Startup and shutdown click noise elimination for class D...

Details Startup and shutdown click noise elimination for class D... Startup and shutdown click noise elimination for class D...

2007-08-03

2008-08-26

Nguyen, Patricia (Department: 2817)

Amplifiers

With semiconductor amplifying device

Including class d amplifier

C330S20700P, C330S302000

Reexamination Certificate

active

07417504

ABSTRACT:
A method of minimizing an audible click noise from a speaker in a Class D audio power amplifier upon shutdown or startup of a switching stage having two switches series connected at a node, the speaker being connected to the node via an output filter comprising an inductor and a capacitor, the switches being controlled by a controller. The method including the steps of determining a timing interval at the node to transition a peak voltage of the capacitor, the capacitor voltage being a speaker voltage; and eliminating the audible transient voltage excursion across the speaker that causes a click noise during the timing interval, wherein at startup ON and OFF times of the switches are incrementally increased from zero to a normal mode and at shutdown the ON OFF times of the switches are incrementally decreased from the normal mode to zero.

REFERENCES:
patent: 4589136 (1986-05-01), Poldy et al.
patent: 5767744 (1998-06-01), Irwin et al.
patent: 6489840 (2002-12-01), Botti et al.
patent: 6720825 (2004-04-01), Hansen et al.
patent: 6940345 (2005-09-01), Nair et al.
patent: 6998828 (2006-02-01), Casey et al.

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