Apparatus for eliminating audio noise when power is cycled to a

Details Apparatus for eliminating audio noise when power is cycled to a Apparatus for eliminating audio noise when power is cycled to a

1996-01-17

1998-03-31

Isen, Forester W.

Electrical audio signal processing systems and devices

Noise or distortion suppression

Soft switching, muting, or noise gating

381120, H04B 1500

Patent

active

057347298

ABSTRACT:
An audio power management system for a computer to eliminate audible noise associated with the cycling of power to an audio amplifier for a computer is disclosed. A diode is connected between the power supply rail and the power input to the audio amplifier. One or more decoupling capacitors is provided at the power input to the audio amplifier to insulate the audio amplifier from fluctuations at the voltage supply rail. The apparatus also briefly mutes the amplifier when power is cycled to eliminate transient noises.
Additionally, the audio power management system eliminates audible noise associated with the waking-up or putting the computer to sleep. The audio system asserts a speaker mute signal before power is removed from the amplifier to reduce transient conditions. During power up, the speaker mute signal is applied to the amplifier for a period after power has been applied to the amplifier. This control is economically accomplished using a minimal number of digital outputs.

REFERENCES:
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Philips Semiconductors Product Specification, Class AB Stereo Headphone Driver TDA1308 (Aug. 1996).
Philips Semiconductors RF Communications Products Specification, 3-Watt Mono BTL Audio Output Amplifier TDA7056A (Aug. 1991).
National Semiconductor Datasheets for LM4700 Overture.TM. and LM2876 Overture.TM. High Performance 40W Audio Power Amplifier with Mute (1995).
National Semiconductor, AN69, Dec. 1972, p. AN69-4.

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