Audio output drivers for piezo speakers
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United States of America Patent
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Nov 26, 2013
Grant Date -
Dec 15, 2011
app pub date -
Jun 13, 2011
filing date -
Jun 15, 2010
priority date (Note) -
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Abstract
A driver circuit for a piezoelectric speaker is described, wherein charge is transferred from a charge reservoir to the speaker. In a first embodiment a delta sigma circuit uses a pulse width modulated digital audio signal to control a push-pull circuit to drive the piezoelectric speaker. High frequency harmonics are introduced to the delta sigma drive signals to enhance the low frequency response of the speaker. A charge recovery mechanism recovers charge from the speaker to reduce the frequency of replenishing the charge reservoir and to provide additional drive current for the speaker. In a second embodiment the pulse width modulated signal is used to drive a voltage quadrupling circuit that drives the piezoelectric speaker, wherein the reservoir capacitor is integrated with the capacitors of quadrupling circuit, which provides charge recovery.
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