### JPS6019397

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DESCRIPTION JPS6019397

FIELD OF THE INVENTION The present invention relates to a speaker driving device.
[Background of the invention] Generally, in small speakers and the like, the level of the low
frequency component of the reproduced sound is lower than that of the other frequency
components, and in order to improve this, the frequency of the reproduced sound of the speaker
The low frequency included in the original signal on the side of the drive bag N (specifically, the
amplifier of the original signal) that drives the speaker so that the characteristic is flat and not
only in the high region but also in the low region. It has been put to practical use to provide a
boost circuit for amplifying the amplitude of the component in particular. FIG. 1 is a circuit
diagram showing such a conventional boost circuit. In the same figure, the circuit portion from
the input terminal 1 to the output terminal 2 constitutes a low-pass boost circuit A, and such a
circuit A is generally provided in front of the power amplifier 4 for driving the speaker 5. In the
circuit A, 3 is an operational amplifier (operational amplifier), 6 is a variable resistor that
determines the amount of boost, 7 is a capacitor, and 8 is a resistor. The turnover frequency fi at
the time of low-pass boost is determined by the following equation (1). fj = concentrated-fi.degree
.-. degree .- (+> where C is the capacitance of Conden 9'7, n, and the resistance value of the
resistive resistor 8. When this low-pass boost circuit A is used, the frequency characteristic of the
speaker drive voltage shifts from 10 to 10 in FIG. 2 (a), and ft is the turnover frequency), and the
sound pressure frequency characteristic of the speaker is 9 to 9 Shift to 'to expand the frequency
range of bass reproduction. However, as shown in Fig. 2 (1), when KdB low-pass boost is
performed in the frequency characteristic 10 at low output with a low voltage-1-bell, it shifts as it
is at high output with a high voltage level. Then, as seen in the frequency characteristic 10, KdB
′? Since the low band previously boosted reaches the saturation voltage level 11 of the power
amplifier 4 earlier, and the voltage levels except the low band can not reach the voltage level
beyond the margin of K dB. There is a drawback that the dynamic range is reduced by K dB. For
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example, assuming that xodI3 low-pass boost is performed, a power value at which saturation
does not occur even with the use of a 100 W power amplifier is 10 W because it leaves a margin
of 10 dB, which is extremely inefficient. For this reason, it is difficult to increase the low range
boost amount, and the effect of expanding the frequency range of the bass reproduction is also
insufficient.
OBJECTS OF THE INVENTION The present invention has been made to eliminate the drawbacks
in the prior art as described above, and it is therefore an object of the present invention to reduce
the dynamic range of the power amplifier driving the loudspeaker. It is an object of the present
invention to provide a speaker drive device capable of expanding the frequency range of bass
reproduction. [Summary of the Invention] In order to achieve the above object, in a speaker
driving device according to the present invention, a VCA (voltage control amplifier) involved in
amplification of an input signal of a speaker driving power amplifier using a low frequency input
signal level. By controlling the gain or the resistance value of the VCR (voltage control resistor),
the low range boost amount can be automatically varied according to the magnitude of the input
signal level. As a result, as shown in FIG. 3 (R), the frequency characteristic of the drive voltage
changes from 12 to 12 and then to 12 as the voltage repe A increases, and the frequency 'IQ' l '!
? As seen in the figure, it can be concluded that what was the maximum when the low range
boost amount was the frequency characteristic 12 was reduced when it was 12 and was reduced
to 12 ′ ′ to only π 3. In this way, Den IJ :, level high))! There is no loss of gichum mink range
even if you On the other hand, the frequency .DELTA..phi. Of the output sound pressure of the
speaker at this time is 1.multidot.1, as shown in the third I * J (b), the frequency is changed from
13 to 13 'Y to 13 and so on. That is, when the output is low at low sound pressure levels, as the
low-pass boost amount is large, the power of the sound pressure level-= constant area greatly
expands to the low frequency area as seen in the characteristic 13. As the sound pressure level
increases, the low range boost amount decreases, so that the constant region of the sound
pressure level decreases as seen in the characteristic 13.13. However, even if the bass
characteristics are changed in accordance with the magnitude of the power output, the loudness
characteristics of the human auditory sense do not sound so unnaturally in the same ear. This is
because as the sound pressure level increases, the human bass feeling further increases. BRIEF
DESCRIPTION OF THE DRAWINGS The invention will now be described in detail with reference
to the drawings. FIG. 4 is a block diagram showing an embodiment of the present invention. The
circuit configuration between the input terminal 1 and the output terminal 20 is different from
that of the prior art shown in FIG. 1 in the embodiment shown in FIG. Please refer to Fig.4. First,
the original signal input from the input terminal 1 is divided into two paths, while the direct
adder 14 is directly connected to the low pass filter (LPF) 15 and the VCA (voltage control
amplifier) 16 to the other end of the adder 14. Applied to the input terminal of.
That is, after low frequency components extracted from the original signal through LPFI 5 are J-
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amplified in VC′A 16, they are added to the original signal in adder 14 (corresponding to
implementation of low-pass boost), and the added output is It is input to the power amplifier 4
through the output terminal 2'F. Therefore, if the gain of the VCA 16 is changed, the amount of
low-pass booth will be changed. An example of the change of the low range boost amount with
respect to the change of the 1 VCA 16 (7) gain when the gain in LPFI 5 is 0 rlB is as shown in
FIG. In FIG. 5, as the gain to VC reaches a negative four and then to zero, and then changes to a
positive value, the low-pass tooth) U gradually increases from Q dB. Will. On the other hand, the
relationship between gain and control voltage {circle over (1)} input to the control input terminal
k of i in VCAI 6 is as shown in FIG. 6 (a). That is, control? ５１１？ ｆｆ。 The pressure gradually
increases from a negative value of −I to −0, and thereafter reaches a positive value of + VL? It
will be appreciated that the gain is linearly increasing monotonically as Qi's Ki. Return to FIG.
According to the principle of the present invention, if the level (amplitude) of the original signal
input to the input terminal 1 is high (and thus the output level of LPFls is high), the low range
boost amount can not be reduced. The gain of VCAI 6 must be reduced (that is, reduced to the
control voltage 1 input to control input terminal k). A control voltage generation circuit S shown
in FIG. 4 and surrounded by a broken line is a circuit for generating a control voltage Ik3
satisfying the above relationship from the output of the LPFI5. The control voltage generation
circuit S includes a rectification circuit PP117, a limiter circuit 18, an integration circuit 19, an
inversion circuit 20, a level shift circuit 21. It consists of FIG. 6 (b) is a graph showing the change
with respect to the input signal amplitude of each signal in the control voltage generation circuit
SK of FIG. Please refer to FIG. 4 and FIG. 6 (b). The output signal {circle over (1)} of LPFI 5 is
rectified by the rectifier circuit 17 and enters the integrating circuit 19 to be converted into
direct current. The level shift circuit 21 shifts the level of the DC output of the integration circuit
19 in the negative voltage direction! The characteristic is as shown in straight line # 22 shown in
FIG. By inputting the output of the integrating circuit 19 to the inverting circuit 20, the output
characteristic of the inverting circuit 20 becomes a straight line 22 'shown in f'l 6IM (b). In order
to limit the maximum boost p, the limiter circuit 18 is provided on the output side of the
inverting circuit 20 to obtain the control voltage Vk of the polygonal line 22 # shown in FIG. 6
(b).
Control voltage vk, VCAI 6 obtained when the level of the input a number ta in the low frequency
region reaches the power amplifier saturation level 11 (see FIG. 2 (+)) by adjusting the circuit
constant of each part 7 (Kane f) <-tyr, p In other words, if the voltage (-Vt,) necessary for the
output to be zero is set, the power amplifier 4 can keep the margin in the dynamic range. It is a
word that saturation of low frequency signal components occurs. FIG. 7 is a circuit diagram
showing a specific circuit example of the embodiment shown in the block diagram of FIG. 4 and
will be described in detail below. The resistor 23 and the capacitor 24 constitute a low bus ratio
A. The cutoff frequency is expressed by the same equation as the equation (1).
Ａ−１ｐＡ２ｖＡ３ｐＡ４はそれぞれオペアンプ（オペレーショナル・アンブリファイア）であ
る。 The operational amplifier A1 constitutes a double-wave rectifier circuit 17 together with the
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diodes 25 and 26. The operational amplifier A2 constitutes an integration circuit 19 together
with a resistor 30 and a capacitor 29. The integration time constant τ is determined by the
following equation (2). (1) where C1 is the capacitance of the capacitor 29, and Ri is the
resistance value of the resistor 30. It is preferable that the time constant τ be a sufficiently large
value so that a signal of frequency 20 Hz is integrated. The resistor 27 and the constant voltage
source 28 constitute the level shift circuit 21. By applying a positive voltage to the inverting
input side of the operational amplifier A2, the output of the operational amplifier A2 is level
shifted in the negative voltage direction. be able to. The operational amplifier A3 constitutes the
inverting circuit 20, and its gain is set to a resistance value of Q dll. The 0 diode 31 and constant
voltage source 32+: L that form a resistance value are connected, and the relay P-Il path 18 is
formed. The control voltage Vk is limited by the constant voltage source 32 during the control
period. The operational amplifier A4 constitutes a summing circuit 14, and its resistance value is
set to H so that two human powers are added to the output, for example, by the same -I + n
weight I'1. Next, according to the present invention, (111 real 1 (+ r Fll y +> t! ｌｔＺ＞。 FIG. 8
is a blower li9 showing another embodiment of the present invention. The embodiment shown in
the figure is different from the prior art circuit shown in FIG. 1 in the circuit configuration
between the input terminal] J-output insulator 2 in the following. . First, the original signal input
from the input terminal 1 is divided into two paths J, one of which is applied to the low-pass
boost circuit A 'and the other to the low-mass filter 15.
The can open boost circuit A is obtained by changing the variable resistor 6 to the low-pass
booth p ′ + l path shown in FIG. 1 by VC 几 (Ti, pressure control resistor) 33 [7. ローパスフィル
タ１５Ｊｅｔある。 In the case of FIG. 8, the zero operation where the inverting circuit becomes
unnecessary is as follows. The original signal inputted from the input terminal 1 is subjected to
low-pass boost through the low-pass boost circuit A and then inputted to the power amplifier 4
through the output terminal 2. The low-pass boost amount in the circuit A can be variably
controlled by VCl23. Therefore, in the control voltage generation circuit S 1, using a low-pass
signal component extracted from the original signal via the LPF 15 ′, the Vci 23 is increased so
that the boost Ji in the circuit person is small and low when the level is high. The control voltage
Vk is generated and input to the control input terminal k. FIG. 29 is a circuit diagram showing a
specific circuit example of the embodiment shown as a block diagram in FIG. 8, and the details
will be described below. Similar to the operational amplifier 3 shown in FIG. 1, the low-band
boost circuit 6 is configured by the capacitor 7 and the resistor 8 according to the above
equation (1), and the boost amount is Is determined by the following equation (3). 几 X1 (= 1 + i··· (3) where R and x are the resistance exhibited by V CR3: ′ ′, and the ratio is the resistance of
the resistor 8. FIG. 10 is a graph showing the relationship between the relative resistance value t

represented by a curve similar to that in FIG. Be Generally, the relative resistance value RX
'exhibited by VCCa2O monotonously decreases due to the DC control voltage Vk changing from
negative to positive as shown in FIG. 11 (R). Therefore, in order to control the resistance value
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representing CCa2O by the 1-bell of the low band input signal component, the AC signal as the
signal component is converted to a DC signal, and the level is further shifted and then the control
input terminal k Need to be applied. The mebe amplifier A1 e A2 in FIG. 9 is a portion
responsible for converting an alternating current signal into a direct current signal, and performs
the same operation as AI and 82 in FIG. In order to obtain a control voltage Vk indicated by the
straight line 38 in FIG. 11), the DC output of the A bias A2 is level shifted in the negative voltage
direction as in the case of FIG. This is the level shift circuit 21. The G-A 31 and H> voltages i 1 i
32 form a limiter circuit 18 for limiting the maximum boost amount like that of FIG. Is limited to
obtain a control voltage Vk as indicated by the straight line 38 in FIG. 11 (b).
Phrase in which the low-range input signal component reached the saturation repe / 1-11 of the
power amplifier by adjusting the circuit rjH number of each part, the control type fI-Vk is
sufficient for the relative resistance value Rno of V CIN · 33 to be 0 If the voltage (+ 'Vt,')
necessary to obtain a close value is achieved, the dynamic range of the power amplifier 4 is not
reduced as in the previous embodiment. The operational amplifier A5, together with the
condenser 34, the capacitor 35, the resistor 36, and the resistor 37, constitutes an addip low
pass filter 15 'of 12 dB10 Ct (the level decreases by 12 dB when the frequency is doubled). The
cut sub frequency of the low pass filter 15 is the turnover I of the low pass boost circuit A? Each
circuit constant is determined by 8σ ′ until it matches the iJ wave number. i'I ¥ 12 Figure (a)
shows the speaker drive voltage when driving the speaker drive area according to the present
invention (a small skier system with a cabinet volume of 1.0 / by the father i)! ・ Bell frequency
characteristics, and Fig.12 (E) shows 7 frequency (1'1) of 1 speaker driving power as a parameter
7 (Q1) frequency of lid force sound pressure level from the speaker (1) 1) The characteristics
shown in these figures are the power amplifier 4): When using OOW's, it is the same as the one
obtained from When 'J # 1 power at the time of hearing is IW, a significant low range boost is
actually achieved to achieve a significant expansion effect of the bass rrr4tE frequency range,
and the maximum output (100 W), the power It can be seen from the chart that Ct can be used to
reduce the dynamic range of the amplifier and to drive the speaker. [Effects of the Invention] As
described above, in the present invention, in the 1-f shell f, the speaker drive device, the low-pass
boost amount can be automatically varied according to the can-off input signal level. There is an
effect that the reproduction frequency range can be largely expanded to the lower side without
reducing the dynamic range of Further, the low-frequency characteristic realized by the present
invention is sufficiently practical without being unnatural to the human ear in consideration of
the loudness characteristic of the human auditory sense.

Brief description of the drawings
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FIG. 1 is a circuit diagram showing an example of a boost circuit used in a conventional speaker
driving device, and FIG. 2 (a) shows the frequency characteristics of the conventional speaker
driving device with and without low-pass boost. The graph wE2 (b) is a graph showing poor
frequency characteristics showing a drawback when the low-pass boost is carried out in the
conventional speaker driving device, and FIG. 3 (a) is a graph showing the present invention.
Graph showing that frequency characteristics change with voltage level, FIG. 3 (h) is also a graph
showing how frequency characteristics of reproduced voice change with sound pressure level,
t44 FIG. Fig. 5 is a block diagram showing an example, and Fig. 5 is a graph showing the change
in the amount of low-pass booth 1 when the gain of CA1 is changed at 4.5 in the same path of
Fig. 4. Figure 6 (a) is a graph showing the control voltage and the gain of the relationship in
VCA16, 6 (1)) is the fourth diagram of fl + i control voltage generating times!
Input signal tA of each signal at il S (graph showing relation to width with respect to width, FIG. 7
shows a concrete circuit example of the embodiment shown by the block diagram in FIG. 4 lcircuit diagram, 8 is a block diagram showing another embodiment of the present invention, FIG.
9 is a circuit diagram showing an example of a J1 curved circuit of the embodiment shown in the
block diagram of FIG. 8, and FIG. 10 is FIG. Figure 11 (= 1) is a graph showing the relationship
between the resistance value exhibited by VCl and 33 and the low-range goose amount of the
low-range boost circuit A '. Figure 11 (= 1) is the control voltage Vk at VCCaB6 and its
presentation J A graph showing the relationship of resistance, FIG. 11 (I) A graph showing the
relationship of I (the control voltage applied to R 33 to the input voltage 41), FIG. 12 (a) FIG. 12
(1) is a graph showing the characteristics of the speaker drive voltage level to the frequency
when the present invention is implemented. Is a graph, which also shows the frequency
characteristic of output sound pressure level from Subi force. Sign Description ■ ······ input
morning 1 child, 2 ...... output suburbs i Ding, 3, A1, 'A2. A: 'l) A4 + A, ..., l A6 ····························
Power-amplifier, • ·················· Speaker, 6 ··························· , 'T. 24.29, 34. 35 · · · · · · · · · · · Hunden ν, 8,
23. 27 °! 30.36, 37 ・ ・ ・ ・ ・ ・ Resistor, 9-9 t 13 t 13 p 13 · · · · · · Speaker output sound
pressure characteristics, 10.10 ', 10.12 12 12. 12 · · · · · · Drive voltage characteristics 11, power
amplifier saturation voltage level, adder, 15.15, low pass filter, 16. VCA (voltage control
Amplifiers, 17 · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · ·
· · · · · · · · · · · · · · · · · · · · · · · · · · · · · 22. 22 ° 22 · · · · · · · · · · · · · · · · · · 22 · 22 · · · · · · · · · · · · · · control
voltage of the VCA, 25, 26, 31 · · · · · · · · · · · · · · · · · · · · · · · · constant voltage source, 33 · · · ··· V C 電

Attorney Attorney parallel tree Akira husband first view the 2vA FIG. 31 VCA glue pine (dB) rod 1
'+ ZuOsamuri OP 弯Ri圧, p-6 first 7 figure 8 figure 0 figure mho figure TrC1? 44 L 4 i E 'x' (d B)
in the negative phase Fig. 11 Control 4 F mouth m1 nid figure (θ) (b)
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