the central portion of the yoke 104 .

The outer peripheral surface of the center pole 105 near the tip faces the inner peripheral surface of the top plate 102 across a gap. This air gap is the magnetic gap in the magnetic path.

A coil bobbin 112 having one end attached to a diaphragm 111 is arranged in a ring-shaped space between the outer peripheral surface of the center pole 105 and the inner peripheral surface of the top plate 102 . An inner peripheral portion of a damper 113 is attached to the vibrating plate 111 in the vicinity of the portion in contact with the coil bobbin 112 . An outer peripheral portion of the damper 113 is fixed to the frame 101 . Thus, the diaphragm 111 and the coil bobbin 112 are supported by the frame 101 via the damper 113, and constitute a movable portion capable of vibrating in the axial direction of the center pole 105. FIG.

In this embodiment, a plurality of voice coils are provided at different axial positions on the coil bobbin 112 . Also, the coil bobbin 112 is elongated so as to accommodate such a plurality of voice coils. In the specific example shown in FIG. 2, a voice coil 150a, a voice coil 150b positioned closer to the diaphragm 111 than the voice coil 150a, and a position farther from the diaphragm 111 than the voice coil 150a (a position closer to the bottom side of the center pole). ) are wound around the coil bobbin 112 . Note that the number of voice coils is not limited to three, and may be two or four or more.

Next, various sensors provided in the drive control device 1000 will be described. FIG. 3 is a diagram showing the configuration of the position detection sensor 210 used in the drive control device 1000. As shown in FIG.

In this embodiment, the light source 211 is fixed to the diaphragm 111 or coil bobbin 112 of the speaker 100 . The light source 211 is an LED (Light Emitting Diode) and emits light by current supplied from a power source 212 via a resistor 213 . For example, when the light source 211 is fixed to the coil bobbin 112 , the light source 211 vibrates together with the coil bobbin 112 .

The light receiving elements 215 and 216 are phototransistors, for example, and are arranged on the extension of the vibration path of the light source 211 . Here, the light receiving element 215 is connected between the positive terminal of the power supply 217 and the intermediate node 218 , and the light receiving element 216 is connected between the intermediate node 218 and the negative terminal of the power supply 217 . Then, the voltage of the intermediate node 218 is amplified by the buffer 219 shown in FIG. 1 and output as the position detection signal Sp.

If the speaker 100 has a built-in amplifier and is a powered speaker that starts a reproduction operation simply by inserting a power cable into an outlet, the power supply in the powered speaker can be used as the power supply 217.

In this configuration, when the light source 211 moves away from the light receiving element 216 and approaches the light receiving element 215 due to the vibration of the coil bobbin 112, the resistance value of the light receiving element 215 decreases and the resistance value of the light receiving element 216 increases. Voltage value rises. On the other hand, when the light source 211 moves away from the light receiving element 215 and approaches the light receiving element 216 due to the vibration of the coil bobbin 112, the resistance value of the light receiving element 215 increases and the resistance value of the light receiving element 216 decreases. voltage drops. Thus, the position detection signal Sp whose voltage value increases or decreases according to the position of the coil bobbin 112 is obtained.

FIG. 4 is a diagram showing a configuration of acceleration detection sensor 220 provided in drive control device 1000. As shown in FIG. In FIG. 4, a support base 221, which is a plate-shaped conductor, is fixed to the diaphragm 111 in a state of being lifted from the diaphragm 111 by a plurality of legs 222 provided around it. A plate-like piezoelectric element 223 is mounted on the upper surface of the support base 221 , and a conductive signal electrode 224 is mounted on the upper surface of the piezoelectric element 223 . The signal electrode 224 and the support base 221 are connected to the gate and source of an FET (Field Effect Transistor) 225, respectively.

According to this configuration, when the diaphragm 111 vibrates, the support 221 is flexed according to the acceleration of the diaphragm 111, and the voltage corresponding to the flexure of the support 221 is transferred from the piezoelectric element 223 to the gate and source of the FET 225. A drain current corresponding to the acceleration is obtained. As a result, the acceleration detection signal Sa having a voltage value corresponding to the acceleration of the diaphragm 111 is output from the drain of the FET 225 .

FIG. 5 is a cross-sectional view showing a mounting example of the position detection sensor 210 and the acceleration detection sensor 220 in the speaker 100. As shown in FIG. In this example, a cavity 107 is provided from the top surface of the center pole 105 to the bottom surface of the yoke 104 . One light receiving portion 215 of the position detection sensor 210 is fixed to the upper surface of the center pole 105 so as to sandwich the cavity 107, and another light receiving portion 216 of the position detection sensor 210 is fixed to the lower surface of the yoke 104. there is At the bottom of diaphragm 111, one end of rod portion 211b extending downward in cavity 107 is fixed to the back side of flat plate portion 111a facing center pole 105. As shown in FIG. A light source 211 of a position detection sensor 210 is fixed to the other end of the rod portion 211b. The light source 211 is sandwiched between the light receiving surface of the light receiving portion 215 and the light receiving surface of the light receiving portion 216 . On the other hand, an acceleration detection sensor 220 is fixed to the surface of the flat plate portion 111a. According to this configuration, the position detection signal Sp indicating the position of the flat plate portion 111a on the diaphragm 111 is obtained from the position detection sensor 210, and the acceleration detection signal Sa indicating the acceleration generated in the flat plate portion 111a is obtained from the acceleration detection sensor 220. be done.

Next, the configuration of the drive control device 1000 shown in FIG. 1 will be described. The drive control device 1000 has the position detection sensor 210 and the acceleration detection sensor 220 described above as sensors for detecting vibration generated in the movable portion of the speaker 100 . In this embodiment, the drive control device 1000 is not provided with a speed detection sensor, but is provided with a speed detection circuit 300 instead.

The speed detection circuit 300 detects the speed of the flat plate portion 111a of the diaphragm 111 of the speaker 100 based on the position detection signal Sp output by the position detection sensor 210 and the acceleration detection signal Sa output by the acceleration detection sensor 220. A circuit for generating a detection signal Sv. More specifically, the speed detection circuit 300 according to the present embodiment includes components in a band below a predetermined frequency of differentiation of the output signal of the position detection sensor 210 and components in a band above a predetermined frequency of integration of the output signal of the acceleration detection sensor 220. component is added to output a speed detection signal.

Details of the speed detection circuit 300 will now be described with reference to FIGS. 6 and 1. FIG. Assume that a position detection sensor, a speed detection sensor, and an acceleration detection sensor for detecting vibration of the flat plate portion 111a of the diaphragm 111 of the speaker 100 are provided. In this case, by vibrating the coil bobbin 112 in the axial direction, a position detection signal, a speed detection signal, and an acceleration detection signal having waveforms illustrated in FIGS. 6(a) to 6(c) are obtained. In these figures, the horizontal axis is time. The vertical axis of FIG. 6A is the position of the flat plate 111a indicated by the position detection signal, the vertical axis of FIG. 6B is the speed of the flat plate portion 111a indicated by the speed detection signal, and the acceleration detection signal is shown in FIG. is the acceleration of the flat plate portion 111a indicated by .

In this embodiment, no speed sensor is provided, and the output signals of the position sensor and the acceleration sensor are used to generate a speed detection signal indicating the speed of the flat plate portion 111a of the diaphragm 111. FIG. FIG. 6(d) illustrates the waveform of the speed detection signal obtained by differentiating the position detection signal output by the position sensor. FIG. 6(e) exemplifies the waveform of the velocity detection signal obtained by integrating the acceleration detection signal output by the acceleration sensor.

Here, the optical position detection sensor used in this embodiment has a high position detection capability in a low frequency range up to DC. Therefore, the speed detection signal (see FIG. 6(d)) obtained by differentiating the position detection signal has accurate speed detection capability in the low frequency region including DC. However, in the position detection sensor, the response speed of the light receiving element is slow. Therefore, the speed detection signal (see FIG. 6(d)) obtained by differentiating the position detection signal has poor detection accuracy in the high frequency region.

On the other hand, an acceleration detection sensor generally has a capacitive output impedance, and a sensor amplifier for amplifying this is required to have a high impedance input (high resistance input). However, the input impedance of the sensor amplifier cannot be infinite. Also, the integration circuit that integrates the acceleration detection signal cannot integrate the DC signal. Therefore, the velocity detection signal (see FIG. 6(e)) obtained by integrating the acceleration detection signal has poor detection capability in the DC and low frequency regions. Instead, the velocity detection signal obtained by integrating the acceleration detection signal (see FIG. 6(e)) has velocity detection capability in a high frequency region up to the resonance frequency of the acceleration detection sensor.

Therefore, as shown in FIG. 6(f), a velocity detection signal (see FIG. 6(d)) obtained by differentiating the position detection signal is selected in a low frequency region below a predetermined cutoff frequency. In a high-frequency region equal to or higher than the cutoff frequency, it is conceivable to select a velocity detection signal (see FIG. 6(e)) obtained by integrating the acceleration detection signal and add the selected signal.

Specifically, a differentiating circuit that differentiates the position detection signal, a first-order LPF that selects a low-frequency signal below a predetermined cutoff frequency fc in the output signal of this differentiating circuit, and an integration that integrates the acceleration detection signal. a circuit, a first-order HPF that selects a high-frequency signal above the cutoff frequency fc in the output signal of the integration circuit, and an addition circuit that adds the output signal of the first-order LPF and the output signal of the first-order HPF. Thus, a crossover filter having flat transfer characteristics in a wide frequency band from low to high frequencies including DC is constructed. By doing so, it is considered that a velocity detection signal having a flat velocity detection capability in a wide frequency band can be obtained.

However, it is difficult to realize an ideal differentiator and an ideal integrator. Therefore, in the present embodiment, as shown in FIGS. 7A and 7B, the transfer characteristics of the series circuit of the differential circuit and the first-order LPF are the same as the transfer characteristics of the first-order HPF. and replace the former with the latter. More specifically, in FIG. 7A, the gain G1 of the first-order LPF is 1 at frequencies below the cutoff frequency fc, but at frequencies above the cutoff frequency fc, the gradient is -6 dB/oct. decreases with On the other hand, the gain G2 of the differentiating circuit increases with a slope of +6 dB/oct as the frequency increases. Since the gain G3 of the series circuit of the differential circuit and the first-order LPF is the product of the gain G1 and the gain G2, as shown in FIG. , and the gain becomes flat at frequencies equal to or higher than the cutoff frequency fc. Therefore, the transfer characteristic of the series circuit of the differentiation circuit and the first-order LPF is the same as the transfer characteristic of the first-order HPF, and the former can be replaced with the latter.

Further, in this embodiment, as shown in FIGS. 8A and 8B, the fact that the transfer characteristics of the series circuit of the integrating circuit and the first-order HPF and the transfer characteristics of the first-order LPF are the same is used. and replace the former with the latter. More specifically, in FIG. 8A, the gain G4 of the first-order HPF is 1 at frequencies above the cutoff frequency fc, but rises at a gradient of +6 dB/oct at frequencies below the cutoff frequency fc. do. On the other hand, the gain G5 of the integration circuit decreases with a slope of -6 dB/oct as the frequency rises. Since the gain G6 of the series circuit of the integrating circuit and the first-order HPF is the product of the gain G4 and the gain G5, as shown in FIG. The gain decreases with a gradient of oct, and the gain becomes flat at frequencies below the cutoff frequency fc. Therefore, the transfer characteristic of the series circuit of the integrating circuit and the first-order HPF is the same as the transfer characteristic of the first-order LPF, and the former can be replaced with the latter.

By replacing the series circuit of the differentiating circuit and the first-order LPF with the first-order HPF and replacing the series circuit of the integrating circuit and the first-order HPF with the first-order LPF, the following results are obtained: , the speed detection circuit 300 shown in FIG.

In speed detection circuit 300 shown in FIG. 1, resistor 311 has one end connected to the output node (drain) of FET 225 and the other end grounded via capacitor 312 . The voltage at the connection node of resistor 311 and capacitor 312 is output via voltage follower amplifier 313 . The resistor 311 , capacitor 312 and voltage follower amplifier 313 constitute a primary LPF 310 that passes signals in the band below the cutoff frequency fc in the acceleration detection signal Sa output by the FET 225 .

In speed detection circuit 300 shown in FIG. 1, capacitor 321 has one end connected to the output node of buffer 219 and the other end grounded through resistor 322 . The voltage at the connection node of this capacitor 321 and resistor 322 is output via voltage follower amplifier 323 . The capacitor 321 , resistor 322 and voltage follower amplifier 323 constitute a primary HPF 320 that passes signals in a band equal to or higher than the cutoff frequency fc in the position detection signal Sp output from the buffer 219 .

In speed detection circuit 300, adder 330 adds the output signal of primary LPF 310 and the output signal of primary HPF 320 to output speed detection signal Sv. In this embodiment, the cutoff frequency fc of the first order HPF 320 is equal to the cutoff frequency fc of the first order LPF 310 . At this cutoff frequency fc, the gains of both the first-order LPF 310 and the first-order HPF 320 are -3 dB. At the cutoff frequency fc, the phase of the first-order LPF 310 lags by 45°, and the phase of the first-order HPF 320 leads by 45°. Therefore, at the cutoff frequency fc, the gain of the circuit composed of the first-order LPF 310, the first-order HPF 320 and the adder 330 is 0 dB. In the band below the cutoff frequency fc, the output signal of the first-order LPF 310 is dominant in the output signal of the adder 330, and in the band above the cutoff frequency fc, the output signal of the first-order HPF 320 is dominant in the output signal of the adder 330. signal becomes dominant. Therefore, the overall gain of speed detection circuit 300 is a flat gain over a wide frequency band. In this way, the speed detection signal obtained from the acceleration detection signal Sa and the speed detection signal obtained from the position detection signal Sp are band-limited and then added to obtain a stable wideband speed detection signal Sv.
The above is the configuration of the speed detection circuit 300 according to this embodiment.

The drive control device 1000 according to this embodiment has variable gain amplifiers 410, 420 and 430 that amplify the acceleration detection signal Sa, the speed detection signal Sv and the position detection signal Sp, respectively. These variable gain amplifiers 410, 420 and 430 constitute a parameter generating circuit for generating control parameters for drive control of the object to be driven. Note that the control parameters for this drive control will be described later in order to avoid duplication of description.

Variable gain amplifier 410 has resistors 411 and 412 , sliding resistor 413 , and operational amplifier 414 . Here, resistor 411 is connected between the output node of FET 225 and the inverting input terminal of operational amplifier 414 , and resistor 412 is connected between the output node and the inverting input terminal of operational amplifier 414 . The sliding resistor 413 has one end connected to the output node of the FET 225 , the other end grounded, and the wiper connected to the non-inverting input end of the operational amplifier 414 .

In this configuration, if Ra is the resistance value from the wiper position to the output node of the FET 225 in the sliding resistor 413, and Rb is the resistance value from the wiper position to the ground line, then the non-inverting input terminal of the operational amplifier 414 is The voltage V1 of is given by the following equation.
V1=Sa.(Rb/(Ra+Rb)) (1)

Assuming that the resistance value of the resistor 411 is Rc and the resistance value of the resistor 412 is Rd, the output voltage V2 of the operational amplifier 414 is given by the following equation.
V2=V1+(V1-Sa).(Rd/Rc)
=V1.(1+(Rd/Rc))-Sa.(Rd/Rc)
=Sa.(Rb/(Ra+Rb)).(1+(Rd/Rc))
-Sa (Rd/Rc)
=Sa・(Rb・Rc−Ra・Rd)/((Ra+Rb)・Rc) ……(2)
Therefore, the gain G of variable gain amplifier 410 is given by the following equation.
G = (Rb · Rc - Ra · Rd) / ((Ra + Rb) · Rc) …… (3)

Here, for simplicity, it is assumed that Ra+Rb=Rb=Rc=R. In this case, assuming that the slider of the sliding resistor 413 is connected to the output node of the FET 225 and that Ra=0, Rb=R, and Rd=R, the gain G of the variable gain amplifier 410 is as follows: become that way.
G = (Rb · Rc - Ra · Rd) / ((Ra + Rb) · Rc)
= (R · R) / (R · R)
= 1 ……(4)

Also, if the slider of the sliding resistor 413 is at the grounded position and Ra=R, Rb=0, and Rd=R, then the gain G of the variable gain amplifier 410 is as follows.
G = (Rb · Rc - Ra · Rd) / ((Ra + Rb) · Rc)
= (-R R) / (R R)
=-1 ……(5)

When the slider of the sliding resistor 413 is continuously changed from the position connected to the output node of the FET 225 to the grounded position, the gain G of the variable gain amplifier 410 continuously changes from 1 to -1. becomes.

The drive control device 1000 according to this embodiment is provided with an operator (not shown) for operating the position of the slider of the sliding resistance 413 . Therefore, in this embodiment, the gain G of the variable gain amplifier 410 can be continuously changed from 1 to -1 by operating this operator. The configurations of other variable gain amplifiers 420 and 430 are similar to variable gain amplifier 410 .

In this embodiment, the maximum positive feedback gain must be 1 in order to prevent oscillation. Also, in the case of negative feedback, the feedback amount may be larger than -1. For example, if you want to change the parameter by a factor of 10 at most, you can set the feedback amount to -10. Therefore, the resistance values of resistors 411, 412 and sliding resistor 413 are determined so that the gains of variable gain amplifiers 410-430 vary from 1 to -10.

The buffer 520 is supplied with the input sound signal Vin to be reproduced. The weighted adder 500 is a circuit that performs weighted addition of the input sound signal Vin supplied via the buffer 520 and the output signals of the variable gain amplifiers 410, 420 and 430, and outputs the result.

In this weighted adder 500, an operational amplifier 512 has a non-inverting input terminal grounded, and a resistor 511 is connected between the inverting input terminal and the output terminal. Resistors 501 to 504 are connected between the inverting input terminal of operational amplifier 512 and the output nodes of variable gain amplifiers 410, 420, 430 and buffer 520, respectively.

According to this configuration, currents supplied through resistors 501 to 504 are added at the inverting input terminal of operational amplifier 512 which is a virtual ground point, and the added currents flow through resistor 511 . Therefore, the output voltages of variable gain amplifiers 410 , 420 , 430 and buffer 520 are multiplied by weighting coefficients proportional to the inverses of the resistance values of resistors 501 to 504 , and added together.

A PWM (Pulse Width Modulation) section 600 is a circuit that outputs a PWM pulse pulse width modulated by the output signal of the weighting adder 500 .

The selector 700 is connected to buffers 701 to 704 for applying drive currents to the voice coils 150b, 150a and 150c. An output node of the buffer 701 is connected to a terminal of the voice coil 150b on the yoke 104 side. An output node of the buffer 702 is connected to each terminal of the voice coils 150b and 150a on the diaphragm 111 side. An output node of the buffer 703 is connected to terminals of the voice coils 150a and 150c on the yoke 104 side. An output node of the buffer 704 is connected to a terminal of the voice coil 150c on the diaphragm 111 side. The selection unit 700 selects one or two voice coils within the magnetic field of the magnetic gap from among the voice coils 150b, 150a, and 150c based on the position detection signal Sp, and stores the selected voice coils in the buffer 701. . . 704 flow a current having a polarity and magnitude corresponding to the level of the PWM pulse supplied from the PWM section 600 .

For example, when only the voice coil 150b is within the magnetic field of the magnetic gap and the PWM pulse from the PWM section 600 is at H level, the selection section 700 causes the buffer 702 to output an H level voltage and the buffer 701 to output an L level voltage. A voltage is output and the output nodes of buffers 703 and 704 are brought into a floating state. As a result, a current flows from the diaphragm 111 side to the yoke 104 side only in the voice coil 150b.

Next, when voice coils 150b and 150a are in the magnetic field of the magnetic gap and the PWM pulse from PWM section 600 is at H level, selection section 700 causes buffer 702 to output a voltage of H level, buffers 701 and 703 to output an L level voltage, and the output node of buffer 704 is brought into a floating state. As a result, a current flows from the diaphragm 111 side to the yoke 104 side in the voice coils 150b and 150a.

Next, when only the voice coil 150a is in the magnetic field of the magnetic gap and the PWM pulse from the PWM section 600 is at H level, the selection section 700 causes the buffer 702 to output an H level voltage, and the buffer 703 to output an L level voltage. , and the output nodes of buffers 701 and 704 are brought into a floating state. As a result, a current flows through the voice coil 150a from the diaphragm 111 side to the yoke 104 side.

Next, when voice coils 150a and 150c are in the magnetic field of the magnetic gap and the PWM pulse from PWM section 600 is at H level, selection section 700 causes buffers 702 and 704 to output H level voltage, and buffer 703 to output an L level voltage, and the output node of buffer 701 is brought into a floating state. As a result, a current flows from the diaphragm 111 side to the yoke 104 side in the voice coils 150a and 150c.

Next, when only the voice coil 150c is within the magnetic field of the magnetic gap and the PWM pulse from the PWM section 600 is at H level, the selection section 700 causes the buffer 704 to output an H level voltage and the buffer 703 to output an L level voltage. , and the output nodes of buffers 701 and 702 are brought into a floating state. As a result, a current flows through the voice coil 150c from the diaphragm 111 side to the yoke 104 side.

When the PWM pulse from the PWM section 600 is at L level, the selection section 700 selects voice coils in the same manner as described above and causes each buffer to output a voltage of opposite polarity. As a result, a current flows from the yoke 104 side to the diaphragm 111 side to the selected voice coil.
The details of the drive control device 1000 according to the present embodiment have been described above.

In this embodiment, the input sound signal Vin is supplied to the PWM section 600 via the weighting adder 500, and the PWM section 600 and the selection section 700 drive the voice coils 150a to 150c based on the input sound signal Vin. At this time, the position detection signal Sp, velocity detection signal Sv, and acceleration detection signal Sa indicating the vibration of the vibration system of the speaker are fed back to the PWM section 600 via the variable gain amplifiers 410 to 430 and weighting adder 500 .

According to this embodiment, variable gain amplifiers 410 to 430 are inserted in the feedback paths of the position detection signal Sp, velocity detection signal Sv and acceleration detection signal Sa. Therefore, by controlling the feedback amount and polarity of the position detection signal Sp, velocity detection signal Sv, and acceleration detection signal Sa, it is possible to control the properties of the vibration system.

In the case of a speaker, the equivalent mass Mms of the vibration system, the damping coefficient Qts of the low-frequency resonance, and the springiness Cms of the suspension are important among the parameters called TS parameters (Tiel-Small parameters) that indicate the properties of the speaker unit.

In this embodiment, the equivalent mass Mms of the vibration system can be adjusted by adjusting the gain of the variable gain amplifier 410, and the damping coefficient Qts of the low-frequency resonance of the vibration system can be adjusted by adjusting the gain of the variable gain amplifier 420. By adjusting the gain of the variable gain amplifier 430, it is possible to adjust the springiness Cms of the vibration system suspension.

Specifically, by adjusting the gain of the variable gain amplifier 410, the vibration system equivalent mass Mms becomes lighter when the positive feedback of acceleration becomes stronger, and the vibration system equivalent mass Mms becomes heavier when the negative feedback becomes stronger. Further, by adjusting the gain of the variable gain amplifier 420, the damping coefficient Qts increases as the positive feedback of speed increases, and the damping coefficient Qts decreases as the negative feedback increases. Further, by adjusting the gain of the variable gain amplifier 430, the springiness Cms of the vibration system is weakened when the positive feedback of the position is strengthened, and the springiness Cms is strengthened when the negative feedback of the position is strengthened.

Here, the purpose of the feedback is to improve actuator linearity in addition to parameter control. Therefore, it is effective to use a negative feedback region that basically has the effect of improving linearity. Specifically, by adjusting the amount of negative feedback of acceleration and position, the equivalent mass Mms of the vibration system is set to an appropriate size, the springiness Cms is set to an appropriate strength, and the vibration system is adjusted to the desired resonance frequency F0. set. In this state, the damping coefficient Qts can be appropriately set by adjusting the negative feedback amount of the speed.

Further, according to this embodiment, since the speed detection signal Sv is obtained from the position detection signal Sp and the acceleration detection signal Sa by the speed detection circuit 300, it is necessary to provide a speed detection sensor for detecting the speed of the movable portion of the speaker 100. There is no Therefore, it is possible to avoid an increase in the size, weight, and cost of the drive control device 1000 due to the installation of the speed detection sensor.

In the present embodiment, the speed detection circuit 300 detects the differential of the output signal of the position detection sensor 210 in a band below a predetermined frequency and the integral of the output signal of the acceleration detection sensor 220 in a band above a predetermined frequency. is added to generate a speed detection signal Sv. Therefore, a speed detection signal Sv having a high detection capability over a wide frequency band can be obtained, and the precision of adjustment of the damping coefficient Qts for low-frequency resonance of the vibration system can be improved.

Further, according to the present embodiment, the primary HPF 320 realizes a circuit that obtains the components of the band below a predetermined frequency of the differentiation of the output signal of the position detection sensor 210, and the integration of the output signal of the acceleration detection sensor 220 A first-order LPF 310 realizes a circuit for obtaining the band component of . Therefore, even in a situation where it is difficult to realize an ideal differentiating circuit and an ideal integrating circuit, it is possible to obtain a speed detection signal Sv with high detection capability over a wide frequency band.

In this embodiment, the coil bobbin 112 is provided with a plurality of voice coils 150b, 150a, and 150c, and the speaker 100 is driven by applying current only to the voice coils within the magnetic field of the magnetic gap. Therefore, the following effects are obtained.

In order to realize a vibration system with long stroke and linear characteristics in a loudspeaker such as a subwoofer, it is necessary to provide a difference between the length of the magnetic gap and the length of the voice coil by the length of the stroke. For example, when designing a speaker having a diaphragm with a stroke of 50 mm, a voice coil of 20 mm requires a magnetic gap length of 70 mm, and a voice coil of 70 mm requires a magnetic gap length of 20 mm.

A configuration with a long magnetic gap length is called a short voice coil, but it is very costly due to the use of many expensive magnets. For this reason, in general, a long voice coil configuration that lengthens the voice coil is often adopted.

However, the long voice coil has a large efficiency loss due to the fact that only part of the voice coil enters the magnetic field.

In this embodiment, the position of the voice coil is determined using the position detection signal Sp, and current is applied only to the voice coil in the magnetic field, thereby suppressing wasteful power consumption and achieving high efficiency.

<Other embodiments>
Although one embodiment of the present invention has been described above, other embodiments of the present invention are conceivable. For example, in the above-described embodiments, the speed detection circuit according to the present invention is applied to a drive control device for a speaker, but it may be applied to a drive control device for other devices having movable parts such as robots and actuators.

100...Speaker 150a, 150b, 150c...Voice coil 112...Coil bobbin 111...Diaphragm 220...Acceleration sensor 210...Position sensor 300...Speed detection circuit 410, 420, 430 ... variable gain amplifier, 500 ... weighting adder, 520, 701 to 704 ... buffer, 600 ... PWM section, 700 ... addition section, 700 ... selection section.

Claims (3)

a position detection sensor that detects the position of the diaphragm of the speaker;
an acceleration detection sensor that detects acceleration of the diaphragm;
The sum of a component in a band below a predetermined cutoff frequency of the signal obtained by differentiating the output signal of the position detection sensor and a component in a band above the cutoff frequency of the signal obtained by integrating the output signal of the acceleration detection sensor, a speed detection circuit that outputs a speed detection signal for the diaphragm;
A parameter generation circuit for generating control parameters for drive control of the diaphragm based on respective output signals of the position detection sensor, the acceleration detection sensor, and the speed detection circuit, The feedback gain of the acceleration is used to control the equivalent mass Mms of the diaphragm, the feedback gain of the speed detection signal is used to control the damping coefficient Qts of the diaphragm, and the feedback gain of the detected position in the drive control and a parameter generating circuit for controlling the springiness Cms of the diaphragm. The speed detection circuit includes a high-pass filter that passes components in a band equal to or higher than the cutoff frequency of the output signal of the position detection sensor, and filters components in a band equal to or lower than the cutoff frequency of the output signal of the acceleration detection sensor. 2. The speed detection signal according to claim 1, further comprising: a low-pass filter to pass through; and an adder for adding output signals of the high-pass filter and the low-pass filter and outputting the speed detection signal. drive controller. A plurality of voice coils arranged in the axial direction through which the magnetic field passes are attached to the diaphragm,
4. A selection means for selecting a voice coil positioned within a magnetic field from among the plurality of voice coils based on the output signal of the position detection sensor, and for energizing the selected voice coil. 3. The drive control device according to 1 or 2.

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