Texas Instruments Corporation

Anker Bjørn-Josefsen

Lars Risbo

Douglas Allen Roberson

Venkateswar Reddy Kowkutla

Thomas Holm Hansen

Kim Nordtorp Madsen

Claus Niels Neesgaard

Josey George Angilivelil

David Edward Zaucha

A predictive back-emf protection methodology for an electromechanical system, including a signal processor that processes a source signal to provide a modified source signal, a driver that converts the modified source signal to a drive signal, and an electromechanical transducer that generates, from the drive signal, a transducer response, and a back-emf signal coupled back to the driver output. A predictive back-emf generator (such as a routine in the signal processor) is characterized by a back-emf transfer function (linear parameterized model of the electromechanical transducer) for transforming an input signal into a transform back-emf representation of a back-emf signal predicted by the back-emf transfer function as a response of the electromechanical transducer to such input signal. The signal processor processes the source signal based on the transform back-emf representation to generate the modified source signal input to the driver. An example application is limiting peaking current in an audio system.

Electromechanical system with predictive back-EMF protection

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

Overcurrent and overload protection for the power output of a pulse-width-modulated digital audio system is disclosed. The overcurrent protection circuitry includes a latch that is set in responsive to output current from the power output stage that exceeds an overcurrent threshold; the output of the latch gates the pulse-width-modulated control signal to block power output for the remainder of the current pulse-width-modulated cycle; upon the end of the cycle, or the beginning of the next, the latch is cleared to enable power output in that next cycle. Overload protection is provided by circuitry including counters for counting the relative number of overcurrent cycles to normal, non-overcurrent cycles, and generating an overload signal to block power output in the event of too frequent overcurrent cycles.

Output current control and overload protection in digital audio amplifiers

A multiple-channel audio processor () and an associated plurality of power stages () in an audio system are disclosed. The audio processor () includes a plurality of audio amplifier channels (), each of which includes a pulse-code-modulation (PCM) to pulse-width-modulation (PWM) conversion function (), which generates PWM signals for application to the plurality of power stages (). The audio amplifier channels () each also include an interchannel delay function () for delaying the PWM edges relative to other channels (), for reducing noise. The audio amplifier channels () each also include delay adjust circuitry () for gradually increasing and decreasing the interchannel delay of the channel () on startup and shutdown. This permits a single control terminal (VALID) at the processor to globally enable and disable all of the power stages ().

Growing community of inventors

Lynge, Denmark

Anker Bjørn-Josefsen