US-12627926-B2 - Thermal protection for system with driver driving multiple transducers

US12627926B2US 12627926 B2US12627926 B2US 12627926B2US-12627926-B2

Abstract

An audio system may include a plurality of transducers, a temperature estimator, and a thermal control subsystem. The temperature estimator may be configured to monitor physical quantities associated with a plurality of transducers and based on the physical quantities, determine an estimated temperature associated with a first transducer of the plurality of transducers. The thermal control subsystem may be configured to generate an output signal based on an input signal, the output signal for driving the plurality of transducers and control the output signal based on the estimated temperature.

Inventors

Roberto Napoli
Philip B.J. CLARKIN
Zhengyi Xu
Chris RATTRAY
Edward CRANEY

Assignees

CIRRUS LOGIC INTERNATIONAL SEMICONDUCTOR LTD.

Dates

Publication Date: 20260512
Application Date: 20240215

Claims (18)

1 . A method comprising: receiving an input signal; generating an output signal based on the input signal, the output signal for driving a plurality of transducers; monitoring physical quantities associated with the plurality of transducers; based on the physical quantities, determining an estimated temperature associated with a first transducer of the plurality of transducers; determining based on the physical quantities a first estimated power delivered to the first transducer and a second estimated power delivered to a second transducer of the plurality of transducers; and determining a second estimated temperature of the second transducer from a thermal model of the plurality of transducers based on the estimated temperature, the first estimated power, and the second estimated power; and controlling the output signal based on the estimated temperatures.
2 . The method of claim 1 , wherein the physical quantities comprise a voltage applied to the plurality of transducers and a current delivered to the plurality of transducers.
3 . The method of claim 1 , wherein the plurality of transducers comprises a woofer for playback of low-frequency content and a tweeter for playback of high-frequency content higher in frequency than the low-frequency content.
4 . The method of claim 3 , wherein the tweeter and the woofer are integral to a single integrated speaker module.
5 . The method of claim 1 , further comprising: driving a first pilot tone on the output signal at a first frequency; extracting a response of the physical quantities responsive to the first pilot tone; and determining the estimated temperature based on the response.
6 . The method of claim 5 , further comprising: driving a second pilot tone on the output signal at a second frequency; extracting a second response of the physical quantities responsive to the second pilot tone; and determining the estimated temperature and the second estimated temperature of the second transducer of the plurality of transducers based on the response and the second response.
7 . A system comprising: a temperature estimator configured to: monitor physical quantities associated with a plurality of transducers; based on the physical quantities, determine an estimated temperature associated with a first transducer of the plurality of transducers; determine based on the physical quantities a first estimated power delivered to the first transducer and a second estimated power delivered to a second transducer of the plurality of transducers; and determine a second estimated temperature of the second transducer from a thermal model of the plurality of transducers based on the estimated temperature, the first estimated power, and the second estimated power; and a thermal control subsystem configured to: generate an output signal based on an input signal, the output signal for driving the plurality of transducers; and control the output signal based on the estimated temperatures.
8 . The system of claim 7 , wherein the physical quantities comprise a voltage applied to the plurality of transducers and a current delivered to the plurality of transducers.
9 . The system of claim 7 , wherein the plurality of transducers comprises a woofer for playback of low-frequency content and a tweeter for playback of high-frequency content higher in frequency than the low-frequency content.
10 . The system of claim 9 , wherein the tweeter and the woofer are integral to a single integrated speaker module.
11 . The system of claim 7 , further comprising a pilot tone injection subsystem configured to drive a first pilot tone on the output signal at a first frequency, and wherein the temperature estimator is further configured to: extract a response of the physical quantities responsive to the first pilot tone; and determine the estimated temperature based on the response.
12 . The system of claim 11 , wherein: the pilot tone injection subsystem is configured to drive a second pilot tone on the output signal at a second frequency; and the temperature estimator is further configured to: extract a second response of the physical quantities responsive to the second pilot tone; and determine the estimated temperature and the second estimated temperature of the second transducer of the plurality of transducers based on the response and the second response.
13 . An audio system comprising: a plurality of transducers; a temperature estimator configured to: monitor physical quantities associated with the plurality of transducers; and based on the physical quantities, determine an estimated temperature associated with a first transducer of the plurality of transducers; determine based on the physical quantities a first estimated power delivered to the first transducer and a second estimated power delivered to a second transducer of the plurality of transducers; and determine a second estimated temperature of the second transducer from a thermal model of the plurality of transducers based on the estimated temperature, the first estimated power, and the second estimated power; and a thermal control subsystem configured to: generate an output signal based on an input signal, the output signal for driving the plurality of transducers; and control the output signal based on the estimated temperatures.
14 . The audio system of claim 13 , wherein the physical quantities comprise a voltage applied to the plurality of transducers and a current delivered to the plurality of transducers.
15 . The audio system of claim 13 , wherein the plurality of transducers comprises a woofer for playback of low-frequency content and a tweeter for playback of high-frequency content higher in frequency than the low-frequency content.
16 . The audio system of claim 15 , wherein the tweeter and the woofer are integral to a single integrated speaker module.
17 . The audio system of claim 13 , further comprising a pilot tone injection subsystem configured to drive a first pilot tone on the output signal at a first frequency, and wherein the temperature estimator is further configured to: extract a response of the physical quantities responsive to the first pilot tone; and determine the estimated temperature based on the response.
18 . The audio system of claim 17 , wherein: the pilot tone injection subsystem is configured to drive a second pilot tone on the output signal at a second frequency; and the temperature estimator is further configured to: extract a second response of the physical quantities responsive to the second pilot tone; and determine the estimated temperature and the second estimated temperature of the second transducer of the plurality of transducers based on the response and the second response.

Description

RELATED APPLICATION The present disclosure claims priority to U.S. Provisional Patent Application Ser. No. 63/520,973, filed Aug. 22, 2023, which is incorporated by reference herein in its entirety. FIELD OF DISCLOSURE The present disclosure relates in general to estimating parameters of an electromagnetic load, for example, a haptic transducer. BACKGROUND Modern electronic devices, including smart phones, tablets, computers, and other devices, often include one or more transducers (e.g., one or more speakers and/or one or more haptic transducers) that may generate audio and/or haptic effects to a user of the devices. Such transducers may be damaged when they are pushed to their limits. One common failure mode for over-driven transducers (e.g., speakers/haptics) is thermal damage. As an example, for speakers, if the voice coil exceeds a maximum temperature, the glues that hold the voice coil together and connect it to the diaphragm can melt and cause irreparable damage. As another example, at higher temperatures, magnets in a haptic transducer may become demagnetized and/or a coil of the haptic transducer may fuse, causing an electrical short. Speaker protection algorithms are commonly used to drive the speaker to its maximum volume while ensuring it does not exceed its rated limits, and similar protection algorithms may be used in connection with haptic transducers. In conventional configurations, a single amplifier typically drives a single transducer. In order to determine thermal conditions of the transducer, a pilot tone, usually of low frequency (e.g., 12 Hz or 48 Hz) may be injected into the playback signal for the system. Often, such pilot tone is injected in the digital domain of the playback path, upstream of any digital-to-analog converter and amplifier in the playback path. A processing system may then monitor voltage and current signal feedback from the transducer (e.g., via analog-to-digital converters), and from such monitored voltage and current feedback, calculate resistance of a coil of the transducer. The calculated resistance Re may then be mapped directly to coil temperature through the following linear relationship: T=(RemeasuredRecal-1)α+Tamb wherein T is the temperature of the coil, α is the temperature coefficient of the coil (e.g., nominally 0.00393 Ω/° C. for copper), Remeasured is the calculated value of resistance, and Recal is the calibrated value of resistance at an ambient temperature Tamb. However, more modern transducer systems may include multiple transducers driven from a single amplifier. For example, a modern transducer system may include a single amplifier driving a dual audio transducer comprising a woofer (for playback of audio at lower audible frequencies) and a tweeter (for playback of audio at higher audio frequencies) in parallel. By using conventional approaches of monitoring voltage and current delivered from the amplifier, the impedance measured using the single pair of feedback voltage and current signals is the parallel impedance of the two transducers (including any impedance of electrical components between the output of the amplifier and the transducers). However, existing approaches only enable measurement of this lumped parallel combination, but do not enable the determination of the individual coil resistances of the multiple transducers, and thus do not enable determination of individual coil temperatures of the multiple transducers. SUMMARY In accordance with the teachings of the present disclosure, the disadvantages and problems associated with thermal control of multiple transducers driven from a single amplifier may be reduced or eliminated. In accordance with embodiments of the present disclosure, a method may include receiving an input signal, generate an output signal based on the input signal, the output signal for driving a plurality of transducers, monitor physical quantities associated with the plurality of transducers, determining an estimated temperature associated with a first transducer of the plurality of transducers based on the physical quantities, and control the output signal based on the estimated temperature. In accordance with these and other embodiments of the present disclosure, a system may include a temperature estimator and a thermal control subsystem. The temperature estimator may be configured to monitor physical quantities associated with a plurality of transducers and based on the physical quantities, determine an estimated temperature associated with a first transducer of the plurality of transducers. The thermal control subsystem may be configured to generate an output signal based on an input signal, the output signal for driving the plurality of transducers and control the output signal based on the estimated temperature. In accordance with these and other embodiments of the present disclosure, an audio system may include a plurality of transducers, a temperature estimator, and a thermal control subsystem. The tempe