Time-Domain Analysis of Sampling Effect in DPWM of DC–DC Converters

This paper investigates time-domain analysis of sampling effect in digital pulsewidth modulation (DPWM) of dc-dc converters. The relation between the sampling delay, duty ratio, and multisampling factor (sampling to carrier frequency ratio) has been characterized. The sampling delay of the digital controller used for DPWM of the DC-DC converter has close relation with the actual pulsewidth-modulation output. An increase in the multisampling factor can reduce the delay effect of the DPWM. The output voltage varies as a stepped function of the duty ratio instead of the linear function as observed in ideal modulation. It is shown in this paper that this delay is a periodic function of the duty ratio. The effect of variations in the sampling frequency, switching frequency, and modulation index has been analyzed. The proposed sampling effect has been verified analytically for the buck, boost, and buck-boost dc-dc converters. The experimental results for the buck and boost converters have been obtained with the control circuit realized through a field-programmable gate array-based digital controller.