Influence of the pattern of pulse-width and frequency-pulse-width modulation on the ripple level of the output signal of the first-order aperiodic link

Abstract

This paper presents the results of comparative analysis of restoration quality of the input signal at the output of the systems with width-pulse (PWM) and frequency-width-pulse modulation (FPWM). The ripple level of the output smoothing filter signal is selected as the criterion. The output filter is the first-order aperiodic link. The ripple signal often plays the role of interference in systems for automatic control, thus degrading the quality indicators of the process control. Therefore, the relevance of such an analysis is evident. This paper compares push-pull and single-cycle modulation, with one PWM pattern and three, most common in practice, FPWM patterns. In addition, it considers three FPWM patterns: FPWM-1 with a quadratic, in the input signal function, decrease in the output signal, and FPWM-2 and FPWM-3 with a linearly increasing and decreasing, in the input signal function, frequency of carrier waves, respectively. The design ratios and graphic dependencies of the ripple levels of the output signal of the demodulation filter on the input action, taking into account the influence of the time constant of the output smoothing filter, are given. Recommendations on the fields of application of the considered modulation patterns are provided.