Abstract: Systems and methods for over-current protection in all-digital amplifiers using low-cost current sensing mechanisms. An over-current hard clipping unit receives a digital audio signal, clips the signal according to a clip level, and provides the signal to a modulator. The modulator modulates the signal to produce, e.g., a PWM signal and provides the modulated signal to an output stage which generates an output current to drive a speaker. An over-current sensing unit is compares the output current to a threshold value and generates a binary signal indicating whether the output current exceeds the threshold value. The hard clipping unit receives the binary signal and ramps down the clip level during time periods in which the binary signal indicates that the output current exceeds the threshold. When the binary signal indicates that the output current does not exceed the threshold value, the hard clipping unit ramps up the clip level.

Abstract: Systems and methods implemented in a multi-bit digital noise shaper for reducing or eliminating undesirable transient response when the noise shaper exits a clipping state. In one embodiment, the noise shaper includes a quantizer, a filter, and a filter control unit that detects clipping in the quantizer and dynamically adjusts the allowable range of the internal state values of the filter. In one embodiment, a clipping mechanism is provided for each state value within the filter to clip the state value if it exceeds a corresponding clipping level. The clipping level for each state value is lower when the quantizer is clipping, and higher when the quantizer is not clipping. The clipping level for each state value may be transitioned either immediately or gradually from a current level to a target level (which is lower when the quantizer is clipping, and higher when the quantizer is not clipping.

Abstract: Systems and methods for performance improvements in digital switching amplifiers using simulation-based feedback. In one embodiment, a digital pulse width modulation (PWM) amplifier includes a signal processing plant configured to receive and process an input audio signal. The amplifier also includes a simulator configured to model processing of audio signals by the plant. The outputs of the plant and the simulator are provided to a subtractor, the output of which is then added to the input audio signal as feedback. The plant may consist of a modulator and power switch, a noise shaper, or any other type of plant. An analog-to-digital converter (ADC) may be provided to convert the output audio signal to a digital signal for input to the subtractor. Filtering may be implemented before or after the ADC, and a decimator may be placed after the ADC if it is an oversampling ADC.

Abstract: A delta-sigma modulator for driving an output stage is disclosed. The delta-sigma modulator operates between first and second voltages and includes a loop filter, a quantizer, and a feedback loop coupling an output of the quantizer and an input of the loop filter. The feedback loop includes compensation circuitry for compensating for variations in the first and second voltages in response to a measured average of the first and second voltages and a measured difference between the first and second voltages. Measuring circuitry measures the average and the difference of the first and second voltages.

Abstract: A delta-sigma modulator for driving an output stage is disclosed. The delta-sigma modulator operates between first and second voltages and includes a loop filter, a quantizer, and a feedback loop coupling an output of the quantizer and an input of the loop filter. The feedback loop includes compensation circuitry for compensating for variations in the first and second voltages in response to a measured average of the first and second voltages and a measured difference between the first and second voltages. Measuring circuitry measures the average and the difference of the first and second voltages.