US-12619271-B2 - Devices and methods to control dynamic audio range in boosted audio systems

US12619271B2US 12619271 B2US12619271 B2US 12619271B2US-12619271-B2

Abstract

A controller regulates the voltage delivered to the load and current drawn from the battery in an audio system depending on ripple in the battery voltage which is input to the controller to allocate power for audio playback. Regulation maximizes available headroom while avoiding audio clipping. The effect of internal battery and external parasitic resistance (ESR) on ripple is compensated by an iterative process. ESR is rapidly increased whenever the minimum of the battery voltage input to the controller falls below a clipping threshold and slowly decreased whenever such voltage exceeds such threshold and the audio is under compression. A limiter allocates power to utilize more of the available audio headroom. A de-emphasis filter in each audio signal path compensates for capacitive ripple in the battery voltage input to the controller. As the frequency of the audio input changes, the filter(s) allow frequency-dependent power/current regulation to fill the full audio range without distortion.

Inventors

Supriyo Palit
Mohit Chawla

Assignees

TEXAS INSTRUMENTS INCORPORATED

Dates

Publication Date: 20260505
Application Date: 20210607
Priority Date: 20210120

Claims (18)

1 . An audio system comprising: a voltage estimator having inputs, a first output, and a second output, wherein the first output of the voltage estimator is configured to provide a voltage that represents an estimate of a voltage input of the audio system based on voltages provided at the inputs of the voltage estimator; a current regulator having a first input, a second input, and an output, wherein the first input of the current regulator is coupled to the second output of the voltage estimator and the second input of the current regulator is coupled to the first output of the voltage estimator; a filter disposed in an audio signal path, the filter having an output; and an audio limiter having a first input coupled to the output of the filter, a second input configured to receive a voltage limit voltage.
2 . The audio system of claim 1 , wherein the audio limiter is configured to control power allocated for audio playback based on the output of the filter, the voltage limit voltage, a load resistance value, and an input power voltage.
3 . The audio system of claim 1 , further comprising: a boost circuit having a first input configured to receive a device voltage, and a second input configured to receive a current limit voltage; and an inductor coupled to the first input of the boost circuit, wherein the current limit voltage is configured to limit a peak of a current drawn from a battery via the inductor.
4 . The audio system of claim 3 , further comprising a speaker coupled to an output of the boost circuit.
5 . The audio system of claim 1 , further comprising: a power threshold calculator having a first input coupled to the first output of the voltage estimator, a second input configured to receive a the current limit voltage, and a third input configured to receive a load resistance value.
6 . The audio system of claim 5 , wherein the power threshold calculator is configured to: calculate a scaled input power based on the first output of the voltage estimator, a current limit voltage, and a scale factor; and calculate the voltage limit voltage based on the scaled input power and the load resistance value.
7 . The audio system of claim 6 , wherein the power threshold calculator includes an input power calculator configured to calculate an input power total signal based on the scaled input power.
8 . A method comprising: measuring an input voltage signal to a controller in each of multiple periods of time to calculate, for each period of time, a maximum value of the input voltage signal (maximum value), an average value of the input voltage signal (average value), and a minimum value of the input voltage signal (minimum value); outputting, by the controller, an output voltage for each period of time representing an estimate of an actual value of the input voltage signal based on the maximum value for that period of time and an average of multiple maximum values sampled during that period of time; estimating a resistance for each period of time based on the minimum value for that period of time; and calculating an output current of the controller for each period of time based on the output voltage for that period of time and the estimated resistance for that period of time.
9 . The method of claim 8 , wherein the output voltage for each period of time is determined based on an intermediate value that is determined based on a difference between the maximum value for that period of time and the average value obtained during that period of time compared to a silence voltage threshold.
10 . The method of claim 9 , wherein, for each period of time, the output voltage is determined based on an average of multiple intermediate values, one from a present period of time and each of the others from a respective previous period of time.
11 . The method of claim 9 , wherein, for each period of time, when the comparison indicates that the difference is less than the silence voltage threshold, the intermediate value is determined to be equal to maximum value obtained during that period of time.
12 . The method of claim 9 , wherein, for each period of time, when the comparison indicates that the difference is greater than or equal to the silence voltage threshold, the intermediate value is maintained the same as in an immediate previous period of time.
13 . The method of claim 8 , wherein the estimating of the resistance for each period of time includes comparing the minimum value for that period of time to a clipping voltage threshold.
14 . The method of claim 13 , wherein, for each period of time, when the comparing indicates that the minimum value is less than the clipping voltage threshold, the estimated resistance is determined to be the sum of the estimated resistance for an immediately previous period of time and a first amount of resistance.
15 . The method of claim 13 , wherein, for each period of time, when the comparing indicates that the minimum value is greater than or equal to the clipping voltage threshold, the method further comprises determining whether a signal is under compression.
16 . The method of claim 15 , wherein, for each period of time, when it is determined that the signal is under compression, the estimated resistance is determined to be the difference between the estimated resistance for an immediately previous period of time and a second amount of resistance, and when it determined that the signal is not under compression, the estimated resistance is determined to be the estimated resistance for an immediately previous period of time.
17 . The method of claim 8 , wherein, for each period of time, the output current is calculated to be the difference between the output voltage and a clipping voltage threshold divided by the estimated resistance.
18 . The method of claim 8 , further comprising: filtering an input audio signal to compensate for capacitive ripple.

Description

FIELD OF DISCLOSURE This disclosure relates generally to devices and methods that control and improve dynamic audio range in boosted audio systems, and more particularly to devices and methods that enable full use of the available audio range while limiting clipping, and that enable battery current regulation and preserve battery life. BACKGROUND A boosted audio playback system provides an amplified output voltage via a boost circuit to drive speakers. The voltage input to the boost circuit is provided by the power supply, e.g., battery, of the system. The voltage at the input of the boost circuit typically suffers from ripple due to internal battery resistance and external parasitic resistance (a combination of which is also known as external series resistance or ESR), and capacitive decoupling. Ripple also depends on the instantaneous current drawn from the battery to power the load. If the current drawn from the battery is too high, then the ripple tends to cause the battery voltage at boost circuit input to drop significantly, resulting in the instantaneous input power being less than the output load power. This results in clipping. If the current drawn from the battery is too low, then the ripple too will be low, which results in the instantaneous input power being greater than the output load power. This means that headroom (upper portion of the audio range) is available and that target output power could have been further increased. The resulting effect is reduced output loudness. Thus, regulating the current drawn from the battery is an important consideration in audio systems. Conventional approaches apply a low pass filter in the battery voltage sensing path, and thus only consider the DC component of the ripple. Such approaches do not consider the instantaneous AC drop, which affects the boost circuit of the system. Even adding a margin to account for the AC ripple would not solve the problem, since the AC ripple depends on ESR which depends on ambient conditions such as temperature. Also, the decoupling capacitor causes the ripple to be frequency dependent. Thus, such conventional approaches fail to accurately compensate for the ripple, as they inevitably either over compensate (resulting in lower loudness) or under compensate (resulting in clipping and brown-out). A better solution is thus desirable. SUMMARY In accordance with an example, a controller comprises a voltage estimator having inputs to receive multiple input voltage values obtained from an input voltage signal and an output at which a voltage signal (estimated VBAT) representing an estimate of the true input voltage signal is output. The controller also comprises a current regulator having a first input to receive one of the multiple input voltage values, a second input coupled to the output of the voltage estimator to receive the estimated VBAT, and an output at which a calculated current limit signal is output. The current regulator tracks an estimated resistance and controls the estimated resistance to be a specific value based on the input voltage value received by the current regulator. The current regulator calculates the current limit signal based on the estimated VBAT, a clipping voltage threshold and the specific value of the estimated resistance. In accordance with an example, an audio system comprises a voltage estimator that generates a voltage signal (estimated VBAT) representing an estimate of true voltage input to the audio system based on multiple input voltage values; a current regulator that tracks an estimated resistance and controls the estimated resistance to be a specific value based on one of the multiple input voltage values that is received by the current regulator, the current regulator calculating a current limit signal based on the estimated VBAT, a clipping voltage threshold and the specific value of the estimated resistance; a filter disposed in an audio signal path, the filter having an output at which a filtered audio signal is output; and an audio limiter having a first input at which the filtered audio signal is received, a second input at which a voltage limit signal is received, a third input at which a load resistance value determined from an audio output signal is received, and a fourth input at which an input power signal is received. In accordance with an example, a method comprises measuring an input voltage signal to a controller of an audio system in each of multiple periods of time to calculate, for each period of time, a maximum value of the input voltage signal (maximum value), an average value of the input voltage signal (average value), and a minimum value of the input voltage signal (minimum value); outputting, by the controller, an output voltage for each period of time representing an estimate of the true value of the input voltage signal based on the maximum value for that period of time and the average of multiple maximum values sampled during that period of time; estimating a res