Full-Digital AC-DC Converter With PFC Based on Counting

In this paper, a full-digital ac-dc converter with power factor correction (PFC)-based on counting is presented. As for the digital output voltage information, it is obtained by injecting the positive and negative triangular wave into the sensed output voltage, comparing this resultant signal with the output voltage reference, and counting the low level of the resulting signal based on one counter in the field programmable gate array (FPGA). As for the digital inductor current information, it is obtained by comparing the positive sawtoothed wave with the sensed inductor current after filtering and counting the low level of the resulting signal based on another counter in the FPGA. On the other hand, the sinusoidal reference command for the current controller is obtained by triggering the sinusoidal table in the FPGA via the zero crossing detecting circuit. This sinusoidal reference command, together with the traditional average current control method, generates a suitable control effort to drive the power switch such that the output voltage is controlled at a desired value and at the same time the input current follows the input voltage as tightly as possible. Above all, the proposed sampling method can be applied to the continuous conduction mode (CCM), the discontinuous conduction mode (DCM), or both. Finally, some experimental results are offered to verify the effectiveness of the proposed sampling method.