UPWM distortion correction method based on negative feedback and state-space reconstruction
Aiming at the distortion problem of uniform-sampling pulse width modulation(UPWM)in digital class-D audio power amplifiers,an all-digital uniform-sampling pulse width modulation(UPWM)distortion correction method based on negative feedback and state-space reconstruction is proposed.This method utilizes the high open-loop gain characteristic of the digital Σ-Δ(Sigma-Delta)modulator and constructs a closed-loop negative feedback loop including the digital Σ-Δ modulator and the UPWM generator to make the relationship between the input and the output of the loop approximately linear,thereby the distortion caused by UPWM is corrected.When constructing the closed-loop,the state-space expression of the digital Σ-Δ modulator is reconstructed,and the interpolation block and the decimation block are added to make the loop have the same noise shaping effect as the original digital Σ-Δ modulator while maintaining stability.Experimental results show that compared with other UPWM distortion correction methods,the proposed method can not only reduce harmonic distortion,but also greatly reduce the background noise in the output signal of the digital UPWM modulator.Therefore,the digital UPWM modulator with the proposed method achieves an output signal to noise and distortion ratio(SNDR)of 95.26 dB in the case of sinusoidal digital signal input at the frequency of 6 kHz and the amplitude of-5 dB of the full scale(FS).The proposed method can be implemented by all digital circuits with features of simple hardware implementation and portability.
万方数据
维普
