Current limiting device for driving loudspeaker

Abstract

A method for use with a sound system (125), referred to in the control theory as equipment, comprising a group of loudspeakers (120), the method comprising: obtaining an input audio sample (rn) and a measured current (mn-d) consumed by the group of loudspeakers; generating a state vector (xn) of the current time step and a model-based estimated current (yn) using a state-space model of the loudspeaker group; generating a predicted current (ye, n + 1) of the next time step based on the state vector (xn); generating a replacement audio sample (uL, n) of the current time step based on the state vector (xn); generating a feedback signal (fn) on the basis of the measured current (mn-d) and the time-aligned model-based estimated current (yn-d), which feedback signal helps to generate the state vector (xn + 1) for the next time step; an output audio sample (un) for the current time step is generated, where the output audio sample (un) is the input audio sample (rn) for the current time step, or the output audio sample is the replacement audio sample (uLn) when the magnitude of the predicted current (ye, n + 1) is above a threshold (Imax).

Description

Technical Field

[0001] Various example embodiments are generally directed to a current limiting device for driving a loudspeaker and an associated method. Background Art

[0002] Most audio power amplifiers have a maximum output current limit, above which the output stage may be damaged.

[0003] A common solution for linear amplifiers with push-pull output stages is to provide an additional control loop that measures the output current in an emitter resistor or source resistor of the output stage of the linear amplifier and overrides the common control signal to control the current of the output device to a constant maximum current.

[0004] In a pulse width modulated amplifier or inverter, protection circuits can be implemented in the driver IC (integrated circuit) that controls the switching output device. The output current is detected using various methods. If a threshold value of the output current is reached, the driver IC is configured to completely shut down the output stage and restart after a recovery time. During this time, no output audio signal is sent to the speaker, which is unacceptable during normal operation of the audio amplifier.

[0005] To prevent this from happening, an additional control loop with fast current measurement can be used in the driver IC to perform pulse-by-pulse current limiting to obtain a constant maximum output current.

[0006] Therefore, it seems that an improved solution is needed to limit the current consumed by the speaker. Summary of the invention

[0007] The scope of protection is set forth by the independent claims. Embodiments, examples, and features described in this specification that do not fall within the scope of protection, if any, should be interpreted as examples useful for understanding various embodiments or examples that fall within the scope of protection.

[0008] According to a first aspect, a device for use with a sound system (referred to as a device in control theory) including a speaker group is disclosed. The device is configured to receive an input audio sample and a measured current consumed by the speaker group and generate an output audio sample for a current time step. The device includes: a modeling device configured to generate a state vector for a current time step and a model-based estimated current of the current consumed by the speaker group from the output audio sample using a state space model of the speaker group; a prediction device configured to generate a predicted current for the next time step based on the state vector; a limiting device configured to generate a replacement audio sample for the current time step based on the state vector, wherein the replacement audio sample causes the magnitude of the current consumed by the speaker to be limited to a maximum value; a state feedback controller configured to generate a feedback signal, which is fed to the state space model to help generate the state vector for the next time step, wherein the feedback signal is based on a comparison between the measured current and the time-aligned model-based estimated current; wherein the output audio sample is the input audio sample for the current time step, or when the magnitude of the predicted current is higher than a threshold, the output audio sample is a replacement audio sample.

[0009] The prediction means may be configured to generate a predicted current based on one or more input audio samples.

[0010] The prediction means may be configured to generate the predicted current based on the estimated audio samples for the next time step or the input audio samples for the next time step.

[0011] The limiting device may be configured to generate a replacement audio sample based on a model derived from a state-space model.

[0012] The limiting device may be configured to generate a replacement audio sample based on a threshold value corresponding to the maximum current.

[0013] The replacement audio sample may be generated in such a way that the magnitude of the predicted current is equal to the threshold value.

[0014] The replacement audio sample may be generated based on the sign of the predicted current.

[0015] The replacement audio sample may be generated based on the output sample of the previous time step.

[0016] According to a second aspect, a method for use with a sound system (referred to as a device in control theory) including a speaker group is disclosed. The method includes: obtaining an input audio sample and a measured current consumed by the speaker group; generating an output audio sample for a current time step; generating a state vector for the current time step and a model-based estimated current of the current consumed by the speaker group from the output audio sample using a state-space model of the speaker group; generating a predicted current for the next time step based on the state vector; generating a replacement audio sample for the current time step based on the state vector, wherein the replacement audio sample causes the magnitude of the current consumed by the speaker to be limited to a maximum value; generating a feedback signal, which is fed to the state-space model to help generate the state vector for the next time step, wherein the feedback signal is based on a comparison between the measured current and the time-aligned model-based estimated current; wherein the output audio sample is the input audio sample for the current time step, or when the magnitude of the predicted current is above a threshold, the output audio sample is a replacement audio sample.

[0017] According to another aspect, a computer program is disclosed. The computer program comprises computer executable instructions, which, when executed by at least one processor, cause a device to perform the method according to the second aspect.

[0018] According to a third aspect, a device for use with a sound system (referred to as a device in control theory) including a speaker group is disclosed. The device includes a signal processing device (e.g., a signal processor) for performing a method, the method comprising: obtaining an input audio sample and a measured current consumed by the speaker group; generating an output audio sample for a current time step; generating a state vector for the current time step and a model-based estimated current of the current consumed by the speaker group from the output audio sample using a state-space model of the speaker group; generating a predicted current for the next time step based on the state vector; generating a replacement audio sample for the current time step based on the state vector, wherein the replacement audio sample causes the magnitude of the current consumed by the speaker to be limited to a maximum value; generating a feedback signal, which is fed to the state-space model to help generate the state vector for the next time step, wherein the feedback signal is based on a comparison between the measured current and the time-aligned model-based estimated current; wherein the output audio sample is the input audio sample for the current time step, or when the magnitude of the predicted current is above a threshold, the output audio sample is a replacement audio sample.

[0019] The signal processing device may include at least one processor and at least one memory including computer program instructions, wherein the at least one memory and the computer program instructions are configured to use the at least one processor to cause the device to perform one or more or all steps of the method. The signal processing device may include a circuit configured to cause the device to perform at least one or more or all steps of the method. The signal processing device may include a digital signal processor configured to cause the device to perform one or more or all steps of the method.

[0020] The signal processing apparatus may comprise: a modelling device; a prediction device; a limiting device as defined in the device according to the first aspect and a state feedback controller.

[0021] According to a fourth aspect, a system comprising the apparatus according to the first or third aspect is disclosed. The system comprises a database configured to store model coefficients of a state-space model for a number of speaker groups and means for loading the model coefficients corresponding to the speaker groups. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Example embodiments will be more fully understood through the detailed description given below and the accompanying drawings, which are given by way of illustration only and thus do not limit the present disclosure.

[0023] Figure 1 A block diagram of a current limiting device according to one example is shown.

[0024] Figure 2A An example of an equivalent circuit for an exemplary speaker group is shown.

[0025] Figure 2B An example of an equivalent circuit for an exemplary speaker group is shown.

[0026] Figure 3 An exemplary state-space model that may be used as a speaker group model is shown.

[0027] Figure 4 A closed-loop controlled model according to one example is shown.

[0028] FIG. 5A to FIG. 5B The frequency and phase responses of the admittance of a state-space model simulating a loudspeaker group including a sound enclosure according to one example are shown.

[0029] FIG. 6A to FIG. 6B Signals illustrating the behavior of a current limiting device according to one example are shown.

[0030] FIG. 7A to FIG. 7B Signals illustrating the behavior of a current limiting device according to one example are shown.

[0031] It should be noted that these drawings are intended to illustrate various aspects of the apparatus, methods, and structures used in the example embodiments described herein. The use of similar or identical reference numerals in the various drawings is intended to indicate the presence of similar or identical elements or features. DETAILED DESCRIPTION

[0032] Various example embodiments will now be described more fully with reference to the accompanying drawings, some of which are shown in the accompanying drawings. However, the specific structural and / or functional details disclosed herein are only representative for the purpose of describing the example embodiments. Therefore, these embodiments are shown in the accompanying drawings in an illustrative manner and will be described in detail herein to provide a thorough understanding of various aspects. However, it should be understood by those of ordinary skill in the art that the example embodiments can have various variations and modifications and can be practiced without all the specific details. In addition, systems and processes can be shown in block diagrams to avoid obscuring the example embodiments due to unnecessary details. In other cases, well-known processes, structures, and techniques can be shown without unnecessary details to avoid obscuring the example embodiments.

[0033] An audio system including a current limiting device is described in detail below. The current limiting device is used to implement a prediction algorithm that predicts the current consumed by a speaker group based on a model of a speaker group (e.g., including one or more speakers). A replacement output voltage (corresponding to a sample value generated by the limiting device, also referred to herein as a replacement audio sample) is generated in such a way that the magnitude of the consumed current does not exceed a specified threshold. When the magnitude of the predicted current is higher than the specified threshold, the replacement output voltage (i.e., the replacement audio sample) is output to the device to replace the output voltage of the audio source. The current consumed by the speaker is limited to a maximum value, and the replacement output voltage is determined based on the limited current.

[0034] Figure 1 A block diagram of a current limiting device 100 according to an example is shown. The current limiting device 100 is connected to an audio source 110, the output of which is connected to a sound system 125 through a selector 160, the sound system comprising a speaker group 120 for playing analog audio signals. The sound system 125 is called a device in control theory.

[0035] The sound system or device 125 comprises a signal chain which itself may comprise: a digital to analog converter (DAC) and amplifier stage 119, followed by a speaker group 120, a current measurement device 121 generating a measured current, the current measurement device comprising an analog to digital converter (ADC), which delivers the measured current to the current limiting device 100. The speaker group 120 may comprise one or more speakers, such as speakers of the same type connected in parallel which may be modeled using a single model. The speaker group 120 may alternatively comprise at least one low frequency speaker and at least one high frequency speaker (e.g. a woofer and a tweeter) connected to the output of the amplifier via a passive crossover network. To better understand the time alignment aspect, Figure 1 The schematic diagram of includes a delay element 122, which here represents the delay introduced by the digital-to-analog converter (DAC) and the analog-to-digital converter (ADC).

[0036] exist Figure 1 In the example of , the current limiting device 100 includes means (e.g., software and / or hardware means) configured to implement the following: a speaker group model (modeling device 130), a limiter (limiting device 140), a prediction algorithm (prediction device 150), a selector 160, and an associated threshold determination function (threshold determination device 155). The current limiting device 100 may also include in the feedback loop: a delay element 132, an adder 133, and a state feedback controller 135, the output of which is connected to the modeling device 130. The delayed signal y from the delay element 132 is n-d With the current measurement value m n-d Subtract.

[0037] The audio source 110 generates an audio signal which may be an analog or digital audio signal. If the audio signal is an analog audio signal, the analog audio signal is converted (eg, by an analog-to-digital converter, not shown) into what is referred to herein as input audio samples r n If the audio signal is a digital audio signal, we assume here that it includes input audio samples r n (n=1 to N).

[0038] The current limiting device 100 receives input audio samples r from an audio source 110. n (n=1 to N) as input signal and generates output audio samples u n (n=1 to N), the output audio samples are converted (e.g. by a digital-to-analog converter included in an amplifier stage indicated as 119) to analog signals to be played by a speaker set 120. The input audio samples r nrepresents the output voltage at the output of the audio source. The output audio samples represent the output voltage that is applied internally to the device 125 to drive the speaker group 120, causing the speaker group 120 to consume a current, which is referred to herein as the consumed current.

[0039] The current limiting device 100 may be implemented by a signal processing circuit configured to perform one or more or all of the steps and / or functions disclosed herein of the current limiting device 100. The current limiting device 100 may include or be subdivided into one or more devices and / or signal processing circuits.

[0040] The signal processing circuit may include at least one DSP (digital signal processing) circuit. The signal processing circuit may include at least one processor and at least one memory including computer program code, wherein the at least one memory and the computer program code are configured to use the at least one processor to cause the apparatus to perform one or more or all steps of the current limiting device 100 disclosed herein.

[0041] In the solution described herein, a predictive algorithm is used to predict and limit the current consumed by the speaker group 120 by replacing the output signal at the output of the audio source 110 with a replacement output voltage, which is converted to a voltage and amplified by the amplifier stage 119 and then applied to the speaker group 120.

[0042] The prediction algorithm is based on a loudspeaker group model implemented by a modeling device 130 connected to the output of the audio source 110 via a selector 160. The loudspeaker group model is a model of the driven loudspeaker group 120. A state-space model corresponding to an equivalent circuit of the loudspeaker group may, for example, be used as the loudspeaker group model, as will be described in detail below.

[0043] The prediction device 150 is configured to implement a prediction algorithm to generate a predicted current y e,n+1 The prediction device 150 receives one or more input audio samples r n (n=1 to N) as input, where the index n represents the time step index, for example with respect to a clock signal. The prediction algorithm can use the available input audio samples (e.g. the current sample r n and the previous sample r n-1 ). The prediction algorithm may use the next input audio sample (if available) or at least one prediction sample r of the next time step obtained from one or more input audio samples n+1 . Predicted r n+1 The samples may be obtained, for example, by using 2 or more input audio samples (e.g. n-1 and r n , n=1 to N). The prediction device 150 receives the state vector x from the modeling device 130 nAs input, to generate the predicted current y for the next time step at a given time step e,n+1 .

[0044] By using the feedback error e fed to the state feedback controller 135 of the state space model 130 n-d , the state space model is synchronized with the device 125. The feedback error e n-d Based on the measured current (m n-d ) and time-aligned model-based estimated current (y n-d ) is generated. Feedback error e n-d Can be generated as a measured current (m n-d ) is aligned with the time-based model-based estimated current (y n-d The state feedback controller 135 is configured to generate a feedback signal (f n ), which helps generate the state vector of the next time step. The feedback signal can be a feedback vector that is added to the state vector at the current time step to generate the state vector of the next time step based on the state space model.

[0045] The limiting device 140 is configured to implement a limiter function. The limiting device 140 receives the state vector x from the modeling device 130. n , and generates a replacement audio sample u based on a derivative model obtained by mathematically transforming the speaker group model L,n (n=1 to N). The coefficients of the derived model are based on the coefficients of the speaker group model. Replace the audio sample u L,n represents a replacement audio signal, which is different from the input audio signal (i.e., the input audio sample r) representing the audio content to be played. n ) is different and can be used to replace the corresponding input audio sample r n , so as to prevent the current consumed by the speaker group 120 from being higher than the threshold.

[0046] Additionally, if applied to amplifier stage 119, the replacement output sample u is applied L,n The current consumed by the speaker group 120 is smaller than the corresponding input audio sample r n The magnitude of the current consumed by the speaker group 120. The term "magnitude" used herein refers to the absolute value of the instantaneous amplitude of a time-varying signal (such as a current signal). By convention, the magnitude is always a positive value or a null value.

[0047] Replace audio signal u L,n The current consumed can be n The size is maintained at the maximum value I max, until the input audio signal will again result in a lower current consumption. Since the replacement audio signal is also supplied to the amplifier stage 119, where it is converted into a voltage for driving the loudspeaker group 120, the current consumed by the loudspeaker group is also limited to a maximum value I internal to the sound system or device 125. max . Please note that the current consumed is n The sign can be positive or negative so that the current consumed by y n Can be maintained at + / -I max .

[0048] The threshold determination device 155 receives the predicted current y e,n+1 and compare its magnitude (or absolute value) with the threshold I max (i.e., the maximum value) is compared to generate a control signal for the selector 160. At each time step n, the current y is calculated based on the predicted value. e,n+1 The generated control signal, the selector 160 transmits u n As the output of the current limiting device 100, where u n for:

[0049] - the replacement audio sample u received from the limiting device 140 L,n (If the predicted current y e,n+1 The magnitude is higher than the current threshold I max );

[0050] - or input audio samples received from an audio source r n (If the predicted current y e,n+1 The size is lower than the threshold I max );

[0051] When the predicted current y e,n+1 The size is equal to the threshold I max When the audio sample u is replaced, L,n Or input audio sample r n .

[0052] Based on the above characteristics, the current limiting device 100 is able to predict the situation where the magnitude of the consumed current increases to exceed a maximum value, and is able to correct the output signal u fed to the device before reaching this maximum value. n .

[0053] Using the prediction (as opposed to simply using the measured current m nThe reason for not feeding the limiting algorithm (as opposed to the sampling of the consumed current and its transmission to the current limiting device 100) is that the sampling of the consumed current and its transmission to the current limiting device 100 takes time (one or more time steps), and such delays can limit the ability to react in a timely manner. Furthermore, the state-space model may predict the next sample in advance (even when using block processing as described herein), i.e., at least one sample ahead of the current sample.

[0054] The state-space model is a fixed linear model. Even if the model is slightly different from the speaker group in the device, the feedback signal can keep the model state synchronized with the actual state of the speaker group.

[0055] Furthermore, with the predictive algorithm, simpler hardware protection circuits (eg, protection circuits that simply shut down and restart the audio power amplifier) ​​may also be used and be acceptable because the current limiting device may prevent the protection circuit from being triggered during normal operation.

[0056] Figure 2A An example of an equivalent circuit for a woofer in a double vented box is shown. In this equivalent circuit, the speaker is driven by a voltage source. For more complex speakers with crossover networks and other drivers, more complex equivalent circuits may be used.

[0057] Figure 2B A derived model of the equivalent circuit of a woofer in a double vented box is shown. In this equivalent circuit, the speaker is driven by a current source.

[0058] The amplitude of the current source is set to correspond to the consumed current y n The size of the target maximum value + / - I max When the output voltage u n The output voltage u is obtained at the driving node of the current source. n and the current consumed n The relationship between is given by the loudspeaker group model so that the output voltage u n A target maximum value of the magnitude of the consumed current may be obtained, and the target maximum value may be calculated based on the speaker group model and the state vector x of the speaker group model. n Sure.

[0059] Figure 3 A state space model is shown, which can be used as a speaker group model for a single speaker or a speaker group within a device. The state vector is denoted by x n The state vector x is represented by , and the coefficients of the model are included in matrices and / or vectors A, B, C, and D. n The size of x and likewise the size of the matrices and / or vectors A, B, C and D may depend on the chosen equivalent circuit. nAll currents of the inductors and all voltages of the capacitors of the equivalent circuit of the speaker group model may be included.

[0060] exist Figure 3 In the example:

[0061] -u n represents an input sample (eg, an input voltage); and

[0062] -y n represents an output sample (eg, an estimated current based on a model).

[0063] Unless current limiting occurs, the audio input is n Copy to device input u n . The following calculations are performed at each time step:

[0064] Output y: y n =C·x n +D·u n

[0065] Next state x: x n+1 =A·x n +B·u n

[0066] Next input r: r e,n+1 =2·r n -r n-1 (In this example, e,n+1 The forecast is based on linear extrapolation)

[0067] Next output y: y e,n+1 =C·(A·x n +B·r n )+D·r e,n+1

[0068] If |y e,n+1 |>i max :y e,n+1 =C·(A·x n +B·u L,n )+D·u L,n+1 = ±i max

[0069] Smooth transition: u L,n+1 =(1+λ)·u L,n -λ·u n-1 (λ can be set to 0.5)

[0070] Answer: u L,n =(C·B+(1+λ)·D) -1 ·(±i max -C·A·xn +λ·D·u n-1 )

[0071] Note that ±i max The sign of y e,n+1 The index “e” indicates that the relevant parameter is an estimate for the next time step n+1.

[0072] To improve the accuracy of the speaker group model, a closed-loop controlled model can be used so that the measured value m of the current consumed by the speaker group n-d Available and related to the current y generated by the loudspeaker group model n-d is compared to generate the feedback error e n-d The feedback error is available after a delay d expressed in the number of time steps. The delay may correspond to the number of time steps after which the measured current m is obtained. n-d : The corresponding delay line of d time steps is then applied to the current y n To generate a time-aligned model-based estimate of the current y n-d and feedback error e n-d The state vector x of the speaker group model n Based on the feedback error e n-d Update. The closed loop Figure 1 The block diagram of is shown by the elements represented by dashed lines in the current limiting device. Thus, the state space model is synchronized with the device 125 and the speaker group.

[0073] Measured current m n This can be obtained, for example, by a current probe and sampled by an analog-to-digital converter (ADC) (121) and then provided to the current limiting device. The prediction algorithm can react in time to the likely future current. The state-space model can predict the next sample in advance (one time step ahead) and when used in a closed loop, the model state variables are synchronized with the actual speaker group using the measurement results (see Figure 1 ).

[0074] Back to Figure 1 , the audio system 190 may include

[0075] - audio source 110;

[0076] - a current limiting device 100 configured to implement a loudspeaker group model, a prediction algorithm to generate a predicted current for the next time step for a given loudspeaker group based on the loudspeaker group model;

[0077] - a sound system 125 (eg a device) comprising a processing chain with an amplifier (119) followed by a loudspeaker group 120 comprising one or more loudspeakers;

[0078] - a current probe (121) for sampling the current at the output of the amplifier;

[0079] - an analog-to-digital converter (not shown) for converting the input signal r n ,m n Convert to digital format (if it is not already a digital audio signal n ), which digital format can be processed by the current limiting device 100 and the digital-to-analog converter to convert the output signal u n Convert to analog format;

[0080] - A database (not shown) for storing pre-computed coefficients (pre-computed model matrices) for lists of known loudspeaker groups.

[0081] In one or more examples, the speaker group 120 connected to the amplifier (119) can be detected. This can be done automatically at runtime. To this end, the audio system 190 can include a device for detecting the speaker group connected to the amplifier 119 inside the audio system (125). The device for detecting the speaker group can perform the detection of the speaker group based on the measurement result of the impedance of the connected speaker group.

[0082] The current limiting device 100 may include means for loading model coefficients corresponding to the detected speaker group. The equivalent circuit itself may also be selected for the detected speaker group and used to calculate the coefficients of the speaker group model to be implemented by the current limiting device 100. Loading the model coefficients from the database may be performed when the audio system 190 is turned on or in response to a change of speakers.

[0083] Figure 4 A block diagram of a current limiting device 500 according to one example is shown. Figure 4 shows how it can be used in a closed loop Figure 3 A state-space model of a device 525 in a current limiting device 500 is connected to an audio source 510 and the device 525 .

[0084] exist Figure 4 In the example of , the current limiting device 500 includes devices configured to implement the following items respectively: a speaker group model (modeling device 530), a limiter (limiting device 540), a prediction algorithm (prediction device 550), a selector 560, and a threshold determination (threshold determination device 555). The current limiting device 500 may also include: a delay element 532, an adder 533, and a state feedback controller 535 in the feedback loop, the output of which is connected to the modeling device 530.

[0085] refer to Figure 1The description is applicable to Figure 4 Further computational details of the functions of the modeling device 530, the limiting device 540, the predicting device 550, and the threshold determination device 555 are provided here.

[0086] The current limiting device 500 operates in the following manner.

[0087] The prediction device 550 receives at least one input audio sample r n and the state vector x n The prediction device 550 predicts the input audio sample r based on the coefficients of the speaker group model. n and the state vector x n Generate estimated state vector x e,n +1 :

[0088] X en+1 =A·x n +B·r n

[0089] Where “·” represents matrix product.

[0090] The prediction device 550 generates an estimated audio sample r from one or more input audio samples. e,n+1 :

[0091] r e,n+1 =2·r n -r n-1

[0092] The prediction device 550 estimates the state vector x e,n+1 and estimate the audio sample r e,n+1 Generate predicted current y e,n+1 :

[0093] Y e,n+1 =C·x e,n+1 +D·r e,n+1

[0094] The limiting device 540 receives the output audio samples u n and the state vector x n The limiting device 540 is configured to obtain the current state vector x of the speaker group from n and the predicted current y e,n+1 The symbol generates the replaced audio sample u L,n . Replace the audio sample u L,n Make the predicted current equal to the threshold I max :

[0095] U L,n =M·(I max ·sign{y e,n+1-C·A·x n +λ·D·u n-1 )

[0096] The symbolic function can be defined as:

[0097]

[0098] Depending on the hardware and / or software platform, the function sign{0} may return 0 or 1. The methods described herein work for both options.

[0099] Where the matrix M = (C·B+(1+λ)·D) -1 , and λ is a scalar, 0≤λ≤1. The scalar λ is used to control the previous output sample u n-1 If λ = 0, the previous input sample u is not considered. n-1 When λ = 0.5, voltage smoothing and controlling feedback strength can be well balanced.

[0100] The selector 560 is configured to select the replacement audio sample U L,n Or input audio sample r n To generate output sample u n .

[0101] The threshold determination device 555 is configured to e,n+1 With threshold I max The comparison is made and the selector 560 is controlled so that when the predicted current y e,n+1 Above threshold I max When (that is, if |y e,n+1 |>I max ), replace the audio sample u with L,n Replace the output sample u n If the predicted current y e,n+1 Below threshold I max , then the output sample u n Equal to the input audio sample r n In the case of equality, the replacement audio sample u can be used L,n and the input audio sample r n Any one of .

[0102] The modeling device 530 is configured to update the state vector x n+1 And calculate the current y consumed by the speaker group n The current consumed is calculated as follows:

[0103] y n =C·x n +D·u n

[0104] In the feedback loop, the feedback error can be calculated as follows:

[0105] e n-d =m n-d -y n-d

[0106] Where m n-d is the current measured at time step nd, y n-d is the model-based estimated current y at time step nd n is the time aligned version of , and d is the measurement delay expressed in time steps.

[0107] Finally, by considering the feedback signal generated by the state feedback controller (here the feedback vector L·e n-d ), update the state vector of the next time step: the next state vector x n+1 It can be calculated as follows:

[0108] X n+1 =A·x n +B·u n +L·e n-d

[0109] The coefficients of the vector I matrix A, B, C, D, M, L may be pre-computed for each speaker group model. Figure 2B The equivalent circuit shown is represented by a matrix M. The matrix M corresponds to an inverse matrix, which can be obtained according to the state vector x n , threshold I max , the previous audio sample u n-1 and the predicted current y e,n+1 Calculate the replacement input sample u L,n .

[0110] Note that in this specific implementation, the Figure 2B The current source is set to correspond to the threshold ±I max When the output voltage u n The voltage u is obtained at the driving node of the current source. n It can then be used as an input voltage to the speaker group model 130 or 530 and also applied to the device 125 , 525 comprising the speaker group 120 , 520 .

[0111] The above method aims to limit the current consumed by predicting one time step in advance. First estimate the predicted current y e,n+1 Then calculate the output voltage u n This approach reduces sudden voltage changes and unwanted high-frequency components.

[0112] FIG. 5 shows a diagram showing the magnitude of the admittance of a typical speaker group according to an example ( Figure 5A ) and phase ( Figure 5B ) versus frequency. Each dashed curve corresponds to a curve obtained based on current and voltage measurements, respectively, and each solid curve corresponds to a curve obtained based on current and voltage values ​​generated by a model of the speaker group, respectively. The minimum 51 of the curve occurs at 28 Hz, which corresponds to a case where there is low admittance and a low current is expected when a voltage is applied. The maximum peak 52 of the curve occurs at 47 Hz, which corresponds to a case where there is high admittance and a high current is expected when a voltage is applied. By comparing the dashed curve and the solid curve in each figure, it can be seen that both the phase and the magnitude of the admittance are accurately matched by the model.

[0113] Figure 6 shows a burst signal with a sine wave at 28 Hz. Fig. 6A , corresponding to the input samples from the audio source (r n ) is represented by a solid line, while the output voltage (u L,n ) is represented by a dotted line: This replacement output voltage is generated by the limiter device 140, 540 to replace the input voltage and generate a voltage (u n ), which is also the voltage at the input of the speaker group model 130. Figure 6B represents the output current (y) at the output of the speaker group model 130, 530 n ). Figure 6B The effect of current limitation imposed by the current limiting device is shown in FIG. Fig. 6A By replacing the input voltage with the replacement output voltage during the first peak 61 in the output current limit, the output current is limited and Figure 6B The peak value 62 in the same time period is clipped to I max = 24 A. When the signal frequency is 28 Hz, although we are in a situation where the admittance is low and low current is expected, we are in a transient condition and observe that the current needs to be limited and clipping occurs.

[0114] FIG7 shows the same curve as FIG6 , but with a sine wave at 47 Hz, where the admittance is high and high current is expected. However, in this figure, during the switch-on period (transient condition), we observe that almost no voltage limiting occurs for the first voltage peaks 71, 72, but during the corresponding current peaks 75, 76, clipping to I max = 24A. For the next voltage peaks 73, 74, strong voltage limiting occurs, and for the corresponding current peaks 77, 78, clipping to I max =24A.

[0115] In an embodiment, a device is configured to receive an input audio sample and a measured current consumed by a speaker group, the device comprising: a modeling device configured to generate a state vector for a current time step and a model-based estimated current using a state-space model of the speaker group; a prediction device configured to generate a predicted current for a next time step based on the state vector; a limiting device configured to generate a limited audio sample for the current time step based on the state vector; a state feedback controller configured to generate a feedback signal that helps generate a state vector for the next time step and is based on the measured current and the time-aligned model-based estimated current; wherein the device is configured to generate an output audio sample for the current time step, wherein the output audio sample is the input audio sample for the current time step, or when the magnitude of the predicted current is above a threshold, the output audio sample is a limited audio sample.

[0116] It should be understood by those skilled in the art that any functions, engines, block diagrams, flow charts, state transition diagrams, flowcharts, and / or data structures described herein represent conceptual views of exemplary circuits that embody the principles of the present invention. Similarly, it should be understood that any flowcharts, flow charts, state transition diagrams, pseudocodes, etc. represent various processes that can be substantially represented in a computer-readable medium and executed by a computer or processing device, whether or not such a computer or processor is explicitly shown.

[0117] Although a flowchart may describe operations as a sequential process, many operations may be performed in parallel, simultaneously, or synchronously. In addition, some operations may be omitted, combined, or performed in a different order. A process may terminate when its operations are completed, but may also have other steps not disclosed in the figure or description. A process may correspond to a method, a function, a procedure, a subroutine, a subprogram, etc. When a process corresponds to a function, its termination may correspond to a return of the function to the calling function or the main function.

[0118] Each described function, engine, block, step described herein may be implemented in hardware, software, firmware, middleware, microcode, or any suitable combination thereof.

[0119] In this specification, the term "means for performing a function" or "means configured to perform a function" may correspond to one or more functional blocks including circuits capable of performing or configured to perform the function. The block may perform the function by itself or by cooperating and / or communicating with one or more other blocks. The "means" may correspond to or be implemented as "one or more modules", "one or more devices", "one or more units", etc. The means may include at least one processor, at least one memory storing instructions, and the instructions are configured to cause the target device / system to perform the relevant functions.

[0120] The current limiting device may be implemented in software and / or hardware.

[0121] When implemented in software, the current limiting device may be implemented by a circuit (e.g., one or more circuits). Several types of circuits may be used: digital signal processor (DSP) hardware, processor or microprocessor, application specific integrated circuit (ASIC), field programmable gate array (FPGA), etc. The circuit may be or include, for example, hardware for executing instructions or software and transmission and reception of control signals, programmable logic, a programmable processor executing software or firmware, and / or any combination thereof (e.g., a processor, a control unit / entity, a controller), and a memory for storing data and / or instructions.

[0122] When implemented in software, firmware, middleware or microcode, the instructions for performing the necessary tasks may be stored in a computer-readable medium, which may or may not be included in the target device or system. The instructions may be transmitted on a computer-readable medium and loaded onto the target device or system. The instructions are configured to cause the target device / system to perform one or more functions disclosed herein. For example, as described above, according to one or more examples, at least one memory may include or store instructions, and the at least one memory and the instructions may be configured to use at least one processor to cause the target device / system to perform one or more functions. In addition, the processor, memory and instructions act as a device for providing or causing the target device / system to perform one or more functions disclosed herein.

[0123] An instruction may correspond to a computer program instruction, a computer program code, and may include one or more code segments. A code segment may represent a procedure, a function, a subprogram, a program, a routine, a subroutine, a module, a software package, a class, or any combination of instructions, data structures, or program statements.

[0124] When provided by a processor, the function may be provided by a single dedicated processor, a single shared processor, or by multiple independent processors, some of which may be shared. The term "processor" should not be understood to refer exclusively to hardware capable of executing software, and may implicitly include one or more processing circuits, whether programmable or not. The processing circuit may correspond to a digital signal processor (DSP), a network processor, an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), a system on a chip (SoC), a central processing unit (CPU), a processing unit (CPU), an arithmetic logic unit (ALU), a programmable logic unit (PLU), a processing core, programmable logic, a microprocessor, a controller, a microcontroller, a microcomputer, any device capable of responding and / or executing instructions in a defined manner and / or according to defined logic. Other conventional or customized hardware may also be included. The processor may be configured to execute instructions that enable a target device or system to perform one or more functions of a related device or system disclosed herein.

[0125] Computer readable media or computer readable storage media can be any storage medium suitable for storing instructions readable by a computer or processor. Computer readable media can more generally be any storage medium capable of storing and / or containing and / or carrying instructions and / or data. Computer readable media can be portable or fixed storage media. Computer readable media may include one or more storage devices, such as permanent mass storage devices, magnetic storage media, optical storage media, digital storage optical disks (CD-ROM, DVD, Blu-ray, etc.), USB flash drives or dongles or peripheral devices, memory cards, random access memory (RAM), read-only memory (ROM), core memory, flash memory, or any other non-volatile storage device.

[0126] The memory suitable for storing instructions may be a random access memory (RAM), a read-only memory (ROM) and / or a permanent mass storage device such as a disk drive, a memory card, a random access memory (RAM), a read-only memory (ROM), a core memory, a flash memory or any other non-volatile storage means.

[0127] Although the terms "first", "second", etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another element. For example, without departing from the scope of the present disclosure, a first element may be referred to as a second element, and similarly, a second element may be referred to as a first element. As used herein, the term "and / or" includes any and all combinations of one or more associated listed items.

[0128] When an element is referred to as being "connected" or "coupled" to another element, the element may be directly connected or coupled to the other element or there may be intervening elements. In contrast, when an element is referred to as being "directly connected" or "directly coupled" to another element, there are no intervening elements. Other words used to describe the relationship between elements should be interpreted in a similar manner (e.g., "between" versus "directly between," "adjacent" versus "directly adjacent," etc.).

[0129] The terms used herein are for the purpose of describing specific embodiments only and are not intended to be limiting. As used herein, the singular forms "a", "an", and "the" are also intended to include the plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "comprising", "containing", "including", and / or "comprising" when used herein specify the presence of stated features, integers, steps, operations, elements, and / or parts, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, parts, and / or groups thereof.

[0130] Specific details are provided in the following description to provide a thorough understanding of some examples. However, it should be understood by those of ordinary skill in the art that the example embodiments may be practiced without these specific details disclosed for illustrative purposes. For example, the system may be shown in a block diagram so as not to obscure the examples with unnecessary details. In other cases, well-known processes, structures, and techniques may be shown without unnecessary details so as not to obscure the examples.

[0131] The benefits, other advantages, and solutions to problems have been described above with respect to specific embodiments of the present invention. However, the benefits, advantages, solutions to problems, and any elements that may cause or lead to such benefits, advantages, or solutions, or make such benefits, advantages, or solutions more significant, should not be understood as key, required, or essential features or elements of the present invention.

Claims

1. A device (100, 500) for use with a device (125, 525) comprising a speaker group, wherein the device is configured to receive an input audio sample (r n ) and the measured current consumed by the speaker group (m n-d ) and generates the output audio sample (u n ), the device comprising: a modeling device (130, 530) configured to use a state-space model of the loudspeaker group from the output audio samples (u n ) generates the state vector (x) of the current time step n ) and a model-based estimate of the current consumed by the speaker group (y n ); - a prediction device (150, 550) configured to predict based on the state vector (x n ) generates the predicted current (y) for the next time step e,n+1 ); - a limiting device (140, 540) configured to be based on the state vector (x n ) generates a replacement audio sample (u) of the current time step L,n ), wherein the replacement audio sample (U L,n ) so that the current consumed by the speaker group is limited to a maximum value; - a state feedback controller (135, 235) configured to generate a feedback signal (f n ), the feedback signal is fed to the state space model to help generate the state vector (x) of the next time step n+1 ), wherein the feedback signal (f n ) is based on the measured current (m n-d ) is aligned with the time-based model-based estimated current (y n-d ) between the output audio samples (u n ) is the input audio sample of the current time step (r n ), or when the predicted current (y e,n+1 ) is greater than the threshold (I max ), the output audio sample is the replacement audio sample (u L,n ).

2. The device (100, 500) according to claim 1, wherein the prediction device (150, 550) is configured to predict the audio quality of the input audio sample based on one or more input audio samples (r n ; r n-1 ) generates the predicted current (y e,n+1 ).

3. The device (100, 500) according to claim 1 or 2, wherein the prediction device (150, 550) is configured to estimate the audio sample (r) of the next time step based on the estimated audio sample (r) of the next time step. e,n+1 ) or the input audio sample of the next time step (r n+1 ) generates the predicted current (y e,n+1 ).

4. The device (100, 500) according to any of the preceding claims, wherein the limiting device (140, 540) is configured to generate the replacement audio sample (u) based on a model derived from the state-space model (130, 530). L,n ).

5. The device (100, 500) according to any of the preceding claims, wherein the limiting device (140, 540) is configured to generate the replacement audio sample (u ) based on the threshold value representing a maximum current. Ln ).

6. The device (100, 500) according to any of the preceding claims, wherein the replacement audio sample u L,n So that the predicted current (y e,n+1 ) is equal to the threshold value (I max ) method.

7. The device (100, 500) according to any of the preceding claims, wherein the replacement audio sample u L,n Based on the predicted current (y e,n+1 ) symbol generation.

8. The device (100, 500) according to any of the preceding claims, wherein the replacement audio sample u L,n Based on the output sample u of the previous time step n-1 generate.

9. A method for use with a device (125, 525) comprising a speaker group (120, 520), the method comprising: - Get the input audio sample (r n ) and the measured current consumed by the speaker group (m n-d ); - Generates the output audio sample for the current time step (u n ); - using the state-space model of the speaker group from the output audio samples (u n ) generates the state vector (x) of the current time step n ) and a model-based estimate of the current consumed by the speaker group (y n ); -Based on the state vector (x n ) generates the predicted current (y) for the next time step e,n+1 ); -Based on the state vector (x n ) generates a replacement audio sample (u) of the current time step L,n ), wherein the replacement audio sample (U L,n ) so that the magnitude of the current consumed by the speaker group is limited to a maximum value; - Generate feedback signal (f n ), the feedback signal is fed to the state space model to help generate the state vector (x) of the next time step n+1 ), wherein the feedback signal (f n ) is based on the measured current (m n-d ) is aligned with the time-based model-based estimated current (y n-d ) between; The output audio sample (u n ) is the input audio sample of the current time step (r n ), or when the predicted current (y e,n+1 ) is greater than the threshold (I max ), the output audio sample is the replacement audio sample (u L,n ).

10. A computer program comprising computer executable instructions which, when executed by at least one processor, cause an apparatus to perform the method as claimed in claim 9.

11. A device for use with a device (125, 525) comprising a speaker group (120, 520), the device comprising signal processing means for performing a method comprising: - Get the input audio sample (r n ) and the measured current consumed by the speaker group (m n-d ); - Generates the output audio sample for the current time step (u n ); - using the state-space model of the speaker group from the output audio samples (u n ) generates the state vector (x) of the current time step n ) and a model-based estimate of the current consumed by the speaker group (y n ); -Based on the state vector (x n ) generates the predicted current (y) for the next time step e,n+1 ); -Based on the state vector (x n ) generates a replacement audio sample (u) of the current time step L,n ), wherein the replacement audio sample (U L,n ) so that the magnitude of the current consumed by the speaker group is limited to a maximum value; - Generate feedback signal (f n ), the feedback signal is fed to the state space model to help generate the state vector (x) of the next time step n+1 ), wherein the feedback signal (f n ) is based on the measured current (m n-d ) is aligned with the time-based model-based estimated current (y n-d ) The output audio sample (u n ) is the input audio sample of the current time step (r n ), or when the predicted current (y e,n+1 ) is greater than the threshold (I max ), the output audio sample is the replacement audio sample (u L,n ).

12. The apparatus according to claim 11, wherein the signal processing device comprises at least one processor and at least one memory comprising computer program instructions, wherein the at least one memory and the computer program instructions are configured to utilize the at least one processor to cause the apparatus to perform at least one step of the method.

13. An apparatus according to claim 11 or 12, wherein the signal processing means comprises circuitry configured to cause the apparatus to perform at least one step of the method.

14. An apparatus according to any one of claims 10 to 13, wherein the signal processing means comprises a digital signal processor configured to cause the apparatus to perform at least one step of the method.

15. A system (190) comprising an apparatus (100) according to any one of claims 1 to 8 or 11 to 14, the system comprising a database configured to store model coefficients of a state-space model for a number of speaker groups and means for loading the model coefficients corresponding to the speaker groups.

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