All-digital class-D audio amplifier
First Claim
1. An all-digital class-D audio amplifier comprising:
- a pulse-width modulation (PWM) wave generator adapted to generate a PWM wave;
an interpolator adapted to receive an input audio signal, up-sample said input audio signal; and
down-sample said input audio signal to a PWM wave switching frequency;
an audio speaker adapted to broadcast an amplified version of said input audio signal;
a pair of metal-oxide-semiconductor field-effect transistors (MOSFETs) driven by said PWM wave and said input supply voltage, wherein said pair of MOSFETs transmit said amplified version of said input audio signal to said audio speaker;
a natural-sampling and pre-distortion circuit adapted to (i) generate a pre-distorted natural-sampling frequency point for said PWM wave switching frequency, and (ii) account for digitized power supply ripples for an input supply voltage used to drive said audio speaker; and
an analog-to-digital converter (ADC) adapted to digitize said power supply ripples or any power supply distortion.
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Abstract
An all-digital class-D audio amplifier and method of digitizing an analog signal comprises a pulse-width modulation (PWM) wave generator for generating a PWM wave; an interpolator for receiving an input audio signal, up-sample the input audio signal; and down-sample the input audio signal to a PWM wave switching frequency; an audio speaker for broadcasting an amplified version of the input audio signal; a pair of MOSFETs driven by the PWM wave and the input supply voltage, wherein the pair of MOSFETs transmit the amplified version of the input audio signal to the audio speaker; a natural-sampling and pre-distortion circuit adapted to (i) generate a pre-distorted natural-sampling frequency point for the PWM wave switching frequency, and (ii) account for digitized power supply ripples for an input supply voltage used to drive the audio speaker; and an analog-to-digital converter (ADC) adapted to digitize the power supply ripples or distortion.
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Citations
21 Claims
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1. An all-digital class-D audio amplifier comprising:
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a pulse-width modulation (PWM) wave generator adapted to generate a PWM wave; an interpolator adapted to receive an input audio signal, up-sample said input audio signal; and
down-sample said input audio signal to a PWM wave switching frequency;an audio speaker adapted to broadcast an amplified version of said input audio signal; a pair of metal-oxide-semiconductor field-effect transistors (MOSFETs) driven by said PWM wave and said input supply voltage, wherein said pair of MOSFETs transmit said amplified version of said input audio signal to said audio speaker; a natural-sampling and pre-distortion circuit adapted to (i) generate a pre-distorted natural-sampling frequency point for said PWM wave switching frequency, and (ii) account for digitized power supply ripples for an input supply voltage used to drive said audio speaker; and an analog-to-digital converter (ADC) adapted to digitize said power supply ripples or any power supply distortion. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 14, 15, 16, 21)
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13. An all-digital class-D audio amplifier comprising:
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a pulse-width modulation (PWM) wave generator adapted to generate a PWM wave; an interpolator adapted to receive an input audio signal, up-sample said input audio signal; and
down-sample said input audio signal to a PWM wave switching frequency;an audio speaker adapted to broadcast an amplified version of said input audio signal; a pair of metal-oxide-semiconductor field-effect transistors (MOSFETs) driven by said PWM wave and said input supply voltage, wherein said pair of MOSFETs transmit said amplified version of said input audio signal to said audio speaker; a natural-sampling and pre-distortion circuit adapted to (i) generate a pre-distorted natural-sampling frequency point for said PWM wave switching frequency, and (ii) account for digitized power supply ripples for an input supply voltage used to drive said audio speaker; at least a third order digital sigma-delta type modulator adapted to shape quantization noise out of said input audio signal; and an analog-to-digital converter (ADC) adapted to digitize said power supply ripples or any power supply distortion.
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17. A system for amplifying an audio signal, said system comprising:
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digital circuitry; an audio signal source adapted to generate an input audio signal; an audio speaker adapted to transmit an amplified input audio signal; a pair of metal-oxide-semiconductor field-effect transistors (MOSFETs) adapted to transmit said amplified input audio signal to said audio speaker; and a class-D audio amplifier adapted to achieve a power supply rejection ratio (PSRR) in a range of 20 dB to 80 dB, wherein said class-D audio amplifier comprises; a pulse-width modulation (PWM) wave generator adapted to generate a PWM wave, wherein said PWM wave drives said pair of MOSFETs; an interpolator adapted to receive an input audio signal, up-sample said input audio signal; and
down-sample said input audio signal to a PWM wave frequency;a natural-sampling and pre-distortion circuit adapted to (i) generate a pre-distorted natural-sampling frequency point for said PWM wave frequency, and (ii) account for digitized power supply ripples for an input supply voltage used to drive said audio speaker; at least a third order digital sigma-delta type modulator adapted to shape quantization noise out of said input audio signal; and an analog-to-digital converter (ADC) adapted to digitize said power supply ripples, wherein said ADC operates at a frequency that is higher than said PWM wave frequency; wherein said digital circuitry is adapted to; provide a PSRR performance using digital signal processing and by digitizing said power supply ripples using said ADC; and provide a reduced total harmonic distortion (THD) using digital signal processing and by digitizing said power supply distortion using said ADC.
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18. A method of amplifying an audio signal transmitted through an audio speaker, said method comprising:
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generating an input audio signal; generating a pulse-width modulation (PWM) wave; up-sampling and down-sampling said input audio signal to a PWM wave switching frequency; generating a pre-distorted natural-sampling frequency point for said PWM wave switching frequency; shaping quantization noise out of said input audio signal using at least a third order digital sigma-delta type modulator; digitizing a power supply ripple for an input supply voltage used to drive said audio speaker; and transmitting the digitized audio signal through said audio speaker, wherein said digitized audio signal comprises a power supply rejection ratio (PSRR) in a range of 20 dB to 80 dB. - View Dependent Claims (19, 20)
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Specification