Circuits and methods for reducing pop noise in class D amplifiers
AssigneePacificTech Microelectronics, Inc.
InventorsHongbo Zhang, Vincent Fong, Jing Xu, Yuling Khang
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Abstract
In one embodiment the present invention includes a method for starting up a class D amplifier. The method comprises increasing, gating, and driving. The increasing includes increasing a duty cycle of a pulse train from a first duty cycle to a second duty cycle. The gating includes gating a signal based on the increasing of the duty cycle. The gating results in a gated signal. The driving includes driving an output signal from the gated signal to charge an output capacitor. The output capacitor is coupled to a speaker. The increasing of the duty cycle contributes to the charging of the output capacitor such that switching sounds detectable by the human ear are reduced.
Claims21
A method for starting up a class D amplifier, said method comprising:
- increasing a duty cycle of a pulse train from a first duty cycle to a second duty cycle;
- gating a signal based on said increasing of said duty cycle using a single AND gate, said gating resulting in a gated signal;
- and
- driving an output signal from said gated signal to charge an output capacitor, said output capacitor coupled to a speaker,
- wherein said increasing of said duty cycle contributes to the charging of said output capacitor such that switching sounds detectable by the human ear are reduced.
A circuit comprising:
- a gate circuit having a single AND gate only and coupled to receive a signal and generate a gated signal;
- a pulse generating circuit coupled to provide a control signal to said gate circuit;
- and
- a drive circuit coupled to receive said gated signal and coupled to provide an output signal,
- wherein said output signal charges an output capacitor, said output capacitor coupled to a speaker,
- wherein said control signal includes a pulse train with a duty cycle which increases from a first duty cycle to a second duty cycle,
- wherein said control signal contributes to the charging of said output capacitor such that switching sounds detectable by the human ear are reduced, said switching sounds not corresponding to said signal, wherein said gate circuit includes a single AND gate only, and
- wherein a first terminal of said single AND gate is coupled to receive said signal, a second terminal of said single AND gate is coupled to receive said control signal, and an output terminal of said single AND gate is coupled to provide said gated signal.
A class D amplifier circuit comprising:
- a first modulator coupled to receive a continuous signal;
- a second modulator coupled to receive a startup signal;
- a single AND gate having a first terminal coupled to receive a first modulated signal from said first modulator and a second terminal coupled to receive a second modulated signal from said second modulator;
- and
- a driver circuit coupled to receive a gated signal from an output terminal of said single AND gate and coupled to provide a single output signal to drive a filter coupled in series with a speaker,
- wherein said second modulated signal includes a pulse train having an increasing duty cycle corresponding to said output signal providing increasing levels of charging to said filter such that switching sounds generated from said speaker and detectable by the human ear are reduced, said switching sounds not corresponding to said continuous signal.
Dependencies are inferred from the claim text.