Continuous conductionmode power factor correction (PFC) without input current measurement is a step forward with respect to previously proposed PFC digital controllers. Inductor volt-second (vsL) measurement in each switching period enables digital estimation of the input current; however, an accurate compensation of the small errors in the measured vsL is required for the estimation to match the actual current. Otherwise, they are accumulated every switching period over the half-line cycle, leading to an appreciable current distortion. A vsL estimation method is proposed, measuring the input (vg ) and output voltage (vo). Discontinuous conduction mode (DCM) occurs near input line zero crossings and is detected by measuring the drain-to-source MOSFET voltage vds . Parasitic elements cause a small difference between the estimated voltage across the inductor based on input and output voltage measurements and the actual one, which must be taken into account to estimate the input current in the proposed sensorless PFC digital controller.
This paper analyzes the current estimation error caused by errors in the ON-time estimation, voltage measurements, and the parasitic elements. A new digital feedback control with high resolution is also proposed.