Apparatus and method for muting an output signal in a switching amplifier
AssigneeSGS Microelettronica S.p.A.
InventorsCarlo Cini, Claudio Diazzi, Pietro Erratico
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Abstract
In an audio switching power amplifier, muting apparatus provided for eliminating noise signals associated with turn-on and turn-off operations of the apparatus is disclosed. The muting apparatus disables the output power amplifiers and controls signal levels at various positions in the power amplifier to reduce transient conditions. Control apparatus applies the muting signals to the power amplifier during a predetermined period during start-up of the amplifier and applies the muting conditions immediately upon the turning off of power to the power amplifier.
Claims9
In a power switching amplifier in which an integrating circuit, responding to an input audio signal and signals from output power amplifiers, controls a pulse width of output signals activating a speaker system, apparatus for controlling noise signals resulting from transient conditions comprising:
- switching apparatus for maintaining said output power amplifiers in a non-conducting state;
- and
- transistor apparatus for controlling a signal at an output terminal of said integrating circuit.
The method of preventing noise signals in a power switching amplifier during transient supply voltage conditions in a switching power amplifier comprising the steps of:
- switching off output transistors of said power switching amplifier;
- and
- establishing a predetermined voltage level at an output of an amplifier circuit controlling a pulse width of signals activating said output transistors.
An audio power switching amplifier for driving a speaker circuit comprising:
- a plurality of power transistors;
- driving circuit means coupled to said plurality of power transistors for applying current in alternative directions through said speaker circuit;
- a Schmitt trigger circuit for activating said driving circuit means;
- differential amplifier means coupled to said power transistors and to an input audio signal for controlling output signals of said Schmitt trigger circuit, said Schmitt trigger output signals controlling current applied to said speaker circuit;
- and
- mute control apparatus means for applying a first signal to said driving circuit means, said first signal causing said power transistors to be in a non-conducting state, said mute control apparatus means applying a second signal to an output terminal of said differential amplifier means.
Dependencies are inferred from the claim text.