Frequency Predistortion Strategy Based Digital Phase Locked Loop for PFC Converter

In the high frequency boost power factor correction (PFC) converter, it is necessary to obtain the phase of the grid side voltage. However, in some cost-sensitive applications, there is only a sensor to detect the rectified voltage. This paper proposes a digital phase locked loop (PLL) scheme with a frequency predistortion digital bandpass filter to obtain the rectified voltage phase. Based on analyzing the frequency domain response characteristics of the digital bandpass filter, the continuous bandpass filter is digitized by bilinear transformation with frequency predistortion. On this basis, the rectified voltage is filtered to obtain its fundamental component as the PLL input. Then the grid side voltage phase is obtained at the output side, so the in-phase PFC reference current signal can be generated. Experiments have been carried out on the platform of the 70kHz PFC converter to verify the effectiveness of the strategy.