Texas Instruments Corporation

David Edward Zaucha

Lars Risbo

Venkateswar Reddy Kowkutla

Anker Bjørn-Josefsen

Josey George Angilivelil

Douglas Allen Roberson

Thomas Morch

Anker Bjorn-Josefsen

A digital audio system including a combination of analog and digital volume control is disclosed. A variable power supply voltage biases a power amplifier for each channel, and applies a bias voltage corresponding to an analog volume control signal. In one disclosed embodiment, digital gain control circuitry compares the bias voltage with the level expected for the analog volume control signal; if the bias voltage has not dropped in response to a reduction in the analog volume control signal, the digital gain control circuitry reduces the digital gain of the input digital audio signal, until the bias voltage responds to the reduced volume. In another disclosed embodiment, modeling or characterization of the audio system is used to derive a digital gain control signal based on the desired volume signal and the amplitude of the digital audio signal itself. In another disclosed embodiment, a slew rate limiter slows the rate of change of the control signal applied to the variable power supply, in which case the slowed control signal is used in the comparison or calculations of the reduced digital gain.

Digital compensation of analog volume control gain in a digital audio amplifier

A digital audio processor for a digital audio receiver having an improved automute sequence is disclosed. The digital audio processor includes automute detection circuitry that monitors the amplitude of digital audio signals before and after the application of digital filters by digital audio processing circuitry. The amplitude of the input signals are compared against a first threshold level, while the amplitude of the output signals are compared against a second threshold level. In response to the amplitude of the input signals for all of the audio channels falling below the first threshold for a selected time period, a gain stage in each channel ramps down the volume to a mute level, and pulse-width-modulation circuitry is disabled. If the output signal amplitude falls below a second threshold for a channel, the pulse-width-modulation circuitry for that channel is disabled. Hysteresis for the input signal amplitude is preferably added into the automute exit determination.

Automute detection in digital audio amplifiers

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Carrollton, TX, United States of America

David Edward Zaucha