TW202345980A - Interference mitigation in an impedance sensing system - Google Patents

Abstract

A system may include driving circuitry configured to drive a driving signal to an output transducer, sensing circuitry configured to sense a physical quantity associated with the output transducer in response to the driving signal, and interference detection circuitry configured to detect the presence of interference of the system and mitigate the effect of the interference in the system.

Description

Interference suppression in impedance sensing systems

The present invention generally relates to methods, apparatus or implementations for monitoring loads with complex impedances. The embodiments described herein may also reveal improvements for suppressing noise and other interference that can adversely affect accurate and precise measurements of complex impedances.

Vibrotactile transducers, such as linear resonant actuators (LRA), are widely used in portable devices such as mobile phones to generate vibration feedback to a user. Various forms of vibrotactile feedback produce different touch sensations on a user's skin, and can play an increasing role in human-computer interaction in modern devices.

An LRA can be modeled as a mass-spring electromechanical vibration system. When driven with appropriately designed or controlled drive signals, an LRA can produce certain desired forms of vibration. For example, a sharp and distinct vibration pattern on a user's finger can be used to create a sensation that simulates the click of a mechanical button. This clear vibration can then be used as a virtual switch instead of a mechanical button.

Figure 1 illustrates an example of a vibrotactile system in a device 100. Device 100 may include a controller 101 configured to control a signal applied to an amplifier 102 . Amplifier 102 may then drive a vibration actuator (eg, tactile transducer) 103 based on the signal. The controller 101 can be triggered by a trigger to output to the signal. For example, the trigger may include a pressure or force sensor on a screen or virtual button of device 100 .

Among various forms of vibrotactile feedback, sustained tonal vibrations can play an important role in notifying the user of the device of certain predefined events, such as incoming calls or messages, emergency alarms, and timer warnings. In order to effectively generate tonal vibration notifications, it may be desirable to operate the haptic actuator at its resonant frequency.

The resonant frequency f ₀ of a tactile transducer can be approximately estimated as: (1) Where C is the flexibility of the spring system, and M is the equivalent moving mass, which can be determined based on both the actual moving parts in the tactile transducer and the mass of the portable device that holds the tactile transducer.

Vibrational resonance of tactile transducers due to sample-to-sample variation in individual tactile transducers, mobile device component variations, time component changes due to aging, and usage conditions of varying intensity such as a user grasping the device Can change from time to time.

Figure 2 shows an example of a linear resonant actuator (LRA) modeled as a linear system. LRAs are non-linear components that can behave differently depending on, for example, applied voltage level, operating temperature, and operating frequency. However, under certain conditions, these components can be modeled as linear components. In this example, the LRA is modeled as a third-level system with electrical and mechanical components. Specifically speaking, and are the DC resistance and coil inductance of the coil magnet system respectively; and is the magnetic factor of the coil. The driver amplifier output has an output impedance voltage waveform . Sensing terminal voltage across the terminals of a tactile transducer . Mass Spring System 201 with Velocity Move.

A haptic system may require precise control of the movement of the haptic transducer. This control can rely on magnetic factors , which can also be called the electromagnetic transfer function of the tactile transducer. In an ideal case, the magnetic factor can be obtained by multiplying given where B is the magnetic flux density and l is the total length of an electrical conductor in a magnetic field. In an ideal situation where motion occurs along a single axis, both the magnetic flux density B and the length l should remain constant.

An LRA may experience displacement when tactile vibrations are generated. To protect an LRA from damage, this displacement can be limited. Therefore, accurate measurement of displacement is crucial in optimizing the LRA displacement protection algorithm. Accurate measurement of displacement can also improve the driving level of LRA. Although existing methods measure displacement, these methods have shortcomings. For example, a Hall sensor can be used to measure displacement, but Hall sensors are often expensive to implement.

In accordance with the teachings of the present invention, disadvantages and problems associated with existing methods for monitoring a complex impedance may be reduced or eliminated.

According to embodiments of the present invention, a system may include drive circuitry configured to drive a drive signal to an output transducer, configured to sense in response to the drive signal associated with the output transducer. A sensing circuit for a physical quantity, and an interference detection circuit configured to detect the presence of interference in the system and suppress the effects of the interference in the system.

According to these and other embodiments of the invention, a method may include sensing a physical quantity associated with an output transducer in response to a drive signal to an output transducer, detecting the output transducer including the The existence of interference in a system and suppressing the effect of the interference in the system.

According to these and other embodiments of the invention, an integrated circuit may include a sensing circuit configured to sense a drive signal to an output transducer in response to one associated with an output transducer. a physical quantity; and a disturbance detection circuit configured to detect the presence of a disturbance in a system including the output transducer and to suppress the effects of the disturbance in the system.

The technical advantages of the present invention will be apparent to those of ordinary skill from the drawings, descriptions and technical solutions contained herein. The objectives and advantages of the embodiments will be realized and achieved by at least the components, features and combinations specifically pointed out in the technical solution.

It should be understood that both the foregoing general description and the following detailed description are examples and explanatory, and are not intended to limit the technical solutions set forth in the present invention.

Related applications

The present invention claims priority rights to U.S. Provisional Patent Application No. 63/308230, filed on February 9, 2022, the full text of which is incorporated herein by reference.

The following description sets forth example embodiments in accordance with the invention. Further example examples and implementations will be apparent to those of ordinary skill. Furthermore, those of ordinary skill will recognize that various equivalent techniques may be employed in place of or in combination with the embodiments discussed below, and all such equivalent techniques shall be deemed to be included in the present invention.

Various electronic devices or smart devices may have transducers, speakers, and acoustic output transducers, for example, any transducer that converts a suitable electrical drive signal into an acoustic output, such as a sound pressure wave or mechanical vibration. energy device. For example, many electronic devices may include one or more speakers or amplifiers for sound generation, for example, for playback of audio content, voice communications, and/or for providing audible notifications.

Such speakers or loudspeakers may include an electromagnetic actuator, for example, a voice coil motor, mechanically coupled to a flexible diaphragm, for example, a conventional loudspeaker cone, or its mechanical Coupled to a surface of a device, for example, a glass screen of a mobile device. Some electronic devices may also include acoustic output transducers capable of generating ultrasonic waves, for example, for proximity detection-type applications and/or machine-to-machine communications.

Many electronic devices may additionally or alternatively include more specific sound output transducers, for example, haptic transducers, which are tailored to generate vibrations for tactile control feedback or notification to a user as desired. Additionally or alternatively, an electronic device may have a connector, such as a socket, for a removable snap connection with a corresponding connector of an accessory device and may be configured to provide a connector to the connector. A drive signal to drive an accessory device, when connected, to one or more transducers of one of the above types. Therefore, such an electronic device will include drive circuitry for driving the transducer of the host device or connected accessory with a suitable drive signal. For acoustic or tactile transducers, the drive signal may typically be an analogous time-varying voltage signal, for example, a time-varying waveform.

In order to accurately sense the displacement of an electromagnetic load, the method and system of the present invention can determine the impedance of the electromagnetic load and then convert the impedance into a position signal, as described in more detail below. In addition, to measure the impedance of an electromagnetic load, the method and system of the present invention may utilize a phase measurement method and/or a high-frequency pilot tone driving method, as will be described in more detail below.

To illustrate, an electromagnetic load can be driven by a drive signal Driven to produce a sensed terminal voltage across a coil of an electromagnetic load . Sensing terminal voltage It can be given by: in is the current sensed through one of the electromagnetic loads, Z _COIL is the impedance of one of the electromagnetic loads, and is the back electromotive force (back EMF) associated with the electromagnetic load.

As used herein, "driving" an electromagnetic load means generating and communicating an actuation signal to the electromagnetic load to cause displacement of a movable mass of the electromagnetic load. In addition, "driving" an electromagnetic load may also mean driving a pilot signal or other test signal to the electromagnetic load, from which the electrical parameters of the electromagnetic load can be measured.

Because the back EMF voltage Can be proportional to the speed of the moving mass of the electromagnetic load, so the back EMF voltage An estimate of this speed can then be provided. Therefore, the self-sensing terminal voltage and the sensed current The speed at which the moving mass is restored, if: (a) the sensed current equals zero, in which case = ; or (b) the coil impedance Z _COIL is known or accurately estimated.

The position of the moving mass can be related to the impedance of an electromagnetic load, including the coil inductance L _COIL of the electromagnetic load. At high frequencies significantly above the electromagnetic load bandwidth, the back EMF voltage can become negligible and the inductance dominates the coil impedance Z _COIL . Terminal voltage sensed at high frequency It can be estimated by the following formula:

The inductance component of the coil impedance Z _COIL can indicate a position or a displacement of the moving mass of the electromagnetic load. To illustrate, this inductance can be a nominal value when the moving mass is stationary. As the mass moves, the magnetic field strength can be modulated by the position of the mass, which results in a small alternating current (AC) modulated signal in the inductance as a function of the mass's position.

Therefore, at high frequencies, the position of the moving mass of the electromagnetic load can be self-sensed by the terminal voltage and the sensed current Recovery: (a) Estimate the coil impedance at high frequency as , where R _@HF is the resistive part of the coil impedance at high frequency, L _@HF is the coil inductance at high frequency, and s is the Laplace transform; and (b) convert the measured inductance into a position signal . Speed and/or position can be used to control the vibration of a moving mass of an electromagnetic load.

FIG. 3 illustrates selected components of an example host device 300 having an electromagnetic actuator 304. Host device 300 may include, but is not limited to, a mobile device, home application, vehicle, and/or any other system, device, or device that includes a human-machine interface. Electromagnetic actuator 304 may include any suitable load with a complex impedance, including but not limited to a tactile transducer, a loudspeaker, a microspeaker, a voice coil actuator, a solenoid, or other suitable of transducers.

In operation, the signal generator 324 of the processing subsystem 305 of the host device 300 may generate a raw transducer drive signal. (In some embodiments, this may be a waveform signal, such as a tactile waveform signal or an audio signal). The original transducer drive signal may be generated based on a desired replay waveform received by signal generator 324 .

Waveform preprocessor 326 may receive the raw transducer drive signal , the waveform preprocessor may modify the original transducer drive signal based on parameters received by the self-impedance measurement subsystem 308 and/or based on any other factors. , in order to generate the processed transducer driving signal and . For example, this modification may include changes to the processed transducer drive signal and control to prevent over-driving of the electromagnetic actuator 304 which may cause damage. Additionally, the waveform preprocessor 326 may modify the original transducer drive signal based on the interference suppression signal generated based on the detected interference and received from the impedance measurement subsystem 308 , as described in more detail below.

Processed transducer drive signal It can then be amplified by amplifier 306a to generate a driving signal for driving electromagnetic load 301a. . Similarly, the processed transducer drive signal It can then be amplified by amplifier 306b to generate a driving signal for driving electromagnetic load 301b. . As shown in FIG. 3 , amplifiers 306 a and 306 b may be powered by a power supply voltage V _SUPPLY generated by a power converter 310 or other power source such that the power supply voltage V _SUPPLY exists across a capacitor 312 .

Therefore, the host device 300 is operable such that the electromagnetic actuator 304 is driven by the drive signal and drive signal Alternate drive. Thus, host device 300 may operate in a series of alternating phases: a first phase in which the drive signal to electromagnetic load 301a The electromagnetic actuator 304 is driven, and the electromagnetic load 301b is used to measure the displacement of the electromagnetic actuator 304, and a second phase, in which the driving signal driven to the electromagnetic load 301b The electromagnetic actuator 304 is driven, and the electromagnetic load 301a is used to measure the displacement of the electromagnetic actuator 304.

One of the electromagnetic loads 301a senses terminal voltage Can be sensed by impedance measurement subsystem 308 (eg, using a voltmeter). Similarly, the sensing current through the electromagnetic load 301a Can be sensed by impedance measurement subsystem 308. For example, current The voltage can be sensed across a shunt resistor 302a Sense, shunt resistor 302a has resistance _Rs coupled to one terminal of electromagnetic load 301a.

Likewise, one of the electromagnetic loads 301b senses the terminal voltage Can be sensed by impedance measurement subsystem 308 (eg, using a voltmeter). Similarly, the sensing current through the electromagnetic load 301b Can be sensed by impedance measurement subsystem 308. For example, current The voltage can be sensed across a shunt resistor 302b Sense, shunt resistor 302b has resistance _Rs coupled to one terminal of electromagnetic load 301b.

Although the foregoing considers two sense resistors having resistance _Rs , it should be understood that in some embodiments, the resistance of one of shunt resistor 302a may be different than the resistance of shunt resistor 302b. In fact, even if it is desired that the resistance of shunt resistor 302a be the same as the resistance of shunt resistor 302b, these resistances may be different due to process variations and tolerances.

As shown in Figure 3, and as described in more detail below, processing subsystem 305 may include an impedance measurement subsystem 308 that may estimate the respective coil inductance L _COIL of electromagnetic loads 301a and 301b. Based on the estimated coil inductance L _COIL , the impedance measurement subsystem 308 may determine a displacement associated with the electromagnetic load (301a or 301b). Based on the determined displacement, the impedance measurement subsystem 308 may communicate one or more parameters (including but not limited to the value of the displacement) to the waveform preprocessor 326 , which may cause the waveform preprocessor 326 to modify the original transducer. driving signal . In some embodiments, this displacement may also be indicative of a person's interaction (eg, exerted force) with the electromagnetic actuator 304 .

In operation, to estimate the impedance Z _COIL , the impedance measurement subsystem 308 may measure the impedance in any suitable manner, including but not limited to using the methods described in U.S. Patent Application No. 17/497110 filed on October 8, 2021 Methods, the full text of the case is incorporated herein by reference.

As a specific example, to estimate coil impedance Z _COIL , waveform preprocessor 326 may generate a processed transducer drive signal or (Depending on which solenoid 301 is the actuation coil used to drive the movement of the electromagnetic load (301a or 301b) and which solenoid 301 is used for sensing), the signal includes a high frequency excitation for driving the sensing coil. In response, the impedance measurement subsystem 308 can measure the impedance of the sensing coil.

Various methods can be used to estimate the coil impedance Z _COIL , including time domain and frequency domain methods. For example, frequency domain methods that rely on a discontinuous Fourier transform calculation can have the advantage of an implicit frequency grid of a spectrum that depends on the length of time over which current and voltage samples are collected. As a specific example, a discontinuous Fourier transform is calculated on the sense current and the sense terminal voltage over a duration of 200 μs, resulting in a frequency grid of 5 KHz. Additional windows on a signal before applying a discontinuous Fourier transform filter out harmonics and attenuate frequencies far away from the signal frequency. Therefore, when using this method, the measurement accuracy can only be affected by the interference energy or noise falling within a signal frequency bin or at the peak of the window function.

Accurate estimation of complex impedances may require minimizing noise, offset errors, gain errors, and/or other interference added by the measurement circuitry. Although offset and gain errors can be minimized through calibration, and thermal and quantization noise can be minimized through precise circuit design, power supply noise can still cause degradation in measurement performance.

To account for this source of power noise, various components of host device 300 may operate from different power rails. For example, amplifiers 306a and 306b may operate from supply voltage V _SUPPLY , the analog portion of impedance measurement subsystem 308 may operate from an analog supply rail (eg, the analog supply voltage VDDA shown in Figure 4), and the impedance quantity The digital portion of the measurement subsystem 308 may operate on a digital power rail (eg, the digital power supply voltage VDDD shown in Figure 4). Noise on either of these rails can introduce additional noise into the measured voltage and current, thus affecting the accuracy of the measurements.

In addition, interference signals incident on device pins can increase measurement noise. In addition, the presence of noise in boost rail powered amplifiers 306a and 306b caused by the replay of a tactile tone or a pilot tone on one channel can increase the measurement on the impedance sensing circuit of the other channel. Noise.

Other potential sources of interference may include radio frequency interference directly incident on the device pins coupled to the electromagnetic actuator 304, substrate noise, and/or other spurious noise coupled into the sensing path from adjacent traces or blocks. .

FIG. 4 illustrates selected components of an example impedance measurement subsystem 308 according to an embodiment of the present invention. As shown in Figure 4, the sensing terminal voltage of the electromagnetic load 301a It can be adjusted by an analog front end (AFE) 401a and converted to a sensing terminal voltage by an analog to digital converter (ADC) 403a One digit representation. Similarly, the sensing terminal voltage of the electromagnetic load 301b It can be adjusted by an AFE 401b and converted to the sensing terminal voltage by an analog-to-digital converter (ADC) 403b One digit representation. Similarly, indicating current The sensing voltage May be conditioned by an AFE 402a and converted to a digital representation by an ADC 404a. Similarly, indicating current The sensing voltage Can be adjusted by an AFE 402b and converted to a digital representation by an ADC 404b.

Sense terminal voltage , sensing terminal voltage , sensing voltage and sensing voltage The digital representation may be received and processed by an impedance estimator 410, which may determine the coil impedance Z _COIL based on Ohm's law, as described in greater detail above.

As also shown in FIG. 4 , the impedance measurement subsystem 308 may also include components for detecting and suppressing interference present in the host device 300 that may adversely affect the measurement accuracy of the impedance estimator 410 , including the above. Describe the sources of interference. For example, the impedance measurement subsystem 308 may include a voltage clipping detection circuit 412, a current clipping detection circuit 414, and an interference determination circuit 416. In operation, a larger-than-expected in-band signal may cause signal clipping at any of the AFEs 401a, 401b, 402a, and 402b and/or any of the ADCs 403a, 403b, 404a, and 404d (e.g., the desired The signal amplitude is greater than a supply voltage, causing the signal to be "clipped" by the amplitude of the supply voltage), thus introducing errors into the impedance measurement. Assuming that the downstream processing blocks of the impedance estimator 410 may not be aware of any upstream clipping, the signals measured at the outputs of these processing blocks may not be used to detect the presence of interference. Accordingly, each of voltage clipping detection circuit 412 and current clipping detection circuit 414 may be configured to determine whether signal clipping occurs in either or both of the measured voltage and current signals, for example. In other words, by comparing these signals to a threshold equal to the associated supply voltage (eg, VDDA) minus a predetermined signal tolerance. If one or more of these signals exceeds their respective thresholds, interference determination circuit 416 may determine that interference is present and generate one or more interference suppression signals to suppress the presence of interference, as described in greater detail below.

As also shown in Figure 4, the impedance measurement subsystem 308 may include a plurality of fast Fourier transform (FFT) blocks 418, each FFT block 418 configured to output one of the ADCs 403a, 403b, 404a, and 404b. Perform a fast Fourier transform. In addition to or alternatively to the clipping detection method described above, when no signal is driven to the electromagnetic actuator 304, or as a result of an undesired tactile effect being driven to the electromagnetic actuator 304, or as As a result of a zero-amplitude signal being driven into one of the dedicated detection modes of the electromagnetic actuator 304, the interference determination circuit 416, in cooperation with the FFT block 418, can perform a zero-signal interference detection. When no signal is driven to the electromagnetic actuator 304, both the measured voltage across an electromagnetic load 301 and the current through the electromagnetic load 301 should ideally be zero. However, if one or both of the measured currents is above a respective threshold when no signal is driven to the electromagnetic actuator 304, then the interference determination circuit 416 can safely conclude that an in-band interference exists. This voltage and current comparison can be performed after the FFT bins of the measured voltage and current signals to compare the signal amplitude in each bin to a threshold to ensure measurement and identification of any interference in the band of interest signal.

Although FIG. 4 depicts FFT block 418 as external to impedance estimator 410, in some embodiments, FFT block 418 may be integrated with impedance estimator 410.

In addition to or alternatively to the clipping detection method and/or the zero signal detection method described above, the interference determination circuit 416 cooperates with the FFT block 418 to perform a direct interference detection for an interference. To illustrate, the interference determination circuit 416 may determine a frequency of an interference by calculating a DFT over a period longer than a typical impedance estimation period. This longer estimation period divides the spectrum into narrower bins, helping to pinpoint the frequency of interference relative to the signal frequency. For example, an FFT bin may be f _s /N wide, where N is the number of FFT points and f _s is the sampling frequency. For a first number N ₁ of FFT points, any potential interference falling outside one frequency bin can be rejected as a non-interfering signal. However, any interference falling within the signal bin can be detected by computing a larger FFT with a second number of N ₂ > N ₁ FFT points, with the hope of placing the signal and potential interference in a separate bin. . The presence of energy in a frequency bin adjacent to that of the signal in the larger FFT identifies the presence of in-band interference, while the lack of energy in an adjacent frequency bin in the larger FFT confirms the absence of an interfering signal.

Having detected the presence of interference using one or more of the aforementioned methods, the interference determination circuit 416 may suppress the interference using one or more of the methods described below or using any other suitable method. For example, in some embodiments, the interference determination circuit 416 may suppress the effects of a signal interference by increasing the amplitude of the signal frequency. In such embodiments, it may be preferable to only increase the amplitude as long as no clipping occurs in the signal path of the sensing circuit.

As another example, in these and other embodiments, interference determination circuit 416 may suppress the effects of a signal interference by modifying the signal frequency so that the signal frequency and the interference frequency are not in adjacent FFT bins.

As a further example, in these and other embodiments, the interference determination circuit 416 may also cause a filter of the impedance estimator 410 to apply a notch or zero at the frequency of the interference to further suppress the effects of signal interference.

As yet another example, in these and other embodiments, if a source of interference is known, for example, a ripple on supply voltage V _SUPPLY , interference determination circuit 416 may be configured to cause such The decay of the source. As a specific example, the capacitance of capacitor 312 may be variable (e.g., where capacitor 312 may be implemented with a parallel combination of switched capacitive elements) in the case where the interference comes from a ripple on the supply voltage V _SUPPLY . And the interference determination circuit 416 can generate one or more interference suppression control signals (not clearly shown in FIG. 4 ) to increase the capacitance of the capacitor 312 to reduce the amplitude of the ripple relative to the signal amplitude.

As used herein, when two or more elements are referred to as being "coupled" with each other, this term indicates that the two or more elements are in electronic communication or mechanical communication, as applicable, whether indirectly connected or directly connected. Connections, with or without intervening elements.

The present invention includes all variations, permutations, alterations, alterations and modifications of the example embodiments herein that would be apparent to one of ordinary skill in the art. Likewise, where appropriate, the scope of the accompanying invention claims includes all variations, permutations, alterations, alterations and modifications of the example embodiments herein that would be apparent to one of ordinary skill in the art. Furthermore, within the patent scope of the accompanying invention application, a device or system or one of a device or system that is suitable for, configured to, capable of, configured to, enable, operate or operate to perform a specific function. A reference to a component includes that device, system or component, whether or not it or that particular function is enabled, enabled or unlocked, so long as the device, system or component is so adapted, configured, capable, configured, enabled, operable or operative. Accordingly, modifications, additions, or omissions may be made to the systems, devices, and methods described herein without departing from the scope of the invention. For example, components of systems and devices may be integrated or separated. Furthermore, operations of the systems and devices disclosed herein may be performed by more, fewer, or other components, and the methods described may include more, fewer, or other steps. Additionally, the steps may be performed in any suitable order. As used herein, "each" refers to each component of a collection or a subset of a collection.

Although illustrative embodiments are shown in the figures and described below, the principles of the invention may be implemented using any number of techniques, whether currently known or not. This invention should in no way be limited to the exemplary embodiments and techniques illustrated in the drawings and described above.

Items depicted in the drawings are not necessarily to scale unless expressly stated otherwise.

All examples and conditional language described herein are intended for teaching purposes to help readers understand the present invention and the concepts contributed by the inventor to advance this technology, and are not to be construed as limited to such explicitly stated examples and conditions. Although the embodiments of the present invention have been described in detail, it should be understood that various changes, substitutions and alterations can be made thereto without departing from the spirit and scope of the invention.

Although specific advantages have been enumerated above, various embodiments may include some, none, or all of the enumerated advantages. Additionally, other technical advantages may become apparent to those of ordinary skill upon review of the foregoing figures and descriptions.

To assist the Patent Office and any reader of any patent issued with respect to this application in interpreting the accompanying invention claims, Applicants wish to note that they do not intend that any accompanying invention claims or invention claim elements reference 35 U.S.C. § 112(f), unless the words "means for" or "step for" are expressly used in the patentable scope of a particular invention.

100:Device 101:Controller 102:Amplifier 103:Vibration actuator 201: Mass spring system 300: Host device 301a, 301b: Electromagnetic load 302a, 302b: shunt resistor 304:Electromagnetic actuator 305: Processing subsystem 306a, 306b: Amplifier 308: Impedance measurement subsystem 310:Power converter 312:Capacitor 324: Signal generator 326:Waveform preprocessor 401a, 401b, 402a, 402b: analog front end 403a, 403b, 404a, 404b: analog to digital converter 410: Impedance estimator 412: Voltage clipping detection circuit 414: Current clipping detection circuit 416: Interference determination circuit 418: Fourier Transform (FFT) block

A more complete understanding of this embodiment and one of its advantages may be obtained by referring to the following description taken in conjunction with the accompanying drawings, in which like reference numerals refer to like features, and in which:

Figure 1 illustrates an example of a vibrotactile system in a device known in the art;

Figure 2 illustrates an example of a linear resonant actuator (LRA) known in the art modeled as a linear system;

3 illustrates selected components of an example host device according to one embodiment of the invention; and

Figure 4 illustrates selected components of an example impedance measurement subsystem according to an embodiment of the invention.

300: Host device

301a, 301b: Electromagnetic load

302a, 302b: shunt resistor

304:Electromagnetic actuator

305: Processing subsystem

306a, 306b: Amplifier

308: Impedance measurement subsystem

310:Power converter

312:Capacitor

324: Signal generator

326:Waveform preprocessor

Claims (27)

A system that includes: a drive circuit configured to drive a drive signal to an output transducer; a sensing circuit configured to sense a physical quantity associated with the output transducer in response to the drive signal; and Interference detection circuit configured to: detect the presence of interference in the system; and Suppress the effects of this interference in the system. The system of claim 1, wherein the output transducer is a tactile actuator. The system of claim 1, wherein the output transducer is an audio transducer. The system of claim 1, wherein the driving signal includes a pilot tone. The system of claim 1, wherein the physical quantity is an impedance associated with the output transducer. The system of claim 1, wherein the sensing circuit is configured to sense the physical quantity based on one or more of a voltage associated with the output transducer and a current associated with the output transducer . The system of claim 1, wherein the interference detection circuit is configured to detect the presence of interference in the system by detecting signal clipping within a signal sensing path of the sensing circuit. The system of claim 1, wherein the interference detection circuit is configured to detect the system by detecting the presence of an in-band signal above a threshold level in response to the drive signal being of zero amplitude. The presence of interference. The system of claim 1, wherein the interference detection circuit is configured to detect the system interference by performing a conversion on a quantity measurement measured by the sensing system to directly determine a frequency of the interference exists, and the frequency bin of the conversion is selected to be able to determine the frequency of the interference by the presence of the interference in a first frequency bin adjacent to a second frequency bin that includes the signal. The system of claim 1, wherein the interference detection circuit is configured to suppress the effect of the interference in the system by modifying an amplitude of the drive signal. The system of claim 1, wherein the interference detection circuit is configured to suppress the effect of the interference in the system by modifying a frequency of the drive signal. The system of claim 1, wherein the interference detection circuit is configured to suppress the effect of the interference in the system by causing the sensing circuit to attenuate signal energy at a frequency of the interference. The system of claim 1, wherein the interference detection circuit is configured to suppress the effects of the interference in the system by attenuating a source of the interference. A method including: sensing a physical quantity associated with an output transducer in response to a drive signal to the output transducer; detecting the presence of interference in a system including the output transducer; and Suppress the effects of this interference in the system. The method of claim 14, wherein the output transducer is a tactile actuator. The method of claim 14, wherein the output transducer is an audio transducer. The method of claim 14, wherein the driving signal includes a pilot tone. The method of claim 14, wherein the physical quantity is an impedance associated with the output transducer. The method of claim 14, further comprising sensing the physical quantity based on one or more of a voltage associated with the output transducer and a current associated with the output transducer. The method of claim 14, further comprising detecting the presence of the system interference by detecting signal clipping within a signal sensing path of the sensing circuit. The method of claim 14, further comprising detecting the presence of the system interference by detecting the presence of an in-band signal above a threshold level in response to the drive signal being of zero amplitude. The method of claim 14, further comprising detecting the presence of the system interference by performing a conversion on a quantity measurement measured by the sensing system to directly determine a frequency of the interference, and the converted frequency The frequency bin is selected such that the frequency of the interference can be determined by the presence of the interference in a first frequency bin adjacent to a second frequency bin containing the signal. The method of claim 14, further comprising suppressing the effect of the interference in the system by modifying an amplitude of the drive signal. The method of claim 14, further comprising suppressing the effect of the interference in the system by modifying a frequency of the drive signal. The method of claim 14, further comprising suppressing the effects of the interference in the system by causing the sensing circuit to attenuate signal energy at a frequency of the interference. The method of claim 14, further comprising suppressing the effects of the interference in the system by attenuating a source of the interference. An integrated circuit including: A sensing circuit configured to sense a physical quantity associated with an output transducer in response to a drive signal to the output transducer; and Interference detection circuit configured to: Detect the presence of interference in a system including the output transducer; and Suppress the effects of this interference in the system.