A study on pulse width errors of digitized naturally sampled PWM

Digital system exhibits better accuracy, stability, flexibility, and anti-noise property than analog scheme. Among various existent PWM principles natural sampled PWM (NPWM) is the best one in aspects of the harmonic distortion, attenuation, and time delay of the base-band modulating signals. So the best PWM implementing scheme would be a fully digital implemented scheme based on the natural sampled PWM principle. In this paper a universal digitized naturally sampled PWM (DNPWM) scheme was studied. The pulse width errors of DNPWM output compared with the NPWM output were theoretically analyzed in detail, which are caused by the finite sampling period TADC, the word length nADC in analog-digital conversion (ADC), and digital clock period T0 of the digital system. A set of equations of pulse width errors with respect to various system parameter were derived. The redundant pulses caused by the step effects of sampling and quantization in ADC and quantization in digital carrier, which is inevitable, were analyzed in detail too, and a method to eliminate the redundant pulses is presented. To Cancel redundant pulses would bring about additional pulse errors, which had also been analyzed. Finally, simulation research gave statistical results that demonstrate the validity of the analysis in this paper, and experimental results are given too.