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DESCRIPTION JP2005287050

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DESCRIPTION JP2005287050
PROBLEM TO BE SOLVED: To provide a method that enables maximum use of the power
available by phantom power supply for supplying an audio amplifier. The invention relates to a
method for remote control of a microphone comprising at least one microphone capsule (9) and
at least one auxiliary power receiver. The energy of this microphone is supplied from the
phantom power supply via the cable lead of the audio cable. Also, a feature of the invention is
that the frequency modulation voltage is supplied as a control signal to at least one of the two
cable leads (1, 2), via which leads also to phantom power supply, and a microphone The
frequency modulation voltage on the side is supplied to the control electronics (39) and sends
commands to the individual power receivers according to the frequency modulation control
signal. [Selected figure] Figure 1
Remote control of phantom powered microphones
[0001]
The present invention relates to a method of remotely controlling a microphone, which
comprises at least one microphone capsule, an audio amplifier, a power supply circuit, a
processor, control electronics, an A / D converter, a D / A converter, an LED display etc. And at
least one auxiliary power receiver selected from the group, and this energy is supplied from the
phantom power unit via the cable lead of the audio cable.
[0002]
The power supply of the microphone is conventionally provided by using a power supply, for
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1
example a mixer.
During phantom power supply, the positive terminal of the supply voltage is supplied from two
equal feeder resistors via the two cable leads of the audio cable. The return of current originates
from the third lead connected to pin 1 of the XLR plug. In order to be able to efficiently use the
voltage supplied from the phantom power supply for the condenser microphone power supply,
the microphone current consumption is minimized to prevent an excessively large voltage drop
in the feeder resistance Should be. The maximum current consumption with a 48-V condenser
microphone is 10 mA. Phantom power supply is standardized here according to DIN EN 61938
(formerly IEC 268).
[0003]
In order to generate the polarization voltage of the microphone membrane (generally, the value
of this voltage is in the range of 20 Vdc to 100 Vdc), a combinational circuit part or a voltage
converter is mainly used. The remaining microphone electronics are typically powered by linear
regulation, which maintains either the supply voltage or the supply current at a predetermined
value. For microphones with low power consumption, this type of power supply is appropriate. If
the power consumption in the microphone is increased, for example, if the power consumption is
increased by using a processor, an A / D converter, an LED display, etc, then linear regulation
becomes a problem. In this case, most of the energy made available by the phantom power
supply is canceled within the elements of the linear regulation. However, according to the
standard phantom power supply, this is due to its current being limited by the feeder resistance,
so the maximum supply voltage of the audio amplifier jumps down due to the linear adjustment
of the microphone, reducing the maximum audio output voltage of the microphone Bring.
[0004]
There are other problems with the generation of polarization voltages. This voltage is usually
supplied to the microphone membrane via a high ohmic resistance. The power required here is
very low. Also, it is difficult to fabricate a voltage regulator that efficiently generates this virtually
power-free polarization voltage.
[0005]
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There are other problems with remote control of microphones. The use of a microphone
increases the need to be able to adjust or change important microphone parameters via remote
control. These parameters include the polarization voltage on the membrane of the condenser
microphone and the associated sensitivity, microphone directivity, type of phantom power supply
(12V, 24V or 48V), product number, calibration data from the manufacturer, as well as signals.
And a connectable filter of the audio signal.
[0006]
DE 3933 870 A1 discloses a method of remote control of microphone parameters such as
directivity, step sound filter and pre-attenuation. In this process, the supply voltage transferred to
the cable lead is adjusted via the remote control unit, for example, the amount of supply voltage
is adjusted in the mixing table in such a way that it represents the control information of the
microphone. At the microphone side, the supply voltage is released and supplied to the
evaluation circuit, which generates a control signal as a function of the amount of supply voltage.
By doing the data transfer in this way, only a small amount of control information can be sent to
the microphone, so the parameters can also be remotely controlled with only a small amount of
microphone.
[0007]
US 6028946 A (and corresponding EP 0 794 686 A2) discloses a digital microphone. The audio
signal is digitized using an analog-to-digital converter, and the resulting two-channel digital audio
signal is transmitted via a symmetrical two-wire conductor to the associated amplifier. The power
supply to the microphone is provided from this symmetrical two-wire lead. By the way, it is
implicitly mentioned that in the associated amplifier, the pulses providing remote control of the
microphone settings can be modulated to the voltage of the microphone power supply. It should
be noted in this regard that the notion of digital microphones and the associated transmission of
digital signals is completely different from analog microphones, where analog signals are
transmitted from phantom power lines. The additional modulated signal on the line where the
digital signal is transmitted simultaneously does not cause problems. Because digital audio
signals can be easily separated from the additionally modulated signal.
[0008]
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A problem that has not yet preferably been solved relates to generating a polarization voltage on
the condenser microphone membrane. The degree of polarization voltage is taken directly into
the degree of sensitivity of the microphone capsule. As a result, polarization voltage can also be
used to adjust the sensitivity of the capacitor capsule. This is particularly advantageous with
regard to using a double membrane capsule part. This is because these capsule parts allow not
only adjustment of sensitivity but also adjustment of directivity when separately supplying
individual films having polarization voltage.
[0009]
Methods for adjusting the polarization voltage using fixed or trimmer resistors are well known. In
this process, temporary adjustment of the polarization voltage occurs while assembling the
microphone. The directivity here is once defined by the fixed resistivity. With this method it is
possible, although only difficult, to compensate for the resistance in sensitivity caused by
assembling the microphone capsule part in addition to that by the aging process. For this
purpose, reinforcement of the polarization voltage is required during acoustic measurement of
sensitivity, with the microphone ready to be assembled. Also, if the directivity is different, it is not
possible to reinforce the sensitivity of sensitivity.
[0010]
US Pat. No. 4,541,112 A (and corresponding EP0096778B1) discloses an electroacoustic
transducer with adjustable pulse generator, which converts DC to AC. The transformers
connected to the pulse generator make it possible to inductively isolate the individual power
receivers. The supply loop is inductively connected to the alternating current generated from the
pulse generator using separate windings on the transformer. This document is incorporated
herein by reference.
[0011]
In conjunction with the microphone power supply, the power made available by the phantom
power supply is optimally used, requiring separate output reception such as audio amplifier,
microphone capsule, processor, controller, A / D converter, LED display etc. A solution is needed
if it is converted to an operational voltage.
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[0012]
It is an object of the present invention to provide a method which makes it possible to use the
maximum of the power available by means of the phantom power supply supplying the audio
amplifier.
[0013]
These objects are achieved by a microphone comprising a power supply circuit individually in the
power receiver, which microphone is connected to a control unit for converting direct current,
which is transmitted to alternating current via the cable lead of the audio cable, to this control
unit And a supply loop to each of the power receivers, wherein the supply loop is inductively
coupled to the alternating current generated from the control using separate windings of the
transformer, The feed loops are also inductively coupled.
[0014]
In this process, all the voltages required of the power receiver are generated from a power
supply circuit, for example a DC / DC converter, which has the following properties.
The power supply circuit is regulated or operated in such a way that the power is compatible
with the phantom power supply unit.
Thus, the maximum power available to the phantom power supply unit can always be consumed
by the power supply circuit of the microphone.
The main current consumption of the power supply circuit is constant. The power supply circuit
thus acts like a constant current sink to the phantom power supply. The separate supply loops
for the separate power receivers are separated in the power supply circuit by means of
transformers and the different requirements of the separate power receivers (ie large voltage and
small current to polarization voltage, medium to audio amplifier) Requirements for providing
small voltages and large currents to digital electrons with as little power loss as possible.
[0015]
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The advantageous effect of the condenser microphone according to the invention is clear. That is,
with the provided power supply concept, the power made available by the phantom power unit is
optimally used. As a result, the microphone may be equipped with new functions (e.g. remote
control, new operation concept, possibility of auto-reinforcement etc) while the maximum audio
output voltage of the microphone remains the same. The generation of an essentially power-free
polarization voltage actually occurs as a by-product of the simple additional winding on the
transformer.
[0016]
As a result of using the highest possible ohmic level, with the constant power supply at the input
of the power supply circuit, the switch ripple of the power supply circuit or the DC / DC
converter has the other advantage that it can be removed very easily.
[0017]
Possibility of adapting the microphone, eg changing the polarization voltage to change the
sensitivity, continuously changing the directivity of the double membrane capsule part, and
control to the microprocessor to store the measurement data Control data at a substantially
faster rate, as the possibility of adapting to modify the frequency range, maximum audio output
voltage, amplification, or THD of the audio amplifier increases in addition to changing the signal.
There is a need to transfer to the microphone through.
[0018]
According to the invention, these objects are achieved by a method for remote control of a
microphone.
This means that the frequency modulation voltage is supplied as a control signal to at least one
of the two cable conductors, via which also the phantom power supply is generated, and the
frequency modulation voltage on the microphone side is the control electronics, For example, it is
supplied to a microcontroller or a CPLD (Complex Programmable Logic Device), and sends
commands to individual power receivers according to a frequency modulation control signal.
[0019]
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In this way, the frequency modulation voltage is above the supply voltage of the phantom power
supply.
Data transfer occurs, for example, from a transmitter located in the mixing table or equipment in
front of the mixing table to the microphone via an audio line. The carrier frequency of the FSK
modulation is now higher than the audio frequency range to be transmitted by the microphone.
[0020]
By using frequency modulated signal transmission, substantially faster data rates may be
obtained, as opposed to direct current and transmission. As a result, using a certain protocol,
many parameters may be transmitted. The carrier frequency of the modulation is preferably
approximately 100 kHz and can be separated from the audio signal using a filter.
[0021]
In order to meet the need for low tolerance within the polarization voltage of a condenser
microphone (e.g. ± 0.5 dB tolerance in terms of sensitivity), the flexibility of the polarization
voltage even in the assembled state of the microphone There is a need for a solution that allows
for
[0022]
According to the invention, this is achieved by means of a condenser microphone, which
comprises at least one circuit for adjusting the polarization voltage (the circuit for adjusting this
polarization voltage comprises an analog adjustment loop supplied with the unadjusted voltage).
And providing a digital adjustment loop, wherein the digital adjustment loop comprises control
electronics, such as a microcontroller or CPLD, which provide the analog adjustment loop with
the desired value of the polarization voltage calculated using the correction factor. And, for the
purpose of feedback, the output of the analog regulation loop is connected with the control
electronics.
[0023]
In this process, the polarization voltage is regulated by a voltage regulation loop integrated into
the microphone.
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The desired value of the polarization voltage is preset in this circuit by the control electronics via
the D / A converter.
As a result, adjustments can be made to evaluate the polarization voltage in detail. The desired
value of the polarization voltage can also be transmitted to the control electronics by remote
control. The resistance of the polarization voltage obtained is determined by the resistance and
temperature characteristics of the reference voltage source.
[0024]
By adjusting the polarization voltage through the microphone's digitally controlled adjustment
loop, it is very accurate, resistant to interference, and capable of remotely controllable
adjustment to the voltage divider electrode of the condenser microphone Become. As a result, it
is possible during the manufacture of the capacitor microprocessor and during the measurement
of the measurement technology to reach very limited requirements of tolerance with regard to
sensitivity and directivity. A remotely controllable adjustment of the polarization voltage has the
advantage that readjustment with fixed or trimmer resistance is no longer necessary, this fact
having a positive effect on cost. In addition to the existing solutions with a fixed set of
polarization voltages, the following additional possibilities arise in the context of the condenser
microphone according to the invention.
[0025]
If the directivity is adjusted separately as a function of the individual performance of the double
membrane capsule part, the sensitivity of the different microphones can be reinforced and the
required correction factor needed to reinforce the polarization voltage can be stored .
[0026]
In combination with the remote control, for example, the polarization voltage can be measured
during acoustic measurement with a closed microphone, as described above, and the correction
factor can be stored again.
[0027]
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It is particularly advantageous to have the possibility of changing the polarization voltage of the
remotely controllable microphone and thus changing the directivity effect during operation.
For example, the microphone can acoustically follow the moving actor, for example, during an
opera performance.
[0028]
The condenser microphone according to the invention makes it possible to remeasure the
sensitivity of the microphone due to aging without having to disassemble the microphone, which
also means a cost savings for the user.
Thus, while replacing the microphone capsule, the original sensitivity of the microphone can be
recalibrated by remote control later, ie after capture.
[0029]
Preferably, the carrier frequency of the control signal is approximately 100 kHz. Also, an audio
signal is transmitted via the cable lead and a frequency modulation voltage is fed to the cable
lead.
[0030]
Also preferably, the frequency modulation voltage is supplied to the cable lead and the cable lead
as a common mode signal to the same extent. Also, the frequency modulation voltage is
separated from the audio signal by the input differential amplifier. Alternatively, the frequency
modulation voltage is separated from the speech signal by a low pass filter.
[0031]
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Furthermore, preferably, in response to a control signal from the remote control unit to the
microphone, a data recognition message is sent to the remote control. Here, the data recognition
message is also a frequency modulation signal. SUMMARY The present invention relates to a
method of remotely controlling a microphone, which comprises at least one microphone capsule
part (9), an audio amplifier (10), a power supply circuit (11), a processor, control electronics (39).
, At least one auxiliary power receiver selected from the group of: A / D converter (44), D / A
converter (46), LED display (25), etc., and this energy is an audio cable It is supplied from the
phantom power supply unit (31), so-called phantom power supply, via the cable leads (1, 2) of.
[0032]
The invention provides that the frequency modulation voltage is supplied as a control signal to at
least one of the two cable leads (1, 2) via which also a phantom power supply occurs, and
frequency modulation of the microphone side A voltage is supplied to the control electronics
(39), for example a microcontroller or CPLD, characterized by sending commands to the
individual power receivers according to the frequency modulation control signal.
[0033]
In the following, the invention will be further described with reference to the figures.
[0034]
FIG. 1 is a block diagram showing the main components of a microphone according to the
present invention.
The phantom power supply of this microphone (shown in FIG. 5) is equivalently placed by the
phantom power supply unit 31 behind a plug 4 (eg, an XLR plug) with three poles in or in front
of the mixing table Is carried out via the feeder resistances 32, 33.
Such phantom power supply is shown in FIG. According to the standard, three phantom power
supplies are possible, ie the relevant value of the feeder resistance supplying 12V, 24V or 48V is
680Ω, 1.2kΩ or 6.8kΩ respectively. Line 1 and line 2 here represent the cable leads supplied
from the phantom power supply unit, and line 3 represents the ground line normally connected
to the ground cable shield. The phantom power supply unit 31 is connected to the input of the
power supply circuit 11 according to the invention via an audio cable, that is to say via the line 1,
the line 2 and the resistors 5 and 6. The capacitance 7 smooths the supply voltage to ground.
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The resistors 5 and 6 are feeder resistances of the microphone. These resistors are used to
isolate the microphone power supply from the output of the audio amplifier 10. The microphone
feeder resistors 5 and 6 are assigned as additional internal resistors of the phantom power
supply 31. A power match exists when the internal resistance of the phantom power supply unit
matches the internal resistance of the power supply circuit 11 of the microphone. Thus, in the
case of power adaptation, half of the voltage of the phantom power supply is the supply voltage
to the power supply circuit 11. This power, which is the maximum value that can be generated
from the phantom power unit 31, is now distributed via the power circuit 11 in the form of a DC
/ DC converter to all the energy-consuming parts of the microphone. The overpower is now
generated for the audio amplifier 10 so as to make the maximum audio output voltage of the
microphone as high as possible. For different power supply voltages (according to the standard
12V, 24V or 48V), the circuit can be designed in such a way that the power adaptation for
different phantom power supplies occurs automatically. This task is then performed by the
controller 12 described below.
[0035]
The power supply circuit 11 includes a power supply 13, a control unit 12, and a transformer 14
connected to the control unit 12. The control unit 12 with the transformer 14 forms a circuit unit
in which the DC voltage is converted into an AC voltage. In this case, this transformer is part of
the circuit that generates the oscillation. Naturally, the alternating current can also be generated
by the control unit 12 independently of the transformer. The control unit 12 thus consists of an
oscillating circuit independent of the transformer, which generates an alternating current.
Transformers only provide the function of converting alternating current into discrete output
voltages.
[0036]
In the preferred embodiment, the AC signal has a frequency in the range of 100 kHz to 130 kHz.
AC signals can also oscillate freely. This represents the possibility of the simplest embodiment for
such a circuit. The only important factor is that the frequency range of the AC signal must be
outside the audio frequency range in order not to generate interference with the audio signal
which can not be eliminated by simple filtering. On the one hand, this frequency may not be too
high, otherwise the efficiency of the circuit is reduced and transmission interference can be
expected.
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[0037]
Another advantage of using a frequency of 100 kHz to 130 kHz is that this frequency can also be
used as a circulating pulse to the control electronics 39 provided in the microphone. As a result,
interference signals generated by digital techniques are minimized. Because, besides this, no
mixed product is generated between the digital cycle time and the oscillating frequency of the DC
/ DC converter.
[0038]
The generated AC signal is supplied to the transformer 14. As a result of the discrete windings on
the transformer, discrete current loops 15, 16 and 17 are produced to be supplied to the
individual energy consuming parts. This separation makes it possible to simultaneously supply
high current consumption and low voltage consumers as well as high voltage but low current
consumers while minimizing power losses as much as possible. The diodes 18, 19, 20 and the
capacitors 21, 22, 23 of the individual supply loops 15, 16, 17 represent a rectifier circuit which
converts the AC voltage into a DC voltage. Naturally, more complex and more efficient
rectification circuits can be provided to the individual supply loops from this technical field. The
feed loop 16 serves to provide the microphone capsule 9 with a polarization voltage, which is
supplied to the microphone capsule portion 9 via the resistor 8.
[0039]
The invention is of course not limited to condenser microphones, as any kind of microphone, in
particular a dynamic microphone, can be connected to the phantom power supply. The individual
power receivers are supplied by phantom power in the same manner as shown in FIGS. 1 and 2.
However, in the case of a dynamic microphone, the supply loop 16 is not necessary since no
polarization voltage is required.
[0040]
By using a constant current source 13 at the input of the DC / DC converter, the uptake of a
constant primary current is ensured. The constant current source 13 acts like a constant current
sink with respect to the phantom power supply unit 31 and represents a constant current source
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12
to the power supply circuit 11. The constant current source 13 with the highest possible ohmic
level simplifies, among other effects, the filtering of the switching ripple generated during DC /
AC conversion, which simultaneously overlays the interference present on the audio signal
Electrical components of this type that are very well known to those skilled in the art who are
familiar with this art. Examples of constant current source circuits from this technical field are
shown in FIGS. 3 and 4. FIG. 3 shows a "transistor LED" constant current source with bipolar
transistors. With this current source, the LEDs operate in the flow direction. As a result, at the
same time as a constant voltage is supplied to the LED, such a voltage is also supplied to the
series connection of the basic emitter diode of the transistor having the emitter resistor. The
current delivered by this current source is thus I = (ULED-Ubc) / Re, where ULED is the voltage
drop across the LED, Ubc is the base emitter voltage, and Re is the emitter resistance.
[0041]
The circuit of FIG. 4 includes a constant current source having two counter connected
degeneration transistors 28, 29 and additionally has a constant current source 30 integrated.
This circuit is preferred for better performance in terms of constant current and higher starting
resistance. Current source 30 generates a voltage drop at spare resistor Rc equal to the voltage
drop URc at emitter resistor Re of transistor 28. The current of the constant current source is
now I = URc / Re. The transistor 29 now forms with the transistor 28 a degraded system of
counter connections that guarantees comparable voltage drops in the resistors Rc and Re. As a
result, the current I of the current source is also kept constant. The current of the current source
30 is therefore smaller by a factor of 100 than the constant current finally flowing to the DC /
DC converter 11.
[0042]
Naturally, other types of constant current sources may also be provided, such as current sources
with inverting operational amplifiers, Howland current sources, etc.
[0043]
The supply voltage generated by the power supply circuit 11 to the audio amplifier 10 is not
regulated in the preferred embodiment.
In the supply loop 16 of the microphone capsule 9, adjustment circuits 47 and 48 are provided
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between the diode 18 and the resistor 8, which comprises a digital adjustment loop 47 and an
analog adjustment loop 48 and are supplied to the microphone capsule 9 Provided for the
polarization voltage. FIG. 6 shows, along with FIG. 7, such a preferred remotely controllable
adjustment circuit 47 and 48. The control signal required to adjust the polarization voltage can
be transmitted via at least one cable lead of the two cable leads 1 and 2. The detailed structure
and method by which such conditioning circuits 47 and 48 operate is further described below.
Adjustment circuits can also be provided in the remaining supply loops, if the current and voltage
limits are not already defined in the digital circuit part. In the preferred embodiment of FIGS. 1
and 2, the conditioning circuit is not included in the supply loop 15 to the audio amplifier 10. As
a result, the entire power (processor, control electronics 39, polarization voltage in the
microphone capsule 9, power not used for other circuit parts such as the A / D converter 44, D /
A converter 46, LED display 25) It is available to the amplifier 10. As a result, a high maximum
audio output voltage can be achieved with the current saving design of the audio amplifier 10 to
achieve a high maximum audio output voltage. In principle, the supply voltage of the resulting
audio amplifier 10 may also exceed the voltage made available by the phantom power supply.
From the method of operation of the power supply circuit 11, it is also possible to generate very
simple positive and negative supply voltages for the audio amplifier 10. As a result, the audio
amplifier 10 can also use the ground as a natural potential. The supply voltage of the audio
amplifier (10) can thus be symmetrical with respect to ground.
[0044]
In a more advantageous embodiment, said type of DC / DC converter 11 operates with an
efficiency of approximately 82%. Since power is dissipated in the DC / DC converter, even in the
most advantageous cases, it is advantageous to connect the consumer in series with the DC / DC
converter, if possible. As a result of using the constant current source 13, by connecting the
consumer to a constant current consumption, for example a logic supply 24, a fixed direct
current, for example a control electronics 39 or an LED display 25, an A / D converter 44,
Alternatively, it is readily possible to make available for series connection to the DC / DC
converter 11, such as for the D / A converter 46.
[0045]
A corresponding embodiment of the power supply circuit 11 is shown in FIG. Compared to FIG. 1,
the difference is that only the polarization voltage and the voltage for the audio amplifier 10 are
generated from the DC / DC converter. For example, other consumers, such as the logic supply
24 which makes available a fixed predetermined direct current to the control electronics 39 and
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the LED display 25, are connected in series to the DC / DC converter. The digital feed series
connected DC / DC converter 11 acts as an active load resistor, the energy used in this resistor is
not converted to heat, but in most cases the audio amplifier 10 of the microphone capsule 9 and
the polarization Converted into usable supply power with voltage.
[0046]
As shown in FIG. 2, a zener diode 27 is provided in conjunction with a logic supply 24 which
makes available a reference voltage and additional digital electrons, which Zener diode is
particularly suitable for voltage stabilization. Through the diode 27, any current not dissipated
but sent by the constant current source 13 is released to the ground. In principle, other constant
current sources or shunt regulators can be used instead of the zener diode 27.
[0047]
The released power is a product of the current of the constant current source 13 and the voltage
supplied to the power supply circuit 11. In the block diagram of FIG. 1, the full voltage is
supplied to the DC / DC converter 11 and all the voltages are generated from the DC / DC
converter. In the block diagram of FIG. 2, the voltage is divided into a part that supplies the DC /
DC converter 11 and a second part that supplies the LED 25 and the digital supply. The DC / DC
converter represents an active spare resistance to the LED 25 or digital supply. The current
consumption of the digital supply is not constant, but since the current I is kept constant by the
current source 13, any overcurrent which may be present has to be removed via the zener diode
27 depending on the operating conditions of the digital electronic. For the supply of the audio
amplifier 10, the power P = I × DC / DC converter available voltage × DC / DC converter
efficiency is available. For LEDs and digital electronics, power P = I × voltages at digital
electronics and LEDs are available.
[0048]
Give an example to illustrate. The current consumption of the audio amplifier 10 is
approximately 0.8 mA in an uncontrolled state, and the current consumption of digital electrons
is approximately 4.2 mA. The current source 13 delivers a constant current of approximately 4.7
mA. Thus, in this special case, it is more advantageous to use a series connection to the DC / DC
converter, via the DC / DC converter, to pass the voltage for digital electrons. Furthermore, in
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another development, it is more advantageous for all the required voltages to pass through the
DC / DC converter as in the solution shown in the block diagram of FIG. 1 in terms of energy.
[0049]
By converting the supply voltage to the audio amplifier 10 in this case, the maximum power
available to the amplifier is obtained, ie P = 4.7 mA × 18 V × 0.82 = 69 mW. The voltage at the
audio amplifier 10 is thus U = P / I = 69 mW / 0.8 mA = 55V. This voltage is much higher than
the 24 V voltage delivered by the phantom power supply 31 during power adaptation. However,
since the polarization voltage is also generated on the membrane of the capsule part 9, the
actually obtained supply voltage value of the audio amplifier 10 is slightly lower than this value,
but it can still be used without a DC / DC converter Much higher than 24V.
[0050]
The figure shows a microphone 54, which is connected to a transmitter or remote control unit
55. The remote control of the microphone parameters of interest here takes place directly via the
audio cable, ie line 1, line 2. The control unit 55 is preferably located on or in front of the mixer.
A microcontroller 35 with a parameter control input 34 controls the frequency modulation
device 36 and applies the frequency modulation signal to the two cable leads 1 and 2 of the
audio cable to the same extent. The frequency modulation signal may then be suppressed as a
common mode signal of the input differential amplifier 42. At the same time, the supply voltage
of the phantom power unit 31 is supplied to the two cable conductors 1, 2 via the feeder
resistors 32, 33. In a preferred embodiment, the frequency modulation signal is supplied to only
one of the conductors of the audio cable, ie only to the conductor 2 not intended for audio
signals.
[0051]
In a preferred embodiment, the frequency modulation signal is generated by FSK (frequency shift
keying) or CPFSK (continuous phase FSK). Both modulations are means known from digital data
transfer technology. In principle, it is also possible to use ASK (amplitude shift keying) or PSK
(phase shift keying) modulation. However, ASK is more susceptible to interference, and PSK
modulation is more difficult to perform from the point of view of circuit technology. In contrast
to the known application of the above method, the key element when used in a microphone is
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that the modulation signal has to be separated from the analog signal, ie the audio signal. Even
when the frequency modulation signal is applied only to the conductor 2 not intended for the
audio signal, the capacitive coupling between the two conductors 1 and 2 of the audio cable
causes interference to the audio signal. This capacitive coupling is determined by the structure
and length of the audio cable. Thus, it is difficult to filter out the interference, despite the fact
that the control signal is known.
[0052]
In the microphone, the frequency modulation voltage is separated from the audio signal by
means of a filter 37 (for example a band pass filter) and the control information contained
therein is a control electronics 39 (for example a microcontroller or CPLD (coupled
programmable) Logic circuits)). The cable lead 2 is separated from the ground via a capacitance
43. Control electronics 39 are connected in front of a comparator 38 which functions as a
voltage comparator. The command from the output of the control electronics 39 is, for example,
the power supply circuit 11 (shown in FIGS. 1 and 2), the audio amplifier 10, the processor, the
control electronics 39, the A / D converter 44, the D / A conversion. Reach the container 46 and
so on.
[0053]
The frequency modulation of the two audio lines 1 and 2 is carried out in the remote control unit
55, which is preferably located close to the mixing table. In the remote control unit 55, on the
one hand, the carrier frequency must be applied in the direction towards the microphone 54, and
on the other hand, in the direction of the mixing table, all modulation frequencies have to be
suppressed. Only the audio signal coming from the microphone 54 has to be transmitted. In
order to make the suppression of the modulation frequency simpler, the modulation is performed
on both voice lines 1 and 2 at the same level. In remote control unit 55, as a result, the frequency
modulation signal appears as a common mode signal to input differential amplifier 42, which
may be suitably suppressed as a common mode signal. In a second variant of remote control,
frequency modulation occurs only on the line which does not pass voice signals, ie line 2. In the
direction of the mixing table, in this type of remote control, the frequency modulation signal can
be removed by filtering through the low pass filter 41. The phantom power supply unit 31
comprises, in addition to the feeder resistors 32, 33, a differential amplifier 42 and a low pass
filter, but it does not have to be integrated in the remote control as shown in FIG. For example,
they can also be provided at the mixing table.
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[0054]
During transmission of the control signal from the remote control unit 55 to the microphone 54,
in order to ensure that the control signal has actually reached the control electronics 39, the
control electronics 39 receive the control signal and receive a data recognition message. To the
remote control unit 55. Data recognition messages may also be frequency modulated signals.
Data recognition messages for remote control functions are not absolutely necessary. However,
the cost of adding electronics increases the reliability of the system.
[0055]
Said method of remote control is, of course, not limited to condenser microphones. That is
because any kind of analog microphone, in particular a dynamic microphone, can be activated as
a means of phantom power supply.
[0056]
The microphone according to the invention can be connected to a standard phantom power
supply without affecting the function of the microphone. If the phantom power supply comprises
a device for remote control, the microphone is capable of remote control. The microphone in
other cases may be actuated by a switch attached directly to the microphone.
[0057]
FIG. 6 shows a condenser microphone according to the invention, in which regulation of the
polarization voltage occurs as a means of a two-step control regulation loop. Here, the second
digital adjustment loop 47 overlaps the internal analog adjustment loop 48. As a result, it is
possible to generate a polarization voltage of the microphone capsule 9 that is well tuned and
interference free.
[0058]
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A preferred frequency modulation signal with control information is transmitted via a cable lead
and is further connected to the phantom power unit 31 and reaches the control electronics 39
via the filter 37 and the comparator 38. A detailed description of the remote control of the
microphone according to the invention has already been mentioned above. See also, in particular,
FIG. Control of the control electronics 39 may also occur through adjusting the device of the
microphone itself or activating the elements. Also, the control electronics can be connected to a
wireless or infrared interface or to a lead interface for the purpose of wireless transmission. The
desired value obtained for the control signal due to the polarization voltage is sent by the control
electronics 39 via the D / A converter 46 to the analog adjustment loop 48. Instead of the D / A
converter, it is also possible to use a pulse width modulation circuit (PWM). Although PWM
circuits have lower conversion speeds, they are very suitable for adjusting their level to these
converters since they are inexpensive. FIG. 7 is an example embodiment, where control
electronics 39 (eg, microcontroller, CPLD, D / A converter, or PWM 46) operate in an analog
conditioning loop 48. Many analog tuning loops are well known in the art to those skilled in the
art who are familiar with the present invention, and it is easy to select dimensions for such
tuning loops. In the schematic shown in FIG. 6, the analog regulation loop 48 comprises a
regulation circuit 56 and a voltage divider 49,50. Details of the adjustment circuit 56 and the
analog adjustment loop 48 are shown in FIG.
[0059]
The analog regulation loop 48 is preferably supplied by a power supply circuit 11 having an
unregulated voltage of approximately 100V to 120V. The DC / DC converter may be of the same
type as the converter described above or the converter shown in FIGS. 1 and 2. The resistors 5
and 6 are feeder resistances of the microphone. These are used to isolate the microphone power
supply from the output of the audio amplifier 10. The sizes of the resistors 5 and 6 are equal to
maintain the symmetry of the line 1 and the line 2.
[0060]
The invention is of course not limited to phantom powered condenser microphones. Energizing
the individual power receivers of the condenser microphone can also be performed, for example,
by a battery in the microphone.
[0061]
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The desired value provided by the D / A converter or PWM 46, or more precisely, the correction
value of the polarization voltage, is compared to the actual value via the operational amplifier 52.
The desired values are calculated from the measurement data measured during manufacture of
the microphone and programmed into the control electronics. As a reference value for this
calculation, either the exact reference voltage 45 on the line or the reference voltage
programmed into the control electronics during print measurement is used. The reference value
45 may, for example, be made available by the logic supply 24. Such logic supply 24 is
preferably powered by a DC / DC converter 11 and is not shown in FIG. 7 but is shown in FIGS. 1
and 2.
[0062]
In order to counteract the unwanted effects of high frequency interference on the analog tuning
loop 48, the preferred embodiment is between the D / A converter or PWM 46 and the input of
the analog tuning loop 48, as shown in FIG. , Low pass filter 51 is provided. The actual values
produced from the analog regulation loop 48 are obtained from the voltage divider 49 and the
voltage divider 50 and are fed via the impedance transformation 53 to the inverting input of the
operational amplifier 52. Feedback lines and impedance transformers are not included in the
schematic of FIG. At the same time, this voltage is also supplied to the input of the A / C
converter 44 of the digital regulation loop 47. The resulting digital signal is made available to the
control electronics 39 as feedback. As a result, the outer digital adjustment loop 47 is closed. In
FIG. 7, the voltage divider from which the actual value is obtained is represented by the resistor
49 and the resistor 50. As shown in FIG. 7, in addition to the A / D converter 44, the control
electronics 39, the D / A converter 46 may also be integrated into a single component.
[0063]
The adjusted polarization voltage supplied to the microphone capsule 9 via the high ohmic
resistor 8 is obtained as the output of the analog adjustment loop 48. The correction voltage
required to calculate an adjusted polarization voltage without interference, or the corresponding
correction factor, may correspond to different settings reflecting certain sensitivities, guide
characteristics, and aging parameters. These can then be stored in memory in the control
electronics 39 and can be recalled at any time.
18-04-2019
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[0064]
These correction factors can later be changed by remote control by means of a closed
microphone, for example in an after-sales service department or even by an agent or even a user.
Apart from the possibility of correcting the performance of the microphone by aging and
replacing the microphone capsule, on-site custom limited microphone tuning is also possible.
[0065]
The invention is not limited to the examples of the individual embodiments. Naturally, it is also
conceivable to use microphones in which all or at least some of the circuits are mixed. For
example, remote control of all remotely controllable components may be provided to the
microphone, and the power supply circuit 11 may supply power receivers of all possible
microphones.
[0066]
Fig. 1 is a block diagram of a condenser microphone according to the invention, having a power
supply circuit. 1 is a block diagram of an embodiment of a condenser microphone according to
the present invention having a power supply circuit. FIG. 2 is a circuit diagram of a constant
power supply of a transistor LED according to the technical field of the present invention. FIG. 1
is a circuit diagram of a constant power supply with counter connected transistors according to
the technical field of the present invention. It is a block diagram of a condenser microphone
connected to a remote control unit. FIG. 1 is a block diagram of a condenser microphone having
an integrated circuit that adjusts the polarization voltage. FIG. 5 is a circuit diagram for adjusting
polarization voltage, comprising an analog adjustment loop and a digital adjustment loop.
Explanation of sign
[0067]
DESCRIPTION OF SYMBOLS 1 cable conductor 2 cable conductor 3 ground wire 4 plug 5, 6
resistance 7 capacitance 8 resistance 9 microphone capsule 10 audio amplifier / amplifier 11
power supply circuit 12 control part 13 current source 14 transformer 15, 16, 17 current loop
18, 19 Reference Signs List 20 diode 21, 22, 23 capacitor 24 logic supply 25 LED display 27
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zener diode 28, 29 transistor 30 current source 31 phantom power unit 32, 33 feeder resistor
34 parameter control input 35 microcontroller 36 frequency modulator 37 filter 38 comparator
39 Control electronics 41 Low pass filter 42 Input differential amplifier 43 Capacitance 44 A / D
converter 45 Reference voltage 46 D / A converter 47 Digital adjustment loop 48 analog
regulation loop 49, 50 divider 51 the low pass filter 52 operational amplifier 53 impedance
converter 54 microphone 55 remote control unit 56 adjusting circuit
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