S-Domain Model of Single-Sampling and Multi-Sampling DPWM DC-DC Converter Based on Discrete-Time Analysis

This paper proposes a general s-domain model of the single-sampling and multi-sampling digital pulse width modulation (DPWM) DC-DC converter. The proposed model has two main characteristics. First, the PWM delay is modeled by both time delay and state feedback rather than the time delay only. The time delay and state feedback are decided by the type of converters and carriers together. Therefore, the proposed model can explain the different effects of the PWM delay in different converters and carriers. Then, the time delay in the proposed model is decided by the switching frequency rather than the sampling frequency. Therefore, the multi-sampling cannot reduce the time delay of DPWM, which introduces ripples instead. For different converters and carriers, the influence of the ripple is varying. Therefore, based on the proposed model, the multi-sampling does not always improve the stability of converters, which is more in line with the actual situation. Compared with existing models, the proposed model reflects the complex effects of the PWM delay more accurately. To demonstrate these advantages intuitively, the stability of basic converters is judged by the proposed method, whose results are compared with existing models and experiment results.