Current sensorless Power Factor correction circuit using FPGA

The controller of a Conventional Unity Power factor correction (PFC) rectifier needs three feedback signals sensed from the converter, i.e., rectified input voltage, output voltage and input inductor current. Inductor current is sensed using current sensors, which are often expensive. Eliminating current sensors in PFC circuits is a subject of research interest. This paper gives a novel technique where a digital controller based UPF rectifier is implemented without the need of any current sensor or high speed ADCs. The inductor current sensing is performed using the switch node voltage of the switching converter. The theory of the proposed sensor and its interface to the UPF controller is explained for a boost based UPF rectifier. Experimental results are presented where a 0.97 pf is achieved in a scaled down prototype using the proposed scheme.