Fully Digitalized Implementation of PFC Rectifier in CCM Without ADC

Abstract

As is 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. Consequently, in this paper, the information on the desired signal is obtained from two paired saw-toothed waves compared with the sensed signal, without the use of any ADCs. For the PFC rectifier operating in the continuous conduction mode (CCM) under average current mode control, the two proposed formulas used to calculate the average inductor current, together with the strategy for changing sampling points, are applied to accurately sample the average inductor current of the PFC rectifier. At the same time, based on the slope value of the inductor current obtained from the proposed average current calculation formula, another related formula is derived 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. Furthermore, the information on the output voltage is obtained by one simple approximate formula. Therefore, there is no ADC required to realize the full digital control of the PFC rectifier operating in CCM.