Using Feedforward Digital Control to Improve the Power Quality of a Three-Channel BCM Boost Converter for PFC Applications

This paper proposes a simple and effective digital feedforward algorithm to improve the power quality of a boundary-conduction-mode (BCM) boost converter for power-factor-correction (PFC) applications. BCM boost converters suffer from a zero-crossing distortion of the line current caused by the valley switching of the converter. The feedforward algorithm works by increasing the switch on-time around the zero crossing of the line voltage, which in turn increases the line current at this point. The feedforward algorithm has a very simple design procedure and implementation requiring only a single look-up table (LUT) in microcontroller software. The algorithm is implemented on a 1 kW interleaved 3-channel BCM boost converter which operates with an input rms line voltage of 85 V to 265 V, and an output voltage of 400 V. Experimental results are given for the prototype converter demonstrating a significantly improved power quality, when the feedforward algorithm is used.