JP5749391B1 - Hearing device with switchable power supply voltage - Google Patents

Abstract

A hearing device includes a microphone with a microphone transducer element configured to provide a transducer signal in response to receiving sound, and a microphone amplifier configured to generate an amplified microphone signal based on the transducer signal A microphone amplifier including a circuit, a control processing circuit for receiving the amplified microphone signal and processing in response to a hearing impairment of the user, and a level detector configured to detect the level of the amplified microphone signal The circuit is coupled to a switchable power supply, the switchable power supply having a first power supply voltage having a first DC voltage level or the first DC voltage based on the detected level of the amplified microphone signal. A second power having a second DC voltage level higher than the level; Voltage, configured to selectively connect the microphone amplifier circuit. [Selection] Figure 1

Description

  The present disclosure relates to hearing devices.

  A hearing device or hearing aid typically comprises a microphone amplification assembly. The microphone amplification assembly includes one or several microphones to receive incoming sound, such as speech or music. The incoming sound is converted into an electrical microphone signal (or signals) that is amplified and processed in accordance with one or more preset listening programs in a control processing circuit of the hearing device. These listening programs are typically calculated from the user's specific hearing deficits or disabilities, for example expressed in audiograms. The output amplifier of the hearing device transmits the processed microphone signal to the user's ear canal via a small speaker or receiver. A small speaker or receiver is housed in the hearing device casing with the microphone, or alone in the earplug.

  The noise level at the input stage of the microphone amplifier circuit is generally critical to the overall noise floor of the hearing aid, expressed in terms of the equivalent input noise level, for example in dB SPL units in the microphone. This input stage may comprise a single MOSFET or bipolar transistor with a suitable bias current source. The bias current source determines the bias current through the MOSFET or bipolar transistor. The noise level of this input stage strongly depends on the bias current level, and the noise level increases when the bias current level decreases, so that the bias current can be reduced without making the noise level unacceptably high Is limited. At the same time, the input stage is also required to process the maximum acoustic signal level that the microphone can output without significant distortion, thereby allowing the input stage to accommodate an ac signal that swings at the maximum acoustic signal level. Therefore, it is necessary to supply a relatively high power supply voltage. If the microphone comprises an internal preamplifier (ie, the internal preamplifier is provided in the microphone housing) and it is driven by a DC supply voltage transmitted by the microphone amplifier assembly, the input stage of the microphone amplifier circuit It is customary to use higher DC supply voltages. This high DC supply voltage can be about twice as high as the supply voltage of the built-in microphone preamplifier. At the same time, for the reasons discussed above, a fairly large bias current is still required at the input stage of the microphone amplifier circuit. This means that as much as 25% of the total current consumption in the microphone amplifier circuit, including the analog to digital conversion of the amplified microphone signal, can be consumed at the input stage.

  Given the limited stored energy of battery cells in a typical hearing device, it is desirable to reduce the power consumption of the hearing device circuitry and components as much as possible. Therefore, it may be desirable and advantageous to reduce the power consumption of the input stage of the microphone amplifier circuit without compromising noise performance and maximum acoustic signal level processing capability.

  In one embodiment, the hearing device comprises a microphone with a microphone transducer element provided in the microphone housing. The microphone transducer element generates a transducer signal in response to receiving the sound, and the microphone amplifier circuit is configured to generate an amplified microphone signal from the transducer signal. The control processing circuit of the hearing device is coupled to the microphone amplifier circuit for receiving the amplified microphone signal and processing it in response to the user's hearing impairment. The microphone amplifier circuit has a power supply port coupled to a switchable power supply, the switchable power supply having a first power supply voltage having a first DC voltage level or a second DC voltage level. A second power supply voltage is selectively connected to the power supply port of the microphone amplifier circuit. The second DC voltage level is higher than the first DC voltage level. The level detector is configured to detect the level of the microphone signal and connect the first or second power supply voltage to the power supply port based on the detection level of the microphone signal.

  A 1st aspect is related with the auditory apparatus provided with the microphone provided with the microphone transducer element provided in the microphone housing. The microphone transducer element generates a transducer signal in response to receiving the sound, and the microphone amplifier circuit is configured to generate an amplified microphone signal from the transducer signal. The control processing circuit of the hearing device is coupled to the microphone amplifier circuit for receiving the amplified microphone signal and processing it in response to the user's hearing impairment. The microphone amplifier circuit has a power port coupled to a switchable power source. The switchable power supply selectively connects a first power supply voltage having a first DC voltage level or a second power supply voltage having a second DC voltage level to a power supply port of the microphone amplifier circuit. The second DC voltage level is higher than the first DC voltage level. The level detector is configured to detect the level of the microphone signal and connect the first or second power supply voltage to the power supply port based on the detection level of the microphone signal.

  Those skilled in the art will recognize that the level of the microphone signal is a microphone amplifier circuit such as an amplified microphone signal at the output of the microphone amplifier circuit, a microphone input signal to the microphone amplifier circuit, or even a microphone signal taken directly from the microphone transducer element. It will be appreciated that various types of microphone signals present within can be detected. The level detector may be configured to detect the level of the microphone signal in an indirect manner from another signal that is proportional to the level of the microphone signal. The level detector may form part of an automatic gain control circuit (AGC) of a microphone amplifier circuit, for example. In the latter case, the AGC circuit may derive a gain control signal for the variable gain microphone preamplifier based on the level of the microphone signal. Therefore, the level of the microphone signal can be calculated from the gain control signal of the AGC circuit because the latter is based on a known relationship between the level of the microphone signal and the gain control signal.

  The control processing circuitry of the hearing device can comprise a microprocessor core and / or a DSP core that can be programmed with software to process the digitized microphone signal. The control processing circuit may alternatively comprise a real-wired DSP embodied by an assembly suitably constructed from digital sequence and combinatorial logic. This digitized microphone signal may be generated by an analog-to-digital converter in both examples as discussed below.

  Switching the DC voltage level between the first and second DC voltage levels, due to this feature, drives the microphone amplifier circuit with a lower first DC voltage level at relatively low and normal levels of the microphone signal. This is advantageous. This relatively low and normal level of the microphone signal may correspond to the sound pressure level for a microphone transducer element up to, for example, 90 dB SPL or 100 dB SPL. For higher sound pressure levels, the level detector can connect a second DC voltage level to the power supply port of the microphone amplifier circuit. Thus, in many typical acoustic environments, the sound pressure level is less than 90 dB SPL or 100 dB SPL, so the total operating time that the first power supply voltage is coupled to the microphone amplifier circuit is the second to the microphone amplifier circuit. It can be much longer than the total operating time in which the supply voltages are combined. Thus, the microphone amplifier circuit can, on the one hand, operate with low power consumption without compromising noise performance for most of the time when the sound pressure level is low or normal, and on the other hand, Switching to the second power supply voltage allows large ac signal swings in the microphone amplifier circuit to be tolerated by high DC voltage levels, so it can handle fairly large sound pressure levels without noticeable distortion. It becomes possible. As will be appreciated by those skilled in the art, the level detector may have a predetermined threshold level and be configured to compare the detected level of the microphone signal with the threshold level. The level detector subsequently connects the first power supply voltage to the power supply port of the microphone amplifier circuit when the detected microphone signal level is less than a predetermined threshold level, and the detected microphone signal When the level exceeds a predetermined threshold level, the second power supply voltage can be connected to the power supply port. The predetermined threshold level of the microphone signal corresponds, for example, to the sound pressure level of 90 dB SPL or 100 dB SPL in the microphone transducer element discussed above.

  The microphone amplifier circuit may include a single stage preamplifier, or may include a plurality of preamplifiers connected in series. In both embodiments, the microphone amplifier circuit and the microphone transducer element can be placed inside the microphone housing.

  The microphone amplifier circuit may be housed entirely in the microphone housing, may be distributed between the microphone housing and the control processing circuit, or may be housed entirely in the control processing circuit. The control processing circuit may comprise a mixed signal ASIC in the latter two embodiments. In the first case, the control processing circuit may be an ASIC dedicated to digital logic. An embodiment of a multi-stage microphone amplifier circuit comprises first and second preamplifiers connected in cascade or in series. The first preamplifier is directly coupled to the transducer signal of the microphone transducer element and is powered from the first power supply voltage or a third DC voltage level that is lower than the second DC voltage level. Power is supplied from a third power supply voltage having The second preamplifier further comprises a signal input port coupled to the signal output port of the first preamplifier and a power supply port coupled to a switchable power supply. In this embodiment, the first preamplifier may be a unity gain buffer, such as a single MOSFET or JFET source follower, which limits the demand for its signal processing capability due to unity voltage gain. It may have been made. Thus, the first preamplifier is coupled to a first low power supply voltage or a similarly low DC supply voltage level. The DC level of the first low power supply voltage can be about 1.0V, which can be derived from the battery voltage of the hearing device, for example via a linear voltage regulator or a simple RC low pass filter. .

  Because the second preamplifier has a large voltage amplification, such as between 3 dB and 20 dB, it may require a greater signal processing capability than the first preamplifier. Therefore, the power port of the second preamplifier is coupled to a switchable power supply, so that, for example, the amplified microphone signal must exceed the predetermined threshold level described above to avoid distortion. The second power supply voltage can be selected by the level detector.

  According to embodiments of the multistage and distributed microphone amplifier circuits, the microphone transducer element and the first preamplifier are arranged in a common microphone housing of the microphones. The microphone housing includes a power supply terminal coupled to the first or third power supply voltage. Further, the second preamplifier, the controllable switching mechanism, the first and second power supplies, and the level detector are integrated in the control processing circuit of the hearing device.

  The switchable power supply preferably includes a controllable switching mechanism that responds to a switching control signal generated by the level detector. The controllable switching mechanism is connected to the first power supply voltage and the second power supply voltage via first and second switching inputs, respectively. Furthermore, the switching output of the controllable switching mechanism is connected to the power supply port of the microphone amplifier circuit. The controllable switching mechanism may comprise one or more semiconductor switches, each control terminal connected to a switching control signal, as will be described in more detail below.

  In an advantageous embodiment, the level of the microphone signal is detected in the digital domain. This embodiment of the hearing device comprises an analog-to-digital converter configured to generate a digitized microphone signal based on a microphone signal, such as an amplified microphone signal, and the level detector is digitized A digital level detector configured to calculate a level of the amplified microphone signal. The digital level detector is configured to supply a digital control signal to the controllable switching mechanism. In one embodiment, the digital level detector may comprise a digital logic circuit that is appropriately configured to implement the functionality of the digital level detector in hardware. In an alternative embodiment, the digital level detector may comprise a program routine or software component so that the functionality of the digital level detector is embodied in software. This software component may comprise a predetermined set of program instructions that can be executed by a software programmable DSP core of the aforementioned control processing circuit of the hearing device. As will be appreciated by those skilled in the art, as another alternative, the digital level detector may be implemented as a combination of software component (s) and digital hardware.

  The second aspect relates to a microphone assembly for a hearing device. The microphone assembly includes a microphone with a microphone transducer element provided in a microphone housing. The microphone transducer element generates a transducer signal in response to receiving the sound. The microphone amplifier circuit is configured to generate an amplified microphone signal from the transducer signal. The microphone amplifier circuit has a signal input port coupled to the transducer signal and a power port coupled to a switchable power source. The switchable power supply selectively connects a first power supply voltage having a first DC voltage level and a second power supply voltage having a second DC voltage level to a power supply input of the microphone amplifier circuit. It is configured as follows. Here, the second DC voltage level is higher than the first DC voltage level. The level detector is configured to detect the level of the microphone signal and connect the first or second power supply voltage to the power supply port of the microphone amplifier circuit based on the detection level of the microphone signal.

  The switchable power supply may include a controllable switching mechanism that responds to the switching control signal generated by the level detector, as described above in connection with the first aspect. The controllable switching mechanism is connected to the first power supply voltage and the second power supply voltage via the first and second switching inputs, respectively. A switching output is connected to the power supply port of the microphone amplifier circuit.

  The microphone amplifier circuit can be configured as described above in connection with the first aspect. Thus, in one embodiment, the microphone amplifier circuit is directly coupled to the transducer signal of the microphone transducer element and is powered from the first power supply voltage or a third DC that is lower than the second DC voltage level. A first preamplifier is provided that is powered from a third power supply voltage having a voltage level. Further, the second preamplifier of the microphone amplifier circuit comprises a signal input port coupled to the signal output port of the first preamplifier and a power supply port coupled to a switchable power supply.

  In one embodiment, the second preamplifier comprises a bias current source coupled between the input transistor of the microphone amplifier circuit and the output of the controllable switching mechanism. In this scheme, a bias current source is connected to the output side of the controllable switching mechanism, and the same bias current source can be suitably used to bias the input transistor independent of the state of the switching mechanism. The noise performance of the microphone amplifier circuit is often governed by the noise level of the input transistor of the second preamplifier, and therefore the first power supply voltage is applied to the second preamplifier via a switching mechanism. Regardless of whether the connection or the second power supply voltage is connected, it may be advantageous to maintain the latter noise level substantially constant. In this case, the bias current source can be configured to provide a substantially constant bias current regardless of the level of the microphone signal. The bias current source may be configured to set the DC bias current so that it is between 2 μA and 25 μA in the input transistor. Here, the substantially constant bias current means that the fluctuation of the DC bias current is 10% from the zero level of the microphone signal to the microphone signal level corresponding to a sound pressure level of 100 dB at 1 kHz in the microphone transducer element. Means less than.

  In an alternative embodiment, two independent bias current sources are connected to the input side of the controllable switching mechanism, and different DC bias currents are preferred for the input transistors depending on the state of the controllable switching mechanism. Can be set to According to this embodiment, the first bias current source is coupled between the first power supply voltage and the first input of the controllable switching mechanism, and the second power supply voltage and the second of the controllable switching mechanism are A second bias current source is coupled between the inputs. However, substantially the same DC bias so that a substantially constant bias current is provided to the second preamplifier, regardless of the state of the controllable switching mechanism, as well as two independent bias current sources. It may be configured to provide a current (eg, the bias current value described above). Thus, if the bias current of the first preamplifier is also substantially constant, the entire microphone amplifier circuit may have a substantially constant bias current. Each of the first and second bias current sources may comprise a transistor, such as a PMOS transistor, as will be discussed in more detail below with reference to the accompanying drawings.

  In order to minimize the generation of audible products such as pops and clicks associated with repetitive switching between the first and second supply voltages, the time constant circuit detects the level. May be coupled to the instrument or integrated within the level detector, thereby setting an appropriate attack time and an appropriate release time. This attack time is preferably set to such a small value that the switching frequency component exceeds the audible frequency range (that is, exceeds 20 kHz). This attack time can be less than 50 μs, more preferably less than 10 μs. During the attack time, the switch control signal is used to disconnect the power supply port of the microphone amplifier circuit from the first power supply voltage via the controllable switching mechanism and to connect the microphone amplifier circuit to the second power supply voltage. Can be used. The opposite operation of connect / disconnect is performed during the release time. This release time is preferably set to a value significantly greater than the attack time, so that most of the switching frequency component can be below the audible frequency range (ie, below 20 Hz). Therefore, the release time of the time constant circuit can be set to a value larger than 50 ms.

  As briefly mentioned above, the controllable switching mechanism may comprise one or more semiconductor switches, each control terminal connected to a switching control signal. According to one of such embodiments, the controllable switching mechanism includes a first semiconductor switch connected between the first switching input and the switching output, and between the second switching input and the switching output. And a second semiconductor switch connected thereto. Each of the first and second semiconductor switches has a control terminal coupled to the switching control signal. Each of the first and second semiconductor switches preferably includes a semiconductor switch such as a MOSFET that exhibits a low on-resistance, a high off-resistance, and a high impedance at the control terminal (ie, gate).

  In one advantageous embodiment, each of the first and second bias current sources also functions as a switch of the switching mechanism, whereby the functions described above for the switching mechanism are integrated with the bias current supply to the microphone amplifier circuit. The In one such embodiment, the first bias current source is integrated with the first semiconductor switch of the controllable switching mechanism, and the second bias current source is integrated with the second semiconductor switch of the controllable switching mechanism. Integrated. Each of the first and second bias current sources / switches may comprise a PMOS or NMOS transistor as disclosed in more detail below with reference to the accompanying drawings. According to this embodiment, the number of components of the microphone assembly can be reduced as compared to an embodiment using independent bias current sources and switches.

  The first and second power supply voltages can be generated by various types of voltage supply. As described above, the first and / or third power supply voltages can be generated by a linear voltage regulator or a simple RC low pass filter powered from the battery supply voltage of the hearing device. The battery supply voltage can be generated from a battery source of the hearing device, such as a conventional 1.2V zinc-air battery cell or one or more rechargeable battery cells. The microphone assembly may comprise a DC-DC power converter, such as a boost converter or a charge pump, configured to generate a second power supply voltage. The DC-DC power converter can be supplied from a battery supply voltage or from a first power supply voltage. The second DC voltage level can be 1.5 times or more higher than the first DC voltage level by appropriately applying a DC-DC power converter, for example, than the first DC voltage level. Can also be increased between 1.5 and 3.0 times.

  The microphone amplifier circuit, controllable switching mechanism, voltage supply, and control processing circuit may be integrated on a sub-micrometer digital CMOS-based semiconductor die or substrate.

  The hearing device is provided in the microphone housing and includes a microphone including a microphone transducer element configured to provide a transducer signal in response to receiving sound, and to generate an amplified microphone signal based on the transducer signal. A microphone amplifier circuit configured to: and a control processing circuit coupled to the microphone amplifier circuit for receiving and processing the amplified microphone signal in response to a hearing impairment of the user; and detecting the level of the amplified microphone signal And a level detector configured. The microphone amplifier circuit is coupled to a switchable power source. The switchable power supply includes a first power supply voltage having a first DC voltage level and a second power supply voltage having a second DC voltage level in the microphone amplifier circuit based on a detection level of the amplified microphone signal. Are selectively connected. The second DC voltage level is higher than the first DC voltage level.

  Optionally, the microphone amplifier circuit is coupled to the microphone transducer element and receives power from a first power supply voltage or a third power supply voltage having a third DC voltage level that is lower than the second DC voltage level. And a second preamplifier comprising a signal input port coupled to the signal output port of the first preamplifier and a power supply port coupled to a switchable power supply.

  Optionally, the microphone transducer element and the first preamplifier are disposed in the microphone housing of the microphone. The microphone housing includes a power supply terminal coupled to the first or third power supply voltage. The second preamplifier, the first and second power supplies, and the level detector are integrated by a control processing circuit of the hearing device.

  Optionally, the switchable power supply connects the first power supply voltage to the microphone amplifier circuit when the detection level is below a predetermined threshold level, and the detection level is greater than or equal to the predetermined threshold level. In some cases, the second power supply voltage is connected to the microphone amplifier circuit.

  Optionally, the switchable power supply comprises a controllable switching mechanism that is responsive to a switching control signal generated by the level detector. The controllable switching mechanism is coupled to the first power supply voltage and the second power supply voltage via first and second switching inputs, respectively. The switchable power supply is configured to selectively connect the first power supply voltage or the second power supply voltage to the microphone amplifier circuit by a switching control signal.

  Optionally, the microphone amplifier circuit further comprises an analog to digital converter configured to generate a digitized microphone signal based on the amplified microphone signal. The level detector includes a digital level detector configured to calculate the level of the digitized microphone signal and to provide a switching control signal to the controllable switching mechanism. The switching control signal is a digital switching control signal.

  A microphone assembly for a hearing device is provided on a microphone housing and includes a microphone with a transducer element configured to provide a transducer signal in response to receiving sound, and an amplification based on the transducer signal A microphone amplifier circuit configured to generate a finished microphone signal and a level detector configured to detect the level of the microphone signal. The microphone amplifier circuit is coupled to a switchable power source. The switchable power supply selectively selects the first power supply voltage having the first DC voltage level or the second power supply voltage having the second DC voltage level in the microphone amplifier circuit based on the detection level of the microphone signal. Configured to connect to. The second DC voltage level is higher than the first DC voltage level.

  Optionally, the switchable power supply includes a controllable switching mechanism that is responsive to a switching control signal generated by the level detector, the controllable switching mechanism via first and second switching inputs, respectively. The first power supply voltage and the second power supply voltage are connected. The switchable power supply is configured to selectively connect the first power supply voltage or the second power supply voltage to the microphone amplifier circuit by a switching control signal.

  Optionally, the microphone amplifier circuit is coupled to the microphone transducer element and draws power from a third power supply voltage having a first DC voltage level or a third DC voltage level lower than the second DC voltage level. A first preamplifier configured to receive; a second preamplifier comprising a signal input port coupled to the signal output port of the first preamplifier and a power port coupled to the switchable power source; Prepare.

  Optionally, the microphone assembly further includes a bias current source coupled between the input transistor of the microphone amplifier circuit and the output of the controllable switching mechanism.

  Optionally, the bias current source is configured to provide a substantially constant bias current regardless of the level of the microphone signal.

  Optionally, the microphone assembly includes a first bias current source coupled between the first power supply voltage and the first switching input of the controllable switching mechanism, a second power supply voltage and the controllable switching. A second bias current source coupled between the second switching input of the mechanism.

  Optionally, the microphone assembly further includes a time constant circuit coupled to the level detector and configured to set an attack time and a release time of the switching control signal, the switching control signal comprising: During the attack time, the microphone amplifier circuit is disconnected from the first power supply voltage, and the microphone amplifier circuit is connected to the second power supply voltage via the controllable switching mechanism.

  Optionally, the controllable switching mechanism includes a first semiconductor switch connected between the first switching input and the switching output, and a second semiconductor connected between the second switching input and the switching output. Each of the first and second semiconductor switches has a control terminal coupled to the level detector.

  Optionally, the first bias current source is integrated with the first semiconductor switch of the controllable switching mechanism, and the second bias current source is integrated with the second semiconductor switch of the controllable switching mechanism. ing.

  Other additional aspects and features will become apparent upon reading the following detailed description.

FIG. 1 is a simplified schematic block diagram of a microphone assembly for a hearing device with a switchable power source according to one embodiment. FIG. 2 is a simplified schematic block diagram of a microphone assembly for a hearing device with a switchable power supply according to the second embodiment. FIG. 3 is a simplified schematic block diagram of a microphone assembly for a hearing device with a switchable power source according to a third embodiment.

  The embodiment will be described in more detail with reference to the accompanying drawings.

  Various embodiments will be described below with reference to the drawings. Furthermore, it should be understood that these drawings are only intended to facilitate the description of the embodiments. They are not intended to be an exhaustive description of the invention or to limit the scope of the invention. Furthermore, the illustrated embodiments do not necessarily show all of their aspects and advantages. The aspects and advantages described in connection with a particular embodiment are not necessarily limited to that embodiment, and may be used in any other embodiment (where there is no illustration or an explicit description thereof). (Even if not described).

FIG. 1 is a simplified schematic block diagram of a microphone assembly 100 with a switchable power source for a hearing device. The hearing device may be of any type, such as a behind-the-ear (BTE) type, an in-the-canal type (ITC), a complete external-in-canal type (CIC), or the like. The hearing aid housing style can be provided. The hearing device has certain common components, such as an output amplifier, control processing circuitry, and a small receiver / speaker for generating the ear canal sound pressure (although these are all omitted for simplicity). Can be provided. The control processing circuit can be coupled to a digitized microphone signal that is fed to the output of the microphone assembly 100 via the output of the analog to digital converter ΣΔ1 115. Control processing circuit applies one or more signal processing functions on the digitized microphone signals from the M _M according to the user's hearing impairment of the hearing device, it can be provided with a software programmable DSP core . These signal processing functions can have different processing parameters with respect to functions such as nonlinear amplification, noise reduction, frequency response shaping, etc.

The microphone assembly 100 includes a microphone M _M that is supplied with power through a positive power supply terminal V _DD that is accessible from the outside. The microphone assembly M _M includes a microphone transducer element (not shown) provided in a microphone housing (not shown). The microphone transducer element can include a capacitive electret transducer element that generates a transducer signal in response to receiving sound. The microphone M _M further includes a first preamplifier (not shown) coupled directly to the output of the microphone transducer element. This preamplifier can have a very high input impedance so that it can be coupled to capacitive electret transducer elements with minimal signal loss. The first preamplifier is supplied with power from the positive power supply terminal V _DD . The amplified or buffered microphone signal is supplied by a first preamplifier on the microphone signal output terminal 103 to a second preamplifier integrated with another microphone amplification circuit 101 of the microphone assembly 100. . The second preamplifier comprises an input stage with a PMOS transistor M1 whose gate input is coupled to an amplified or buffered microphone signal. The PMOS transistor M1 is communicated by the microphone M _{M in} conjunction with the drain or load circuit 105 (eg, comprising one or more load resistors) prior to conversion to digital form by the ΣΔ1 analog-to-digital converter 115. Can be configured to provide a predetermined amount of signal amplification to the buffered or amplified microphone signal. As will be appreciated by those skilled in the art, the second preamplifier may comprise a single amplification stage, as shown by PMOS transistor M1, or a plurality of amplification stages (eg, coupled in cascade). Amplifying stage). Further, M1 may include other types of transistor elements other than those shown as PMOS transistors (eg, NMOS transistors, JFETs or bipolar (BJT) transistors).

The microphone amplifier circuit 101 further includes a switchable power supply 102 having a switching mechanism SW1, PMOS transistors M2 and M3, and two independent power supply voltages V _DDL and V _DDH . The first power supply voltage V _DDL provides a first DC voltage level. The second power supply voltage V _DDH has a second DC voltage level that is higher in absolute value than the first DC voltage level (ie, a DC voltage that is larger and positive or a DC voltage that is more negative). First power supply voltage _{V DDL} may be given to the positive power supply terminal _{V DD} of the microphone _{M M.} The absolute values of the first and second DC voltage levels and the difference between them can vary depending on the characteristics of the hearing device. If the hearing device power source is a typical hearing aid battery cell, such as a 1.2V zinc-air battery, the first DC voltage level is reduced by a voltage regulator, such as a linear regulator or a simple RC-based low pass filter. It can be adjusted to be 0.9 to 1.1V. In this situation, the second DC voltage level can be set to be approximately twice the value of the first DC voltage level (ie, approximately 1.8-2.2V). As will be appreciated by those skilled in the art, is the second power supply voltage V _DDH directly coupled to a suitably configured DC-DC power converter 117, for example, the battery voltage terminal VBAT of the microphone amplifier circuit 101? Can be generated by a boost converter or charge pump coupled to the regulated voltage described above. Next to the DC-DC converter 117, in order to suppress supply noise or ripple for the second power supply voltage V _DDH , a linear type voltage regulator is continued, and then the latter is coupled to the source terminal of M3. it can.

The PMOS transistor M3 of the switchable power supply 102 is configured as a first substantially constant bias current source for the input stage around the PMOS transistor M1, and SW1 uses this bias current source as the power supply port or input of M1. When connected to 119, a desired preset DC bias current is supplied to M1 from a first low power supply voltage V _DDH . When the bias current is increased, noise is reduced in exchange for an increase in power consumption. Therefore, the selected level of the DC bias current varies depending on the noise requirements of the input stage transistor M1. However, in a typical hearing aid application, M3 may be configured to deliver a first DC bias current between 2 μA and 25 μA to M1. The desired first DC bias current can be set by a suitably configured current mirror circuit (not shown) coupled to the gate terminal 113 of M3 and providing the appropriate DC bias voltage V _BIAS . The PMOS transistor M2 of the switchable power supply 102 is configured as a second constant bias current source for the input stage around the PMOS transistor M1, and when SW1 connects this bias current source to the power supply port 119 of M1. , M1 is supplied with a desired second DC bias current from a second (higher) power supply voltage V _DDH . In a typical hearing aid application, M2 may be configured to deliver a second DC bias current level between 2 μA and 25 μA for the reasons described above for the same connection. Accordingly, the switching mechanism SW1 is connected to the first bias current source M3 and the first bias current source in order to supply the operating current to the input stage while the cut-off bias current source is cut off and has essentially no current. Any one of the two bias current sources M2 is selectively connected to the power port 119 of M1.

  One skilled in the art will appreciate that the first DC bias current and the second DC bias current can be set to essentially the same level. According to this, the noise level of the input stage of the microphone amplifier circuit can be kept almost constant irrespective of the bias current source that is enabled / selected. This is because when the transistor size of M1 is sufficiently large and the flicker noise can be reduced to an unaffected level, the bias current level becomes a dominant factor regarding the noise level. However, as an alternative embodiment, the first DC bias current level is significantly higher than the second DC bias current level (eg, twice as large) due to the appropriate configuration of M2 and M3. May be set.

The microphone amplifier circuit 101 further comprises a level detector 107 configured to detect the level of the amplified microphone signal 114 at the output node of the second preamplifier. This output node may be the output of the input stage configured around the PMOS transistor M1 as outlined in FIG. One skilled in the art will appreciate that other microphone signals present in the microphone amplifier circuit can be used instead for level detection purposes. The level detector 107 can be configured to perform various types of level estimation on the amplified microphone signal, such as peak voltage or peak power, RMS voltage or power level, average voltage or power level, etc. The level detector 107 compares the detection level of the amplified microphone signal 114 with a threshold voltage or a reference voltage, and based on whether the detection level is greater than or less than the threshold voltage. Two power supply voltages V _DDL , V _DDH can be configured to selectively connect to the power input 119 of the second preamplifier. The level detector 107 generates an appropriate switching control signal 111 through an optional release and attack time circuit 109 and provides the control signal to one or more control inputs of the switching mechanism SW1. Thereby, a desired power supply voltage is selected and conducted through SW1, while other supply voltages are cut off during that time.

The threshold voltage or reference voltage of the level detector 107 is an amplified microphone voltage for which switching from the first power supply voltage V _DDL to the second higher power supply voltage V _DDH is desirable via the switching mechanism SW1. It may be set to a value corresponding to a specific level. Switching the supply voltage means, for example, that the input stage of the second preamplifier around M1 processes the voltage signal swing of the amplified microphone signal 114 generated by the microphone M _M without audible distortion. This is desirable because it is impossible. In this embodiment, the power supply voltage V _DD of the first preamplifier disposed in the microphone housing is substantially equal to the first power supply voltage V _DDL in this embodiment, and the current source M3 and the input transistor M1 can be operated correctly. Is particularly relevant when the second preamplifier has a minimum voltage headroom between the input signal and the V _DD supply voltage. The signal processing capability of the second preamplifier is that, by coupling its power supply port 119 to a higher power supply voltage V _DDH , an undistorted ac signal voltage swing is incidentally increased at the drain of the input stage transistor M1. , Markedly improved. On the other hand, if the DC bias current drawn by M1 is now supplied by the second higher power supply voltage V _DDH , then the power consumption of the second preamplifier if the DC bias current of M1 is held approximately constant. Means a significant increase. Assuming that the first power supply voltage V _DDL has a DC level of 1.0 V and the second power supply voltage V _DDH has a DC level of 2.0 V, the first and second power supplies are switched by switching the power supply voltage. Depending on the actual conversion loss at, the power consumption is roughly doubled. However, the reference sound pressure suitably high level at the position of the microphone M _M by adjusting the threshold voltage of the level detector (e.g., the sound pressure level on the microphone transducer element in excess of more than 90 dB SPL or 100 dB SPL In many practical acoustic environments, the total time that the second preamplifier is coupled to the second power supply voltage V _DDH is It may be shorter compared to the total time coupled to the first power supply voltage V _DDL . Thus, in the long term, the increase in power consumption will only result in a slight increase in the average power consumption of the microphone assembly.

Thus, the switchable power supply 102 in conjunction with the first and second power supply voltages V _DDL and V _DDH allows the second preamplifier to operate without distortion and at a constant high supply voltage even at high sound pressure levels. It is possible to handle the maximum ac signal swing of the microphone signal without a significant increase in the average power consumption of the prior art preamplifier caused by. In this microphone amplifier circuit, when the microphone sound pressure level is at a low or normal level, the power supply of the preamplifier is coupled to the first lower power supply voltage V _DDL , so that the average power of the second preamplifier is Consumption is kept lower. This is the most common acoustic environment, especially in everyday use of hearing devices. Furthermore, as the noise level of the second pre-amplifier by switching to V _DDL is not significantly affected, the switching from the second power supply voltage to the first power supply voltage V _DDL, in the second pre-amplifier It should be noted that the DC bias current can be kept essentially unchanged.

As described above, the level detector 107 generates an appropriate switching control signal 111 through an optional release and attack time circuit 109. One skilled in the art will appreciate that the release and attack time circuit 109 may be integrated with the level detector 107. The role of the release and attack time circuit 109 minimizes audible products such as pops and clicks associated with switching between the first supply voltage V _DDL and the second supply voltage V _DDH. Thus, an appropriate attack time and an appropriate release time of the switching control signal 111 are set. This attack time is preferably set to such a small value that the switching frequency component exceeds the audible frequency range (that is, exceeds 20 kHz). The attack time can be less than 50 μs. During the attack time, the switching control signal disconnects the power port 119 of the second preamplifier from the first power supply voltage V _DDL through the controllable switching mechanism SW1 and supplies it to the second power supply voltage _VDDL. Connect to V _DDH . The release time is preferably set to a value significantly greater than the attack time so that the majority of the switching frequency component falls below the audible frequency range (ie, less than 20 Hz). Further, according to this, the control signal does not change rapidly in response to the pulse-like acoustic pattern, for example, over a reasonable time interval such that the sound pressure falls below the above-described sound pressure threshold. 2 is maintained to be connected to the power supply voltage V _DDH . The release time can be set to a value greater than 50 ms. During the release time, the switching control signal 111 disconnects the power port 119 of the input stage of the second preamplifier from the second power supply voltage V _DDH via the controllable switching mechanism SW1 and 1 is connected to the power supply voltage V _DDL .

The controllable switching mechanism SW1 can be configured in various ways. In one embodiment, SW1 comprises a pair of independently operating semiconductor switches, each of which is controlled by a single switching control signal. Therefore, in this embodiment, the switching control signal can be a binary signal. The first semiconductor switch of the pair of semiconductor switches is connected between the first switching input and the switching output (where the latter is connected to the power port 119 of the second preamplifier). This switching input is connected to one of the first power supply voltage V _DDL and the second power supply voltage V _DDH . A second semiconductor switch is connected between the second switching input and the switching output of the switching mechanism. The input of the second semiconductor switch is connected to the power supply voltage opposite to that of the first semiconductor switch. Each of the first and second semiconductor switches can comprise a MOSFET that exhibits a low on-resistance, a high off-resistance, and a high impedance at the control terminal (ie, gate).

  A ΣΔ1 analog-to-digital converter 115 that converts or digitizes the amplified microphone signal 114 can operate at an oversampling rate, for example, between 1 and 10 MHz. In another embodiment as discussed below in connection with FIG. 2, another type of analog to digital converter is used to minimize the time delay of the power switch process caused by digitizing the amplified microphone signal. Is being used. The short time delay is that when operating the level detector in the digital domain based on the digitized / sampled microphone signal rather than the analog domain utilized in this embodiment, as discussed in detail below. Can be advantageous.

FIG. 2 is a simplified schematic block diagram of a microphone assembly 200 for a hearing device with a switchable power source 202 according to a second embodiment. For ease of comparison, the same features in this embodiment and the first embodiment described above are given corresponding reference numbers. Those skilled in the art will appreciate that the above general observations regarding the characteristics of the microphone M _{M and} the characteristics of the passive and active devices and circuit blocks are the same for the corresponding devices of this embodiment, unless stated otherwise. It will be understood that it is applicable. The main difference between the present microphone assembly 200 and the above-described embodiment of the microphone assembly 100 is that this level detector 207 is supplied to the output of the analog to digital converter 215 at a digitized amplified microphone. Detecting the signal 216 and operating in the digital domain accordingly. The digitized amplified microphone signal 216 is derived by sampling and converting the amplified microphone signal 214 at the location of the output of the second preamplifier. Thus, the level detector 207 can comprise digital logic that is appropriately configured to operate based on the digitized microphone signal 216. As described above, the analog-to-digital converter 215 may have a standby time such as a flash converter in order to minimize the time delay from the amplified microphone signal 214 to the switching control signal 211 at the input of the analog-to-digital converter 215. A low type is preferred. Those skilled in the art will recognize that the level detector 207 and / or the optional release and attack time circuit 209 is a predetermined set of executable program instructions of the software programmable DSP core of the control processing circuit described above of the hearing device. It will be understood that each program routine / software component can be embodied. According to the latter embodiment, a great degree of freedom can be obtained in the design and adaptation of the functions of the level detector 207 and the release and attack time circuit 209.

FIG. 3 is a simplified schematic block diagram of a microphone assembly 300 for a hearing device with a switchable power supply 302 according to a third embodiment. For ease of comparison, the same features in this embodiment and the first embodiment described above are given corresponding reference numbers. Those skilled in the art will appreciate that the above general observations regarding the characteristics of the microphone M _{M and} the characteristics of the passive and active devices and circuit blocks are the same for the corresponding devices of this embodiment, unless stated otherwise. It will be understood that it is applicable. The main difference between the present microphone assembly 300 and the above-described embodiments of the microphone assemblies 100, 200 is that each of the constant bias current sources M3 and M2 further acts as a switch, ie, independent. That is, the above-described functions related to the switching mechanism SW1 are integrated. The control or gate terminal 313b of the constant bias current source M3 is supplied from an optional release and attack time circuit 309 as shown, or directly from the level detector 307. Controlled by. The control or gate terminal 313b is also connected to the appropriate DC bias voltage V _BIAS to set the desired DC bias current to M1 when the constant bias current source M3 is active as discussed with respect to M3 in FIG. Has been. The first control signal 311b may be supplied by a three-state output driver or port so that the first control signal 311b is set to a high impedance state when the constant bias current source M3 is active. When the constant bias current source M3 is turned off instead, the tri-state output driver can pull the control or gate terminal 313b to a fixed logic level or state with low impedance. Accordingly, the control or gate terminal 313b is set to an appropriate potential, and the PMOS transistor M3 is switched to the off state or the non-conduction state. The constant bias current source M2 is controlled by controlling the voltage at the control or gate terminal 313a by the second control signal 311a from the release and attack time circuit 309 or directly from the level detector 307. Can be controlled by.

item:
1. A microphone comprising a microphone transducer element provided in the microphone housing and configured to provide a transducer signal in response to receiving sound;
A microphone amplifier circuit configured to generate an amplified microphone signal based on the transducer signal;
A control processing circuit coupled to the microphone amplifier circuit for receiving the amplified microphone signal and processing it in response to a user's hearing impairment;
With
The microphone amplifier circuit has a power port coupled to a switchable power supply, the switchable power supply having a first power supply voltage having a first DC voltage level or a second DC voltage level. 2 is configured to selectively connect a power supply voltage of 2 to the power supply port of the microphone amplifier circuit, the second DC voltage level being higher than the first DC voltage level;
A level detector configured to detect a level of the amplified microphone signal and to connect the first and second power supply voltages to the power supply port based on the detected level of the microphone signal; Prepare
A hearing device comprising:

2. The microphone amplifier circuit is
A first power coupled directly to the transducer signal of the microphone transducer element and powered from a third power supply voltage having a third DC voltage level lower than the first power supply voltage or the second DC voltage level. 1 preamplifier,
A second preamplifier comprising a signal input port coupled to a signal output port of the first preamplifier and a power supply port coupled to the switchable power supply;
The hearing device according to item 1, comprising:

3. The microphone transducer element and the first preamplifier are disposed in a common microphone housing of the microphones having a power supply terminal coupled to the first or third power supply voltage;
The second preamplifier, the first and second power supplies, and the level detector are integrated in the control processing circuit of the hearing device;
Item 3. The hearing device according to item 2.

4). The hearing device according to item 2, wherein the microphone amplifier circuit and the microphone transducer element are disposed inside a microphone housing.

5. The switchable power supply connects the first power supply voltage to the power supply port of the microphone amplifying circuit when the detection level is less than a predetermined threshold level, and the detection level is the predetermined level. The hearing device according to any of the preceding items, wherein the hearing device is configured to connect the second power supply voltage to the power supply port when the threshold level is equal to or higher than the threshold level.

6). The switchable power source includes a controllable switching mechanism that responds to a switching control signal generated by the level detector,
The controllable switching mechanism is coupled to the first power supply voltage and the second power supply voltage via first and second switching inputs, respectively.
The switching output is connected to the power supply port of the microphone amplifier circuit.
The hearing device according to any of the above items.

7). The microphone amplifier circuit further comprises an analog to digital converter configured to generate a digitized microphone signal based on the amplified microphone signal;
The level detector comprises a digital level detector configured to calculate a level of the digitized microphone signal and to supply a digital switching control signal to the controllable switching mechanism.
Item 6. The hearing device according to item 6.

8). A microphone assembly for a hearing device,
A microphone with a microphone transducer element provided in the microphone housing and configured to provide a transducer signal in response to sound reception;
A microphone amplifier circuit configured to generate an amplified microphone signal based on the transducer signal, having a signal input port coupled to the transducer signal and a power port coupled to a switchable power source. The switchable power supply selectively connects a first power supply voltage having a first DC voltage level or a second power supply voltage having a second DC voltage level to a power supply port of the microphone amplifier circuit. A microphone amplifier circuit, wherein the second DC voltage level is higher than the first DC voltage level;
A level detector configured to detect the level of the amplified microphone signal and to connect the first and second power supply voltages to the power supply port based on the detected level of the microphone signal;
A microphone assembly comprising:

9. The switchable power source includes a controllable switching mechanism that responds to a switching control signal generated by the level detector,
The controllable switching mechanism is connected to the first power supply voltage and the second power supply voltage via first and second switching inputs, respectively.
The switching output is connected to the power supply port of the microphone amplifier circuit.
Item 9. The microphone assembly according to item 8.

10. The microphone amplifier circuit is
A first power coupled directly to the transducer signal of the microphone transducer element and powered from a third power supply voltage having a third DC voltage level lower than the first power supply voltage or the second DC voltage level. 1 preamplifier,
A second preamplifier comprising a signal input port coupled to a signal output port of the first preamplifier and a power supply port coupled to the switchable power supply;
The microphone assembly according to item 8 or 9, comprising:

11. Item 11. The microphone assembly of item 10, further comprising a bias current source coupled between an input transistor of the microphone amplifier circuit and an output of the controllable switching mechanism.

12 12. The microphone assembly of item 11, wherein the bias current source is configured to provide a substantially constant bias current regardless of the level of the microphone signal.

13. A first bias current source coupled between the first power supply voltage and the first switching input of the controllable switching mechanism;
A second bias current source coupled between the second power supply voltage and the second switching input of the controllable switching mechanism;
The microphone assembly according to any of items 9 to 12, further comprising:

14 The first and second bias current sources are configured to provide substantially equal bias currents, thereby providing substantially independent to the microphone amplifier circuit independent of the state of the controllable switching mechanism. 14. A microphone assembly according to item 13, which provides a constant bias current.

15. A time constant circuit coupled to the level detector and configured to set an attack time and a release time of the switching control signal;
In the attack of the switching control signal, the latter disconnects the power supply port of the microphone amplifier circuit from the first power supply voltage via the controllable switching mechanism, and the power supply port is set to the second power supply voltage. The microphone assembly according to any one of items 8 to 14, which is connected.

16. 16. The microphone assembly of item 15, wherein the time constant circuit is configured to provide an attack time of less than 50 μs, more preferably less than 10 μs.

17. The controllable switching mechanism is
A first semiconductor switch connected between the first switching input and the switching output;
A second semiconductor switch connected between the second switching input and the switching output;
17. The microphone assembly according to any of items 8 to 16, wherein each of the first and second semiconductor switches has a control terminal coupled to the switching control signal.

18. A first bias current source is integrated with the first semiconductor switch of the controllable switching mechanism, and a second bias current source is integrated with the second semiconductor switch of the controllable switching mechanism. 18. The microphone assembly according to item 17.

19. A DC-DC power converter, such as a boost converter or a charge pump, configured to generate the second power supply voltage;
A linear voltage regulator configured to generate the first power supply voltage and / or the third power supply voltage;
19. The microphone assembly according to any one of items 8 to 18, further comprising at least one of the following.

20. A microphone comprising a microphone transducer element provided in the microphone housing and configured to provide a transducer signal in response to receiving sound;
A microphone amplifier circuit configured to generate an amplified microphone signal based on the transducer signal;
A control processing circuit coupled to the microphone amplifier circuit for receiving the amplified microphone signal and processing in response to a user's hearing impairment;
A level detector configured to detect the level of the amplified microphone signal;
With
The microphone amplifier circuit is coupled to a switchable power supply, the switchable power supply being a first power supply voltage having a first DC voltage level based on the detection level of the amplified microphone signal or A second power supply voltage having a second DC voltage level is configured to be selectively connected to the microphone amplifier circuit, wherein the second DC voltage level is higher than the first DC voltage level;
Hearing device.

21. The microphone amplifier circuit is
Coupled to the microphone transducer element and configured to receive power from a first power supply voltage or a third power supply voltage having a third DC voltage level that is lower than the second DC voltage level. A first preamplifier;
A second preamplifier comprising a signal input port coupled to a signal output port of the first preamplifier and a power supply port coupled to the switchable power supply;
The hearing device according to item 20, comprising:

22. The microphone transducer element and the first preamplifier are disposed in a microphone housing of the microphone with a power supply terminal coupled to the first or third power supply voltage;
The second preamplifier, the first and second power supplies, and the level detector are integrated in the control processing circuit of the hearing device;
Item 22. The hearing device according to Item 21.

23. The switchable power supply connects the first power supply voltage to the microphone amplifier circuit when the detection level is lower than a predetermined threshold level, and the detection level is equal to or higher than the predetermined threshold level. , The hearing device of item 20, wherein the hearing device is configured to connect the second power supply voltage to the microphone amplifier circuit.

24. The switchable power source includes a controllable switching mechanism that responds to a switching control signal generated by the level detector,
The controllable switching mechanism is coupled to the first power supply voltage and the second power supply voltage via first and second switching inputs, respectively.
The switchable power supply is configured to selectively connect the first power supply voltage or the second power supply voltage to the microphone amplifier circuit according to the switch control signal.
Item 20. A hearing device according to item 20.

25. The microphone amplifier circuit further comprises an analog to digital converter configured to generate a digitized microphone signal based on the amplified microphone signal;
The level detector includes a digital level detector configured to calculate the level of the digitized microphone signal and to supply the switching control signal to the controllable switching mechanism, the switching control signal Is a digital switching control signal,
25. A hearing device according to item 24.

26. A microphone assembly for a hearing device,
A microphone with a microphone transducer element provided in the microphone housing and configured to provide a transducer signal in response to sound reception;
A microphone amplifier circuit configured to generate an amplified microphone signal based on the transducer signal;
A level detector configured to detect the level of the microphone signal;
With
The microphone amplifier circuit is coupled to a switchable power supply, the switchable power supply being a first power supply voltage or a second power supply having a first DC voltage level based on the detection level of the microphone signal. A second power supply voltage having a DC voltage level is selectively connected to the microphone amplifier circuit, the second DC voltage level being higher than the first DC voltage level;
Microphone assembly.

27. The switchable power source includes a controllable switching mechanism that responds to a switching control signal generated by the level detector,
The controllable switching mechanism is connected to the first power supply voltage and the second power supply voltage via first and second switching inputs, respectively.
The switchable power supply is configured to selectively connect the first power supply voltage or the second power supply voltage to the microphone amplifier circuit according to the switch control signal.
27. A microphone assembly according to item 26.

28. The microphone amplifier circuit is
Coupled to the microphone transducer element and configured to receive power from a third power supply voltage having a third DC voltage level that is lower than the first power supply voltage or the second DC voltage level. A first preamplifier,
A second preamplifier comprising a signal input port coupled to a signal output port of the first preamplifier and a power supply port coupled to the switchable power supply;
27. The microphone assembly of item 26, comprising:

29. 28. The microphone assembly of claim 27, further comprising a bias current source coupled between an input transistor of the microphone amplifier circuit and an output of the controllable switching mechanism.

30. 30. The microphone assembly of item 29, wherein the bias current source is configured to provide a substantially constant bias current independent of the level of the microphone signal.

31. A first bias current source coupled between the first power supply voltage and the first switching input of the controllable switching mechanism;
A second bias current source coupled between the second power supply voltage and the second switching input of the controllable switching mechanism;
28. The microphone assembly of item 27, further comprising:

32. A time constant circuit coupled to the level detector and configured to set an attack time and a release time of the switching control signal;
The switching control signal during the attack time disconnects the microphone amplifier circuit from the first power supply voltage and connects the microphone amplifier circuit to the second power supply voltage via the controllable switching mechanism. 28. The microphone assembly according to item 27.

33. The controllable switching mechanism is
A first semiconductor switch connected between the first switching input and the switching output;
A second semiconductor switch connected between the second switching input and the switching output;
28. The microphone assembly of item 27, wherein each of the first and second semiconductor switches has a control terminal coupled to the level detector.

34. A first bias current source is integrated with the first semiconductor switch of the controllable switching mechanism, and a second bias current source is integrated with the second semiconductor switch of the controllable switching mechanism. 34. A microphone assembly according to item 33.

  While specific embodiments have been illustrated and described, it will be understood that they are not intended to limit the claimed invention and those skilled in the art will not depart from the spirit and spirit of the claimed invention. It will be apparent that various changes and modifications can be made. The specification and drawings are, accordingly, to be regarded in an illustrative sense rather than a restrictive sense. The claimed invention is intended to cover alternatives, modifications and equivalents.

Claims (15)

A microphone comprising a microphone transducer element provided in the microphone housing and configured to provide a transducer signal in response to receiving sound;
A microphone amplifier circuit configured to generate an amplified microphone signal based on the transducer signal;
A control processing circuit coupled to the microphone amplifier circuit for receiving the amplified microphone signal and processing in response to a user's hearing impairment;
A level detector configured to detect the level of the amplified microphone signal;
With
The microphone amplifier circuit is coupled to a switchable power supply, the switchable power supply being a first power supply voltage having a first DC voltage level based on the detection level of the amplified microphone signal or A second power supply voltage having a second DC voltage level is configured to be selectively connected to the microphone amplifier circuit, wherein the second DC voltage level is higher than the first DC voltage level;
Hearing device. The microphone amplifier circuit is
Coupled to the microphone transducer element and configured to receive power from a first power supply voltage or a third power supply voltage having a third DC voltage level that is lower than the second DC voltage level. A first preamplifier;
A second preamplifier comprising a signal input port coupled to a signal output port of the first preamplifier and a power supply port coupled to the switchable power supply;
The hearing device according to claim 1, comprising: The microphone transducer element and the first preamplifier are disposed in a microphone housing of the microphone with a power supply terminal coupled to the first or third power supply voltage;
The second preamplifier, the first and second power supplies, and the level detector are integrated in the control processing circuit of the hearing device;
The hearing device according to claim 2.   The switchable power supply connects the first power supply voltage to the microphone amplifier circuit when the detection level is lower than a predetermined threshold level, and the detection level is equal to or higher than the predetermined threshold level. The hearing device according to claim 1, wherein the hearing device is configured to connect the second power supply voltage to the microphone amplifier circuit. The switchable power source includes a controllable switching mechanism that responds to a switching control signal generated by the level detector,
The controllable switching mechanism is coupled to the first power supply voltage and the second power supply voltage via first and second switching inputs, respectively.
The switchable power supply is configured to selectively connect the first power supply voltage or the second power supply voltage to the microphone amplifier circuit according to the switch control signal.
The hearing device according to claim 1. The microphone amplifier circuit further comprises an analog to digital converter configured to generate a digitized microphone signal based on the amplified microphone signal;
The level detector includes a digital level detector configured to calculate the level of the digitized microphone signal and to supply the switching control signal to the controllable switching mechanism, the switching control signal Is a digital switching control signal,
The hearing device according to claim 5. A microphone assembly for a hearing device,
A microphone with a microphone transducer element provided in the microphone housing and configured to provide a transducer signal in response to sound reception;
A microphone amplifier circuit configured to generate an amplified microphone signal based on the transducer signal;
A level detector configured to detect the level of the microphone signal;
With
The microphone amplifier circuit is coupled to a switchable power supply, the switchable power supply being a first power supply voltage or a second power supply having a first DC voltage level based on the detection level of the microphone signal. A second power supply voltage having a DC voltage level is selectively connected to the microphone amplifier circuit, the second DC voltage level being higher than the first DC voltage level;
Microphone assembly. The switchable power source includes a controllable switching mechanism that responds to a switching control signal generated by the level detector,
The controllable switching mechanism is connected to the first power supply voltage and the second power supply voltage via first and second switching inputs, respectively.
The switchable power supply is configured to selectively connect the first power supply voltage or the second power supply voltage to the microphone amplifier circuit according to the switch control signal.
The microphone assembly of claim 7. The microphone amplifier circuit is
Coupled to the microphone transducer element and configured to receive power from a third power supply voltage having a third DC voltage level that is lower than the first power supply voltage or the second DC voltage level. A first preamplifier,
A second preamplifier comprising a signal input port coupled to a signal output port of the first preamplifier and a power supply port coupled to the switchable power supply;
The microphone assembly of claim 7 comprising:   The microphone assembly of claim 8, further comprising a bias current source coupled between an input transistor of the microphone amplifier circuit and an output of the controllable switching mechanism.   The microphone assembly of claim 10, wherein the bias current source is configured to provide a substantially constant bias current independent of the level of the microphone signal. A first bias current source coupled between the first power supply voltage and the first switching input of the controllable switching mechanism;
A second bias current source coupled between the second power supply voltage and the second switching input of the controllable switching mechanism;
The microphone assembly of claim 8 further comprising: A time constant circuit coupled to the level detector and configured to set an attack time and a release time of the switching control signal;
The switching control signal during the attack time disconnects the microphone amplifier circuit from the first power supply voltage and connects the microphone amplifier circuit to the second power supply voltage via the controllable switching mechanism. The microphone assembly of claim 8. The controllable switching mechanism is
A first semiconductor switch connected between the first switching input and the switching output;
A second semiconductor switch connected between the second switching input and the switching output;
9. The microphone assembly of claim 8, wherein each of the first and second semiconductor switches has a control terminal coupled to the level detector.   A first bias current source is integrated with the first semiconductor switch of the controllable switching mechanism, and a second bias current source is integrated with the second semiconductor switch of the controllable switching mechanism. The microphone assembly of claim 14.

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