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JPS5756085

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DESCRIPTION JPS5756085
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a characteristic view of a constant voltage
drive type electrodynamic speaker device, FIG. 2 is a characteristic view of a constant current
drive type electrodynamic speaker device, and FIG. The figure which shows the structure of one
Example of the constant current drive type and electrodynamic-type speaker apparatus of a plan,
FIG. 4 is a figure which similarly shows the structure of one Example of an electrodynamic-type
speaker. 1 is a drive coil, 2 is a Shinsuke coil, 3 is an electrodynamic speaker, 4 is a constant
current amplifier, 5 is a constant voltage; type / differential amplifier.
DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a constant current
drive type electrodynamic speaker device. Generally, in an electrodynamic speaker, a drive coil is
provided integrally with a vibration system, and the drive coil is disposed in a constant magnetic
field so that a drive force proportional to the current (signal) flowing through the drive coil can
be obtained. The electrodynamic speaker has an electrical impedance characteristic with a peak
(Zo) at the lowest resonance frequency 10 as shown by the real z in FIG. 1 when driven by a
constant voltage amplifier. The current flowing through the drive coil is not constant over the
entire frequency band depending on the electrical impedance characteristic as indicated by the
dotted line i in the figure, and causes distortion. On the other hand, in view of such a point, there
is a constant current drive system in which an electrodynamic speaker is driven by a so-current
type amplifier so that the current flowing in the drive coil becomes constant regardless of the
electrical impedance characteristic of the drive coil. Proposed. However, since the constant
current type amplifier has a sufficiently large internal impedance, in other words, the damping
impedance DFDF = −03 but the rated impedance of the two varnish beakers, the internal
impedance of the amplifier including the connecting wire viewed from the RO varnish beaker
side is extremely small. Since Dp is considered to be Dp = O, the vibration system is not damped
near the lowest resonance frequency 10, and there is a fundamental defect that the response
characteristic has a peak as shown in FIG. As a method of improving such a fundamental defect,
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conventionally, an MFB method which detects vibration of a vibration system and feeds back a
detected output to an amplifier and a method which limits current at around the lowest common
jfA frequency 10 inside the amplifier are used. Although it is taken, it is Ofufu which is not so
practical because the configuration of both methods is messy. In addition, although the constant
current amplifier has an output current that is constant regardless of the electrical impedance
characteristic of the drive coil, the current distortion generated inside the amplifier can not be
avoided, and hence the drive power of the drive coil is distorted. There was a drawback of that.
(4) The present invention is an improvement of such a drawback, and in a configuration in which
an electrodynamic speaker is driven by a constant current amplifier, low current distortion of the
current (signal) supplied to the electrodynamic speaker, And it aims at effectively damping |
braking a vibration system in minimum resonance frequency fO vicinity. Hereinafter, the
configuration of the present invention will be described in an embodiment shown in FIG. (3) is an
electrodynamic speaker in which a drive coil (1) and an auxiliary coil (2) are provided integrally
with the vibration system, and the drive coil (1) includes an electric rE amplification unit (4a) and
a speaker!
An output signal (sum of signal component and distortion component) of a known constant
current type amplifier (4) comprising a spur power amplifier (4b) is supplied. (5) is a differential
type, constant voltage amplifier having a non-inverted input and an inverted input. The human
power signal of the constant current amplifier (4) is divided by the resistor 13R2 and the level is
adjusted and input to the non-inverting input of the amplifier (5). The voltage (the voltage drop
due to the emitter current of the emitter resistance 'Re') generated in the emitters of the
transistors Q1 and Q2 constituting the amplification part (4b) is added (P) and input. The voltage
(the signal component and the sum of distortion and warmth) input to the inverting input is
subtracted from the input signal voltage of the constant current amplifier (4), and the distortion
component is extracted at the output, and this distortion component is The coil (2) is input, and
the driving force of the auxiliary coil (2) and the driving coil (1) is reversed in polarity. To reverse
the driving force of the drive coil (1) and the auxiliary coil (2) to n, reverse the winding direction
of the drive coil (1) and the auxiliary coil (2), or constant current type The electrodynamic
speaker (3) may be arranged so that the outputs of the amplifier (4) and the constant voltage
amplifier (5) are in the wrong polarity as shown in FIG. 4], for example, the vibrator (6) The drive
coil (1) and the auxiliary coil (2) are wound around the bobbin (7) fixed to the top of the box, and
both coils (1) and (2) are partially attached to the plate (8), magnesite (9) and the center The
lower plate having a center pole (10) is positioned in the magnetic gap of the magnetic circuit
formed by 6 in (11), and the inner and outer peripheral portions of the L diaphragm (6) are the
central support (12), the periphery It has a structure supported on 7 frames (14) via a support
(13). In the above configuration, assuming that the current flowing through the emitter resistor
ReXRe of the transistor Q1 and Q2 of the push-pull power amplifier (4b) of the constant current
type amplifier (4) to explain the operation of the present invention is II and I2, the emitter
resistor Re , R, the voltage drop due to {circle over (1)}, {circle over (2)} is V + = ReI + V2 = ReI2.
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The current It, I2 is a signal component 1. And the distortion component Id, V1 = Re (Isl + Idt) V2
= Re (Is2 + Id2). Once, the input signal type 1-Eei of the constant voltage amplifier (5),? ei = KVi(V1 + V2) = KVi-Re (ISt + Is2 + 1 + 1t + Id2) where vi: the input signal voltage of the constant
current amplifier (4): The adjustment rate is determined by the resistors' R1 and R2.
Therefore, assuming that the gain of the constant voltage type amplifier (5) is m, the output
signal voltage eo is eo = m (KVi-Re (Ist + Is2 + Idt + Id2))-A (KVi-Re (Isl + l52))-Be (Idl + Id2) ).
Here, if the adjustment ratio K is determined by adjusting the resistance R2 so as to be KVi−Re
(Is1 + Is2), then eo = −Re (Idi + Id2). That is, the output signal voltage e of the constant voltage
type amplifier (5) becomes proportional to the output signal Io of the constant current type
amplifier (4), ie, the distortion Idt-1-Id2 of 11 + I2. Now, assuming that the drive force of the
drive coil (1) is F + and the drive force of the auxiliary coil (2) is F2, Fl = BtlII. 8 = BI 41 (11 + 12)
= Bttt (Is 1 + Is 2 + Iat + Ia 2) where B 1: magnetic flux density of the magnetic field of the drive
coil lll 馳 drive coil coil length, similarly F2 = 8212-! −f − = − B2t2AReId1 + Id2) or B2:
magnetic flux density t2 of the magnetic field of the auxiliary coil: coil length of the auxiliary coil
2: electric impedance of the auxiliary coil once the driving force of the electrodynamic speaker
(3) F becomes F thousand F1 + F2 = Btzt (Ist + Is2 + Idl + Id2) -B2t2R6 (Idl + Id2) 1- 1-9 = B141
(I81 + 152) + 1B1t1-B2t2Re .-. Quadrature.- (Idl + Id2). Here, if each constant is determined such
that ReBltl = B2t2-1, then F = BIA1 (Ist + 152), and the driving force F becomes proportional to
the signal component IS1 + IS2. In the constant voltage type amplifier (5), the internal impedance
of the amplifier including the tangent wire viewed from the side of the electrodynamic slider (s)
coil auxiliary coil (2) is approximately regarded as "0". Both ends of the auxiliary coil (2) are
considered to be electrically short-circuited to form a closed circuit with respect to a back
electromotive force generated in the auxiliary coil (2) vibrating in a magnetic field. In the past,
this counter electromotive charge causes a current to flow to the auxiliary coil (2), and a braking
force proportional to this current is obtained 6, and thus, the braking force causes the vibration
system to be damped near the minimum resonance frequency fO. Since this is effectively
performed, it is possible to effectively suppress the peak around the lowest resonance frequency
fo of the response characteristic. As described above, in the present invention, in the
configuration in which the electrodynamic speaker is driven by the constant current amplifier,
the output signal of the constant current amplifier is input to the drive coil of the electrodynamic
speaker to drive the constant current. The distortion component of the constant current amplifier
detected by the constant voltage amplifier is input to the auxiliary coil for constant voltage
driving, and the driving force of the driving coil and the auxiliary coil is reversed in polarity.
Therefore, the driving force due to the distortion component is canceled and the driving force of
the electrodynamic speaker becomes proportional to the signal component, and the auxiliary coil
is driven with a constant voltage by the distortion component. The vibration system is effectively
damped by the back electromotive force generated in the coil, and it has excellent advantages
such as obtaining a flat response characteristic in which a peak near the lowest resonance
frequency is suppressed..
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