Inductive excursion sensing for audio transducers

Abstract

The present disclosure relates to inductive excursion sensing for audio transducers. Techniques, methods, systems and other mechanisms for measuring the excursion of a loudspeaker when actively driven. Measuring the excursion may involve attaching a flexible printed coil (FPC) including a sensing coil to the loudspeaker and monitoring the induced current as generated by the sensing coil and further detecting a possible violation of the excursion limit of the loudspeaker.

Description

[0001] Description of the case

[0002] This application is a divisional application of Chinese invention patent application No. 201880033704.5, filed on December 14, 2018. Technical Field

[0003] The present application relates to techniques, methods, systems and other mechanisms for measuring the excursion of a loudspeaker when being actively driven. Background Art

[0004] Many electronic devices are capable of presenting multimedia content by including speakers that provide tonal, voice-generated or recorded outputs. Some speakers are designed to have a smaller physical size in order to facilitate integration into various electronic devices (e.g., mobile phones, smart home devices) with a range of different sizes. Typically, a speaker is associated with a limited distance that the speaker's film can move freely before making contact with an obstacle (e.g., a top plate, a bracket). In some cases such as driving a speaker to reproduce lower-frequency sounds (e.g., below the resonant frequency of the transducer), the vibrating film may experience a movement (also referred to as an excursion or excursion range) that reaches a threshold of the limited distance. A speaker driven beyond the excursion constraint may produce an audio output of degraded quality (e.g., friction and noise associated with collisions with the film). Therefore, physical damage to the speaker itself may occur due to exceeding the excursion range or other related factors. Small speakers such as micro speakers have a more stringent excursion range (relative to larger speakers) due to their limited size and may be more easily affected by operations outside the excursion limit. Summary of the invention

[0005] Techniques, methods, systems, and other mechanisms for measuring the excursion of a speaker when actively driven are described herein. Measuring the excursion may involve attaching a flexible printed coil (FPC) including a sensing coil to the speaker and monitoring an induced current such as that generated by the sensing coil and further detecting a possible violation of the excursion limit of the speaker.

[0006] In certain instances, specific implementations of the disclosed technology can achieve one or more of the following advantages. The technology described in the present disclosure involves using an offset measurement component that generates an electrical signal by induction, and the electrical signal is monitored to determine the offset distance associated with the speaker when it is excited. Therefore, the technology enables an electronic device to dynamically detect that the speaker is operating at a level that causes a non-compliant offset of the voice coil, which non-compliant offset can, for example, cause unexpected effects (e.g., degrade audio quality or damage the speaker). The method can achieve improved accuracy compared to technologies that involve estimating and / or modeling offset distances. For example, some technologies that measure various nonlinear parameters of the speaker (e.g., voltage across the speaker, current through the voice coil) to approximate the offset may be less accurate as the speaker oscillates away from its initial resting position and the behavior of the parameter becomes more nonlinear. In addition, the speaker is configured to include an offset measurement component that can be implemented as a sensing coil printed on a flexible printed circuit, which can eliminate the need to add more complex mechanical or processing components to the electronic device intended to perform the offset detection / compensation function. In this way, the disclosed technology can involve various advantages, such as reduced size and / or cost of the electronic device compared to alternative mechanisms.

[0007] The details of one or more embodiments are set forth in the accompanying drawings and the description that follows. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 is a diagram of an electronic device including components configured to measure excursions that a speaker may experience at low frequency levels.

[0009] FIG. 2A to FIG. 2B is a schematic diagram of a loudspeaker including an excursion measurement assembly that may implement the disclosed techniques.

[0010] Figure 3 is a conceptual diagram of a system configured to measure the active excursion distance of an element (eg, a voice coil) of a loudspeaker.

[0011] Figure 4 is a flow chart of an example method for measuring the active excursion distance of an element of a loudspeaker during excitation.

[0012] Like reference numbers in the various drawings indicate like elements. DETAILED DESCRIPTION

[0013] Figure 11 is a diagram of an electronic device 100, such as a mobile phone as depicted, that includes a speaker 102 and a system 120 for measuring excursions of one or more components of the speaker 102, such as at low frequency levels. During operation, the electronic device 100 generates audible sounds for a user using the speaker 102. Such sounds may include sounds from voice phone calls, may include recorded sounds (e.g., voice messages, music files, etc.), and may also include sounds generated by applications operating on the electronic device 100.

[0014] The speaker 102 includes an electroacoustic transducer that converts an electrical audio signal into a corresponding sound. Figure 1 The speaker 102 is shown as an internal component of the electronic device 100, but it should be appreciated that the speaker 102 can also be implemented as an external and / or independent device. For example, the speaker 102 can be an independent micro speaker that communicates with the electronic device 100 using a wireless technology standard such as Bluetooth to output the audio produced by the electronic device 100. For the purpose of discussion, the speaker 102 and the excursion measurement technique are discussed with reference to a micro speaker. However, it should be appreciated that the technique can be applied to larger scale transducers, such as home speakers, car speakers, etc.

[0015] As shown, speaker 102 has a membrane 125 located over at least one surface. Membrane 125 may be a thin sheet of semi-rigid material that transmits sound while acting as a barrier to prevent liquids, such as water, from entering speaker 102 and potentially damaging its electrical components. Figure 1 Also illustrated are examples of the excursions associated with the speaker 102 and the physical location of the membrane 125. In this example, the excursion limit is shown as the distance between the membrane 125 and a surface of the electronic device 100 that may serve as a front plate or partial cover for the speaker 102. In some cases, this distance is approximately measured in millimeters, such as 0.5 mm. Thus, the membrane 125 is physically prevented from moving outward beyond the displacement of the front surface, and in this case, the excursion limit is a physical constraint defined by the mechanical configuration of the speaker 102. That is, the membrane 125 is prevented from reaching its full range of motion in one direction due to its placement. Although not shown in FIG. Figure 1 1, but the membrane 125 may also be associated with an excursion limit in the opposite direction, which involves inward movement toward other elements of the speaker 102. As a result, the excursion measurement system 120 is configured to measure positive excursion (e.g., +x-axis direction), negative excursion (e.g., -x-axis direction), or both. In some embodiments, the technique takes into account the excursion from an initial resting position, also referred to as a DC level or zero position of the transducer.

[0016] In some cases, the speaker 102 can be driven at various low frequencies and high pressure conditions, which can cause the membrane 125 to oscillate farther, have a larger displacement, and potentially contact the surface of the electronic device 100. In the case of high pressure, the pressure level output can be directly related to the amount of air volume displacement. Higher pressures can cause the membrane 125 to displace, such as pushing the membrane 125 outward because the pressure inside the speaker 102 is greater than the pressure outside the device.

[0017] As some background on speaker operation, the membrane 125 or diaphragm of the speaker 102 oscillates to generate sound waves in the air and thus produce sound. It does so by oscillating back and forth through a determinable center position, which may be the same position where the membrane 125 would rest when no electrical signal is provided to the speaker 102 (and when the pressures on both sides of the membrane are equal). Figure 1 In the illustrated lower frequency case, the speaker 102 can output an audio signal 106 associated with a low frequency. Thus, when an oscillating electrical signal at a lower frequency is applied to the speaker 102, the speaker membrane 125 can undergo a larger oscillation. The membrane 125 can be pushed farther outward due to the air displacing a larger amount of air in order to produce an audio signal 106 with a lower audible tone (e.g., bass). In other words, a signal at a higher frequency that would not normally cause the speaker 102 to reach its limit of movement in any given direction can reach such a limit due to the speaker membrane 125 being pushed in that direction due to the displacement of air across the speaker membrane 125. As a result, the membrane 125 can begin to reach the limit of its ability to protrude in that direction when the audio output is played. This contact between the membrane 125 and the top surface can cause audible distortion of the audio output 106 to the user, such as a hum that can be heard when playing bass.

[0018] To correct for degradation of the audio signal 106 that may be caused by excursion-related factors, the speaker 102 includes an excursion measurement system 120. The system 120 may include electronics configured to determine the active excursion distance of an element while the speaker 102 is excited, and then detect whether continuing to drive the speaker 102 may violate any known excursion limit constraints. Figure 1, the measured excursion distance can be the current position of the membrane 125 relative to movement within the excursion-limited free space. For example, the excursion measurement system 120 can measure that the membrane 125 is located at a distance of 0.4 mm within a 0.5 mm excursion space (e.g., a distance of 0.1 mm from the top surface). Subsequently, based on this measurement, the excursion measurement system 120 can further detect that the speaker 102 has reached or exceeded a threshold corresponding to an acceptable excursion distance (e.g., no audible distortion or device damage). Optionally, in some embodiments, the excursion measurement system 120 also performs actions that allow the speaker 102 to compensate for any such displacement (e.g., reducing gain, activating a compressor).

[0019] As a general description, the offset measurement system 120 includes an offset measurement component implemented as a sensing coil. The system 120 monitors an electrical signal generated by a magnetic field inductively coupled to the sensing coil to measure the offset distance. Figure 2A-2B The offset measurement techniques and systems are discussed in more detail.

[0020] Figure 2A-2B is a schematic diagram of a speaker 200 including an excursion measurement assembly that can implement the disclosed techniques. The speaker 200 or an audio transducer can be used to implement the disclosed techniques. As some background on the operation of the speaker, the speaker 200 can be configured to convert an electrical signal into acoustic energy. Many variations of existing transducers, including Figure 2A-2B The moving coil-permanent magnet transducer shown in FIG. The loudspeaker 200 includes a membrane 205, an excursion measurement assembly 210, a magnetic system 215, and a diaphragm 220. The membrane 205 is located above the magnetic system 215 and can be configured to oscillate to generate sound waves in the air. The diaphragm 220 is located above the membrane 205 and can be configured to oscillate to transmit sound. Figure 2A-2B In FIG, the excursion measurement component 210 is shown as a sensing coil printed on a flexible printed circuit (FPC) and attached to the frame of the speaker. Figure 2A In FIG. 2 , a loudspeaker 200 is configured with an excursion measurement assembly 210 at the top of the driver. Figure 2B An alternative configuration of a loudspeaker 200 is shown that includes an excursion measurement assembly 210 at the base of the driver. Figure 2B still Figure 2B The configurations of the speaker 200 may be based at least in part on various physical and / or functional aspects of the speaker 200 (eg, associated with the manufactured product).

[0021] refer to Figure 2A, the deflection range can be generally described as the space between the magnetic system 215 and the bottom of the diaphragm 220. Therefore, the deflection measurement assembly 210 can be placed at the top of the diaphragm 220. This design can provide improved accuracy when tracking upward displacement (+y-axis direction).

[0022] refer to Figure 2B , the excursion measurement assembly 210 is positioned on the back of the magnetic system 215. This configuration may have functional constraints due to placing the sensing coil at the bottom of the magnetic element of the speaker 200. In some cases, the DC magnetic field may interfere with the measurement. In other cases, the bottom metal plate may shield the magnetic field generated by the voice coil of the speaker 200, which in turn may adversely affect the inductive coupling to the sensing coil. Figure 2B A system of configuration can be designed to take into account these and other constraints. The system can be calibrated to subtract the DC component from the electrical signal. For example, a high pass filter can be placed near the ADC path to subtract the DC component. In addition, the reference signal can be amplified to compensate for any shielding experienced.

[0023] The speaker 200 includes a voice coil that can be constructed using a thin wire suspended within a magnetic field generated by a magnet. In addition, the voice coil can be used as an electromagnet because the speaker 200 includes a soft metal core formed in a magnet by passing an electric current through the voice coil around it, thereby creating an electromagnetic field. The voice coil is configured to move or rotate within the magnetic field.

[0024] When the speaker 200 is excited, the speaker 200 oscillates and causes the voice coil to also become displaced by moving. As an example, when an analog signal, which may be an input voltage signal, passes through the coil of the speaker 200, an electromagnetic field is generated and its signal strength is determined by the current flowing through the coil. The electromagnetic force generated by this field opposes the main permanent magnetic field around it and tries to push / pull the coil in one direction or the other depending on the interaction with the magnet.

[0025] The coil is coupled to a diaphragm 220, which also moves back and forth, and whose movement can cause disturbances in the air around it, thus producing sound. In the example where the input signal is a sine wave, then the diaphragm will pulse (e.g., in and out), the pulses pushing air as it moves, and generating audible tones representing the frequency of the signal. The strength and therefore the speed at which the diaphragm 220 moves and pushes the surrounding can be determined at least in part based on the input signal 204 applied to the electromagnet.

[0026] Since the voice coil is made of an inductive material (e.g., a metal wire), the coil may have inductance and impedance characteristics. In addition, the magnetic field from the voice coil close to the sensing coil may also induce a current flow in the sensing coil. In an instance where the voice coil moves closer to the sensing coil, the induced current flow increases, thereby increasing the amplitude of the current signal. Conversely, when the voice coil moves farther away from the sensing coil, the amplitude of the induced current flow decreases. Therefore, the system monitors the amplitude of the induced current signal to measure the offset. As an example, the induced current signal may be represented by an oscillating (e.g., a sinusoidal) signal having a peak-to-peak amplitude. The system may actively monitor changes in the amplitude of the signal while the speaker is driven. Subsequently, any monitored amplitude fluctuations such as increases or decreases may be associated with the physical distance between the voice coil and the sensing coil. Therefore, the system may use the known position of the sensing coil to determine the physical position of the voice coil indicating the offset distance. Therefore, the offset measurement component 210 implements a solution that provides actual measurement, rather than an estimate of the offset of the sensing voice coil, which may improve the overall accuracy of the system. In some cases, the disclosed techniques may be used to measure the deflection of other elements in loudspeaker 200 , such as diaphragm 220 and membrane 205 .

[0027] In some embodiments, various calibration techniques may be used to determine the association between the signal measurement and the active offset distance measurement. As an example, a calibration laser is employed to obtain feedback from the sensing coil during a measurement performed on a set of samples (e.g., 32 samples). Thus, a direct association or one-to-one relationship from the calibration may be stored in the system to implement the disclosed offset measurement technique. Continuing with this example, the calibration may determine that a peak voltage of 1.0V is received in the feedback from the sensing coil, which corresponds to 0.5mm. The calibration may be performed at the module level to account for assembly and static distance from the sensing coil to the voice coil. Calibration may also be required at the system level to account for ADC variations, which depend at least in part on the resolution required.

[0028] Figure 3 3 is a conceptual diagram of a system configured to measure the active excursion distance of an element (eg, a voice coil) of a speaker 300. As shown, the speaker 300 may receive as input an electrical signal that has been output from an amplifier 310. In addition, Figure 3An offset sensing component 305 is shown that generates an electrical signal in response to inductive coupling. The electrical signal can be an induced current signal propagated through a sensing coil, which is then received as an input at an analog-to-digital converter (ADC) 310. Subsequently, the induced current signal is analyzed by the system to monitor its amplitude. Moreover, for example, a direct current (DC) component of the electrical signal can be tracked by applying a low pass that averages the electrical signal over time to detect DC changes. In some cases, any amplitude changes that may not be considered to be generated as a DC component are tracked. DC can be used to determine the absolute resting position of the speaker and components. For example, the speaker can be considered to be at rest when no electrical signal is provided to the speaker 300.

[0029] In addition, the system is configured to apply an electrical signal at a high frequency (e.g., 21-22kHz) to the incoming electrical audio signal. Combining the signal is possible because, for example, at a depth of 16 or 24 bits, the playback sampling rate can be 48kHz or higher and the Nyquist frequency can be 24kHz or higher. In addition, the ADC can be clocked with a high oversampling to obtain a higher fidelity capture of the coil position. A reference electrical signal is generated as a result of combining the high frequency and audio signals. In instances where the speaker 300 has a small size, such as in the case of a micro speaker, the inductance of the coil is very low (e.g., a signal with a small peak-to-peak amplitude). The use of a reference signal is used to address the defects associated with analyzing small induced currents, and the accuracy of the system can be improved.

[0030] Figure 4 The present invention is a flow chart of an example method for measuring the active excursion distance of an element of a loudspeaker during excitation. The systems and techniques described herein can calculate real-time measurements of the position (and similar excursions) of components of a loudspeaker that may be associated with an excursion range, including a voice coil, a diaphragm, a magnet, and a membrane. The position measurement is based on an electrical parameter monitored while the loudspeaker reproduces audio, namely, the amplitude of an induced current signal of a sensing coil.

[0031] The process begins at block 405, where the system applies a high frequency signal to an incoming audio signal. The incoming audio signal may be audio content, such as music, to be reproduced by a speaker. Mixing the incoming audio signal with the high frequency signal results in a reference signal that is further analyzed by the system.

[0032] Next, at block 410, the system monitors the electrical signal generated by the inductive excursion measurement component. As disclosed, the system is configured to generate an induced current flow in the sensing coil. Subsequently, the system monitors the amplitude of the induced current flow.

[0033] Next, at box 415, an active offset distance, for example, associated with the displacement of the voice coil is determined. The system can use the amplitude of the induced current signal (obtained from monitoring) and the predetermined association between the physical position and the amplitude (previously stored in the system) to determine the active offset distance of the voice coil. Next, the system performs a check at box 420. The check determines whether the active offset distance is greater than a threshold value, and may potentially violate any offset constraints set by the system. For example, the system can compare the measured active offset distance for the voice coil with a predetermined threshold value associated with an acceptable offset. For example, the threshold value can be a predetermined distance about an offset range (e.g., ±0.5 mm) in which the voice coil has been observed to move freely (avoiding any accidental contact with other elements / obstructions), for example. In the case where the system determines that the voice coil has moved to a distance that reaches or exceeds the threshold value (i.e., yes), the process proceeds to box 430, and one or more actions are performed to compensate for the potential adverse polarization distance.

[0034] Alternatively, in the event that the system determines that the voice coil has moved to a distance below the threshold (ie, no), the system may continue to operate normally. Figure 4 In FIG. 4 , this is shown as block 425 , where the audio signal is output without performing any compensating actions or signal modification. Figure 4 The excursion measurement is illustrated as an iterative process of repeatedly measuring the induced current signal at various time intervals (while driving the loudspeaker), thereby achieving continuous and / or real-time excursion sensing.

[0035] Various implementations of the systems and techniques described herein can be implemented in digital circuitry, integrated circuitry, specially designed ASICs (application specific integrated circuits), computer hardware, firmware, software, and / or combinations thereof. These various implementations may include implementation in one or more computer programs that can be executed and / or interpreted on a programmable system that includes at least one programmable processor, which may be special-purpose or general-purpose, coupled to receive data and instructions from and transmit data and instructions to a storage device, at least one input device, and at least one output device.

[0036] These computer programs (also referred to as programs, software, software applications or code) include machine instructions for a programmable processor and may be implemented in high-level procedural and / or object-oriented programming languages, and / or in assembly / machine language. As used herein, the terms "machine-readable medium" and "computer-readable medium" mean any computer program product, apparatus and / or device (e.g., a disk, optical disk, memory, programmable logic device (PLD)) for providing machine instructions and / or data to a programmable processor, including a machine-readable medium that receives machine instructions as a machine-readable signal. The term "machine-readable signal" means any signal used to provide machine instructions and / or data to a programmable processor.

[0037] To provide interaction with a user, the systems and techniques described herein can be implemented on a computer having a display device (e.g., a CRT (cathode ray tube) or LCD (liquid crystal display) monitor) for displaying information to the user and a keyboard and pointing device (e.g., a mouse or trackball) through which the user can provide input to the computer. Other types of devices can also be used to provide interaction with the user; for example, the feedback provided to the user can be any form of transducer feedback (e.g., visual feedback, auditory feedback, or tactile feedback); and the input from the user can be received in any form including sound, voice, or tactile input.

[0038] Further to the above description, the user may be provided with controls that allow the user to select whether and when the systems, processes, or features described herein can collect user information (e.g., information about the user's social network, social actions or activities, occupation, user preferences, or the user's current location) and whether to send content or communications from the server to the user. In addition, certain data may be processed in one or more ways before it is stored or used so that personally identifiable information is removed. For example, the user's identity may be processed so that personally identifiable information cannot be determined for the user, or the user's geographic location may be summarized so that the user's specific location cannot be determined when location information (such as city, zip code, or state level) is obtained. Therefore, the user can control what information is collected about the user, how the information is used, and what information is provided to the user.

[0039] Although several embodiments have been described in detail above, other modifications are possible. In addition, other mechanisms for executing the system and method described herein may be used. In addition, the logic flow depicted in the figure does not require the particular order or continuous order shown to achieve the desired result. Other steps may be provided, or steps may be omitted from the described flow, and other components may be added to the described system or components may be removed therefrom. Therefore, other embodiments are within the scope of the following claims.

Claims

1. An audio speaker system, include: a frame having a surface extending in a plane; a flexible printed circuit (FPC) coupled to the surface of the frame, wherein the FPC includes a sensing coil; magnet; a voice coil coupled to a diaphragm parallel to the surface of the frame, the voice coil defining a central axis extending in a first direction and positioned in the magnetic field of the magnet, the voice coil being configured to oscillate in the first direction when the voice coil is energized, wherein the FPC is positioned above the magnet in the first direction or below the magnet in the first direction; and An offset measurement system is configured to perform operations including: determining an electrical parameter of the current in the sensing coil; and Based on the electrical parameter, a distance between the voice coil and the sensing coil in the first direction is determined.

2. The system according to claim 1, in, The voice coil is coupled to the membrane and is configured to drive the membrane to generate sound waves.

3. The system according to claim 2, in, The voice coil includes a first end coupled to the membrane and a second end without the membrane, wherein determining the distance between the voice coil and the sensing coil in the first direction includes determining the distance between the sensing coil and the second end of the voice coil.

4. The system according to claim 1, in, Determining the electrical parameter of the current in the sensing coil includes measuring the amplitude of the current in the sensing coil.

5. The system according to claim 1, wherein the operation include: determining that the distance between the voice coil and the sensing coil violates a threshold distance; and Actions are performed to compensate for the distance between the voice coil and the sensing coil violating a threshold distance.

6. The system according to claim 5, in, Determining that the distance between the voice coil and the sensing coil violates a threshold distance includes determining that the distance between the voice coil and the sensing coil exceeds a maximum threshold distance.

7. The system according to claim 5, in, Determining that the distance between the voice coil and the sensing coil violates a threshold distance includes determining that the distance between the voice coil and the sensing coil is less than a minimum threshold distance.

8. The system according to claim 5, in, Performing the actions to compensate for the distance between the voice coil and the sensing coil violating the threshold distance includes performing at least one of: reducing the gain of the electrical audio signal applied to the voice coil, or Audio compression of the electrical audio signal applied to the voice coil is adjusted.

9. The system according to claim 5, in, The threshold distance is associated with an acceptable excursion range for the audio speaker system.

10. The system according to claim 9, in: The voice coil is configured to oscillate about a center position, and The acceptable deviation range is the range measured from the center position.

11. The system according to claim 1, in, The voice coil is energized by applying an electrical audio signal to the voice coil.

12. The system according to claim 11, in, Oscillation of the voice coil induces a current signal in the sensing coil. 13 . The system of claim 12 , further comprising a high pass filter configured to subtract a DC component from the sensed current signal.

14. The system of claim 12, further comprising an analog-to-digital converter receiving the sensed current signal as an input.

15. The system according to claim 14, in, The analog-to-digital converter is clocked at a sampling rate greater than a frequency of the electrical audio signal.

16. The system of claim 1, wherein the operation further comprises: include: calibrating the FPC to determine a direct correlation between the electrical parameter of the current in the sensing coil and the distance between the voice coil and the sensing coil; and Data related to the direct association is stored.

17. The system of claim 16, the operations comprising using the data related to the direct association to determine the distance between the voice coil and the sensing coil in the first direction.

18. A method for measuring the excursion of an audio speaker, the audio speaker comprising a magnet and a voice coil positioned in a magnetic field of the magnet, the voice coil defining a central axis extending in a first direction and coupled to a diaphragm parallel to a surface of a frame of the audio speaker, the method include: energizing the voice coil, wherein the voice coil is configured to oscillate in the first direction when energized; determining an electrical parameter of a current in a sensing coil included in a flexible printed circuit (FPC) coupled to the surface of the frame of the audio speaker, wherein the FPC is positioned above the magnet in the first direction or below the magnet in the first direction; and Based on the electrical parameter, a distance between the voice coil and the sensing coil in the first direction is determined.

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