Fully-digitalized implementation of PFC rectifier in CCM without ADC

As generally acknowledged, the main drawback of a fully-digitalized power-factor-correction (PFC) rectifier is that too many analog-to-digital converters (ADCs) are used, and hence the corresponding cost is high. Hence, in this paper, the information on the required signal is obtained via two paired sawtoothed waves compared with the sensed signal, without any ADC used. For the PFC rectifier operating in the continuous conduction mode (CCM), two proposed formulas used to figure out the average inductor current, together with the strategy for changing sampling points, are applied to accurately sampling the average inductor current of the PFC rectifier. At the same time, based on the slope value of the inductor current obtained from the first average current calculation formula, another formula used to calculate the input voltage is derived so as to obtain the input voltage information used to feed the partial feedforward controller. As for the sinusoidal current command, it is generated by a sinusoid table along with a zero crossing detector. On the other hand, the information on the output voltage is obtained by one approximate formula. Therefore, there is no ADC required to realize full digital control of the PFC rectifier operating in CCM. Furthermore, the feasibility and effectiveness of the proposed sampling topology are verified by experimental results.