EP2806656B1 - Régulation thermique de haut-parleur avec observation d'état - Google Patents

Régulation thermique de haut-parleur avec observation d'état Download PDF

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EP2806656B1
EP2806656B1 EP13368015.7A EP13368015A EP2806656B1 EP 2806656 B1 EP2806656 B1 EP 2806656B1 EP 13368015 A EP13368015 A EP 13368015A EP 2806656 B1 EP2806656 B1 EP 2806656B1
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Prior art keywords
loudspeaker
temperature
voice
coil
controller
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EP2806656A1 (fr
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Michel Menu
Stéphan Tassart
Simon Valcin
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ST Ericsson SA
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ST Ericsson SA
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R3/00—Circuits for transducers, loudspeakers or microphones
    • H04R3/007—Protection circuits for transducers

Definitions

  • This invention relates to loudspeakers, and in particular, but without limitation, to compact loudspeakers suitable for use in mobile telephones and the like. More particularly, this invention relates to a method and apparatus for monitoring and/or controlling the temperature of loudspeakers.
  • Loudspeakers are transducers that convert an electrical signal into sound waves.
  • the transduction of electrical energy into acoustic energy that is to say the sound waves, is relatively inefficient, typically less than 5% for usual direct-radiator loudspeakers, as used in the mobile phone industry.
  • high electric power levels must be applied, but since about 95% to 99% of the input energy is converted into heat in the voice-coil, loudspeakers tend to heat up in use.
  • the rate of heat dissipation being closely related to the size, and in particular, to the surface area, of the loudspeaker.
  • the rate of heat dissipation is closely related to the size, and in particular, to the surface area, of the loudspeaker.
  • the maximum achievable sound pressure level is limited by the rate of heat loss because smaller loudspeakers have proportionately less efficient heat dissipation properties compared with larger loudspeakers.
  • the overheating of the voice-coil is one of the main causes of damage and faults in loudspeakers.
  • a smaller loudspeaker requires proportionately higher cone displacements to achieve the same output sound pressure as a larger loudspeaker. Increased cone displacements can lead to undesirable changes in the performance of the loudspeaker, which can ultimately lead to its failure. From the foregoing, therefore, it will be appreciated that the miniaturisation of loudspeakers introduces a number of design considerations that can affect the performance and durability of the loudspeaker.
  • AHC Active Heat Control
  • AHC involves monitoring the voice-coil temperature and then adapting the amplification rate accordingly. In most situations, the direct observation of the voice-coil temperature is not possible, and so indirect observation techniques are required.
  • the voice-coil temperature can be monitored indirectly, for example, by monitoring an observable parameter having a known relationship to the voice-coil's temperature.
  • Re T dRe dT a Re T 1 + T ⁇ T 0
  • dRe dT a . Re T . 1 ⁇ T ⁇ T 0 . b
  • the DC resistance, Re can be measured from the voltage, v(t), and the current, i(t), at the loudspeaker terminals. Since it is not possible to operate on DC signals with A/D convertors, indirect measurement is again necessary, and so it is known to use an additional signal probe at ⁇ 5Hz, although in the invention, any low frequency probe signal can be used, typically, around 20Hz, such that a relationship between the voice coil temperature and the impedance is validly maintained.
  • the probe frequency should be low enough to limit interference with audio signals, but because demodulation is used at the end, very low frequencies (e.g. 1-5 Hz) can become difficult to use in fixed point arithmetic. As such, a probe frequency of about 20Hz has been found to provide a useful and practical compromise.
  • a normalised, least means squared algorithm can then be applied to the signal path between the voltage and the current signals (possibly down-sampled, for instance, at a rate of 20:1) during the operation of the loudspeaker, with music or speech signal playing with or without probe signal.
  • the resulting filter models the impedance of the loudspeaker, with a filter length set to, say, 180ms.
  • a set of five parameters originating from a simple physical model is optimized in order to fit (with a spectral least quadratic error criterion) the observed magnitude impedance spectrum
  • the DC resistance, Re is finally extracted from those physical model parameters by simple evaluation of the model spectrum at DC.
  • Thermal control and/or protection of the loudspeaker can therefore be achieved by the application of a variable gain to the signal driving the loudspeaker. In most cases, this is applied via a feedback loop derived from the indirectly-observed voice-coil temperature such that the higher the observed temperature, the greater the attenuation of the driving signal.
  • variable gain the controlling law attempts to force the temperature of the voice-coil back below the threshold temperature by applying an increasingly negative gain (in dB) to the driving signal until the temperature has returned to its limiting threshold value.
  • DRC Dynamic Range Controller
  • adaptive gain attenuation of the driving signal when it is based on an estimation of the voice-coil temperature alone, may introduce unpleasant audio artefacts, such as pumping; and secondly, the complete signal (or frequency band in the case of a multi-band approach) is influenced by the gain control, even the lower-amplitude segments that do not cause thermal heating of the voice-coil.
  • the known estimation of the voice-coil temperature is either: not fully reliable; or is only available from the control system with a significant delay.
  • a compromise needs to be struck between high estimate reliability (that is to say, signal-to-noise ratio for the temperature signal) and low delay (latency), but the introduction of a delay in the control feedback loop is known to cause damped or un-damped oscillations.
  • a voice-coil temperature sensing solution is based on a low-power and transparent probe signal at 20Hz
  • reliability is achievable only with a long integration time and the where estimated voice-coil temperature is available with a latency of 1s.
  • the use of a feedback loop may introduce oscillation of the compression ratio parameter at a rate of 1Hz, which causes unpleasant audio artefacts.
  • an Active Heat Controller suitable for controlling the temperature of a loudspeaker connected to it, the Active Heat Controller comprising a Dynamic Range Controller intended to be operatively interposed, in use, between an input driving signal terminal of the loudspeaker and the terminals of a voice-coil of the loudspeaker, the Dynamic Range Controller being configured to variably attenuate an input driving signal and to provide the attenuated signal as an output at the voice-coil's terminals, the Active Heat Controller comprising: a probe intended to be operatively connected, and being adapted to provide a probe signal, to the terminals of the loudspeaker's voice-coil for estimating an instantaneous temperature of the voice-coil and the Active Heat Controller being characterised by: a state observer for estimating, on the basis of a thermal model and the voice coil temperature, an instantaneous temperature of a magnet of the loudspeaker; and means for controlling an instantaneous attenuation provided by the Dynamic Range Controller in response
  • the invention provides an Active Heat Controller (AHC) that changes the attenuation of the driving signal applied to the loudspeaker's voice-coil terminals in response to the instantaneous temperature of the voice-coil and a parameter that is indicative of the temperature of the speaker's surroundings, that is to say, the temperature of the loudspeaker's magnet, which varies relatively slowly over time.
  • AHC Active Heat Controller
  • the invention overcomes the problem of over-attenuation of the driving signal in cold environments because the ambient temperature is used to modify the DRC's parameters, as well as the voice-coil temperature.
  • the AHC of the invention may act to reduce the amount of DRC attenuation, which may also be, the amount of signal processing required.
  • Such a configuration may improve the sound quality of the loudspeaker, and/or alleviate adverse audio artefacts, such as distortion, un-damped oscillation and/or pumping, and/or reduce the signal processing demand on the DRC.
  • the temperature of the voice-coil is estimated using a probe signal applied to the loudspeaker, which probe signal suitably yields an output related to the loudspeaker's DC resistance.
  • the loudspeaker's DC resistance is related to its voice-coil temperature, thus enabling the voice-coil's temperature to be estimated using the probe.
  • the state observer is used to estimate the temperature of the loudspeaker's magnet.
  • the magnet's temperatures typically varies slowly over time, and is in any event indicative of the ambient temperature by virtue of the fact that the rate of heat dissipation from the loudspeaker depends on the ambient temperature.
  • the magnet of a loudspeaker in a cold environment will cool more quickly for a given thermal input that in a warmer environment with the same thermal input.
  • the means for controlling the instantaneous attenuation of the Dynamic Range Controller in response to the estimated voice-coil and magnet temperatures suitably translates the voice-coil and loudspeaker magnet temperature estimates into DRC parameters. This is suitably performed in a translator, which serves to limit the driving signal such that the temperature of the voice-coil is maintained below a desired upper threshold temperature.
  • the state observer compares the heat input with the heat output to yield a value reflecting the heat flux of the loudspeaker. More specifically, the state observer monitors the heat input, that is to say the temperature of the voice-coil, and estimates the heat output based on a thermal model for the loudspeaker's magnet using the voice-coil temperature as an input parameter, to determine whether the loudspeaker's temperature is likely to rise or fall at any particular time. The rising or falling temperature state observed can then be passed into a translator, which shapes the parameters for the DRC, or the magnitude of the attenuation (weight) of the DRC, to maintain the loudspeaker's temperature below an upper threshold value.
  • a weight of 0 can be applied to the DRC meaning that no temperature-regulating attenuation is applied.
  • a finite weighting can be applied to the DRC meaning that a finite temperature-regulating attenuation is applied.
  • the application of the weighting is suitably determined by the translator, which can apply a linear or non-linear weighting in response to the observed state of the loudspeaker.
  • the Zuccati-Button thermal model of a loudspeaker (cf. Thermal Parameters and Power Ratings of Loudspeakers, C. Zuccatti, JAES Volume 38 Issue 1/2 pp. 34-39; February 1990 ) explains the dynamic of the voice-coil temperature, T(t), as a mass-spring system operating on the temperature difference T(t) - Tm(t), where Tm(t) represents the temperature of the loudspeaker magnet.
  • an-efficient temperature control strategy for limiting the voice-coil temperature involves applying a variable gain to the incoming signal (for example, by modulating the compression rate of a DRC) to ensure the bounding of r(t) by: 1 Rb Tmax ⁇ Tm
  • control strategy is open loop so that the control law does not need to monitor the voice-coil temperature.
  • the invention is based, in one aspect, on the fact although the temperature of the loudspeaker's magnet is not directly observable, assuming the parameters of the thermal model are known, the magnet's temperature can be tracked by the state observer from the measurements of the voice-coil temperature. This can be accomplished because the magnet, in most practical situations, is thermally coupled to the voice-coil, and so it is possible to estimate the magnet's temperature if the voice-coil's temperature over time is known, and the thermal parameters (thermal coupling of the voice-coil to the magnet and the dissipation of heat from the magnet) of the system are known also.
  • the rate of change of the magnet's temperature is usually several orders of magnitude slower than that of the voice-coil, typically at least 100 times slower in experiments. Therefore, the AHC of the invention makes use of the reasonable assumption that the temperature of the magnet over time, Tm(t), is almost constant over the time-frame of the control parameters, therefore justifying the use of open-loop system.
  • x Tmb Tam is the column state vector
  • C and Y are respectively the thermal capacity and thermal impedance matrices
  • r is the power produced by the voice-coil and T
  • Tm and Ta are respectively the voice-coil, magnetic and ambient air temperatures.
  • Tmb and Tam are, by definition, T - Tm and Tam is, by definition, Tm - Ta.
  • Tmb is, by definition, T - Tm
  • Tam is, by definition, Tm - Ta.
  • Tmb Tm + 1 0 . r + vq vm T 1 1 * . Tmb Tm + v 0
  • Tmb Tm is the new state vector
  • v q a Gaussian noise representing the uncertainty of the voice-coil model
  • v m a Gaussian noise representing the seed of the random walk from Tm
  • v o the measurement noise on the voice-coil temperature.
  • T ⁇ Tm + Rb . r ⁇ r t ⁇ r ⁇ and ⁇ Tmb t ⁇ Rb . r ⁇ Tmb ⁇ Rb . r ⁇ because if we assume that it exists a time t for which Tmb(t) is greater than Rb . r ⁇ , then, by continuity of the solution Tmb(t), there exists a point where the function for Tmb(t) crosses Rb . r ⁇ .
  • the function derivative dTmb dt is negative: the only possibility for Tmb(t) to cross Rb . r ⁇ is with a negative slope, forbidding the function from passing from the domain Tmb(t) ⁇ Rb . r ⁇ to its complementary domain. In other words, once Tmb(t) is lower than Rb . r ⁇ , it remains lower than Rb . r ⁇ at any subsequent time.
  • Tm slow-varying magnetic temperature
  • the AHC applies a variable gain to the audio signal, measures the voice-coil temperature, provides an estimate of the slow varying magnetic temperature, given the measurements of the voice-coil temperature, and then translates the magnetic temperature estimates into compression parameters.
  • an Active Heat Controller (AHC) 10 for a loudspeaker 12 comprises a Dynamic Range Controller (DRC) 14 interposed between an audio input signal 16 and the loudspeaker 12.
  • the DRC 14 comprises an attenuator 18 that can reduce the magnitude of the audio input signal 16 so that the loudspeaker 12 does not overheat in use.
  • the output 20 of the DRC 14 passes through a digital-to-analogue converter 22, before being amplified 24 and passed to the terminals 26 of the loudspeaker 12.
  • the output 20 of the DRC 14 is overlaid with a 20Hz probe signal 28, which is fed to the loudspeaker 12 also.
  • the attenuator 18 of the DRC 14 is controlled in a known manner by an analyser by different amounts over different amplitude ranges. This is achieved, in a known manner by an envelope follower 30 and a gain processor 32 which operates between a linear-to-logaritmic 34 and a logarithmic-to-linear 36 converter. The gain processor 32 thus adjusts the attenuator 18,.
  • the envelope follower 30 is also connected to an output of the parameter estimator 51 because the envelope follower 30 aims to estimate the power r from the source signal 16, which estimate is based on the system impedance.
  • the gain control of the DRC uses a table similar to that shown in Figure 4 , an illustration of a compression curve with a so-called "hard-knee” shape, i.e. resulting from a piece-wise affine function.
  • a DRC as a variable gain
  • a multi-band DRC can be applied to the signal, with one DRC channel allocated for the loudspeaker resonance and a second channel for the rest of the spectrum.
  • the attenuator 18 is then implemented respectively either as a variable parametric equalizer configured as band pass centred on the resonant frequency or as a complementary filter.. Separate compression setting and weight application are possible.
  • the invention 10 additionally comprises a weighting module 38 that multiplies the output of the gain processor 32 by a value ranging from 0 to 1, thus overriding the attenuation setting of the DRC.
  • the weighting module applies a weighting of 0 to the gain processor 32 thus deactivating the DRC 14.
  • T max the predefined threshold value
  • the weighting increases to a finite value thus overriding the gain processor's setting 32, which relatively under-drives the loudspeaker 12 by over-attenuating the output signal 20 at the output of the DRC 14, thus allowing the loudspeaker 12 to cool.
  • FIG. 2 is a schematic of the multiband DRC, which is represented by block 14 in Figure 2 .
  • the multiband DRC there is a variable attenuator 18 whose gain is controlled by an analyser as described herein, which maps the input audio signal 16 to an attenuated signal by different amounts over different frequency and amplitude ranges.
  • this is achieved by an envelope follower 30 and a number (in this case, a pair of) gain processors 32, 32a which operate between a linear-to-logarithmic 34 and a logarithmic-to-linear 36 converter.
  • the first gain processor 32 provides an output that is fed to a first weighting module 38 that multiplies the output of the gain processor 32 by a value ranging from 0 to 1, thus overriding the default attenuation setting of the DRC.
  • the weighting module also receives an input from the translator 46 before outputting a first gain modification to a pre-equaliser 70, which is also connected to a low impedance estimation signal outputted from the parameter estimator 51.
  • the pre-equaliser 70 output signal feeds into the probe signal 28.
  • a second signal processor acts on a different portion of the linear-to-logarithmic converted signal via a second gain processor 32a.
  • the output of the second gain processor 32a is fed to a second weighting module 38a, which also multiplies the output by a value ranging from 0 to 1, as determined by the translator 46.
  • the output of the second weighting module is fed, via a logarithmic-to-linear converter 36a directly to the attenuator 18 of the DRC 14.
  • the multiband DRC is able to modify the gain using two sets of parameters simultaneously.
  • the invention is predicated on knowing the instantaneous state of the loudspeaker, that is to say the thermal flux being the heat input, the heat output and hence whether the temperature of the voice-coil is likely to continue increasing, or remain in a steady-state condition whereby the thermal input balances the thermal output of the loudspeaker 12.
  • the state observer monitors DC resistance of the loudspeaker's 12 voice-coil, which is indicative of the voice-coil's temperature. This is accomplished by applying the probe signal 28, the level of the probe signal 28 being chosen so that it does not interfere with the music or speech signal. It has been found that a sinusoidal probe signal at 20Hz, and -60dBFS is substantially transparent for music and speech signals, although different algorithms are possible in order to evaluate the impedance from the probe signal.
  • the probe 28 applies a signal on top of an output signal 20 of the DRC 14, and a first analogue-to-digital converter 45 connected to the terminals 26 of the loudspeaker 12 is provided for measuring the probe signal voltage across the loudspeaker terminals 26.
  • a second analogue-to-digital converter 47 connected in parallel to a resistor 49 wired in series across the terminals 26 of the loudspeaker 12, which is used for measuring the probe signal current in the loudspeaker 12.
  • a parameter estimator 51 is operatively connected to the analogue-to-digital converters 47, 49 for calculating the DC resistance of the loudspeaker 12 based on the probe signal's voltage and current, the DC resistance being indicative of the loudspeaker's voice-coil temperature.
  • One solution consists in applying a succession of resonant filters tuned at the probe frequency and down-samplers to both the voltage and the current signals.
  • the resulting signal sampled at a very low frequency (e.g. 300 Hz)
  • the level difference between both envelops, in the dB or logarithmic domain, is an image of the loudspeaker resistance at 20Hz.
  • the impedance and voice-coil temperature (the building block parameter estimation) can thus be estimated with a voltage directly sensed from the terminals of the loudspeaker (direct v-sensing).
  • direct v-sensing is possible instead by processing in the digital domain the signal sent to the DAC 22.
  • the bilinear transform is a popular scheme that preserves most of the spectral properties of the system. Formally, it consists in substituting the Laplace variable s: s ⁇ ⁇ 2 / Ts * z ⁇ 1 / z + 1 where Ts represents the sampling rate and z the discrete shift operator.
  • the transformation of the stochastic thermal model results in a second order linear system, in which the form of a linear quadratic estimator is usually: e k
  • k T k ⁇ H x k
  • k Phi x k
  • k x k
  • T[k] represents the current voice-coil measurement, r[k] the current feeding power estimate, e[k
  • Kf and Kp are respectively the Kalman filter and predictor gains (they are both matrices).
  • the Kalman gains represent a sort of weight or trade-off between the confidence of the observation and the confidence the state estimate. In its asymptotic form, those weights are constant; so the Kalman gains are.
  • a more general form includes a time variation of the Kalman gains, illustrating the fact that initially, the confidence of the state estimate is very poor, but confidence grows gradually as more observations become available. In practical cases, the Kalman gains reach their asymptotic limits after a few seconds.
  • the actual observer can tabulate the first values of the Kalman gains and switch to constant gains after a while.
  • a predictive model, interpolation, re-sampling are alternate solutions for the tabulation of the Kalman gains.
  • any kind of approximation for the Kalman gains is usually suitable, resulting only in a moderate loss of performance.
  • the constructed state observer 40 uses a measurement of T and the estimation of r as inputs and generates an estimation of Tm, which is based on a thermal model 42 of the loudspeaker 12.
  • T usually involves a latency which must be compensated by a synchronization delay 50 in the estimation of r.
  • the operation rate of the state observer, Ts is dictated by the spectral characteristics of the thermal system (typically a few Hz). However, it has been found to be simpler to operate the state observer at a higher rate, synchronous to the rate of control of the DRC, which is still low and acceptable for complexity purposes.
  • the additional degree of freedom (the parameters r0 and Tm min are related together, which relationship is used for trading smoothness against loudness.
  • Tm min is far from Tm max, smoothness in the variation of the DRC parameters is maximized, limiting therefore transient artefacts.
  • the invention has every advantage of known systems, but without their limitations.
  • the control strategy of the invention is (mainly) open-loop, therefore oscillation of the control parameters is not possible.
  • the dynamic of the magnetic temperature, Tm(t), is very slow (in laboratory measurements, the half-life duration of the magnetic system was greater than 3 minutes); so this temperature can be reliably estimated despite unfavourable SNR ratio on the voice-coil because long integration time generates latency durations that are not significant relative to the time parameters of the magnetic system.
  • the signal processing effort is greater when the magnetic temperature, Tm(t), is high, which can happen either because the loudspeaker has been exposed to a long heating stimulus or because the ambient air is hot.
  • the thermal control system described in this invention applies moderate signal dynamic compression when the ambient air is cold or when the loudspeaker has not been exposed to a long heating stimulus.
  • this invention is in general more transparent and produces less audio artefacts than any other solution.

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Claims (12)

  1. Régulateur de chaleur actif (10) approprié pour réguler la température d'un haut-parleur (12) connecté à celui-ci, le régulateur de chaleur actif (10) comprenant un dispositif de commande de plage dynamique (14) interposé de manière opérationnelle entre une borne d'un signal de commande d'entrée (16) pour le haut-parleur (12) et les bornes (26) d'une bobine acoustique du haut-parleur (12), le dispositif de commande de plage dynamique (14) étant configuré pour atténuer de manière variable un signal de commande d'entrée et pour fournir le signal atténué en tant que sortie au niveau des bornes de la bobine acoustique (20), le régulateur de chaleur actif (10) comprenant : une sonde (28) connectée de manière opérationnelle, et étant adaptée pour fournir un signal de sonde, aux bornes (26) de la bobine acoustique du haut-parleur (12) pour estimer une température instantanée de la bobine acoustique et le régulateur de chaleur actif étant caractérisé par : un observateur d'état (40) permettant d'estimer, sur la base du modèle thermique et de la température de la bobine acoustique, une température instantanée d'un aimant du haut-parleur (12) ; et un moyen (38) permettant de commander une atténuation instantanée fournie par le dispositif de commande de plage dynamique (14) en réponse aux températures estimées de l'aimant et de la bobine acoustique ; et dans lequel l'observateur d'état (40) compare l'entrée de chaleur à une sortie de chaleur du haut-parleur pour produire une valeur reflétant le flux de chaleur du haut-parleur, la température (T) de la bobine acoustique est relative à l'entrée de chaleur du haut-parleur (12) et la sortie de chaleur de l'aimant du haut-parleur est basée sur le modèle thermique (42) et utilise la température (Tm) estimée de la bobine acoustique en tant que paramètre d'entrée, la différence entre l'entrée de chaleur et la sortie de chaleur étant indicative de l'état de température du haut-parleur ascendante ou descendante.
  2. Régulateur de chaleur actif (10) selon la revendication 1, dans lequel la sonde est adaptée pour recouvrir un signal de sonde à la sortie (20) du dispositif de commande de plage dynamique (14), ce signal de sonde est également alimenté vers le haut-parleur (12), et dans lequel le régulateur de chaleur actif comprend un premier convertisseur analogique à numérique (45) connecté aux bornes (26) du haut-parleur (12) permettant de mesurer la tension du signal de sonde à travers les bornes de haut-parleur (26) et un second convertisseur analogique à numérique (47) connecté en parallèle à une résistance (49) câblé en série par l'intermédiaire des bornes (26) du haut-parleur (12) adapté pour mesurer le courant du signal de sonde dans le haut-parleur (12), et un estimateur de paramètre (51) connecté de manière opérationnelle aux convertisseurs analogiques à numériques (47, 49) adapté pour calculer la résistance CC du haut-parleur sur la base de la tension et du courant du signal de sonde, la résistance CC indiquant la température de la bobine acoustique du haut-parleur.
  3. Régulateur de chaleur actif (10) selon la revendication 2, dans lequel l'observateur d'état (40) est connecté de manière opérationnelle à l'estimateur de paramètre (51) et le contrôleur de chaleur actif (10) consiste à estimer un moyen adapté pour estimer la température de l'aimant du haut-parleur (12) à l'aide du modèle thermique (42) du haut-parleur (12) appliqué à la température (T) mesurée de la bobine acoustique.
  4. Régulateur de chaleur actif (10) selon la revendication 3, dans lequel le modèle thermique (42) comprend des paramètres thermiques du haut-parleur, les paramètres thermiques étant n'importe lequel ou lesquels parmi le groupe comprenant : l'efficacité de couplage thermique de la bobine acoustique à l'aimant ; la conductivité thermique de l'aimant ; et le taux de dissipation thermique dépendant de la température de l'aimant.
  5. Régulateur de chaleur actif (10) selon l'une quelconque des revendications précédentes, dans lequel l'observateur d'état (40) comprend un moyen d'estimation adapté pour estimer la température de l'aimant du haut-parleur (12) à l'aide d'un modèle thermique (42) du haut-parleur (12) appliqué à la température (T) mesurée de la bobine acoustique, le modèle thermique étant un modèle thermique de Zuccati-Button pour le haut-parleur (12).
  6. Régulateur de chaleur actif (10) selon l'une quelconque des revendications précédentes, dans lequel l'observateur d'état (40) comprend un moyen d'estimation adapté pour estimer la température de l'aimant du haut-parleur (12) à l'aide d'un modèle thermique (42) du haut-parleur (12) appliqué à la température (T) mesurée de la bobine acoustique, le modèle thermique constituant une transformée bilinéaire des équations : Cb 0 0 1 ⋅ d Tmb Tm dt = 1 Rb 0 0 0 ⋅ Tmb Tm + 1 0 . r + vq v ⋅ m
    Figure imgb0044
     et T = 1 1 * ⋅ Tmb Tm + v 0
    Figure imgb0045
     dans lesquelles : Tmb est T - Tm ; Tm est la température de l'aimant ; Rb est la résistance thermique ; r est la puissance produite par la bobine acoustique et T, Tm et Ta sont respectivement les températures de l'air ambiant, de l'aimant et de la bobine acoustique ; où vq et vm sont des pondérations ; et dans lesquelles v est un vecteur.
  7. Régulateur de chaleur actif (10) selon l'une quelconque des revendications précédentes, comprenant en outre un translateur (46) adapté pour limiter le signal de commande de telle sorte que la température de la bobine acoustique est maintenue sous une température de seuil supérieur souhaitée, le translateur (46) étant connecté de manière opérationnelle au moyen (38) permettant de commander l'atténuation instantanée du dispositif de commande de plage dynamique (14) en réponse aux températures estimées de l'aimant (Tm) et de la bobine acoustique (T).
  8. Régulateur de chaleur actif (10) selon la revendication 7, dans lequel le translateur (46) commande un module de pondération (38) permettant de pondérer l'amplitude de l'atténuation du dispositif de commande de plage dynamique (14).
  9. Régulateur de chaleur actif (10) selon la revendication 8, dans lequel lorsque l'observateur d'état (40) détermine que le haut-parleur (12) se trouve dans un état de température descendante, une pondération appliquée par le module de pondération (38) de 0 peut être appliquée au dispositif de commande de plage dynamique (14).
  10. Régulateur de chaleur actif (10) selon la revendication 8 ou la revendication 9, dans lequel lorsque l'observateur d'état (40) détermine que le haut-parleur (12) se trouve dans un état de température ascendante, une pondération finie est appliquée par le module de pondération (38) au dispositif de commande de plage dynamique (14).
  11. Régulateur de chaleur actif (10) selon la revendication 9, la revendication 10 ou la revendication 11, dans lequel le translateur (46) applique une pondération linéaire ou non linéaire par le module de pondération (38) en réponse à l'état observé du haut-parleur (12).
  12. Régulateur de chaleur actif (10) selon l'une quelconque des revendications précédentes, dans lequel le signal de sonde (28) comprend un signal de sonde sinusoïdal essentiellement à 20Hz et essentiellement à -60dBFS.
EP13368015.7A 2013-05-21 2013-05-21 Régulation thermique de haut-parleur avec observation d'état Not-in-force EP2806656B1 (fr)

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US9609450B2 (en) 2015-06-05 2017-03-28 Apple Inc. Method and system for monitoring speaker temperature for speaker protection
US9794687B2 (en) * 2015-09-28 2017-10-17 Cirrus Logic, Inc. Loudspeaker protection circuitry and methods
EP3480952A3 (fr) * 2017-11-01 2019-06-12 Xiamen Fourier Electronics Co., Ltd. Dispositif d'intégration de détection et de commande de température et procédé de commande de température appliqué pour micro haut-parleur
CN107702813A (zh) * 2017-11-01 2018-02-16 厦门傅里叶电子有限公司 微型扬声器控制测温整合装置及方法
GB2569809A (en) * 2017-12-27 2019-07-03 Nokia Technologies Oy An apparatus, method and computer program for controlling an audio transducer
TWI698130B (zh) 2018-12-20 2020-07-01 瑞昱半導體股份有限公司 溫度計算參數提供電路、溫度計算參數提供方法以及溫度監控方法
CN110113694B (zh) * 2019-04-30 2021-07-20 广州三星通信技术研究有限公司 用于在电子设备中控制音频播放的方法和设备
US11333622B2 (en) 2019-05-01 2022-05-17 Cirrus Logic, Inc. Thermal model of transducer for thermal protection and resistance estimation
CN117795979A (zh) * 2021-11-11 2024-03-29 华为技术有限公司 一种限幅装置及限幅方法
CN114630257B (zh) * 2022-02-28 2024-03-12 歌尔股份有限公司 扬声器电热转换效率测试方法

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EP2398253A1 (fr) * 2010-06-16 2011-12-21 Nxp B.V. Contrôle de la sortie d'un haut-parleur
US20130083928A1 (en) * 2011-09-30 2013-04-04 Apple Inc. Speaker temperature control

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