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Thermal Modelling of Voicecoils in Microspeakers
Linköping University, Department of Electrical Engineering, Automatic Control.
2016 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

Microspeakers can overheat and break if not monitored and regulated. This monitoringis usually done by adding a pilot tone that introduces energy to the signal.A problem with this approach is the slow update rate of the temperature estimate.This in combination with a fast temperature rise could result in an audible regulationof the input. By simulating the voice coil temperature these problems couldbe mitigated. In this thesis, two existing grey box models and one novel black boxmodel are estimated for different speakers and evaluated using different signals.The results are promising and indicate that all models can estimate the voice coiltemperature with a mean error below one degree. The tests show that a correctinitialization of the model is crucial. Therefore the suggestion to Cirrus Logic,who hosted this thesis project, is to combine a feedforward model with eithertemperature sensor data from the mobile device or a pilot tone.

Abstract [sv]

Mikrohögtalare kan överhettas och gå sönder ifall temperaturen inte övervakasoch regleras vid behov. Denna övervakning sker med hjälp av en pilotton somtillför energi till högtalarens insignal. Ett problem med denna lösning är att övervakningenär relativt långsam. Detta gör att en snabb temperaturökning kan geen oönskad hörbar reglering av insignalen. Genom att modellera spolens temperaturkan detta problem hanteras. I detta examensarbete tas två fysikaliska modelleroch en konfektionsmodell fram och testas på olika högtalare och signaler.Resultaten är lovande och visar att alla modeller kan skatta spoltemperaturenmed ett medelfel under en grad. Utvärderingen visar att initiering av modellensstarttemperatur är viktig. Därför är förslaget till Cirrus Logic att kombinera en simuleringsmodellsom initieras med antingen temperatursensordata från mobileneller med hjälp av en pilotton.

Place, publisher, year, edition, pages
2016. , 52 p.
Keyword [en]
Thermal Modelling, microspeaker, voice coil, loudspeaker
National Category
Control Engineering
URN: urn:nbn:se:liu:diva-130337ISRN: LiTH-ISY-EX--16/4975--SEOAI: diva2:954210
External cooperation
Cirrus Logic International (Sweden) AB
Subject / course
Automatic Control
Available from: 2016-09-15 Created: 2016-07-28 Last updated: 2016-09-16Bibliographically approved

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