Real time correction of a digital PWM amplifier
AssigneeCirrus Logic, Inc.
InventorJohn Laurence Melanson
Life of this patent
Estimating the term…
Abstract
Distortion and noise in high power digital PWM amplifiers is reduced by measuring the difference between the desired output signal and the actual output signal on a pulse by pulse basis. This analog error is converted into a digital signal with an analog to digital converter (ADC). The digital error signal is then used to correct the feedback of the delta sigma modulator in real time. Preferably, more than one moment of the modulator signal is corrected via the feedback. Preferably, the predictable error of the circuitry which is known a priori is also corrected by correcting the delta sigma modulator feedback. A specialized ADC allows the loop delay to be low, without compromising accuracy.
Claims20
A digital PWM amplifier of the type having a multilevel delta sigma modulator of at least second order, having at least two state variables feeding a quantizer which provides feedback to the state variables and an output signal driving a PWM, the PWM feeding Class D output stage drivers, wherein the improvement comprises:
- means for comparing the output of the PWM with the output of the drivers, and generating an analog error signal based upon the comparison;
- an analog to digital converter (ADC) for converting the analog error signal into a digital error signal;
- and
- real time correction means for correcting the feedback of the delta sigma modulator on an ongoing basis based upon the digital error signal.
A method for improving the performance of a digital PWM amplifier of the type having a multilevel delta sigma modulator of at least second order, having at least two state variables feeding a quantizer which provides feedback to the state variables and an output signal driving a PWM, the PWM feeding Class D output stage drivers, wherein the method comprises the steps of:
- comparing the output of the PWM with the output of the drivers, and generating an analog error signal based upon the comparison;
- converting the analog error signal into a digital error signal;
- and
- correcting the feedback of the delta sigma modulator on an ongoing basis based upon the digital error signal.
Dependencies are inferred from the claim text.